EE Toolbox

57 calculators plus reference tables, analyzers, and field tools for electrical engineering, commissioning, and maintenance. Start with a task group or use / to search.

⚡Fundamentals
◈Electronics & Digital Design
🔌Distribution
🧪Field Test & Fault Locating
🔋Power Systems
🚲E-Bike Build
🔋Battery Build
📋Reference Tables
🔥Heater Wizard
📡RF & Circuit Tools
📚STEM Toolkit
📐NEC Calculations
🔧Tools
🔬Advanced Tools
⚠Hazardous / Safety
🗂Workspace
🎛Control theory

⚡ Ohm's Law

Enter any two values to solve for the third. Power is also calculated.

ℹ More Info — Ohm's Law
Ohm's Law relates voltage (V), current (I), and resistance (R) in any DC or resistive AC circuit. Enter any two known values and the calculator solves for the unknown plus power.

Key relationships:
  • V = I × R — Voltage equals current times resistance
  • I = V / R — Current equals voltage divided by resistance
  • R = V / I — Resistance equals voltage divided by current
  • P = V × I = I² × R = V² / R — Power in three equivalent forms
Units: V = Volts, I = Amperes, R = Ohms (Ω), P = Watts (W)
Ohm's Law Calculator
V = I × R  |  I = V / R  |  R = V / I
P = V × I = I² × R = V² / R
Ohm's Law — Quick Reference
Voltage: V = I × R
Current: I = V / R
Resistance: R = V / I

Power — 3 forms:
P = V × I
P = I² × R
P = V² / R

1 kW = 1000 W  |  1 HP = 746 W
ℹ Some references use E for EMF/voltage and I for current. Both notations are standard.

🔋 DC Power Formulas

Solve for power using any valid pair of electrical quantities.

ℹ More Info — DC Power
DC Power is the rate of energy transfer in a direct current circuit. Choose the formula that matches your known quantities:

Formulas:
  • P = V × I — when voltage and current are known
  • P = I² × R — when current and resistance are known
  • P = V² / R — when voltage and resistance are known
Tip: 1 kW = 1,000 W. For high-power systems, results are shown in both W and kW. All three formulas are mathematically equivalent via Ohm's Law.
DC Power Calculator
P = V × I  |  P = I² × R  |  P = V² / R
Power Triangle Reference
Given V & I: P = V × I
Given I & R: P = I² × R
Given V & R: P = V² / R

Derived quantities:
I = P / V  |  V = P / I
R = V / I  |  R = V² / P
R = P / I²

1 kW = 1,000 W  |  1 MW = 1,000 kW

〰 Reactance & Impedance

Calculate inductive/capacitive reactance and series impedance.

ℹ More Info — Reactance & Impedance
Reactance is the opposition to AC current flow caused by inductors and capacitors:

  • Inductive Reactance (XL): XL = 2π × f × L — increases with frequency
  • Capacitive Reactance (XC): XC = 1 / (2π × f × C) — decreases with frequency
  • Impedance (Z): Z = √(R² + (XL − XC)²) — total opposition to AC current
  • Phase Angle (θ): θ = arctan((XL − XC) / R) — positive = inductive, negative = capacitive
At 60 Hz: ω = 377 rad/s. Enter capacitance in Farads (e.g., 100 µF = 0.0001 F).
Inductive Reactance (XL)
XL = 2π × f × L
Capacitive Reactance (XC)
XC = 1 / (2π × f × C)
ℹ For µF, divide by 1,000,000 (e.g. 100 µF = 0.0001 F)
Series Impedance (Z)
Z = √(R² + X²)
θ = atan2(X, R)
PF = cos(θ) = R / |Z| (when |Z| > 0)
+X = inductive (lagging); −X = capacitive (leading). XL and XC calculators above report positive magnitudes.
Reactance & Impedance Reference
Inductive Reactance:
XL = 2πfL = ωL

Capacitive Reactance:
XC = 1/(2πfC) = 1/(ωC)

Series Impedance:
Z = √(R² + X²)   where X = XL − XC

Ohm's Law for AC:
V = I × Z  |  I = V / Z

At 60 Hz: ω = 2π×60 ≈ 377 rad/s
XL = 377L  |  XC = 1/(377C)

🔔 Resonance

Series and parallel LC circuit resonant frequency and Q factor.

ℹ More Info — Resonance
Resonance occurs when inductive and capacitive reactances are equal (XL = XC), causing them to cancel. The circuit then behaves as purely resistive.

  • Resonant Frequency: f₀ = 1 / (2π√LC) — depends only on L and C values
  • Q Factor: Q = XL / R — measures sharpness of the resonance peak. High Q = narrow bandwidth
  • Bandwidth: BW = f₀ / Q — frequency range over which the circuit responds
Applications: Tuned filters, RF circuits, power factor correction capacitor banks, and harmonic resonance analysis in distribution systems.
Resonant Frequency
f₀ = 1 / (2π√LC)
Q Factor & Bandwidth
Q = XL / R = (1/R)×√(L/C)
BW = f₀ / Q
Resonance Reference
At resonance:
XL = XC (reactances cancel)
Z = R (minimum impedance — series)
Z = L/(RC) (maximum impedance — parallel)

Resonant frequency:
f₀ = 1 / (2π√LC)

Q Factor (series circuit):
Q = XL/R = (1/R)√(L/C)
High Q → narrow bandwidth, sharp tuning

Bandwidth:
BW = f₀/Q = R/(2πL)

📐 Power Factor Correction

Size capacitor banks to improve power factor and reduce apparent current.

ℹ More Info — Power Factor Correction
Power Factor Correction (PFC) adds capacitors to counteract inductive reactive power, bringing PF closer to unity. This reduces apparent current and lowers demand charges.

Formula: kVAR = kW × (tan θ₁ − tan θ₂), where θ = arccos(PF)

  • Enter the load's true power in kW, existing PF (e.g., 75%), and target PF (e.g., 95%)
  • Result is the capacitor bank size (kVAR) needed to reach the target PF
  • Utility penalties typically apply when PF drops below 0.85–0.90
Caution: Over-correction (PF > 1.0 leading) can cause voltage rise and equipment damage. Target PF of 0.95–0.98 lagging is typical.
Capacitor Bank Sizing
kVAR = kW × (tan θ₁ − tan θ₂)
θ₁ = cos⁻¹(PF₁)  |  θ₂ = cos⁻¹(PF₂)
Power Factor Reference
Power Factor:
PF = cos θ = P (kW) / S (kVA)

Power Triangle:
kVA² = kW² + kVAR²

Benefits of high PF:
• Lower apparent current (smaller conductors)
• Reduced utility demand charges
• Improved voltage regulation

Utility target: PF ≥ 0.90–0.95

Capacitor bank formula:
kVAR = kW × (tan θ₁ − tan θ₂)

🔗 Series / Parallel Circuits

Add components and calculate total resistance, capacitance, or inductance.

ℹ More Info — Series / Parallel Circuits
Series vs. Parallel configurations change how component values combine:

  • Resistors Series: RT = R₁ + R₂ + … (total increases)
  • Resistors Parallel: 1/RT = 1/R₁ + 1/R₂ + … (total decreases, always less than smallest)
  • Capacitors Series: 1/CT = 1/C₁ + 1/C₂ + … (total decreases)
  • Capacitors Parallel: CT = C₁ + C₂ + … (total increases)
  • Inductors Series: LT = L₁ + L₂ + … (total increases, opposite of capacitors)
  • Inductors Parallel: 1/LT = 1/L₁ + 1/L₂ + … (total decreases)
Use the + Add button to add more components. Remove with the × button.
Series Resistors
RT = R₁ + R₂ + … + Rn
Parallel Resistors
1/RT = 1/R₁ + 1/R₂ + … + 1/Rn
Two resistors: RT = (R₁×R₂)/(R₁+R₂)
Target RT — parallel pair finder
RT = (R₁ × R₂) / (R₁ + R₂)
Searches standard resistor pairs for the closest target.
Series Capacitors
1/CT = 1/C₁ + 1/C₂ + … + 1/Cn
Parallel Capacitors
CT = C₁ + C₂ + … + Cn
Series Inductors
LT = L₁ + L₂ + … + Ln
Parallel Inductors
1/LT = 1/L₁ + 1/L₂ + … + 1/Ln

Digital Logic Workbench

Build small combinational circuits, simulate signals, view truth tables, and convert between gate diagrams and Boolean expressions.

ℹ More Info — Boolean logic
Boolean expression: use AND, OR, NOT, and XOR, or the symbols *, +, !, and ^. Parentheses control grouping. This workbench is for combinational logic; it does not model propagation delay, flip-flops, or physical wiring constraints.
Boolean expression ⇄ logic diagram
Use A–D as inputs. The diagram and truth table update from the active expression.
Y = —
Gate diagram editor

Create named intermediate gates, then extract an equivalent Boolean expression. Gates may reference A–D or an earlier gate.

Live logic diagram
Truth table

Analog Design Workbench

Size common op-amp stages and explore practical analog-filter families with a live response plot. Includes a generic analog-computer lead network Gc = (Ts+1)/(αTs+1) from R/C.

ℹ More Info — Analog design
Ideal first-pass calculations only: verify supply range, input/output swing, gain-bandwidth, slew rate, noise, stability, component tolerance, source/load impedance, and the exact topology before building hardware.
Op-amp topology
Result
Choose a topology and calculate its ideal transfer relationship.
Circuit
Transfer function

Semiconductor Device I-V

Shockley diode (optional series Rs), npn β-forced Q-point, and long-channel NMOS cutoff / triode / sat. Homework device curves — not the op-amp / filter workbench.

ℹ More Info — Device I-V
Three first-pass models on one page. None of them is a SPICE deck.

Formulas:
  • Diode: I = Is (evD/(η VT) − 1), VT = kT/q. Optional Rs is solved so V = vD + I Rs
  • BJT: Ib = (Vcc − Vbe,on)/Rb, Ic = β Ib until Vce would fall below Vce,sat (then the collector resistor sets Ic)
  • NMOS: kn = μCox W/L. Cutoff Vgs < Vt; triode Vds < Vov; sat Id = (1/2) kn Vov². Optional λ multiplies by (1 + λ Vds)
Honest limits: no reverse breakdown, no charge storage, no Gummel-Poon, no short-channel or subthreshold. Saturation on the BJT tab is a Vce,sat clamp, not a full Ebers-Moll pair.

Citations: standard device-physics identities (Shockley, long-channel square law, β-forced Q-point). Cal Poly semiconductor-device course topics used only to pick this device set — notes are not reproduced. This is not a foundry process-recipe tool.
Device
I-V
Shockley diode
I = Is (evD/(η VT) − 1)  |  VT = kT/q  |  V = vD + I Rs
Results

🧲 Magnetic Circuit Workbench

Homework magnetostatics: series or parallel reluctance, optional air gap, Φ = NI / Rtot, B, H, and MMF drops. Not a transformer kVA sizer.

ℹ More Info — Magnetic circuits
A magnetic circuit is the Ampere-loop analog of Ohm’s law. MMF F = N I plays the role of voltage, flux Φ plays the role of current, and reluctance R = ℓ / (μ A) plays the role of resistance.

Formulas:
  • R = ℓ / (μ A), with μ = μr μ0 and μ0 = 4π × 10−7 H/m
  • Series steel: Rsteel = Σ Ri. Parallel steel: 1/Rsteel = Σ 1/Ri
  • Optional air gap sits in series with the steel network: Rtot = Rsteel + Rgap
  • Φ = F / Rtot, B = Φ / A, H = B / μ. Ampere: the MMF drops sum to N I
  • Gap fringing (optional, editable): A_eff = (√A + k ℓ_g)². k = 1 is the square-equivalent first-order start; change k if you have a published geometry factor
Honest limits: this tool is linear. Saturation is a Bsat warning, not a B–H curve. Leakage flux, 3-D end effects, and eddy-current heating are out of scope.

Citations: Magdy F. Iskander, Electromagnetic Fields and Waves, 2nd ed., Waveland Press, 2013 (magnetic circuits discussion). Ampere ∮ H · dℓ = N I, Faraday v = N dΦ/dt, and R = ℓ / (μ A) are standard identities. Gap-fringing area growth is generic EE machines-course practice, not a traced publisher figure.
Laminated core and gap
B vs N I (linear)
Core and network
R = ℓ / (μ A)  |  Φ = N I / Rtot  |  B = Φ / A  |  H = B / μ
Ampere: ∮ H · dℓ = N I
The air gap, if enabled, is always in series with that steel network — the usual gapped-core model.
Air gap and extra paths
Results

📉 Transient Circuit Lab

Closed-form first-order RC/RL and second-order series or parallel RLC. Source-step or source-free. Time-domain homework — not the resonance calculator, not the MNA simulator.

ℹ More Info — Lumped transients
One energy-storage element gives a first-order exponential. Two (L and C) give a second-order characteristic equation s² + 2αs + ω0² = 0.

Formulas:
  • RC: τ = RC, vC(t) = Vf + (vC(0) − Vf) e−t/τ
  • RL: τ = L/R, iL(t) = If + (iL(0) − If) e−t/τ
  • Series RLC: α = R/(2L), ω0 = 1/√(LC). Parallel RLC: α = 1/(2RC), same ω0
  • Overdamped α > ω0, critical α = ω0, underdamped α < ω0 with ωd = √(ω0² − α²)
Source-step applies a DC Vs (or Is for parallel) at t = 0 with the entered initial conditions. Source-free dumps stored energy with the forced response set to zero.

Citations: standard lumped circuit-theory identities (Faraday on the inductor, Ampere/KCL on the capacitor node, the RLC characteristic equation). This is not a transmission-line tool; Iskander’s wave chapters are out of scope here.
Circuit and drive
RC: τ = RC  |  RL: τ = L/R
series: α = R/(2L)  |  parallel: α = 1/(2RC)  |  ω0 = 1/√(LC)
Waveform

Original SVG — not a lab screenshot. Blue dashed lines mark 10% and 90% of the step; amber is the ~2% settling estimate.

Closed form

∠ Phasor Diagram Workbench

Interactive RMS phasors for a series or parallel R-L-C plus a source. Voltage or current triangle, θ, PF, and S/P/Q. Balanced Δ-Y conversion sits in the side panel — not a 3-phase kVA sizer.

ℹ More Info — Phasors
In sinusoidal steady state every derivative becomes a jω multiply. Impedances add in series; admittances add in parallel. The source phasor sits on the real axis so θ is simply arg(I).

Formulas:
  • Series: Z = R + jωL + 1/(jωC), I = Vs / Z, VR = I R, VL = I jωL, VC = I /(jωC)
  • Parallel: I_R = Vs/R, I_L = Vs/(jωL), I_C = Vs jωC, I = sum
  • S = Vrms Irms*, P = Re(S), Q = Im(S), PF = cos θ
  • Q > 0 lagging (inductive); Q < 0 leading (capacitive)
  • Balanced Δ-Y: ZΔ = 3 Zy
Toggle RMS vs peak on the source; results are reported as RMS and polar. Peak = RMS × √2.

Citations: standard EE phasor analysis. Optional secondary: Magdy F. Iskander, Electromagnetic Fields and Waves, 2nd ed., Waveland Press, 2013 (time-harmonic / phasor-fields chapter) — identities only, not a copy source. This panel does not rebuild the three-phase power wizard.
R-L-C and source
Z = R + jωL + 1/(jωC)  |  I = Vs / Z
S = V I*  |  PF = cos θ  |  ZΔ = 3 Zy
Phasor diagram
Phasor results
Balanced Δ-Y impedance
ZΔ = 3 Zy  |  Zy = ZΔ / 3  (balanced only)
Δ and Y sketch

Battery Build Designer

Plan 18650 series/parallel packs and nickel-strip cross sections with transparent, editable assumptions. For interactive cell painting on an e-bike pack, use the Battery Pack Designer in the E-Bike Build tools.

ℹ More Info — Battery safety
This is a planning tool, not a build approval. Verify the exact cell datasheet, BMS, fusing, insulation, busbar/strip temperature rise, weld quality, enclosure clearances, charger, fault protection, and applicable transport/fire requirements before assembling a lithium-ion pack.
Nickel strip cross section
Strip result
Common pure-nickel strip planning table

Battery Bank Calculator

Forward-size a bank from load and backup time, reverse-solve runtime from installed strings, and lay out series/parallel from module V and Ah.

ℹ More Info — Planning math, not a listing
Usable energy per unit = nameplate Wh × depth of discharge. Inverter-side energy = AC watts × hours / efficiency. Unit count = ceil of that quotient.

Chemistry presets seed DoD and inverter efficiency. DoD and efficiency stay editable — presets never lock them. LFP is typically ~90–95% usable; flooded and AGM lead-acid are typically ~50%.

Series = round(Vsys / Vmod). Parallel = ceil(Ahsys / Ahmod) when a target capacity is entered.

This is planning math only — not a UL listing, fire-code, ventilation, BMS, or PE review. Verify the battery datasheet, inverter continuous rating, and cable ampacity.
Shared specs

DoD and efficiency are never locked. Change the preset, then edit the numbers.

Forward — how many units?
AC Wh = P × t
Battery Wh = AC Wh / η
Units = ceil(battery Wh / (nameplate × DoD))

Daily kWh is a 24-hour total. Backup hours is how long the bank must run — not the window that produced that daily energy.

Reverse — how long will it last?
Runtime = (units × nameplate × DoD × η) / P
Series / parallel helper
Series = round(Vsys / Vmod)  ·  Parallel = ceil(Ahsys / Ahmod)

📉 Voltage Drop

NEC recommends ≤3% voltage drop on branch circuits; ≤5% total (feeder + branch).

ℹ More Info — Voltage Drop
Voltage Drop occurs across conductor resistance in long runs. Excessive VD causes equipment malfunction, motor overheating, and NEC compliance issues.

Formula: VD = (M × K × I × L) / CM, where M = 2 (single-phase) or √3 (three-phase), K = 12.9 (Cu) or 21.2 (Al), L = one-way feet, CM = circular mils

  • NEC Recommendation: ≤3% on branch circuits; ≤5% total (feeder + branch) — NEC 210.19(A) Informational Note
  • Calculate VD%: Select conductor size and enter run parameters to check compliance
  • Min Wire Size: Enter max allowed VD% and the tool finds the minimum conductor size
Tip: For long runs, consider going up 1–2 wire sizes to reduce VD even if ampacity allows smaller conductors.
Single-Phase Voltage Drop
VD = (2 × K × I × L) / CM
VD% = (VD / V_supply) × 100
K = 12.9 (Cu) | 21.2 (Al)
Three-Phase Voltage Drop
VD = (√3 × K × I × L) / CM
VD% = (VD / V_supply) × 100
Min Wire — Single-Phase
CM_min = (2 × K × I × L) / VD_max
Min Wire — Three-Phase
CM_min = (√3 × K × I × L) / VD_max
3Ø System Topology — Voltage Drop Notes
Wye (Y) Systems:
L-N loads: VD formula uses 2×K (single-phase, 2-wire return)
L-L loads: VD formula uses √3×K (3-phase)

High-Leg Delta (Wild Leg):
Do NOT use B-phase for single-phase L-N loads (208V, not 120V)
Use A or C phases only for 120V single-phase circuits

Corner-Grounded Delta:
No neutral conductor — all loads must be 3-wire 3-phase or L-L only
Single-phase 120V loads are NOT supported

Ungrounded (IT) Delta:
Ground faults produce no fault current — requires ground fault monitoring
Voltage drop calculations above use standard formulas. For grounded systems, verify that the correct supply voltage (L-L or L-N) is entered per your topology.

📏 Conductor Length by Resistance

Estimate length from a milliohm (mΩ) reading — end-to-end or shorted to a parallel.

ℹ More Info — Conductor Length by Resistance
This tool solves conductor length from the resistivity relationship R = ρ × L / CM, rearranged as L = R × CM / ρ.

Use a milliohm / Kelvin reading. End-to-end is one conductor measured from end to end (distance = solved path). Short to parallel is a measurement between two parallels that are shorted or bonded somewhere along the run (distance to the short = path ÷ 2). 3-phase far-end short is the same ÷2 rule on a symmetrical far-end short. Not a cable locator or TDR — contact resistance and stranding shift the estimate.

Temperature compensation: RT2 = RT1 × [1 + α × (T2 − T1)]
The calculator uses this form to convert measured resistance at ambient temperature to the selected reference temperature before solving length.
Inputs
Ltotal = (Rref × CM) / ρ  |  Rref = Rmeasured / [1 + α × (Tmeasured − Tref)]

Measure between two parallels shorted/bonded along the run; distance to short = path ÷ 2

Presets: Cu ρ = 10.371 @20°C / 12.9 @75°C, Al ρ = 17.02 @20°C / 21.2 @75°C. Hard-drawn copper uses the copper preset as a starting point; edit ρ when you have manufacturer-specific data.
Measurement Circuit Diagram
Conductor resistance measurement circuit Selectable wiring diagrams for end-to-end, short-to-parallel, and 3-phase far-end short milliohm measurements. DMM mΩ / Ω Near End Short / bond Parallels shorted or bonded along the run Distance to short = total solved path ÷ 2 Path factor: ÷2 — distance to short is one-way

⚙ Motor Calculations

Calculate motor HP or full-load amperes (FLA) for single- and three-phase motors.

ℹ More Info — Motor Calculations
Motor Calculations convert between horsepower (HP), voltage, current, efficiency, and power factor.

  • HP from FLA: Calculates shaft output horsepower given measured current — useful for verifying actual motor loading
  • FLA from HP: Calculates expected nameplate current from rated HP — used for conductor and OCPD sizing
  • NEC Branch Circuit: Size conductors at FLA × 1.25 per NEC 430.22
Typical values: Efficiency 88–95% (NEMA Premium), Power Factor 0.80–0.92 lagging.
Note: Always verify against NEC Tables 430.248/430.250 for conductor sizing — do not use calculated FLA alone.
Calculate Horsepower from FLA
HP = (V × I × Eff × PF) / 746   [1Ø]
HP = (V × I × √3 × Eff × PF) / 746   [3Ø]
Calculate FLA from Horsepower
I = (HP × 746) / (V × Eff × PF)   [1Ø]
I = (HP × 746) / (V × √3 × Eff × PF)   [3Ø]
NEC Branch Circuit = FLA × 1.25
3Ø Supply Topology — Motor Considerations
High-Leg Delta (Wild Leg):
B-phase to neutral ≈ 208V (on 240V system)
Motors: connect L-L only (never use B-phase for 120V control)
NEC 110.15 requires orange conductor identification

Corner-Grounded Delta:
One phase bonded to ground — asymmetric fault currents
Motors run normally (L-L balanced), but grounding/protection differs
NEC 250.26 governs grounded conductor identification

Wye Systems (208/120 or 480/277):
V_LN = V_LL / √3  |  Balanced neutral current = 0 for 3Ø motors
For motor calculations above, always use the line-to-line voltage (V_LL) regardless of system topology.

Cable Schedule Generator

Catalog of cable types, a quantity build list, sequential Cable IDs, an in-browser grid, and CSV / XLSX / JSON export. Length, routing, and comments stay blank for the field.

ℹ More Info — How numbering and ampacity notes work
Pick a project prefix (for example C-) and a starting number. Quantity 3 of one type becomes C-001, C-002, C-003.

Ampacity notes reuse NEC Table 310.16 copper 75°C (≤3 current-carrying conductors) from the existing wire calculator — tables are not copied here. Optional length on a generated row can add a voltage-drop note from Chapter 9 Tables 8 and 9. Those notes flag size; they are not a substitute for a full feeder calculation.
Project numbering
Cable type catalog (editable)
Add cables to the build list
Editable cable schedule

Columns: Cable ID, From, To, Cable Type, Conductor Size, Conductor Count, Insulation, Voltage Rating, Length, Routing / Tray, Ampacity, Voltage Drop, System, Termination From, Termination To, Comments. Length, routing, and comments start blank. Filling Length writes a voltage-drop note when system voltage is set.

Motor Nameplate Analyzer

Photograph a nameplate, correct the OCR draft, then estimate overload, branch-circuit SCPD, and conductor size from NEC 430.32, Table 430.52, and 430.22. On-device Tesseract is the default. Optional AI enhance is a draft — not perfect OCR and not an AI electrician.

ℹ More Info — Citations and limits
Overload (separate device, motors more than 1 hp): NEC 430.32(A)(1) — 125% of nameplate FLA when service factor is 1.15 or greater or temperature rise is 40°C or less; 115% for all other motors. NEC 430.32(C) allows the next higher size not exceeding 140% or 130% if needed to start.

Branch-circuit short-circuit and ground-fault protection: NEC 430.52 using Table 430.52 percentages of motor FLA. The percentage used is shown with the result.

Conductors: NEC 430.22 — ampacity at least 125% of FLA, using Table 310.16 75°C copper via the existing wire math helper. Optional run length adds a Chapter 9 voltage-drop note.

Locked-rotor current: NEMA code letter ranges from NEC 430.7(B) / NEMA MG-1 Table 10-1. That is a table range, not a substitute for manufacturer LRA.

Use nameplate FLA for overload (430.6(A)(2)). Use Tables 430.248 / 430.250 FLA for conductors and SCPD except as 430.6 allows. Informational estimate, not an inspection.
Optional nameplate photo
Privacy: the default path is on-device Tesseract.js. The photo stays here and is never uploaded unless you turn on Enhance with AI and then click Read nameplate. The photo is not saved after you leave or reset.
Before you pick a photo: square the nameplate to the camera, fill the frame, use even light, and avoid glare on the metal. OCR is not perfect and this is not an AI electrician — treat every filled field as a draft you must correct. You can skip the photo and type every field by hand.

No photo required. Fill the fields below, or choose a photo after reading the privacy note. On-device OCR is the default.

Reviewed nameplate fields
Protection options

Transformer — Ratio & Current

Primary/secondary current, turns ratio, and winding topology. Protection uses the real Table 450.3(B) tiers on the Sizing & 450.3 view — not a flat 125%.

ℹ More Info — Transformer Basics
This view is the first mode of the Transformer tool: currents and topology only.

  • Turns Ratio: a = Vp/Vs = Np/Ns = Is/Ip
  • Primary Current: Ip = kVA×1000/Vp (1Ø) or kVA×1000/(√3×Vp) (3Ø)
  • Protection: use Sizing & 450.3 for primary-only vs primary+secondary, Note 1, and continuous 125%.
  • Conductors: Cu/Al, insulation, parallels, VD, conduit, EGC/GEC live on Conductors / OCPD / VD.
  • High-Leg Delta: B-phase to neutral = V_LL × √3/2 ≈ 208V on 240V system. Tag orange per NEC 110.15.
  • Corner-Grounded Delta: One corner at ground potential — no neutral for single-phase loads.
Current, Sizing & Conductor Selection
1Ø: Ip = kVA×1000/Vp  |  Is = kVA×1000/Vs
3Ø: Ip = kVA×1000/(√3×Vp)  |  Is = kVA×1000/(√3×Vs)
Turns Ratio a = Vp/Vs  |  450.3(B) lives on Sizing & 450.3
kVA from Voltage & Current
1Ø: kVA = V × I / 1000
3Ø: kVA = √3 × V × I / 1000
Standard Transformer kVA Sizes (ANSI/NEMA)
Single-PhaseThree-PhaseVoltage Classes
1, 1.5, 2, 3 kVA3, 6, 9, 15 kVA120, 208, 240 V
5, 7.5, 10 kVA30, 45, 75 kVA480 V (primary)
15, 25, 37.5 kVA112.5, 150 kVA208/120 V (sec)
50, 75, 100 kVA225, 300 kVA480/277 V (sec)
167, 250 kVA500, 750 kVA2400, 4160 V
333, 500 kVA1000, 1500 kVA12.47, 13.8 kV
2000, 2500 kVA34.5 kV
ANSI C57.12.20 / NEMA ST-20 standard ratings. Sizes up to 2500 kVA available dry-type; liquid-filled extends higher.
3Ø Topology Quick Reference
TopologyNeutral?V_LN from V_LLNotes
Δ–Y (Delta-Wye)Yes (Y side)V_LL / √3Most common; 480→208/120V
Y–Y (Wye-Wye)Yes (both)V_LL / √3Neutral both sides; triplen harmonics can circulate
Δ–Δ (Delta-Delta)NoN/AMotor loads; open-delta possible
High-Leg ΔPartialA,C: V_LL/2; B: V_LL×√3/2B-phase (wild leg) = 208V on 240V; NEC 110.15 orange tag
Corner-Gnd ΔNoOne phase = 0V to gndPhase grounded; NEC 250.26; no single-phase neutral loads
Y–Δ (Wye-Delta)Yes (Y side)V_LL / √3Step-up apps; no neutral on secondary
For High-Leg: V_B-N = V_LL × sin(60°) = 240 × 0.866 = 208V. For Corner-Grounded: the grounded conductor is at 0V potential — all phase-to-ground voltages are asymmetric.

🔵 Conduit Fill Calculator

NEC Chapter 9 — maximum allowable fill percentages for raceways.

ℹ More Info — Conduit Fill
Conduit Fill limits how many conductors can be installed in a raceway to prevent overheating and allow future pulls.

NEC Chapter 9, Table 1 limits:
  • 1 conductor → 53% maximum fill
  • 2 conductors → 31% maximum fill
  • 3 or more conductors → 40% maximum fill
This calculator uses EMT conduit areas and THHN/THWN-2 conductor areas from NEC Annex C. For mixed sizes, sum the individual conductor areas manually and compare to the conduit's allowed fill area.
Conduit Fill — THHN/THWN-2 in EMT
Fill% = (Total Wire Area / Conduit Area) × 100
Max Fill: 1 wire=53% | 2 wires=31% | 3+=40%
NEC Fill % Reference
NEC Chapter 9, Table 1:
1 conductor → max 53% fill
2 conductors → max 31% fill
3+ conductors → max 40% fill

Always check:
• All conductors same type & size
• Different sizes: sum individual areas
• Use NEC Table 5 for conductor areas
• Use NEC Table 4 for conduit areas
ℹ This calculator uses EMT conduit areas and THHN/THWN-2 conductor areas from NEC Annex C.

🔵 Conduit Fill — Mixed Conductors

Any Chapter 9 raceway, any mix of conductor sizes and insulations, with the minimum size recommended for you.

ℹ More Info — Mixed Conduit Fill
Unlike the single-size calculator, this one sums each conductor group separately, so a run carrying 3 × 250 kcmil phases, 1 × 2/0 neutral and 1 × 4 AWG ground is handled in one pass.

NEC Chapter 9, Table 1 fill limits:
  • 1 conductor → 53%
  • 2 conductors → 31%
  • Over 2 conductors → 40%
  • Nipples 24 in or shorter → 60% (Table 1, Note 4)
Raceway areas come from Chapter 9, Table 4 and conductor areas from Table 5. Because Table 5 areas are published rounded, a computed conductor count can land one below the Annex C table at an exact boundary — Annex C governs when every conductor is the same size.
Conductors & Raceway
Fill% = (Σ conductor areas / raceway area) × 100
Limit: 1 wire = 53% | 2 wires = 31% | 3+ = 40% | nipple = 60%
How the limits work
NEC Ch.9 Table 1
ConductorsMax fill
153%
231%
Over 240%
Nipple ≤ 24 in60%

The two-conductor case is the tightest because two round conductors in a round raceway leave the most unusable space. Equipment grounding conductors count toward the conductor total for fill even though they are not current-carrying — that distinction only matters for the ampacity adjustment in the Wire Size tool.

🏗 Transformer & Conductor Selection Engine

Designs both feeders end to end — OCPD, conductors, grounding, voltage drop and conduit — and shows every step.

ℹ More Info — Selection Engine
This models a complete transformer installation on both sides of the unit and states the code basis for each result.
  • Full load amps — kVA × 1000 ÷ V for single-phase, ÷ (√3 × V) for three-phase.
  • Overcurrent protection — NEC Table 450.3(B). Primary-only protection uses the 125% / 167% / 300% tiers; adding a secondary device raises the primary allowance to 250% because the secondary device then provides the closer protection.
  • Conductors — 125% of FLA per NEC 215.2(A)(1), checked against Table 310.16 with ambient correction 310.15(B)(1) and bundling adjustment 310.15(C)(1), then capped by the termination rating in 110.14(C).
  • Equipment grounding conductor — Table 250.122, sized from the overcurrent device ahead of the circuit, never from the phase conductor.
  • Grounding electrode conductor — a transformer secondary is a separately derived system, so 250.30(A)(5) sends you to Table 250.66 sized on the derived ungrounded conductors.
  • Voltage drop — Z = R·cosθ + X·sinθ using Chapter 9 Table 8 resistance and Table 9 reactance. The 3% per feeder and 5% total figures are informational notes in 210.19(A) and 215.2(A), not enforceable limits.
  • Conduit — Chapter 9 Table 1 at 40% fill for more than two conductors, against Table 4 raceway areas and Table 5 conductor areas.
Results are shareable: the URL updates with your inputs, so a link reproduces the whole design.
Transformer
3Ø: I = kVA × 1000 ÷ (√3 × V)  |  1Ø: I = kVA × 1000 ÷ V
Installation Conditions
Primary Feed
Secondary Feed

⏱ 555 Timer Calculator

Astable oscillator and monostable one-shot timing, with the output waveform drawn to scale.

ℹ More Info — 555 Timer
The 555 charges its timing capacitor toward Vcc and switches at two internal comparator thresholds set by a resistor divider: 1/3 Vcc and 2/3 Vcc.

Where the magic numbers come from. Charging between those two thresholds takes ln(2) = 0.6931 time constants, which is the 0.693 in every astable formula. A monostable runs from 0 V to 2/3 Vcc instead, which takes ln(3) = 1.0986 time constants — the familiar 1.1. Neither is an empirical fudge factor.

Astable: the capacitor charges through R1+R2 and discharges through R2 alone, so thigh is always longer than tlow and the duty cycle cannot reach 50% in the standard circuit. A diode across R2 gives the charge path R1 only, which unlocks the full range.

Practical limits: keep R ≥ 1 kΩ so the discharge transistor is not overloaded, and below about 10 MΩ so bias currents and capacitor leakage do not dominate. Above a few hundred kHz, use a CMOS 7555/TLC555 rather than the bipolar NE555.
Astable — Free-Running Oscillator
t1 = ln(2) × (R1 + R2) × C  |  t2 = ln(2) × R2 × C
f = 1.44 / ((R1 + 2·R2) × C)  |  D = (R1 + R2) / (R1 + 2·R2)
Monostable — One-Shot
t = 1.1 × R × C   (1.1 = ln(3), the 0 → 2/3 Vcc charge interval)
Output Waveform

Green is the output pin; amber is the timing capacitor charging toward 2/3 Vcc and discharging to 1/3 Vcc. Two full cycles are shown so the duty cycle is visible at a glance. Run the astable calculation to draw it.

Power Wizard

One guided path for DC, single-phase AC, and three-phase AC power, current, kVA, kW, and motor horsepower.

ℹ How to use the Power Wizard
Pick which quantity you already know and the rest are derived from it. The relationships are:
  • DC — S = V × I, and there is no power factor
  • Single-phase — S = V × I, P = S × PF
  • Three-phase — S = √3 × VL-L × IL, P = S × PF
Horsepower is shaft output, not electrical input. A 10 HP motor at 90% efficiency draws 10 × 746 ÷ 0.90 = 8,289 W from the supply, not 7,460 W. Mixing those up is the usual source of an undersized motor circuit.

For motor conductor and overcurrent sizing the NEC requires the table value from Article 430 (Tables 430.248 and 430.250), not a current you calculated from nameplate horsepower — see NEC 430.6(A)(1). Use this tool for load estimating and the Motor FLA tables for code compliance.
Convert
1Ø: kVA = V × I ÷ 1000  |  3Ø: kVA = √3 × VL-L × IL ÷ 1000
kW = kVA × PF  |  HP = kW × 1000 × Eff ÷ 746
AC waveformChoose an AC system to compare voltage and current phase.
Voltage V Current I DC

For AC, the horizontal separation is the phase angle θ. The current curve shifts right as power factor falls, while real power follows kW = kVA × PF.

Which formula applies
Solving forSingle-phaseThree-phase
Amps from kWkW×1000 / (V×PF)kW×1000 / (√3×V×PF)
Amps from kVAkVA×1000 / VkVA×1000 / (√3×V)
Amps from HPHP×746 / (V×PF×Eff)HP×746 / (√3×V×PF×Eff)
kVA from ampsV×I / 1000√3×V×I / 1000
kW from kVAkVA × PFkVA × PF

Three-phase voltage is always line-to-line and current is line current. Power factor is the cosine of the angle between voltage and current, so at PF = 1 the kVA and kW are equal and the reactive component is zero.

🔄 Transformer Sizing & Protection

Pick a standard kVA for a load, then size the overcurrent protection per NEC Table 450.3(B).

ℹ More Info — Transformer Protection
NEC Table 450.3(B) gives the maximum overcurrent protection for transformers rated 1000 V or less. There are two permitted methods:

Primary protection only
  • Primary current 9 A or more → 125% (next standard size up permitted, Note 1)
  • Primary current 2 A up to 9 A → 167%
  • Primary current under 2 A → 300%
Primary and secondary protection
  • Primary → 250%
  • Secondary 9 A or more → 125% (next size up permitted)
  • Secondary under 9 A → 167%
The primary device is allowed to be much larger under the second method because the secondary device provides the closer protection. Note 1 permits rounding up to the next standard rating from 240.6(A) only where the calculation is 125% and does not land on a standard size — the 167% and 300% rows are hard ceilings.

These limits protect the transformer. Conductors need their own protection under Article 240, and secondary conductors under 240.21(C).
Load & Connection
1Ø: I = kVA × 1000 ÷ V  |  3Ø: I = kVA × 1000 ÷ (√3 × V)
NEC Table 450.3(B) — 1000 V and Less
MethodCurrentMax OCPD
Primary only≥ 9 A125%
Primary only2 A to < 9 A167%
Primary only< 2 A300%
Pri + SecPrimary250%
Pri + SecSecondary ≥ 9 A125%
Pri + SecSecondary < 9 A167%

Note 1 permits the next higher standard rating from 240.6(A) where 125% does not correspond to a standard size. The 167% and 300% rows are ceilings, so the device must land at or below them.

Result

Conductors — Ampacity & Cost

Lowest modeled planning-allowance cost across compliant sizes and parallel runs, plus optional I²R energy. Not a live quote.

ℹ More Info — Wire Sizing
Conductor selection has to clear two independent hurdles, and on long runs the second one usually governs:
  • Ampacity — NEC Table 310.16, corrected for ambient temperature (310.15(B)(1)), adjusted for more than three current-carrying conductors (310.15(C)(1)), then capped by the equipment termination rating (110.14(C)). Continuous loads are sized at 125% per 210.19(A)/215.2(A).
  • Voltage drop — not a hard NEC requirement, but 3% on a branch circuit and 5% total is the long-standing informational-note guidance (210.19(A) and 215.2(A) FPNs).
Parallel runs are permitted in 1/0 and larger only (310.10(G)), and every conductor of a paralleled set must be the same length, size, material and insulation, and terminate the same way. The default planning allowance ($/ft) is a modeled comparison book — not live market, LME, or a bid. Optional I²R uses NEC Chapter 9 Table 8 DC Ω/kft and the operating current, not the 125% design current. There is no lb/kft table in this toolbox; enter $/kft if you have a takeoff.
Circuit & Load
Conductor & Conditions

Planning allowance, not a live quote or PE stamp. Use 1.00 for the default book. Optional energy fields persist in this browser.

Result
Ampacity: Idesign ≤ Table 310.16 × Cambient × Abundle, capped at the termination column
Voltage drop: ΔV = (2 or √3) × I × L × (R·cosθ + X·sinθ) / (1000 × runs)

MV Cable

Medium-voltage feeder: class, 100%/133%, construction, Art. 311 / 310.60 series ampacity, and voltage drop. Distinct from LV Table 310.16.

ℹ More Info — MV Cable
Ampacity is transcribed from the published NEC 2001–35 000 V solid-dielectric tables (2020 Table 310.60(C) series; 2023 Article 311.60), via Fehr, Industrial Power Distribution, 2nd ed., IEEE/Wiley 2016 Appendix E, cross-checked against OmniCable’s 310.60(C)(69) reprint. R/X is Southwire SPEC 46503 (Cu 25 kV 133% 1/C, Table 2, 2024-12-31) — not Chapter 9 LV cable. Aluminum and missing sizes need a user Ω/kft. Tray needs datasheet ampacity. Design aid — not a PE stamp, pulling study, or soil-rho calculation.
Load & System
3Ø: I = kVA / (√3 × kV)  |  example 4000 / (√3 × 23.2) ≈ 99.56 A
Cable
Result

⚡ Short Circuit — Available Fault Current

Simplified transformer-only calculation. For full arc flash studies, use IEEE 1584.

ℹ More Info — Short Circuit
Available Fault Current is the maximum short-circuit current that can flow at a given point in the electrical system. All equipment must be rated to safely interrupt this current.

Simplified formula: I_SC = (kVA × 1000) / (√3 × V × %Z/100)

  • Assumes infinite bus primary (unlimited source capacity) — conservative/worst-case
  • Does not account for conductor impedance between transformer and fault point
  • Asymmetrical multiplier of ~1.25 applied (actual value depends on X/R ratio)
  • NEC 110.9/110.10: All equipment must be rated ≥ available fault current
For arc flash analysis: Use IEEE 1584-2018 with a full Short Circuit Study including all cable and bus impedances.
Available Fault Current
3Ø: I_base = kVA × 1000 / (√3 × V_sec)
1Ø: I_base = kVA × 1000 / V_sec
I_SC = I_base / Z_pu    (Z_pu = %Z / 100)
K = √(1 + 2·exp(−2π/(X/R)))
I_asym = I_SC × K
⚠ This is a simplified calculation assuming infinite bus primary and no conductor impedance. Always perform a full short circuit study for equipment selection.
Short Circuit Reference
Available Fault Current:
I_SC = (kVA × 1000) / (√3 × V × %Z/100)

Typical transformer %Z:
≤ 15 kVA dry-type: 2–4%
15–500 kVA dry-type: 4–6%
Liquid-filled: 5.75% (common)

Asymmetrical factor:
Multiply by 1.25–1.732 (X/R ratio dependent)

NEC 110.9 / 110.10:
Equipment must be rated for the available fault current.

📋 Conductor Reference Table

NEC Table 310.16 — Copper & Aluminum ampacity at 75°C, ≤3 current-carrying conductors in raceway or cable.

ℹ More Info — Conductor Reference
NEC Table 310.16 provides ampacity for conductors installed in a raceway, cable, or earth with ≤3 current-carrying conductors at 30°C ambient.

Important derating rules:
  • More than 3 conductors: Apply NEC 310.15(C)(1) adjustment factors (e.g., 4–6 conductors = 80% of listed ampacity)
  • Ambient temperature: Apply NEC Table 310.15(B)(2) correction factors for temperatures other than 30°C
  • Continuous loads: Conductor must be sized at 125% of continuous load per NEC 210.19
  • Terminal ratings: Most equipment is rated 75°C; do not use 90°C column for final ampacity (only for derating math)
AWG / kcmil — Copper & Aluminum (75°C)
Size Circular Mils Cu Ampacity (75°C) Al Ampacity (75°C) Max OCPD per NEC 240.4(D) THHN Area (sq in)
14 AWG4,11020 A—15 A0.0097
12 AWG6,53025 A20 A20 A0.0133
10 AWG10,38035 A30 A30 A0.0211
8 AWG16,51050 A40 A—0.0366
6 AWG26,24065 A50 A—0.0507
4 AWG41,74085 A65 A—0.0824
3 AWG52,620100 A75 A—0.0973
2 AWG66,360115 A90 A—0.1158
1 AWG83,690130 A100 A—0.1562
1/0 AWG105,600150 A120 A—0.1855
2/0 AWG133,100175 A135 A—0.2223
3/0 AWG167,800200 A155 A—0.2679
4/0 AWG211,600230 A180 A—0.3237
250 kcmil250,000255 A205 A—0.3970
300 kcmil300,000285 A230 A—0.4608
350 kcmil350,000310 A250 A—0.5242
400 kcmil400,000335 A270 A—0.5863
500 kcmil500,000380 A310 A—0.7073
600 kcmil600,000420 A340 A——
750 kcmil750,000475 A385 A——
ℹ NEC 310.16 (75°C column). Derate for ambient temperature, more than 3 conductors, or continuous loads. NEC 240.4(D) small-conductor OCPD caps are shown for 14/12/10 AWG copper. 14 AWG aluminum not listed in NEC for service conductors. Consult current NEC edition for complete rules.
K Values for Voltage Drop
K = resistance constant in ohms/circular mil/foot

Copper (Cu): K = 12.9
Aluminum (Al): K = 21.2

Used in: VD = (M × K × I × L) / CM
M = 2 (single-phase) | √3 ≈ 1.732 (three-phase)

CM = circular mils of conductor
L = one-way length in feet
I = current in amperes

⚙ Motor FLA Reference Tables

NEC Table 430.248 (single-phase) and NEC Table 430.250 (three-phase, squirrel-cage).

ℹ More Info — Motor FLA Tables
NEC Motor FLA Tables provide Full-Load Ampere values used for conductor and OCPD sizing — not necessarily the nameplate current.

  • NEC 430.248: Single-phase AC motors
  • NEC 430.250: Three-phase AC induction motors (squirrel-cage and wound-rotor)
  • Conductor sizing: Size at 125% of NEC table FLA per NEC 430.22
  • OCPD sizing: Use NEC Table 430.52 multipliers (inverse-time breaker: 250% of FLA typical)
  • Overload protection: Set at ≤115–125% of nameplate FLA per NEC 430.52
Note: For motors rated at voltages other than listed, use the closest listed voltage that is ≥ actual voltage.
Source: NEC Table 430.248 (single-phase) and Table 430.250 (three-phase squirrel-cage). Use these table values for conductor and OCPD sizing per NEC 430.6(A)(1) — not motor nameplate current.
Single-Phase AC Motor FLA — NEC Table 430.248
Horsepower115 V200 V208 V230 V
1/64.4 A2.5 A2.4 A2.2 A
1/45.8 A3.3 A3.2 A2.9 A
1/37.2 A4.1 A4.0 A3.6 A
1/29.8 A5.6 A5.4 A4.9 A
3/413.8 A7.9 A7.6 A6.9 A
116 A9.2 A8.8 A8.0 A
1-1/220 A11.5 A11 A10 A
224 A13.8 A13.2 A12 A
334 A19.6 A18.7 A17 A
556 A32.2 A30.8 A28 A
7-1/280 A46 A44 A40 A
10100 A57.5 A55 A50 A
ℹ Values from NEC Table 430.248. Use for conductor sizing, OCPD sizing, and overload protection. Not to be confused with nameplate FLA.
Three-Phase AC Motor FLA — NEC Table 430.250 (Squirrel-Cage)
HP115 V200 V208 V230 V460 V575 V
1/24.4 A2.5 A2.4 A2.2 A1.1 A0.9 A
3/46.4 A3.7 A3.5 A3.2 A1.6 A1.3 A
18.4 A4.8 A4.6 A4.2 A2.1 A1.7 A
1-1/212 A6.9 A6.6 A6.0 A3.0 A2.4 A
213.6 A7.8 A7.5 A6.8 A3.4 A2.7 A
3—11 A10.6 A9.6 A4.8 A3.9 A
5—17.5 A16.7 A15.2 A7.6 A6.1 A
7-1/2—25.3 A24.2 A22 A11 A9.0 A
10—32.2 A30.8 A28 A14 A11 A
15—48.3 A46.2 A42 A21 A17 A
20—62.1 A59.4 A54 A27 A22 A
25—78.2 A74.8 A68 A34 A27 A
30—92 A88 A80 A40 A32 A
40—120 A114 A104 A52 A41 A
50—150 A143 A130 A65 A52 A
60—177 A169 A154 A77 A62 A
75—221 A211 A192 A96 A77 A
100—285 A273 A248 A124 A99 A
125—359 A343 A312 A156 A125 A
150—414 A396 A360 A180 A144 A
200—552 A528 A480 A240 A192 A
ℹ NEC Table 430.250 — Induction-type squirrel-cage and wound-rotor motors. For 460 V values, multiply 230 V by 0.5. Common 460 V motors operate on 480 V systems; use NEC table for sizing, not nameplate FLA.

🔵 Conduit Fill Reference Tables

EMT internal dimensions and maximum conductor counts from NEC Annex C, Table C.1.

ℹ More Info — Conduit Fill Tables
NEC Annex C, Table C.1 gives maximum conductor counts for THHN/THWN-2 wire in EMT conduit at the 40% fill limit (3+ conductors).

  • Values are for same-size conductors only. For mixed sizes, use the Conduit Fill Calculator
  • EMT (Electrical Metallic Tubing) is the most common raceway in commercial/industrial facilities
  • Other conduit types (RMC, IMC, PVC) have different internal diameters — use the appropriate NEC Annex C table
  • Other insulation types (XHHW, THW, RHH) have different cross-sectional areas — check NEC Table 5
Source: NEC Annex C, Table C.1 — maximum THHN/THWN-2 conductors in EMT at the 40% fill limit. Chapter 9 Table 4 gives raceway areas; Table 5 gives conductor areas.
EMT Trade Sizes — Internal Dimensions & Fill Areas
Trade Size Inside Dia (in) Total Area (sq in) 1 Wire (53%) 2 Wires (31%) 3+ Wires (40%)
1/2"0.6220.3040.1610.0940.122
3/4"0.8240.5330.2830.1650.213
1"1.0490.8640.4580.2680.346
1-1/4"1.3801.4960.7930.4640.598
1-1/2"1.6102.0361.0790.6310.814
2"2.0673.3561.7781.0401.342
2-1/2"2.4694.7882.5381.4841.915
3"3.0687.3933.9182.2922.957
3-1/2"3.5489.8935.2433.0673.957
4"4.02612.726.7413.9435.088
THHN/THWN-2 Max Conductor Count in EMT (3+ Wires, 40% Fill)
AWG/kcmil1/2"3/4"1"1-1/4"1-1/2"2"2-1/2"3"4"
14 AWG1222356184138197305524
12 AWG916264561101144222382
10 AWG5101628386390140241
8 AWG3691622365280138
6 AWG1471216263858100
4 AWG12471016233561
2 AWG1135711162543
1 AWG—11458111831
1/0 AWG—11347101526
2/0 AWG—1123681322
3/0 AWG——113571018
4/0 AWG——11246915
250 kcmil———1134712
300 kcmil———1134611
350 kcmil———112359
500 kcmil————11247
ℹ Based on NEC Annex C, Table C.1 (EMT, THHN/THWN-2 conductors). For mixed sizes, use the conduit fill calculator.

📐 Conduit & Fittings Guide

Complete reference for all NEC wiring methods — cross-section illustrations, selection guidance, fitting types, and Air Force / Space Force / NASA special requirements.

ℹ More Info — Conduit & Fittings Guide
This guide covers all major wiring methods listed in NEC Chapter 3. Each type includes:

  • Cross-section illustration — wall thickness and bore drawn to proportion, with flexible conduit side-profile showing corrugation
  • NEC article reference — permitted uses, not-permitted uses, support spacing
  • Location matrix — dry / damp / wet / direct burial / hazardous class ratings
  • Pros, cons, and common applications
  • Project-facility advisory — verify owner, AHJ, and Range Safety criteria separately from NEC wiring-method screening
Use the Conduit Type Selector at the top to answer a few questions and get a ranked recommendation.
⚙ Conduit Type Selector
Answer the questions below for a ranked NEC wiring-method screen. Facility, owner, hazardous-location, and Range Safety criteria require independent verification.
Recommendation
Conduit Types — NEC Chapter 3 Wiring Methods
NEC Article358
MaterialSteel (galvanized) or Aluminum
Wall typeThin (0.042" at 1" trade size)
Max trade size4"
Threaded?No — set-screw or compression fittings
Temp rating−20 °C to +75 °C
Support spacingEvery 10 ft; within 3 ft of each box (358.30)
EGC functionYes — when bonded per 250.118(4)

Electrical Metallic Tubing (EMT) — “Thin-Wall”

The most widely used metallic conduit in commercial construction. EMT’s thin wall makes it easy to cut and bend, and it installs faster than any other rigid metal conduit. Not threaded — uses mechanical set-screw or compression connectors.

✓ Permitted Uses (358.10)
  • Exposed and concealed locations
  • In concrete (above earth)
  • Damp & wet locations (listed fittings)
  • Fished in existing walls
  • All atmospheric conditions with listed fittings
✗ Not Permitted (358.12)
  • Direct contact with earth or fill
  • Severe physical damage exposure
  • Class I, Div. 1 hazardous locations
  • Destructive corrosive agents
⚡ Pros & Cons
  • Lightest metallic conduit
  • Fastest to install
  • Lowest metallic-conduit cost
  • No threading required
  • Serves as EGC when bonded
  • Thin — crushes under mechanical damage
  • No threads — weaker joint than RMC/IMC
  • Galvanized version may corrode coastal
Fittings: Set-screw connectors & couplings, compression connectors (watertight), conduit bodies (LB, LL, LR, C, T, X), 1-hole straps, beam clamps, lay-in straps. Compression fittings are required for wet locations.
🚀 AF/SF/NASA: NOT permitted in launch complexes, propellant areas, Class I hazardous locations, or within ESQD arcs. Approved for general office/support areas only. AFSPCMAN 91-710 Vol. 3; AFI 32-1064 §3; UFC 3-550-01.
NEC Article342
MaterialSteel (galvanized) — medium wall
Wall typeMedium (heavier than EMT, lighter than RMC)
Max trade size4"
Threaded?Yes — same NPT thread as RMC
Temp rating−20 °C to +75 °C
Support spacingEvery 10 ft; within 3 ft of each box (342.30)
EGC functionYes — when bonded per 250.118(5)

Intermediate Metal Conduit (IMC) — Medium Wall

IMC provides the threaded joint strength of RMC at roughly 25% less weight. It is listed for all the same locations as RMC and is an acceptable substitute in most applications. Common in industrial and outdoor installations where RMC cost is a concern.

✓ Permitted Uses (342.10)
  • All atmospheric conditions
  • Direct burial in earth or concrete
  • Hazardous locations (Class I Div. 1 & 2, Class II)
  • Wet and corrosive locations (with suitable material)
  • Exposed, concealed, outdoor
✗ Not Permitted (342.12)
  • Severe corrosion without protective coating or stainless material
  • Lighter than RMC
  • Threaded — same fittings as RMC
  • Listed for all RMC applications
  • Good balance of strength and workability
  • More expensive than EMT
  • Requires threading tools
  • Heavier than EMT
Fittings: Threaded couplings, locknuts, insulating bushings, Myers hubs, conduit bodies, weatherproof fittings, expansion fittings.
🚀 AF/SF/NASA: Acceptable substitute for RMC in most Air Force/Space Force applications. Preferred over EMT for outdoor, exposed, or industrially classified areas. UFC 3-550-01 §3-3; AFSPCMAN 91-710 Vol. 3.
NEC Article344
MaterialSteel (hot-dip galv.), stainless steel, or aluminum
Wall typeHeavy — thickest metallic conduit
Max trade size6"
Threaded?Yes — tapered NPT threads
Temp rating−20 °C to +75 °C
Support spacingEvery 10 ft; within 3 ft of each box (344.30)
EGC functionYes — when bonded per 250.118(6)

Rigid Metal Conduit (RMC / GRC) — Heavy Wall ★ Gold Standard

RMC is the most universally permitted wiring method in the NEC — it is listed for every location type. The thick, threaded wall provides maximum mechanical protection. Stainless steel variants are used in corrosive, coastal, or propellant environments. This is the baseline requirement for Air Force/Space Force critical infrastructure.

✓ Permitted Uses (344.10) — Universal
  • All atmospheric conditions
  • Direct burial in earth or concrete
  • All hazardous location classes/divisions
  • Severe physical damage exposure
  • Corrosive environments (with suitable material)
  • Marine / coastal / launch facility
  • Explosion-proof systems
✗ Not Permitted (344.12)
  • Severe corrosion without protection — specify galvanized, stainless, or PVC-coated RMC as appropriate
  • Maximum physical protection
  • Threaded joints — strongest connection
  • No location restrictions in NEC
  • Can use as EGC
  • Stainless / PVC-coated for severe corrosion
  • Heaviest — labor-intensive
  • Requires threading equipment
  • Highest cost of rigid conduit
Fittings: Threaded couplings (NPT), union couplings, threaded conduit bodies, Myers hubs, weatherproof hubs, explosion-proof fittings, rain-tight connectors, expansion fittings, bonding locknuts.
🚀 AF/SF/NASA REQUIRED: Mandatory in launch complex structures, propellant/explosive handling areas, Class I Div. 1 locations, within ESQD arcs, and all outdoor exposed runs in operational facilities. Stainless steel RMC required for propellant piping areas, salt-air coastal facilities. AFSPCMAN 91-710 Vol. 3 §3-2; AFI 32-1064 §3-1; UFC 3-550-01 §3-2; NASA KSC-E-165 §4.2.
NEC Article348
MaterialInterlocked steel or aluminum spiral strip
Wall typeFlexible armor — no fixed wall thickness
Max trade size4"
Threaded?No — squeeze or screw connectors
Temp rating−20 °C to +60 °C
Support spacingEvery 4.5 ft; within 12 in of boxes (348.30)
EGC functionOnly in specific sizes with specific listings — verify; usually run a separate EGC inside (348.60)

Flexible Metal Conduit (FMC) — “Greenfield”

FMC’s spiral armor allows it to flex around obstacles and absorb vibration, making it ideal for equipment connection whips. It is NOT a general wiring method — it is restricted to dry locations and short runs. Always verify whether the FMC alone qualifies as an EGC for the application; when in doubt, run a separate copper EGC inside.

✓ Permitted Uses (348.10)
  • Dry locations
  • Exposed or concealed
  • Equipment whips (motors, transformers, HVAC)
  • Where flexibility is required for routing
  • Connection to luminaires (ceiling fan whips)
✗ Not Permitted (348.12)
  • Wet or damp locations (use LFMC)
  • Direct burial
  • Concrete encasement
  • Hazardous locations (except listed types)
  • Physical damage exposure
  • Over 6 ft for equipment whips (general rule)
  • Excellent vibration isolation
  • Easy routing around obstacles
  • No bending tools needed
  • Dry-only — no outdoor use
  • Short whips only
  • EGC often required inside
Fittings: Squeeze connectors (straight & 90°), screw-in connectors, die-cast fittings for liquid-tight applications, strain-relief fittings.
🚀 AF/SF/NASA: Permitted for equipment whip connections only (≤ 6 ft, dry locations). Not a general wiring method in mission-critical areas. Always verify a separate EGC is present. UFC 3-550-01 §3-5; AFI 32-1064.
NEC Article350
MaterialInterlocked metal core + PVC or thermoplastic jacket
Wall typeFlexible armored core with liquidtight outer jacket
Max trade size4"
Threaded?No — liquidtight connectors
Temp rating−40 °C to +60 °C (type-dependent)
Support spacingEvery 4.5 ft; within 12 in of boxes (350.30)
EGC functionSeparate EGC required inside (350.60) in most cases

Liquidtight Flexible Metal Conduit (LFMC) — “Sealtite”

LFMC adds a liquidtight PVC jacket over flexible metal armor, making it suitable for outdoor and wet equipment connections. It is the preferred choice for outdoor motor whips, rooftop HVAC connections, and any wet-location equipment requiring vibration isolation. Like FMC, it is limited to short whip connections — not general wiring.

✓ Permitted Uses (350.10)
  • Wet and damp locations
  • Outdoor equipment connections
  • Class I, Div. 2 and Class II (when listed)
  • Where LFMC is direct-burial-listed
  • Oil and chemical resistant jacket types
✗ Not Permitted (350.12)
  • Direct burial (unless specifically listed)
  • Concrete encasement
  • Class I, Div. 1
  • Physical damage exposure
  • Over 6 ft whip length
  • Weatherproof — outdoor-rated
  • Vibration isolation
  • Oil/chemical-resistant jackets available
  • More expensive than FMC
  • Short whips only
  • EGC required inside
Fittings: Liquidtight straight & 90° connectors, strain-relief fittings, weatherproof box connectors, O-ring seal types for Class I Div. 2.
🚀 AF/SF/NASA: Required for all outdoor motor and equipment whip connections. Preferred over FMC for any damp or wet environment equipment connection. Confirm EGC is inside. UFC 3-550-01 §3-6; AFI 32-1064.
NEC Article352
MaterialPVC — gray or orange
Wall typeThin-wall plastic
Max trade size6"
Threaded?No — solvent-cement joints (bell end or couplings)
Temp rating−20 °C to +75 °C (derating may apply)
Support spacingPer Table 352.30(B): 3 ft (1/2") to 8 ft (>2")
EGC functionNever — always run separate EGC inside

Rigid PVC Conduit — Schedule 40 (RNC Type A)

PVC Sch. 40 is the workhorse for underground and direct-burial electrical work. Its corrosion immunity makes it ideal for underground feeders, duct banks, and chemical-area wiring. Thermal expansion is significant — expansion fittings are required for long runs. It cannot serve as an EGC, so a separate copper or aluminum grounding conductor must always be included.

✓ Permitted Uses (352.10)
  • Underground direct burial (352.10(B))
  • Concrete-encased duct banks
  • Wet and corrosive locations above grade
  • Concealed in walls, ceilings, floors
  • Exposed (not subject to physical damage)
✗ Not Permitted (352.12)
  • Hazardous locations
  • Exposed where physical damage likely
  • Ambient > 50 °C without derating
  • Direct sunlight (without UV-stabilized type)
  • Support of luminaires
  • Corrosion-proof — ideal underground
  • Lightweight — easy to install
  • Low friction for long cable pulls
  • Solvent-cement joints — fast
  • Lowest-cost conduit per foot
  • No EGC function — always add ground wire
  • Brittle below −10 °C
  • High thermal expansion — needs exp. fittings
  • Not for above-grade exposed (mechanically weak)
Fittings: Solvent-cement couplings, bell-end adapters, PVC expansion joints (required > 25 ft runs above grade), PVC conduit bodies, PVC-to-metallic adapters, PVC LB bodies.
🚀 AF/SF/NASA: Permitted underground only. NOT above grade in AF/SF operational or mission buildings. Transition to RMC at building entries. Concrete-encased PVC duct banks standard for site distribution. UFC 3-550-01 §3-4; AFSPCMAN 91-710 Vol. 3 §3-5; NASA KSC-E-165 §4.3.
NEC Article352
MaterialPVC — gray, heavy wall
Wall typeMedium-heavy plastic (thicker than Sch. 40)
Max trade size6"
Threaded?Yes — can be threaded (unlike Sch. 40)
Temp rating−20 °C to +75 °C
Support spacingPer Table 352.30(B)
EGC functionNever — always run separate EGC inside

Rigid PVC Conduit — Schedule 80 (RNC Type B — Heavy Wall)

Sch. 80 has a thicker wall than Sch. 40, making it suitable for exposed above-grade runs in areas with moderate physical damage potential. It can be threaded, enabling metal-type fittings. The thicker wall reduces internal bore area — conductor capacity per Table C.12 is lower than Sch. 40 for the same trade size. Ideal for chemical plants and coastal facilities where metallic conduit would corrode.

✓ Permitted Uses — superset of Sch. 40
  • All Sch. 40 applications
  • Exposed above grade with moderate damage risk
  • Chemical / wash-down / coastal areas
  • Threaded fittings (Schedule 80 ends)
✗ Same restrictions as Sch. 40
  • Hazardous locations
  • Severe physical damage (use RMC)
  • Cannot serve as EGC
  • Better physical protection than Sch. 40
  • Corrosion-proof
  • Threadable
  • Higher cost than Sch. 40
  • Smaller bore for same trade size
  • Still not for severe damage / hazardous
Fittings: Same as Sch. 40 plus threaded couplings (Schedule 80 threaded ends match NPT but lighter wall — confirm listing).
🚀 AF/SF/NASA: Preferred over Sch. 40 for corrosive above-grade areas where RMC is not required. Not a substitute for RMC in hazardous or mission-critical locations. UFC 3-550-01 §3-4.
NEC Article362
MaterialCorrugated PVC — typically blue or orange
Wall typeThin corrugated plastic (flexible)
Max trade size2"
Threaded?No — snap-in or push fittings
Temp rating−10 °C to +60 °C
Support spacingEvery 3 ft; within 3 ft of each box (362.30)
EGC functionNever — always run separate EGC inside

Electrical Nonmetallic Tubing (ENT) — “Smurf Tube”

ENT is a corrugated, flexible PVC conduit used almost exclusively in residential and light-commercial concealed rough-in. Its trademark blue color (though not required) makes it easy to spot in walls during construction. ENT cannot be used exposed, is limited to 3 floors max, and is entirely unsuitable for industrial or mission-critical use. Separate EGC is always required.

✓ Permitted Uses (362.10)
  • Concealed in walls, ceilings, floors
  • Concrete encasement (in slabs)
  • Residential and light commercial (≤ 3 floors)
  • Pre-wired stud-wall rough-in
✗ Not Permitted (362.12)
  • Exposed locations — never
  • Direct burial
  • Wet or damp locations
  • Hazardous locations
  • Buildings exceeding 3 floors
  • Ambient over 50 °C
Fittings: Snap-in box connectors, ENT-to-EMT transition adapters, push-in couplings, plastic box adapters.
🚀 AF/SF/NASA: NOT PERMITTED in Air Force, Space Force, or NASA facilities. Residential rough-in only. Never appropriate for any commercial, industrial, or mission-critical application. UFC 3-550-01 (not listed as a permitted type).
NEC Article356
MaterialFlexible PVC corrugated tube with smooth PVC jacket
Wall typeFlexible plastic (Type B: smooth outer; Type A: corrugated outer)
Max trade size4"
Threaded?No — liquidtight nonmetallic connectors
Temp rating−10 °C to +60 °C
Support spacingEvery 3 ft; within 12 in of each termination (356.30)
EGC functionNever — always run separate EGC inside

Liquidtight Flexible Nonmetallic Conduit (LFNC)

LFNC serves the same role as LFMC but without any metallic component, making it useful where metallic conduit would cause galvanic corrosion or where non-magnetic properties are needed. Common in food processing, chemical plants, and wash-down areas. Like all flexible conduit, it is limited to short whips — not general wiring.

✓ Permitted Uses (356.10)
  • Wet / damp / outdoor locations
  • Where flexibility is required
  • Corrosive chemical environments
  • Food processing / wash-down areas
✗ Not Permitted (356.12)
  • Direct burial / concrete
  • Hazardous locations
  • Physical damage exposure
  • Over 6 ft length
Fittings: Liquidtight nonmetallic connectors (straight & 90°), snap-in type, LFNC-to-PVC adapters.
🚀 AF/SF/NASA: Seldom used. When needed for corrosive-environment equipment whips, verify EGC is inside and confirm AHJ acceptance. Not appropriate for mission-critical installations. UFC 3-550-01.
NEC Article353
MaterialHDPE — black, orange (telecom), or yellow (gas)
Wall typeMedium-heavy plastic — direct-burial rated
Max trade size6"+
Threaded?No — heat-fusion or mechanical couplings
Temp rating−40 °C to +75 °C (excellent cold resistance)
Support spacingPer manufacturer; typically used in duct banks
EGC functionNever — always run separate EGC inside

HDPE Conduit — High-Density Polyethylene (Type RTRC)

HDPE is the material of choice for large underground duct banks, telecom infrastructure, and medium-voltage cable systems. Its extreme chemical resistance, excellent cold-weather performance, and low friction coefficient (great for long cable pulls) make it the preferred underground option for site distribution networks. Above-grade use is not permitted.

✓ Permitted Uses (353.10)
  • Direct burial in earth
  • Concrete-encased duct banks
  • High water-table or coastal underground
  • Corrosive soil environments
  • Medium-voltage cable duct banks
  • Telecom and fiber-optic underground
✗ Not Permitted (353.12)
  • Above grade or exposed
  • Hazardous locations
  • Above temperature rating
  • Extreme corrosion resistance
  • Lowest friction — longest cable pulls
  • Excellent cold-weather performance
  • Long service life underground
  • Above-grade not permitted
  • Requires heat-fusion tools
  • Cannot serve as EGC
Fittings: Heat-fusion couplings, mechanical compression couplings, bell-end insert adapters, pull boxes (for direction changes), manhole entries.
🚀 AF/SF/NASA: Used for underground site-utility duct banks at AF/SF installations. Transition to RMC required at building entries per UFC. Typical for medium-voltage underground cable and telecom duct banks. Coordinate design with civil engineering. UFC 3-550-01 §3-4; AFSPCMAN 91-710 Vol. 3; NASA KSC-E-165 §4.3.
Fittings Guide
Set-Screw Connector/Coupling (EMT)

A machined steel or die-cast connector that accepts the EMT end and clamps it with one or two set screws. Fast installation. The set-screw provides mechanical and ground continuity. NOT approved for wet locations without a listed rain-tight type — use compression fittings instead for wet/damp.

  • NEC 358.42 — connectors must be made up tight
  • Steel or die-cast zinc; steel preferred in damp areas
  • Duplex (two set-screw) types preferred for vibration resistance
Compression Connector/Coupling (EMT)

A two-piece fitting with a ferrule that is compressed onto the EMT end by tightening a threaded nut. Provides a more positive mechanical and electrical bond than set-screw. Rain-tight compression fittings are required for wet locations per 358.42. More expensive but recommended for damp, wet, or vibrating installations.

  • Use for all wet/damp EMT installations
  • Listed as rain-tight or concrete-tight per listing
  • Copper-free aluminum versions for aluminum EMT
Threaded Coupling / Connector (RMC, IMC)

RMC and IMC use NPT (National Pipe Taper) threads. Couplings join two conduit lengths. Connectors terminate conduit into a box or enclosure with a locknut and insulating bushing. Threaded connections provide the strongest mechanical joint and reliable ground continuity. Use a bonding locknut or bonding bushing wherever continuity is critical.

  • Thread lubricant (anti-gall) recommended for stainless
  • Myers hubs (watertight): 344.42 — use where water entry must be prevented
  • Explosion-proof fittings: RMC threaded into explosionproof equipment per 501.10(A)
  • Bonding bushings at service equipment (250.92)
PVC Solvent-Cement Coupling

PVC conduit is joined with a primer and solvent cement that chemically fuses the mating surfaces. Joints are permanent and watertight. Primer is usually required (clear or purple) — check local requirements. For above-grade runs, expansion fittings must be installed where temperature variation exceeds 25 °F (approximately every 25 ft for 100 °F range).

  • Primer: ASTM F656; Cement: ASTM D2564
  • Allow cure time before cable pull
  • Expansion fittings required per Table 352.44
  • Bell-end (factory socket) preferred for underground — no separate coupling needed

Conduit bodies (NEC 314.16(C)) provide access for wire pulling and changes of direction. They may NOT be used as splice points unless listed for the purpose and the fill limits of 314.16(C) are met. Each body’s internal cross-sectional area must be ≥ twice the cross-sectional area of the largest conduit connected to it.

LB — back entry
LL — left exit
LR — right exit
C — inline pull
T — tee (3 ports)
X — cross (4 ports)
Selection guide: LB = 90° change of direction (wall penetration, most common). LL / LR = 90° turn to the left / right. C = inline — straight pull to access conductors. T = 3-way split, branch takeoff. X = 4-way crossing.
NEC 314.16(C): Conduit bodies with fewer than 3 conduits may be used as a junction point when accessible; fill must not exceed the limits for that conduit body size. Conduit bodies with 3 or more conduits must be listed for splicing.
Expansion Fittings — PVC (NEC 352.44)

PVC expands significantly with temperature — approximately 3.4 in per 100 ft per 100 °F change. Expansion fittings (slip-joint telescoping fittings) absorb this movement without stressing conduit or fittings. Required wherever temperature swing creates movement that would crack joints or pull conductors. NEC Table 352.44 gives maximum spacing based on temperature range.

  • NEC Table 352.44: place at intervals per table based on local temperature range
  • Provide for conductor slack at each expansion fitting
  • Available for 1/2" through 6" PVC
Expansion Fittings — Metallic (NEC 344.44, 358.44)

Metal conduit expands less than PVC but long straight runs across building expansion joints require expansion/deflection fittings. Combination expansion-deflection fittings accommodate both linear growth and lateral movement. Required at structural expansion joints in buildings and bridges.

  • Required at building/structural expansion joints (344.44)
  • Combo expansion-deflection types accommodate ±3/4" to ±3" movement
  • Bonding jumper required across expansion fittings (250.98)
Conduit Sealing Fittings (Explosive Locations, NEC 501.15)

In Class I hazardous locations, conduit seals prevent the passage of flammable gases or vapors from one area to another and prevent the propagation of an explosion through conduit. Required within 18 in of explosion-proof equipment and at all conduit entries into enclosures, at boundaries between hazardous and non-hazardous areas, and at changes of direction in certain applications.

  • NEC 501.15(A)(1): within 18 in of explosion-proof equipment entries
  • NEC 501.15(A)(2): at boundary when conduit leaves Class I Div. 1
  • 501.15(C)(1): fill compound fills at least 85% of interior cross-section
  • Must be accessible after installation
  • 🚀 AF/SF/NASA: All conduit penetrations of Class I boundaries in propellant areas require seals. Verify seals are listed for the gas/vapor group (Group C, D, etc.). AFSPCMAN 91-710 Vol. 3 §3-4; NEC 501.15.
Drain / Breather Fittings (Outdoor Metallic Conduit)

Temperature cycling in sealed metallic conduit systems causes condensation inside. Breather fittings allow pressure equalization and drain accumulated moisture. They are required in some NEC applications and are best practice for all outdoor metallic conduit runs longer than a few feet to prevent corrosion and moisture damage to conductors and equipment. UL-listed types include combined drain/breather units.

  • Install at low points of outdoor conduit runs
  • Required in explosion-proof systems where liquid seals are impractical
  • Best practice for all coastal/outdoor metallic conduit
One-Hole & Two-Hole Straps

Standard steel straps (one-hole and two-hole) screw directly to walls, studs, or framing. Two-hole straps are preferred wherever vibration is present. Strap spacing must meet the conduit article requirements (e.g., every 10 ft for EMT/RMC, every 3 ft for ENT). Use stainless steel straps in corrosive or coastal environments.

  • EMT/RMC/IMC: max 10 ft on center, within 3 ft of each termination (art. 358.30, 344.30, 342.30)
  • ENT: max 3 ft on center (362.30)
  • Rigid PVC: per Table 352.30(B) — 3 ft (1/2") to 8 ft (over 2")
Conduit Hangers & Beam Clamps

Conduit hangers are used for suspended ceiling runs and exposed runs from overhead structure. Beam clamps attach to structural steel without drilling. Conduit hangers come in one-hole (single conduit), multi-conduit (trapeze/rack), and adjustable versions. Seismic bracing is required in high-seismic zones (IBC Seismic Design Category C through F) per ASCE 7 and NEC 517 (healthcare).

  • Trapeze hangers for multiple parallel runs — most efficient above ceilings
  • Spring-steel clips (EMT, small sizes): quick install, verify load capacity
  • 🚀 AF/SF/NASA: Seismic restraint required for all conduit systems in launch facilities per ASCE 7 and UFC 3-310-04. Verify lateral bracing intervals with structural engineer. UFC 3-310-04; UFC 3-550-01.
Conduit Nipples

A nipple is a short (usually 6" or less) conduit piece used to directly connect two adjacent enclosures. Fill limit is 60% for nipples 24 in or less in length per NEC Ch. 9 Table 1, Note 4 — significantly more than the standard 40% for longer runs. Nipples must still be supported per the conduit article unless the enclosures provide adequate support.

  • NEC Ch. 9 Table 1 Note 4: 60% fill for nipples ≤ 24 in
  • Use close (extra-close) nipples for panel-to-panel connections
  • Size the nipple for the actual conductors at 60% fill
Reducing Fittings & Unions

Conduit reducers allow connection between different trade sizes. Unions allow disconnection of rigid conduit sections without cutting (e.g., at equipment that must be removed). Concentric and eccentric reducing washers are used to step down a knockout to accept a smaller conduit size.

  • Eccentric reducers preferred at conduit stubs entering panels — allows conduit to exit horizontally without offset
  • Insulating bushings required at conduit ends where conductors 4 AWG and larger enter metallic enclosures (300.4(F) / 312.6(C))
Liquidtight Connectors (LFMC)

LFMC liquidtight connectors use a compression ferrule and O-ring (or neoprene gland) to seal the conduit entry at a box or enclosure. Available in straight and 90° configurations. Rated for wet locations and NEMA 3R / 4 enclosures when listed. Use insulated-throat types where conductors 4 AWG or larger enter (300.4(F)).

  • Verify connector is rated to match enclosure NEMA rating (e.g., NEMA 4 for hose-down)
  • Anti-short sleeve required where insulation could be damaged
  • Stainless steel versions for corrosive environments
Strain Relief / Cord Grips

Where flexible conduit enters equipment, strain-relief fittings prevent mechanical load from being transferred to the conductors inside. Conduit LFMC fittings with integral strain relief are available. For portable cord entries, listed cord grips (cord connectors) are required by Article 400 and the equipment listing.

  • Required at all portable/flexible cord entries to equipment (400.10)
  • Sized for the specific cord diameter — do not over-torque on flexible conduit
NEMA Enclosure Ratings Reference
NEMA TypeProtectionConduit Fittings Required
1Indoor general purposeStandard knockouts, locknuts
3ROutdoor rain/sleetRain-tight compression fittings or LFMC connectors
4Watertight, hose-directedListed watertight LFMC connectors, Myers hubs
4XWatertight + corrosionSS or listed corrosion-resistant LFMC/LFNC connectors
7/9Explosion-proof (Class I/II)Listed explosion-proof hubs, threaded RMC only
12Industrial dust-tightCompression fittings, gasketed connectors
NEC Wiring Methods — Quick Reference
TypeArticleThreadedDryDamp/Wet Direct BurialCl. I Div. 1Cl. I Div. 2EGCAF/SF Level
RMC/GRC344✓ NPT✓✓✓✓✓✓★ Required
IMC342✓ NPT✓✓✓✓✓✓Acceptable
EMT358—✓Listed———ListedSupport only
FMC348—✓————Size/listingWhips only
LFMC350—✓✓Listed—ListedSeparate EGCOutdoor whips
PVC Sch. 40352—✓✓✓——NeverUnderground
PVC Sch. 80352✓ ends✓✓✓——NeverUnderground
ENT362—Concl.————NeverNot permitted
LFNC356—✓✓———NeverCorrosive whips
HDPE353——✓✓——NeverUnderground UG
✓ = permitted; — = not permitted or not applicable; "Listed" = only when specifically listed for that application. "EGC" column: whether the conduit itself is listed as equipment grounding conductor. Always consult the current NEC and local amendments.
Facility and Range-Safety Review

This guide screens NEC wiring-method characteristics only. It does not establish Air Force, Space Force, NASA, Range Safety, or owner requirements.

  • Use the current hazardous-location classification drawing and NEC requirements for classified locations.
  • Evaluate corrosion, physical damage, burial, seismic, and environmental exposure as engineering design inputs.
  • Obtain the current owner specification and AHJ/Range Safety approval before selecting a wiring method for a launch or mission facility.

Verified public references: UFC 3-550-01, Exterior Electrical Power Distribution (2016, Change 3); SSCMAN 91-710 Volume 6 (27 Dec 2022). NASA identifies KSC-E-165 Rev. F as an Electrical Ground Support Equipment Fabrication specification, not a universal KSC conduit standard.

🔌 Transformer Design Wizard

Step-by-step transformer selection, type guidance, winding configuration, NEC-compliant protection, conductor sizing with parallel run cost optimization, and a generated single-line diagram.

ℹ More Info — Transformer Design Wizard
NEC References:
  • NEC 450.3(B) — Overcurrent protection for transformers 600V and below
  • NEC 450.14 — Disconnecting means: within sight, ≤30 ft
  • NEC 215.2(A) — Feeder conductor ampacity: 125% of continuous load
  • NEC 250.30(A) — Grounding of separately derived systems
  • NEC 250.122 — Equipment grounding conductor sizing
  • NEC 310.16 — Conductor ampacity table (ambient/bundling corrections)
Standard kVA sizes per ANSI/NEMA ST-20, up to 4000 kVA.
System Parameters
Common Primary / Secondary Voltage Pairs
PrimarySecondaryUse
13,800 V480/277 VUtility substation → distribution
4,160 V480/277 VMedium voltage → MCC
480 V208/120 VDistribution → lighting/receptacle
480 V240/120 VHigh-leg delta (legacy)
240 V120 VSingle-phase step-down
120 V24 VControl power / HVAC

🔥 Heater Design Wizard

Size industrial resistive heaters across voltage, phase and wye/delta wiring, then design a custom Nichrome or Kanthal heating element by wire gauge and length.

ℹ More Info — Heater Design Wizard
Electrical sizing treats the heater as a balanced resistive load (power factor ≈ 1.0). Wye and delta connections carry the same line current for the same total power and line voltage — they only differ in the voltage and current each individual leg or element sees, which is why a delta-connected element needs three times the resistance of a wye-connected element for the same job.
  • Wye: R_leg = V_LL² / P_total, each leg sees V_LL/√3 to the star point.
  • Delta: R_leg = 3 × V_LL² / P_total, each leg sees the full V_LL.
  • Line current is P_total / (√3 × V_LL) either way.
  • Branch circuit conductor and OCPD use the general 125%-continuous-load practice (NEC 210.19(A)(1)/210.20(A), 422.10(A)). If this heater is specifically classified as fixed electric space-heating equipment, also check NEC Article 424 Part III, which has its own branch-circuit and overcurrent provisions.
Element design uses the AWG standard's own diameter formula (exact for any gauge) together with an alloy resistivity you can edit. Nichrome and Kanthal resistivity, maximum element temperature, and any surface-power-density guidance shown here are typical published reference figures, not a specific spool's measured properties — confirm against your wire supplier's own datasheet before fabricating an element, particularly for safety-critical or high-power work.
Electrical System
Wye: R = V_LL² / P  |  Delta: R = 3 × V_LL² / P  |  I_line = P / (√3 × V_LL)
Branch Circuit Conditions
Element Alloy & Target
d = 0.005 × 92^((36−AWG)/39) in  |  R' = ρ / A  |  L = R / R'  |  I = √(P / R)
Resistivity and max temperature are typical published values, not a specific spool's measured properties — both are editable, so confirm against your wire supplier's datasheet.
Wire Gauge & Coil

☀ Solar Design Wizard

Size PV arrays from rooftop homes to utility facilities, aim panels with phone sensors, and optionally size energy storage.

ℹ More Info — Solar Design Wizard
Array sizing uses Daily_kWh / (PSH × η × orientation factor) to find DC kW, then ceil-divides by module wattage for panel count.

  • Optimal tilt ≈ |latitude| year-round; summer ≈ lat−15°; winter ≈ lat+15°. Azimuth 180° (true south) in the northern hemisphere, 0° (true north) in the southern.
  • Orientation factor is a transparent cosine model of tilt and azimuth error — not Perez/Hay-Davies and not a shade study.
  • PSH presets and system efficiency are editable planning defaults, not measured site data.
  • Storage (optional) sizes nameplate kWh = usable / (DoD × round-trip η) for autonomy, peak-shave, or self-consumption modes.
  • Phone sensors use DeviceOrientation: lay the phone face-up on the module for tilt; point the top of the phone toward the skyward edge for azimuth.
Planning aid only — not a PE stamp, interconnection study, structural calc, or fire-code review.
1 · Site & load
Array_kW ≈ Daily_kWh / (PSH × η × f_orient)
Panels = ceil(Array_kW × 1000 / W_module)
Suggested fixed tilt updates from latitude.
2 · Modules & orientation
3 · Phone sensor — panel aim
Lay the phone face-up on the module for tilt. Point the top of the phone toward the skyward (high) edge of the array for azimuth. On iOS Safari you must grant orientation permission. Magnetic interference near steel racks can skew heading.
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Sensors idle
Start sensors to compare against your design targets.
N S W E
4 · Energy storage (optional)

⚡ Circuit Simulator

Build and solve resistor, capacitor, inductor, voltage-source, and current-source circuits with Modified Nodal Analysis (MNA). Edit component values and node connections, then inspect the schematic and circuit parameters.

ℹ More Info — Circuit Simulator
Modified Nodal Analysis (MNA) formulates circuit equations as a matrix system Ax = b:

  • Resistors: stamp conductance G = 1/R into the G matrix
  • Capacitors: DC = open circuit; AC = admittance Y = jωC
  • Inductors: DC = short circuit (very large G); AC = admittance Y = 1/(jωL)
  • Voltage sources: add current variable, stamp into B/C matrices
The system is solved using Gaussian elimination with partial pivoting, extended to complex arithmetic for AC analysis.

📡 Smith Chart

Interactive Smith chart for RF impedance matching. Click to plot impedances, compute VSWR and return loss, apply transmission line rotations, and work through student examples step by step.

ℹ More Info — Smith Chart Theory
Reflection Coefficient: Γ = (Z − Z₀) / (Z + Z₀)
Normalized impedance: z = Z/Z₀ = r + jx
VSWR: (1 + |Γ|) / (1 − |Γ|)
Return Loss (dB): −20 log₁₀|Γ|

Constant-R circles: center (r/(r+1), 0), radius 1/(r+1)
Constant-X circles: center (1, 1/x), radius 1/|x|

Moving toward the generator rotates Γ clockwise (add electrical degrees).
Smith Chart
Plot Impedance
Transmission Line Rotation
Results
Plotted Points

EMP / EMC Shielding

Protection-side Faraday-loop, aperture, and skin-depth estimates for cages, seams, and cable entries. Educational design aid — not a TEMPEST or MIL-STD test lab, not a PE stamp, not a weapon.

ℹ More Info — Shielding and victim-circuit coupling
What this tool is: a physics and EMC education aid for people who need to protect a circuit or enclosure. It applies Faraday’s law to a victim loop, estimates how a slot leaks, and shows a simple sheet shielding-effectiveness bound.

What this tool is not: a pulse-source designer, a field-generation procedure, or a substitute for IEEE 299 / IEC 61000 chamber data. Source-side design content does not belong here.

Formulas:
  • Induced voltage: V = −N dΦ/dt, with Φ = B A for a uniform field normal to the loop. Magnitude used here: |V| = N A |dB/dt|.
  • Rise time to bandwidth: f ≈ 0.35 / tr (10–90% rule of thumb).
  • Aperture term: SE ≈ 20 log10((λ/2) / ℓ) for a single slot shorter than λ/2; 0 dB at or above half-wave. Optional depth uses a waveguide-below-cutoff extra term.
  • Skin depth: δ = 1 / √(π f μ σ). Sheet estimate SE ≈ A + R + B (Schelkunoff), with limits called out in the result.
Citations (environments a shield or SPD is specified against): IEC 61000-4-2 (ESD), IEC 61000-4-5 (combination-wave surge), IEC 62305 (lightning protection), IEC 61000-2-9 / 61000-4-25 (HEMP waveform taxonomy, open summaries), NERC TPL-007 (GMD planning order-of-magnitude). Enclosure bonding and SPDs: NEC 250.4 / 250.96, NEC 285. Cable shields and entry: IEEE 1100 (Emerald Book) practice, not a code calculator.
This calculator describes incident environments and victim circuits so you can shrink loop area, close slots, bond the enclosure, and filter cable entries. It does not tell anyone how to produce those fields.
Victim loop in a changing B field
Cage with a slot
Protected cable entry
Victim loop
|V| = N × A × |dB/dt|
dB/dt ≈ ΔB / tr when a change and rise time are given
I ≈ V / R only if R is entered (loop inductance ignored)
Result
Default example: a 10 cm × 10 cm single-turn loop, 1 mT in 1 µs → |V| = 10 V. Shrink the loop, twist pairs, and keep cables against a bonded surface to cut A.
Longest slot or seam
SEslot ≈ 20 log10((λ/2) / ℓ)   for ℓ < λ/2
SEslot ≈ 0 dB when ℓ ≥ λ/2
λ = c / f  |  f ≈ 0.35 / tr from a rise time
Optional depth: extra ≈ 27.3 (t/ℓ) √(1 − (f/fc)²), fc = c/(2ℓ)
Result
Gaskets, overlapping seams, and honeycomb vents are how real cages keep ℓ electrically small. A painted joint or a display window is often the whole enclosure.
Barrier
δ = 1 / √(π f μ σ)
A ≈ 8.686 (t / δ) dB
R ≈ 168.2 + 10 log10(σr / (μr f)) dB  (far-field, σr relative to Cu)
B ≈ 20 log10(1 − e−2t/δ) when t < δ
SE ≈ A + R + B
Result
A seamless copper sheet at RF can look like >100 dB on paper. Real cabinets are aperture- and cable-limited. Bond seams; do not trust paint as a contact. Magnetic fields at 50/60 Hz need thickness, permeability, or distance — foil cages do little.
Incident environment to design against
Pick a published waveform family used to specify shields and SPDs.
Where a victim-loop estimate is valid, Faraday’s law is applied to your loop — never as a source-design step.
Result
NEC 285 covers SPD installation; NEC 250.4 and 250.96 cover bonding metal enclosures and raceways. Those articles do not define HEMP test levels — they tell you how to land a shield and a surge device once you have chosen a protection scheme.

📚 STEM Toolkit

Comprehensive calculators for students and engineers — differential equations, trigonometry, linear algebra, chemistry, calculus, optics, quantum physics, and linear programming.

2nd-Order ODE: ay″ + by′ + cy = 0
Numerical IVP: dy/dt = f(t, y)
Unit Circle
Drag the angle control or click the circle to read coordinates and trig values.
Triangle Solver
Enter any 3 of 6 values (at least one side). Leave unknowns blank.
Trigonometric Identities Reference
Matrix Operations
 
Matrix A
Matrix B
Dot & Cross Product (3D Vectors)
Molar Mass Calculator
Ideal Gas Law — PV = nRT
Enter any 3 of 4 variables. Leave the unknown blank.
Henderson-Hasselbalch
Periodic Table — First 20 Elements
Numerical Derivative
Numerical Integration
Taylor Series
Function Explorer
Projectile Motion Lab
2D Vector Projection
Thin Lens / Mirror: 1/f = 1/dₒ + 1/dᵢ
Enter any 2 of 3. Leave unknown blank.
Snell's Law: n₁ sin θ₁ = n₂ sin θ₂
Diffraction Grating & Double Slit
Diffraction Grating: d sin θ = mλ
Double Slit: Δy = λL/d
Particle in a Box
Hydrogen Energy Levels
de Broglie Wavelength & Heisenberg Uncertainty
de Broglie: λ = h/(mv)
Heisenberg: ΔxΔp ≥ ℏ/2
Photoelectric Effect
Linear Program Setup
z = x₁ + x₂
Subject to (≤ constraints):
x₁ + x₂ ≤
x₁ + x₂ ≤
x₁ + x₂ ≤
x₁, x₂ ≥ 0 (non-negativity)
Feasible Region
Solution & Simplex Tableau

Gaussian Beam

TEM00 envelope: w(z), Rayleigh range, curvature, confocal parameter. Not a thin-lens imager and not a double-slit.

ℹ More Info — Gaussian beams
A TEM00 beam has a 1/e² intensity radius that is smallest at the waist and grows as a hyperbola along z.

Formulas:
  • zR = π w0² / λ
  • w(z) = w0 √(1 + (z/zR)²)
  • R(z) = z (1 + (zR/z)²), infinite at the waist
  • Confocal parameter b = 2 zR. Far-field half-angle θ = λ / (π w0)
Cavities, ABCD matrices, and lens focusing are out of scope — the STEM toolkit already has a thin-lens solver.

Citations: Bahaa E. A. Saleh and Malvin Carl Teich, Fundamentals of Photonics (Wiley). No edition is claimed here. zR, w(z), R(z), and b = 2 zR are standard identities.
Beam envelope
Waist and wavelength
zR = π w0² / λ  |  w(z) = w0 √(1 + (z/zR)²)
R(z) = z (1 + (zR/z)²)  |  b = 2 zR
Results

📊 Linear Programming Optimizer

Find the best feasible solution of a small linear program: maximize or minimize c·x subject to Ax ≤ / ≥ / = b, with x ≥ 0 and optional upper bounds. Educational operations research — not related to EMP sources or shielding.

ℹ More Info — Linear Programming Optimizer
A linear program is an ordinary optimization model: a linear objective over a polyhedron defined by linear inequalities. This tool uses a two-phase simplex method in plain JavaScript (Bland’s rule, no WASM).
  • Phase I drives artificial variables to zero. If they cannot reach zero, the program is infeasible.
  • Phase II optimizes the original objective. If a variable can enter with no leaving row, the program is unbounded.
  • Two variables: the feasible region is drawn (constraint lines, vertices, objective through the optimum).
  • n variables: labelled status, z*, primal x*, and slack / surplus — not a wall of unlabeled numbers.
Presets cover product mix, a cheapest kW source-mix blend, and a textbook 2-variable graphical example. Units are shown next to the values they belong to.
Program
max / min   c · x  |  A x { ≤, ≥, = } b  |  x ≥ 0

Formulation

            
The statement updates as you edit. Share the page URL to send this program; it live-recomputes on every change.

          

        


        

          
Constraints  A x  {≤, ≥, =}  b

          

            

          

        


        

          
Solution

          

            

            

          

        

      

    


    
    

      

        
I/O List Generator

        
Scaffold a PLC I/O list from a brand catalog, generic channel counts, or a typed instrument takeoff. Pick a platform per station (Beckhoff, Rockwell, Siemens, WAGO, … or No brand). Couplers and license cards consume a slot with a blank channel. Optional extended columns stay off so the 26-column template still exports. Design aid only; not a PE stamp, wiring schedule, or submittal.

        

          ℹ More Info — I/O List Generator
          

            Each station is one brand unless you explicitly allow mixed catalogs. A project can mix brand stations with generic-count stations. Slots number in add order. Channels on each module run 1…N. Generate expands to one spreadsheet row per channel (zero-channel modules still emit one row).
            
    
              
  • Brand mode: picker is filtered to that platform. Add/edit/remove catalog rows (PN, description, channels, signal type, raw min/max, optional width and signed E-bus mA) so any family can be extended in-browser.
    • 
              
  • No brand / generic: enter channel points and density (defaults DI 16, DO 8, AI 8, AO 4, RTD 4, TC 8). Part numbers become “Generic DI” etc. Card names still use the editable prefixes.
    • 
              
  • Card Name: independent coupler / I/O / power prefixes, padded as prefix + (100+seq) → KEC0101. Beckhoff defaults KFD / KEC / XDC; other brands ship different defaults; all are editable.
    • 
              
  • 26-column IO List: Controller … Comments, including Page, EPLAN Updated, Electrical Check Complete, Scaling Verified, T&LO V&V. DO rows seed Min/Max 0/1, Units BOOL, Raw 0/1. Coupler and license rows consume a slot with a blank channel. Spare channels stay empty-description rows.
    • 
              
  • Extended columns (off by default): Control Zone, Sample Rate (Slow / Fast / Event or custom), Data Type (BOOL / INT / UINT / DINT / REAL / STRING — DO still seeds BOOL), Location, Serial Number, Find # / tag stem, Signal Suffix, and Wire Color From/To. The 26-column export is unchanged until you turn this on.
    • 
              
  • Tag suffixes: editable catalog of generic signal endings (status, pressure, temp, flow, position, cmd, limits). Linked PLC Variable auto-builds as stem+suffix and stays editable. Not a fluid or commodity library.
    • 
              
  • Instrument takeoff: type Device, Qty, Signal (DI/DO/AI/AO), and Electrical type (BOOL, 4–20, mV/V). Rows sum into generic counts, then Generate expands the list. No project device names are preloaded.
    • 
              
  • Export writes .xlsx sheets Ebus Current, IO List, Scaling, and Summary (type-colored fills) via a vendored SheetJS copy, or .csv of the grid. Extra columns appear in the spreadsheet only when enabled. Save/Load JSON v2 keeps the build list; v3 also stores extended columns, suffix catalog, takeoff, and edited extra fields.
    • 
            

            Seed catalogs are short public part-number lists, not a vendor price book. Verify channel counts and analog process-image ranges against the manufacturer’s datasheet. No proprietary project tags are included.
          

        

      


      
        
        
        
        
        
        
        
        
        
        
        
        
        
        
        
        
      
      
        
        
        
        
        
        
      
      
        
        
        
      
      
        
        
        
        
      
      
        
        
        
        
      
      
        
        
        
      
      

      

        

          
Module catalog

          

            
Public seed PNs per brand — not a price book. Add, edit, or remove rows. Channel count 0 still consumes a slot. E-bus mA is signed (coupler supply positive, terminals negative). Raw min/max apply to AI, AO, RTD, and TC.

            

              

                
                
              

            

            

            
          

        


        

          
Stations and parts cart

          

            
One brand per station (or No brand / generic counts). Card-name prefixes are per family and stay editable. Multiple stations in one project may be different brands.

            

            

              
              
            

          

        


        

          
Instrumentation takeoff

          

            
Optional count-up from field devices you type. Each row is Device, Qty, Signal (DI/DO/AI/AO), and Electrical type (BOOL, 4–20, mV/V). Apply writes the sums into generic channel points. Generate then expands the list. No project names are preloaded.

            

            

              
              
            

          

        


        

          
Signal suffix catalog

          

            
Generic tag endings only (status, pressure, temp, flow, position, cmd, limits). Edit freely. Find # (tag stem) plus a suffix auto-builds Linked PLC Variable as stem+suffix; you can still overwrite the variable. This is not a fluid or commodity list.

            

            

              
            

          

        


        

          
Summary

          

            

            
Totals count generated or edited grid rows. Analog Inputs includes RTD and TC. Spare = channel rows with blank Description and blank Linked PLC Variable Name.

          

        


        

          
Save, load, export

          

            

              
              
              
              
              
            

            
JSON v2 stores brand, mode, catalog, and the station cart. v3 also stores extended-column flag, suffix catalog, takeoff, and extra field values. Spreadsheet export is the editable grid plus Ebus Current / Scaling / Summary. Extra columns appear only when enabled. SheetJS is loaded from this site, not a CDN.

          

        


        

          
I/O list grid

          

            
            

              
            

            

          

        

      

    


    
    

      

        
Process Value / Signal Scaling

        
Linear or square-root (DP flow) scaling between a raw instrument signal and engineering units. Live, both directions, with the actual numbers plugged into the formula. Design aid only — not a transmitter download, loop check sheet, or PE stamp.

        

          ℹ More Info — Signal Scaling
          

            Forward: raw (for example 14.2 mA) + signal range + engineering range → process value.

            Reverse: desired engineering value → raw to inject on the bench.


            A 4–20 mA loop is live-zero: 4 mA is 0% of span, not 0 mA. Values below 4 mA are flagged as a live-zero fault / under-range; values above 20 mA are over-range. Other signal types flag when raw is outside the configured min/max. Pt100 resistance mode still uses a linear Ω span for the scale; an IEC 60751 temperature is shown as a reference only.


            Square-root / DP flow: flow = engMin + (engMax − engMin) × √((raw − rawMin)/(rawMax − rawMin)). Reverse squares the normalized engineering value. Same 4–20 live-zero flags apply to the raw mA.
          

        

      


      

        

          
Signal and ranges

          

            

              Linear: eng = engMin + (raw − rawMin) × (engMax − engMin) / (rawMax − rawMin)

              Square-root: eng = engMin + (engMax − engMin) × √((raw − rawMin)/(rawMax − rawMin))
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

            

            

              

                
                
              

              
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            
          

        


        

          
Live scale

          

            

              

                
                
              

              

                
                
              

            

            

              
              
            

            
            

          

        


        

          
Forward formula

          

            

          

        


        

          
Reverse formula (bench inject)

          

            

          

        


        

          
Named presets (this browser)

          

            

              

                
                
              

              

                
              

            

            

            
Presets store signal type, ranges, and unit in localStorage. They never leave this device.

          

        

      

    


    
    

      

        
E-bus / Rack Current Budget

        
Running remaining current down a rack. Coupler supply is positive mA; terminals draw (negative). A power-refresh module resets remaining to its own supply. Flag when remaining goes negative or below a reserve. Design aid only — not a thermal study or PE stamp.

        

          ℹ More Info — E-bus / Rack Current
          

            Beckhoff seed figures are typical published E-bus consumption and a 2000 mA coupler/EL9410 supply. Other brands: type the milliamps from the datasheet (signed). Width mm is optional. The I/O List Generator export also writes an Ebus Current sheet from that tool’s build list.
          

        

      

      

        

          
Rack modules

          

            

              

                
                
              

              

                
                
              

              

                
              

            

            

          

        

        

          
Budget

          

            

            
Remaining starts at 0 until a coupler or refresh supplies current. Check the Flag column when it drops below the reserve or goes negative.

          

        

      

    


    
    

      

        
Modbus Address Converter

        
Function codes 01/02/03/04, 0-based PDU offset vs 1-based number, 5-digit 00001/10001/30001/40001 and 6-digit 400001 long addressing. Not a slave simulator.

        

          ℹ More Info — Modbus Address
          

            Holding register 40001 is 1-based number 1 and 0-based offset 0 (the first holding register on the wire). Long addressing uses six digits (400001). The PDU carries a 16-bit big-endian starting address that is always 0-based; this tool does not send frames.
          

        

      

      

        

          
Address

          

            

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            

          

        

        

          
Wire format

          

            

          

        

      

    


    
    

      

        
PLC Timer Preset

        
TON / TOF / RTO: desired seconds or milliseconds → preset counts at a timebase (1 ms, 10 ms, 100 ms, 1 s, custom, or scan-time). Reverse too. Not a timing-chart IDE.

        

          ℹ More Info — PLC Timer Preset
          

            The instruction type does not change the count math: preset = round(desired time / timebase). Scan-time mode uses your entered scan as the timebase so a “counts = number of scans” timer is honest. Rounding residual is shown when the timebase cannot hit the desired time exactly.
          

        

      

      

        

          
Time and timebase

          

            

              

                
                
              

              

                
                
              

            

            
            
            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

            

            

          

        

        

          
Result

          

            

            

          

        

      

    


    

    

      

        
Pitch / Hum Frequency Identifier

        
Electrical diagnostic helper — not a music tuner. Dominant frequency of an audible hum or whine, plus what that frequency commonly indicates. Associations only; never a confirmed cause.

        

          ℹ More Info — Pitch / Hum Identifier
          

            The fundamental is extracted with autocorrelation on the live microphone buffer (more robust than grabbing the raw FFT peak for a single tone). A Hann-windowed FFT is shown only as a spectrum helper.


            Typical associations (worth investigating, not a diagnosis):
            
    
              
  • 50 Hz / 60 Hz — mains-frequency hum, often grounding or induction
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  • 100 Hz / 120 Hz — consistent with full-wave-rectified ripple (2× mains)
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  • 150 Hz / 180 Hz — 3rd harmonic; transformer magnetostriction or mechanical buzz
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  • 300 Hz / 360 Hz — higher rectifier harmonics on 50/60 Hz systems
    • 
            

            Phone mics roll off and distort. Use this to compare “before vs after” or to decide whether a calibrated meter is worth pulling out.
          

        

        
Phone microphones are not calibrated instruments; sensitivity varies device to device. This is a relative field check and rough diagnostic — not a substitute for a calibrated sound-level meter or frequency counter, and not for compliance, code-acceptance, or safety-certification measurements.

        
Audio is processed live, on this device, for display only. Nothing is recorded, stored, or transmitted.

      


      

        
Show the work — why autocorrelation, not FFT-peak?

        
f0 = fs / τpeak

        
A 60 Hz hum is rarely a clean sine. Harmonics make the FFT’s tallest bin a multiple of the fundamental. Autocorrelation looks for the lag where the waveform repeats; that lag is the period. The FFT is still useful for a spectrum — it is just the wrong first answer for “what is the hum?”

      


      

        

          
Microphone

          

            

              
This tool listens through your phone mic to estimate a hum frequency. It does not record or upload audio. The browser will ask for microphone permission after you tap Start — not before.

              

                
                
                
              

              
Idle. Sensors stay off until you tap Start.

            

          

        


        

          
Dominant frequency

          

            
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            Hz (autocorrelation)
            
Waiting for Start.

            
Start listening, then hold the phone near the source — not a diagnosis.

            
Spectrum helper appears once the mic is live. Hann window, documented bin Hz.

          

        


        

          
Common frequencies — typical associations

          

            
Language is “worth investigating,” never a confirmed cause. Include 50 Hz regions for completeness.

            

              

                
                  
HzTypical association — not a diagnosis

                
                
                  
50Mains-frequency hum in 50 Hz regions (grounding or induction). Worth investigating.

                  
60Mains-frequency hum in 60 Hz regions (grounding or induction). Worth investigating.

                  
100Consistent with full-wave-rectified ripple on 50 Hz mains (2×). Worth investigating.

                  
120Consistent with full-wave-rectified ripple on 60 Hz mains (2×). Worth investigating.

                  
150 / 1803rd harmonic of 50/60 Hz — transformer magnetostriction or mechanical buzz is a common association.

                  
300 / 360Higher rectifier harmonics on 50/60 Hz systems. Worth investigating.

                
              

            

          

        

      

    


    

      

        
FFT / Audio Spectrum Analyzer

        
General-purpose real-time spectrum for transformer buzz, motor harmonics, and noise characterization. Shared Hann FFT with the pitch and lux tools.

        

          ℹ More Info — Audio Spectrum
          

            Time-domain samples come from the shared microphone engine (one stream for pitch, spectrum, and sound level). The spectrum is a Hann-windowed radix-2 FFT. Bin width = sampleRate / FFT size (default N = 2048).


            Linear vs log frequency axis, exponential averaging, and a peak-hold overlay are display controls — they do not change the underlying FFT. Export is a PNG of the canvas and/or CSV of bin magnitudes. No raw audio leaves the device.
          

        

        
Phone microphones are not calibrated instruments; sensitivity varies device to device. This is a relative field check and rough diagnostic — not a substitute for a calibrated analyzer, and not for compliance, code-acceptance, or safety-certification measurements.

        
Audio is processed live, on this device, for display only. Nothing is recorded, stored, or transmitted. PNG/CSV exports are the drawn spectrum and numeric bins — never raw audio.

      


      

        

          
Microphone and display

          

            

              
This tool uses the microphone to draw a live spectrum. It does not record or upload audio. Permission is requested only after Start.

              

                
                
              

              
Idle. Sensors stay off until you tap Start.

            

            

              

                
                
              

              

                
                
              

            

            
            

              
              
              
            

          

        


        

          
Live spectrum

          

            
            
Hann window · N = 2048 · bin Hz = sampleRate / N. Start to plot.

          

        

      

    


    

      

        
Sound Level Meter

        
Relative dB meter for equipment-room noise and before/after checks. Not a calibrated SPL meter unless you supply a one-point reference.

        

          ℹ More Info — Sound Level Meter
          

            RMS is taken from the shared microphone’s time-domain buffer and converted to dBFS (full-scale float = 1.0). Optional A-weighting is an IEC 61672-shaped approximation applied to the FFT bins — not a certified analog filter, not dB(A) you can write on a report.


            One-point calibration: hold a known meter next to the phone, enter that dB, and this device stores an offset in localStorage. Without it, the unit stays clearly relative (dBFS / rel dB). Logged CSV rows are location, timestamp, and the numeric reading — never raw audio.
          

        

        
Phone microphones are not calibrated instruments; sensitivity varies device to device. This is a relative field check and rough diagnostic — not a substitute for a calibrated sound-level meter, and not for compliance, code-acceptance, OSHA, or safety-certification measurements.

        
Audio is processed live, on this device, for display only. Nothing is recorded, stored, or transmitted. CSV export is numeric readings only.

      


      

        

          
Microphone

          

            

              
This tool estimates a relative level from the microphone. It does not record or upload audio. The browser asks for permission only after Start.

              

                
                
                
              

              
Idle. Sensors stay off until you tap Start.

            

            
            

              

                
                
              

            

          

        


        

          
Level

          

            
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            dBFS
            
            

              
Running peak—

              
Leq-style—

            

          

        


        

          
One-point calibration

          

            
Enter a known dB from a reference meter under the current conditions. Offset is stored per-device in localStorage. Without it, this display stays a relative unit — not dB(A).

            

              

                
                
              

            

            

              
              
            

            
Uncalibrated: showing dBFS-relative, not unearned-precision dB(A).

          

        


        

          
Logged readings

          

            

              

                
                
              

            

            

              
              
            

            

          

        

      

    


    

      

        
Lux / Light Level Meter

        
Camera-based relative light-level estimate. Useful for before/after LED retrofit at the same fixture position — not certified photometry.

        

          ℹ More Info — Lux / Light Meter
          

            The rear camera (when available) is sampled over a center-weighted region, not the full frame. Readings are averaged over ~1/60 s+ of frames so LED PWM flicker is not a single glowing instant.


            Without calibration the unit is a clearly labeled relative/arbitrary scale — never implied to be lux. One-point calibration: enter a known lux from a meter, stored per-device in localStorage.


            Flicker frequency runs the brightness time series through the same Hann FFT as the audio tools. It is camera-frame-rate limited (Nyquist ≈ fps/2). Do not photograph the sun or stare into high-intensity sources. Point the camera at the lighted task surface or luminaire housing, not at the lamp arc.
          

        

        
Phone cameras are not calibrated photometers; sensitivity varies device to device. This is a relative, comparative field check — not a substitute for a calibrated lux meter, and not for compliance, code-acceptance, or safety-certification measurements. Do not look at the sun or stare into high-intensity sources.

        
Camera frames are processed live, on this device, for display only. Nothing is recorded, stored, or transmitted. CSV export is position, timestamp, and the numeric reading — never raw frames.

      


      

        

          
Camera

          

            

              
This tool uses the camera on lighting only — a task surface or fixture, not the sun and not a stare into a high-intensity source. Permission is requested only after Start. Nothing is uploaded.

              

                
                
                
              

              
Idle. The camera stays off until you tap Start.

            

            

              
              
            

            
          

        


        

          
Reading

          

            
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            rel (not lux)
            
Relative mode — these numbers are not lux until you calibrate.

            

              
Min—

              
Max—

              
Average—

            

            
Flicker check runs after Start. Camera-frame-rate limited estimate.

          

        


        

          
One-point calibration

          

            
Same fixture position, known lux from a meter. Scale factor stays on this device in localStorage. Without it, the big number stays a relative unit.

            

              

                
                
              

            

            

              
              
            

            
Uncalibrated: relative/arbitrary units only.

          

        


        

          
Logged readings

          

            

              

                
                
              

            

            

              
              
            

            

          

        

      

    


    
    

      

        
⚡ NEC Code Tables

        
Key National Electrical Code reference tables for conductor sizing, derating, protection, and conduit fill.

        

          ℹ More Info — NEC Code Tables
          

            National Electrical Code (NEC) reference tables used in everyday electrical design. All values are from the 2023 NEC unless noted.


            
    
              
  • Table 310.16: Allowable ampacity for conductors in raceways and cables at 30°C ambient, ≤3 current-carrying conductors.
    • 
              
  • Table 310.15(C)(1): Adjustment factors when more than 3 current-carrying conductors are bundled in a conduit or cable.
    • 
              
  • Table 310.15(B)(2)(a): Ambient temperature correction factors applied to ampacity values.
    • 
              
  • Table 240.6(A): Standard ampere ratings for fuses and inverse-time circuit breakers.
    • 
              
  • Table 250.122: Minimum equipment grounding conductor (EGC) sizes based on OCPD rating.
    • 
              
  • Table 430.52: Maximum motor branch-circuit OCPD ratings as a percentage of motor FLA.
    • 
              
  • Table 450.3(B): Transformer overcurrent protection requirements for transformers ≤600V.
    • 
              
  • Chapter 9 Table 4: Conduit dimensions and fill areas (EMT, IMC, RMC, PVC).
    • 
              
  • Chapter 9 Table 5: Conductor dimensions and areas for THHN/THWN-2 insulation.
    • 
            

            Always refer to the current edition of the NEC and local amendments. These tables are provided for reference only.
          

        

      


      

        

          
          
          
          
          
          
        


        
        

          

            

              
NEC Table 310.16 — Allowable Ampacity, 30°C Ambient, ≤3 Current-Carrying Conductors in Raceway

              

                
ⓘ Use 75°C column for terminals rated 75°C (most equipment). Use 90°C column only as the starting point for derating calculations — final ampacity is limited to the terminal rating. 14 AWG aluminum not listed for service conductors. Based on NEC 2023 Table 310.16.

                

                  

                    
                      

                        Size
                        Copper
                        Aluminum / Copper-Clad Al
                        THHN Area (in²)
                        Circular Mils
                      

                      

                        60°C (A)
                        75°C (A)
                        90°C (A)
                        60°C (A)
                        75°C (A)
                        90°C (A)
                      

                    
                    
                      
14 AWG152025———0.00974,110

                      
12 AWG2025301520250.01336,530

                      
10 AWG3035402530350.021110,380

                      
8 AWG4050553040450.036616,510

                      
6 AWG5565754050600.050726,240

                      
4 AWG7085955565750.082441,740

                      
3 AWG851001106575850.097352,620

                      
2 AWG9511513075901000.115866,360

                      
1 AWG110130150851001150.156283,690

                      
1/0 AWG1251501701001201350.1855105,600

                      
2/0 AWG1451751951151351500.2223133,100

                      
3/0 AWG1652002251301551750.2679167,800

                      
4/0 AWG1952302601501802050.3237211,600

                      
250 kcmil2152552901702052300.3970250,000

                      
300 kcmil2402853201902302600.4608300,000

                      
350 kcmil2603103502102502800.5242350,000

                      
400 kcmil2803353802252703050.5863400,000

                      
500 kcmil3203804302603103500.7073500,000

                      
600 kcmil3504204752853403850.8676600,000

                      
700 kcmil3854605203153754200.9887700,000

                      
750 kcmil4004755353203854351.0496750,000

                      
800 kcmil4104905553303954451.1085800,000

                      
1000 kcmil4555456153754455001.34781,000,000

                    
                  

                

                
ⓘ NEC 110.14(C): Conductor ampacity is limited by the temperature rating of terminations. Use the 75°C column when terminations are rated 75°C (most commercial/industrial equipment). Only use the 90°C column when both the conductor AND terminations are rated 90°C.

              

            

          

        


        
        

          

            

              
NEC Table 310.15(C)(1) — Adjustment Factors, More Than 3 Current-Carrying Conductors

              

                
ⓘ Apply this multiplier to the base ampacity when more than 3 current-carrying conductors (CCC) are installed in a raceway, cable, or earth. Does not apply to conductors in free air or to EGC/neutral conductors under NEC 310.15(E)(2).

                

                  

                    
                      

                        Number of Current-Carrying Conductors
                        Adjustment Factor
                        Example Application
                      

                    
                    
                      
1–3100% (no derating)Standard circuit — no adjustment

                      
4–680% (×0.80)Two 3-wire circuits in same conduit

                      
7–970% (×0.70)Three 3-wire circuits in conduit

                      
10–2050% (×0.50)Multiple circuits, shared raceway

                      
21–3045% (×0.45)Large shared raceway

                      
31–4040% (×0.40)High-density raceway

                      
41 and above35% (×0.35)Very high-density raceway

                    
                  

                

                

                  Counting rules (NEC 310.15(E)):

                  • Grounded (neutral) conductor counts IF it carries significant harmonic current

                  • 3-wire single-phase (2 ungrounded + 1 neutral) = 2 CCC

                  • 3-phase 4-wire wye (3 ungrounded + 1 neutral) = 3 CCC (balanced linear loads)

                  • EGC and bonding conductors do NOT count

                  • Neutral carrying >50% of phase current (harmonic loads) DOES count
                

              

            

            

              
NEC Table 310.15(B)(2)(a) — Ambient Temperature Correction Factors

              

                
ⓘ Multiply the base ampacity by the correction factor for the actual ambient temperature. Base ampacity is at 30°C (86°F). Apply BOTH CCC and temperature factors simultaneously: Derated Ampacity = Base × CCC Factor × Temp Factor.

                

                  

                    
                      

                        Ambient Temp (°C)
                        Ambient Temp (°F)
                        60°C Insul.
                        75°C Insul.
                        90°C Insul.
                      

                    
                    
                      
10 or less50 or less1.291.201.15

                      
11–1552–591.221.151.12

                      
16–2061–681.151.111.08

                      
21–2570–771.081.051.04

                      
26–3079–861.001.001.00

                      
31–3588–950.910.940.96

                      
36–4097–1040.820.880.91

                      
41–45106–1130.710.820.87

                      
46–50115–1220.580.750.82

                      
51–55124–1310.410.670.76

                      
56–60133–1400.00*0.580.71

                      
61–70142–158—0.330.58

                      
71–80160–176——0.41

                    
                  

                

                
* 60°C conductors are NOT rated above 60°C ambient — must use higher-rated insulation. Correction factor formula: CF = √[(Trating − Tambient) / (Trating − 30)]

              

            

          

        


        
        

          

            

              
NEC Table 240.6(A) — Standard Ampere Ratings for Fuses and Inverse-Time Breakers

              

                
ⓘ When sizing an OCPD, the next standard rating above the calculated minimum may be used per NEC 240.4(B), provided the conductor is not smaller than the minimum ampacity rating. NEC 240.4(D) limits protection for small conductors: 15A max for 14 AWG, 20A max for 12 AWG, 30A max for 10 AWG.

                

                  

                    
                      
Standard Ampere Ratings — NEC 240.6(A)

                    
                    
                      
152025303540

                      
455060708090

                      
100110125150175200

                      
225250300350400450

                      
50060070080010001200

                      
160020002500300040005000

                      
6000—————

                    
                  

                

                

                  NEC 240.4(D) — Maximum OCPD for Small Conductors:

                  14 AWG Cu → 15 A maximum

                  12 AWG Cu → 20 A maximum

                  10 AWG Cu → 30 A maximum


                  NEC 240.4(B) — Next Standard Size Up rule:

                  Allowed when the calculated OCPD does not correspond to a standard size AND the conductor ampacity is not less than the load.
                

              

            

            

              
NEC Table 250.122 — Minimum Equipment Grounding Conductor (EGC) Size

              

                
ⓘ The EGC must be sized based on the rating of the overcurrent protective device ahead of the equipment. Where conductors are increased in size for voltage drop, the EGC must be proportionally increased. Min. 14 AWG Cu or 12 AWG Al.

                

                  

                    
                      

                        Rating of OCPD (A)
                        Copper EGC Min
                        Aluminum EGC Min
                      

                    
                    
                      
1514 AWG12 AWG

                      
2012 AWG10 AWG

                      
6010 AWG8 AWG

                      
1008 AWG6 AWG

                      
2006 AWG4 AWG

                      
3004 AWG2 AWG

                      
4003 AWG1 AWG

                      
5002 AWG1/0 AWG

                      
6001 AWG2/0 AWG

                      
8001/0 AWG3/0 AWG

                      
10002/0 AWG4/0 AWG

                      
12003/0 AWG250 kcmil

                      
16004/0 AWG350 kcmil

                      
2000250 kcmil400 kcmil

                      
2500350 kcmil600 kcmil

                      
3000400 kcmil600 kcmil

                      
4000500 kcmil750 kcmil

                      
5000700 kcmil1200 kcmil

                      
6000800 kcmil1200 kcmil

                    
                  

                

              

            

          

        


        
        

          

            

              
NEC Table 430.52 — Maximum Rating or Setting of Motor Branch-Circuit SCGFPD (% of Motor FLA)

              

                
ⓘ Values are the MAXIMUM allowed ratings for motor branch-circuit short-circuit and ground-fault protective devices. Apply to full-load current from NEC Tables 430.248 (single-phase) or 430.250 (three-phase). If the calculated value does not correspond to a standard rating, use the next standard size up per NEC 240.6(A). Per NEC 430.52(C)(1), if the percentage does not correspond to a standard rating, use the next lower standard rating unless it is not sufficient to carry the starting current.

                

                  

                    
                      

                        Motor Type
                        Non-TD Fuse (%)
                        Dual-Element TD Fuse (%)
                        Inst.-Trip Breaker (%)
                        Inverse-Time Breaker (%)
                      

                    
                    
                      
Single-phase AC, all types300175800250

                      
AC squirrel-cage (other than single-phase): Design B, D, E300175800250

                      
AC squirrel-cage (other than single-phase): Design B, E energy efficient3001751100250

                      
AC synchronous (full voltage, resistor or reactor start)300175800250

                      
AC synchronous (part-winding)150150800200

                      
AC wound-rotor150150800150

                      
DC (constant voltage)150150250150

                    
                  

                

                

                  Common sizing example (NEC 430.52):

                  10 HP, 230V, 3-phase squirrel-cage motor: FLA (NEC Table 430.250) = 28 A

                  Max inverse-time breaker = 28 × 250% = 70 A → Next standard = 70 A ✓

                  Max non-time-delay fuse = 28 × 300% = 84 A → Next standard = 90 A


                  NEC 430.52(C)(1) Exception: If 250% is not sufficient to carry motor starting current, the next larger standard rating up to 400% of FLA may be used for inverse-time breakers.
                

              

            

            

              
NEC Table 430.52 — Conductor Sizing (NEC 430.22 / 430.24)

              

                

                  Single motor branch circuit (NEC 430.22):

                  Conductor ampacity ≥ 125% × motor FLA


                  Several motors on one circuit (NEC 430.24):

                  Conductor ampacity ≥ 125% × largest motor FLA + sum of all other motor FLAs


                  Overload protection (NEC 430.32):

                  Overload device ≤ 115% of nameplate FLA (service factor ≥ 1.15 or temp rise ≤ 40°C)

                  Overload device ≤ 125% of nameplate FLA (all other motors)


                  Motor feeder (NEC 430.62):

                  Rating ≥ largest motor branch-circuit OCPD + sum of all other motor FLAs
                

              

            

            

              
NEC 430.6 — FLA Reference Tables

              

                

                  For conductor and OCPD sizing, use NEC table FLA — NOT nameplate FLA:


                  NEC Table 430.248 — Single-phase AC motors (see Motor FLA Tables section)

                  NEC Table 430.250 — Three-phase AC motors (see Motor FLA Tables section)

                  NEC Table 430.247 — DC motors

                  NEC Table 430.249 — Single-phase AC, 2-pole, 50 Hz motors


                  Exception: For multi-speed motors and motors with unusual starting conditions, use nameplate FLA for overload protection.
                

              

            

          

        


        
        

          

            

              
NEC Table 450.3(B) — Maximum Rating or Setting of Overcurrent Protection for Transformers ≤ 600V (as a Secondary Voltage)

              

                
ⓘ Ratings are expressed as a percentage of rated transformer current. "Primary only" protection means no secondary OCPD is required. "Primary and secondary" means both primary and secondary OCPDs are provided. Values apply to supervised and unsupervised locations (supervised locations may use slightly different percentages). From NEC 2023 Table 450.3(B).

                

                  

                    
                      

                        Primary Current Rating
                        Primary OCPD Max (%)
                        Secondary OCPD Max (%)
                        Notes
                      

                    
                    
                      
≥ 9 A primary (supervised)125%250%Both primary + secondary OCPDs provided

                      
≥ 9 A primary (unsupervised)125%125%Standard commercial installation

                      
< 9 A primary, ≥ 2 A secondary167%167%Small transformer

                      
< 2 A primary (any)300%167%Very small transformer

                    
                  

                

                

                  Typical dry-type transformer sizing example:

                  75 kVA, 480VΔ Primary / 208Y/120V Secondary

                  Primary FLA = 75,000 / (√3 × 480) = 90.2 A

                  Primary OCPD max (125%) = 90.2 × 1.25 = 112.8 A → 110 A (next standard rating down per NEC 240.6(A))

                  Secondary FLA = 75,000 / (√3 × 208) = 208.2 A

                  Secondary OCPD max (125%) = 208.2 × 1.25 = 260.3 A → 250 A


                  NEC 450.3(B) Exception: If 125% does not correspond to a standard OCPD rating, the next higher standard rating may be used.
                

              

            

            

              
Standard Dry-Type Transformer kVA Ratings (ANSI/NEMA)

              

                

                  

                    
                      
Single-Phase kVAThree-Phase kVA

                    
                    
                      
0.050, 0.100, 0.150, 0.2503, 6, 9, 15

                      
0.500, 0.750, 1.0, 1.530, 45, 75, 112.5

                      
2.0, 3.0, 5.0, 7.5150, 225, 300, 500

                      
10, 15, 25, 37.5750, 1000, 1500, 2000

                      
50, 75, 100, 1672500, 3000, 3750, 5000

                      
250, 333, 5007500, 10000

                    
                  

                

                
For transformer sizing, calculate required kVA then select next standard size up. Apply 80% loading guideline for continuous loads to allow thermal headroom.

              

            

            

              
NEC Article 450 — Key Transformer Requirements

              

                

                  NEC 450.14 — Disconnecting Means:

                  Must be within sight of transformer OR lockable in open position


                  NEC 450.9 — Ventilation:

                  Adequate ventilation required; clearances per manufacturer


                  NEC 450.21 — Indoor Dry-Type Location:

                  Transformers >112.5 kVA must be in fire-resistant rooms

                  Transformers 600V or less: 1.83 m (6 ft) clearance from combustibles


                  NEC 450.13 — Accessibility:

                  Must be accessible to qualified persons only


                  NEC 450.3(B) Note: If OCPD rating does not correspond to standard size, next higher standard permitted
                

              

            

          

        


        
        

          

            

              
NEC Chapter 9, Table 4 — Dimensions and Percent Area of Conduit / Tubing

              

                
ⓘ Internal diameter and total internal area values from NEC 2023 Chapter 9, Table 4. Fill areas are calculated at the NEC Chapter 9 Table 1 percentages (53% for 1 conductor, 31% for 2 conductors, 40% for 3 or more conductors).

                

                  

                    
                      

                        Trade Size
                        EMT (Electrical Metallic Tubing)
                        IMC (Intermediate Metal Conduit)
                        RMC (Rigid Metal Conduit)
                      

                      

                        ID (in)
                        Total Area (in²)
                        40% Fill (in²)
                        ID (in)
                        Total Area (in²)
                        40% Fill (in²)
                        ID (in)
                        Total Area (in²)
                        40% Fill (in²)
                      

                    
                    
                      
1/2"0.6220.3040.1220.6600.3420.1370.6320.3140.125

                      
3/4"0.8240.5330.2130.8640.5860.2350.8360.5490.220

                      
1"1.0490.8640.3461.1010.9510.3801.0630.8870.355

                      
1-1/4"1.3801.4960.5981.4521.6570.6631.3941.5260.610

                      
1-1/2"1.6102.0360.8141.6822.2230.8891.6242.0710.828

                      
2"2.0673.3561.3422.1573.6561.4632.0833.4081.363

                      
2-1/2"2.7315.8582.3432.7936.1272.4512.4894.8661.946

                      
3"3.3568.8463.5383.4329.2473.6993.0907.4993.000

                      
3-1/2"3.83411.5454.6183.91712.0394.8163.57010.0104.004

                      
4"4.33414.7535.9014.36014.9295.9724.05012.8825.153

                    
                  

                

                

                  NEC Chapter 9, Table 1 — Fill Percentages:

                  1 conductor: 53% maximum fill

                  2 conductors: 31% maximum fill

                  3 or more conductors: 40% maximum fill


                  PVC Schedule 40 / Schedule 80 have slightly smaller IDs than RMC at the same trade size — use NEC Table 4 or the conduit manufacturer data for those types.
                

              

            

            

              
NEC Chapter 9, Table 5 — Dimensions of Insulated Conductors and Fixture Wires (THHN / THWN-2)

              

                
ⓘ Areas shown for THHN/THWN-2 insulation (the most common insulation type). For other insulation types (XHHW, THW, RHH/RHW-2, USE-2), see NEC Chapter 9 Table 5 — areas will differ. Use these areas when calculating conduit fill.

                

                  

                    
                      

                        Conductor Size
                        OD (inches)
                        Area (in²)
                        Circular Mils
                        Conductors per 1" EMT
                        Conductors per 1-1/4" EMT
                        Conductors per 2" EMT
                      

                    
                    
                      
14 AWG0.1110.00974,1103561138

                      
12 AWG0.1300.01336,5302645101

                      
10 AWG0.1640.021110,380162863

                      
8 AWG0.2160.036616,51091636

                      
6 AWG0.2540.050726,24061126

                      
4 AWG0.3240.082441,7404716

                      
3 AWG0.3520.097352,6203613

                      
2 AWG0.3840.115866,3602511

                      
1 AWG0.4460.156283,690238

                      
1/0 AWG0.4860.1855105,600137

                      
2/0 AWG0.5320.2223133,100126

                      
3/0 AWG0.5840.2679167,800125

                      
4/0 AWG0.6420.3237211,600114

                      
250 kcmil0.7110.3970250,000—13

                      
300 kcmil0.7660.4608300,000—12

                      
350 kcmil0.8170.5242350,000—12

                      
400 kcmil0.8640.5863400,000—12

                      
500 kcmil0.9490.7073500,000——1

                      
600 kcmil1.0510.8676600,000——1

                      
700 kcmil1.1220.9887700,000——1

                      
750 kcmil1.1561.0496750,000——1

                      
800 kcmil1.1901.1085800,000———

                      
1000 kcmil1.3051.34781,000,000———

                    
                  

                

                
ⓘ Conductors per conduit values are for 3 or more conductors (40% fill limit) in EMT. Verify using the Conduit Fill Calculator for mixed sizes or other conduit types. Based on NEC Annex C, Table C.1.

              

            

          

        


      

    


    
    

      

        
🔁 Unit Conversions

        
Common electrical unit conversions for field and engineering use.

        

          ℹ More Info — Unit Conversions
          

            Quickly convert between electrical and related engineering units. Select compatible unit categories (e.g., power → power).


            Supported categories:
  • Power: W, kW, MW, HP, BTU/h
  • Apparent/Reactive: VA, kVA, MVA, VAR, kVAR
  • Voltage: V, kV, mV  |  Current: A, mA, kA
  • Resistance: Ω, kΩ, MΩ  |  Capacitance: F, mF, µF, nF, pF
  • Inductance: H, mH, µH  |  Frequency: Hz, kHz, MHz
  • Length: ft, m, in
  • Illuminance: lux, foot-candles (fc)
  • Temperature: °C, °F, K
  • Energy: J, Wh, kWh, MWh, BTU

            Note: Cross-category conversions (e.g., W → A) require additional parameters not available here — use the Ohm's Law or Power calculators for those.
          

        

      

      


        

          
Unit Converter

          

            

              

            

            

              

                
                
              

              

                
                
              

            

            
            

            
ℹ Select compatible unit types (e.g., power → power). Mixing types (W → A) is not valid without additional parameters.

          

        


        

          
Quick Reference Conversions

          

            

              Power:

              1 HP = 746 W = 0.746 kW

              1 kW = 1.341 HP

              1 BTU/h = 0.29307 W

              1 kW = 3,412 BTU/h


              Electrical Prefixes:

              pico  (p) = 10⁻¹²

              nano  (n) = 10⁻⁹

              micro (µ) = 10⁻⁶

              milli (m) = 10⁻³

              kilo  (k) = 10³

              mega  (M) = 10⁶

              giga  (G) = 10⁹


              Length:

              1 ft = 0.3048 m  |  1 in = 25.4 mm


              Illuminance:

              1 fc = 10.764 lux  |  1 lux = 0.0929 fc


              Temperature:

              °F = (°C × 9/5) + 32  |  K = °C + 273.15


              Energy:

              1 kWh = 3,600,000 J = 3,412 BTU

              1 BTU = 1,055.06 J
            

          

        


      

    


    
    

      

        
🔢 Number-Base Converter

        
Convert among hexadecimal, decimal, octal, and binary. Typing in any base updates the others, with an 8 / 16 / 32 / 64-bit wrap and optional two’s-complement signed decimal.

        

          ℹ More Info — Number-Base Converter
          

            Every integer is a weighted sum of digits: n = Σ di · bi for base b ∈ {2, 8, 10, 16}. The bit-width selector wraps the unsigned value to 0 … 2w−1. When two’s-complement signed decimal is on, the same bit pattern is read with the high bit as sign: if n ≥ 2w−1 then the signed value is n − 2w.
            
    
              
  • Hex groups by nibble (one hex digit = 4 bits). Binary groups by 4 and 8.
    • 
              
  • Click a bit in the bit field to flip it. Bits that just changed are highlighted.
    • 
              
  • 64-bit values use exact integer arithmetic, so numbers past 253−1 stay precise.
    • 
            

          

        

      


      

        

          
Bases

          

            

              n = Σ di · bi  |  wrap at 2w  |  signed: n ≥ 2w−1 → n − 2w
            

            

              

                
                
              

              

                
                
              

            

            
8-bit unsigned range: 0 … 255

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            
n = 0

            

          

        


        

          
Place values & bit field

          

            
Place-value chips follow the field you last edited. The bit field is grouped by nibble and byte — click a bit to flip it. Newly changed bits glow.

            

            

          

        

      

    


    
    

      

        
🔵 Circular Mils (CM)

        
Convert between circular mils and wire diameter in inches.

        

          ℹ More Info — Circular Mils
          

            Circular Mils (CM) is the standard unit for conductor cross-sectional area used in NEC voltage drop calculations. It simplifies calculations by eliminating π.


            Formulas:
  • CM = (d × 1000)² where d is diameter in inches
  • d (in) = √CM / 1000

            Why CM? For a circle with diameter d mils (thousandths of an inch), the area in circular mils = d². This makes wire area comparisons and VD formulas much simpler than using π/4 × d².


            Key values: 14 AWG = 4,110 CM | 4/0 AWG = 211,600 CM | 500 kcmil = 500,000 CM
          

        

      

      


        

          
Circular Mils Calculator

          

            

              CM = (d × 1000)²    (d in inches)

              d = √CM / 1000
            

            

              

                
                
              

            

            

              

                

              

            

            
            
            

          

        


        

          
Circular Mils Reference

          

            

              Definition:

              1 circular mil = area of a circle with 1 mil (0.001 in) diameter


              Formula:

              CM = (d_mils)² = (d_in × 1000)²


              Why use CM?

              Eliminates π from wire area calculations.

              Standard unit in NEC for conductor sizing.


              Common wire areas:

              14 AWG = 4,110 CM

              12 AWG = 6,530 CM

              10 AWG = 10,380 CM

              4/0 AWG = 211,600 CM

              500 kcmil = 500,000 CM
            

          

        


      

    


    
    

      

        
🔋 UPS Sizing Calculator

        
Size an uninterruptible power supply: load kVA, battery Ah, and recommended UPS tier.

        

          ℹ More Info — UPS Sizing
          

            UPS Sizing determines the minimum UPS kVA rating and battery capacity for a given load and runtime requirement.


            
  • Load kVA: kVA = kW / PF — apparent power drawn from the UPS
  • Design kVA: Load kVA × 1.25 — adds 25% headroom for future growth and non-linear load derating
  • Battery Ah: Ah = (Load W / η) × (Runtime_min / 60) / V_DC — amp-hours required at the DC bus voltage

            Types: Double-conversion (online) offers full isolation; Line-interactive suits smaller loads. For life-safety (NFPA 111), verify Level 1 (≥10 sec) or Level 2 requirements.

            Li-ion batteries offer ~2× energy density vs VRLA but higher upfront cost.
          

        

      

      


        

          
UPS Parameters

          

            

              Load kVA = Load kW / PF

              Design kVA = Load kVA × 1.25 (25% headroom)

              Battery Ah = (Load W / η) × (Runtime min / 60) / VDC
            

            

              

              

            

            

              

              

            

            

              

            

            
            

          

        


        

          
UPS Sizing Reference

          

            

              Standard UPS kVA Tiers:

              500VA, 1kVA, 2kVA, 3kVA, 5kVA, 7.5kVA

              10kVA, 15kVA, 20kVA, 25kVA, 30kVA, 40kVA

              50kVA, 60kVA, 75kVA, 100kVA, 125kVA, 150kVA

              200kVA, 250kVA, 300kVA, 400kVA, 500kVA+


              Design Rules:

              • Add 25% capacity headroom for growth

              • Battery: (Load × Runtime) / (VDC × η)

              • Common DC bus: 48V, 120V, 240V, 480V

              • Double-conversion: 92–97% efficiency

              • Li-ion: ~2× energy density vs VRLA


              NFPA 111:

              Level 1 = 10-sec min | Level 2 = 0-sec min
            

            
ⓘ Add 25% capacity headroom for growth. Verify input kVA rating for non-linear loads (derating may be needed for harmonic content).

          

        


      

    


    
    

      

        
🔌 Generator Sizing

        
Size emergency/standby generators per IEEE 446 / NFPA 110 load inventory method.

        

          ℹ More Info — Generator Sizing
          

            Generator Sizing uses the load inventory method to total all connected loads with demand factors, then applies a safety margin.


            
  • Design kW: Σ(kW × qty × DF%) for each load category
  • Design kVA: Design kW / PF — size the generator to this kVA rating
  • Safety margin: IEEE 446 recommends ≥25% headroom for motor starting transients and future growth
  • Motor starting: Optional starter type scales starting kVA vs FLA kVA (DOL ≈ 6×, wye-delta ≈ 2×, autotransformer 65/80% taps ≈ 2.1× / 3.2×). Inventory check only — not a voltage-dip study.

            NFPA 110 Level 1: Transfer in ≤10 seconds; minimum 96-hour fuel supply. Used for life-safety loads (exit lighting, fire pumps, hospital critical branches).
          

        

      

      


        

          
Load Inventory

          

            

              Total kW = Σ(Load kW × Qty × Demand Factor)

              Total kVA = Total kW / PF

              Design kVA = Total kVA × (1 + Safety Margin)
            


            
► Motor Loads

            

              

              

              

            

            

              

                
                
              

            


            
► Lighting / Receptacle Loads

            

              

              

            


            
► HVAC Loads

            

              

              

            


            
► Other Critical Loads

            

              

              

              

            


            
            

          

        


        

          
Generator Sizing Reference

          

            

              Standard Sizes (kW):

              20, 25, 30, 40, 50, 60, 75, 100, 125

              150, 175, 200, 250, 300, 350, 400

              500, 600, 750, 1000, 1250, 1500+


              Typical Demand Factors:

              Motors: 50–80% (not all run simultaneously)

              HVAC: 60–80% (climate/season dependent)

              Lighting: 100% (on in emergency)

              Critical loads: 100% (full capacity)


              IEEE 446 Rules:

              Min 25% safety margin

              Motor starting kVA = 6–8× FLA

              Diesel: 0.07–0.09 gal/hr/kW full load


              NFPA 110 Level 1:

              Transfer in 10 sec | Run 96+ hrs on fuel
            

            
ⓘ Motor starting (locked-rotor) current can be 6–8× FLA. Verify the generator can handle the largest motor start without excessive voltage dip (<15%).

          

        


      

    


    
    

      

        
⚡ Hybrid Generator Calculator

        
Compare conventional vs battery-hybrid genset: fuel savings, CO₂ reduction, and payback period.

        

          ℹ More Info — Hybrid Generator
          

            Hybrid Generator systems combine a diesel engine with a battery energy storage system (BESS) to reduce fuel consumption, emissions, and engine wear.


            
  • How it works: The battery absorbs load transients and supplies power at low-demand periods, allowing the engine to run at higher, more efficient loading
  • Best use case: Generators operating at <30% average load — this is where fuel efficiency is worst for conventional sets
  • Fuel savings: Typically 15–40% depending on load profile and battery sizing
  • CO₂ reduction: Calculated using EPA factor of 22.4 lbs CO₂/gallon of diesel
  • Simple payback: Battery system cost / annual fuel savings in dollars

          

        

      

      


        

          
Operational Parameters

          

            

              Fuelconv = Rate × Load% × Hrs/Day × Days/Yr

              Fuelhybrid = Fuelconv × (1 − HybridGain)

              Payback = Battery Cost / Annual Fuel Savings ($)
            

            

              

              

            

            

              

              

            

            

              

              

            

            

              

              

            

            

              

            

            
            

          

        


        

          
Hybrid Genset Reference

          

            

              Typical Fuel Consumption (diesel):

              50 kW: ~3.5 gal/hr full load

              100 kW: ~7.0 gal/hr full load

              200 kW: ~14 gal/hr full load

              500 kW: ~35 gal/hr full load


              CO₂ Emissions (EPA):

              Diesel: ~22.4 lbs CO₂/gallon

              = 10.15 kg CO₂/gallon


              Hybrid Efficiency Gains:

              Load leveling: 15–25% fuel savings

              Peak shaving: 20–35% fuel savings

              Stop/start cycles: 25–40% savings


              Battery Sizing Rule:

              Storage ≥ 15–30 min of average load
            

            
ⓘ Hybrid gains are greatest at low average loads. Diesel generators run inefficiently below 30% rated load — batteries absorb/supply transient demand.

          

        


      

    


    
    

      

        
🚲 E-Bike Drivetrain & Build Tools

        
Torque/RPM conversion, sprocket sizing from performance targets, battery range planning, and a visual pack designer for series/parallel cell layouts.

      

      


        

          
Torque ↔ RPM from Power

          

            

              P(W) = T(N·m) × 2π × RPM / 60

              T(N·m) = P × 60 / (2π × RPM)

              RPM = P × 60 / (2π × T)
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

              
            

            
            

          

        


        

          
Sprocket Ratio Calculator

          

            

              Ratio = Driven Teeth / Drive Teeth

              Output RPM = Motor RPM / Ratio

              Output Torque = Motor Torque × Ratio × η
            

            

              

              

            

            

              

              

            

            

              

              

            

            
            

            
              E-bike drivetrain single line diagram
              Single-line drivetrain view
              
              
              
              
              
              
              Motor
              14T
              56T
              Ratio 4.00:1
              Output 800 rpm
              Wheel
            
          

        


        

          
Target Torque / RPM → Sprocket Size

          

            

              Ratio for target RPM = Motor RPM / Target Output RPM

              Ratio for target torque = Target Output Torque / (Motor Torque × η)

              Suggested driven teeth = Drive teeth × required ratio
            

            

              

              

            

            

              

              

            

            

              

              

            

            
            

          

        


        

          
E-Bike Range Planner

          

            

              Battery Wh = V × Ah

              Range (mi) = Battery Wh / Wh-per-mile

              Runtime (h) = Battery Wh / Average Power (W)
            

            

              

              

            

            

              

              

            

            
            

            
Real-world range varies with rider mass, grade, wind, tire pressure, assist level, and ambient temperature.

          

        


        

          
Battery Pack Designer

          

            

              Assign cells to series groups · match the parallel target in every group · Vpack = S × Vcell · Ahpack = P × Ahcell
            

            
Paint cells into color-coded series groups until each group hits the parallel target. Drag to paint, switch groups with the selector or keys 1–9, press E to erase, V to toggle 3D inspect.


            

              

                
                
              

              

                
                
              

              

                
                
              

            


            

              

              

              

              

            


            

              

              

              

              

              

            


            

              

              

                
                
              

              

                Tools
                

                  
                  
                  
                  
                

              

            


            
Paint cells into series groups until each group reaches the parallel target.

            

              
              
            

            

              
            

            
            

            
Planning layout only. Verify the cell datasheet, BMS, fusing, nickel strip or busbar ampacity, weld quality, insulation, enclosure clearances, and charger before assembling a lithium pack. For strip current estimates, use the 18650 pack planner.

          

        


      

    


    
    

      

        
⚡ NEC Circuit Calculator

        
Full NEC-compliant circuit sizing: conductor, OCPD, voltage drop, conduit fill, and EGC. NEC 310, 430, 440, 424, 240.4, 250.122.

        

          ℹ More Info — NEC Circuit Calculator
          

            NEC Circuit Calculator performs comprehensive circuit design per the National Electrical Code for a single circuit.


            What it calculates:
  • Design Current: Applies NEC multiplier (×1.25 for motors/lighting, ×1.0 for others)
  • Conductor Size: Minimum AWG/kcmil from NEC 310.16 75°C column, derated for ambient temp and conductor count
  • OCPD: Minimum and maximum breaker/fuse ratings per NEC 240.4 and 430.52
  • Voltage Drop: Calculated at design current for the given run length
  • Conduit: Minimum EMT trade size for the conductors at 40% fill
  • EGC: Equipment grounding conductor size per NEC 250.122

            Enter FLA directly or enter kW/kVA and PF to calculate FLA automatically.
          

        

      

      


        

          
Circuit Parameters

          

            

              Design I = FLA × NEC Multiplier  |  Conductor: NEC 310.16 75°C col per NEC 110.14(C)

              VD% = (K × I × L × Phasefactor) / (CM × V) × 100  —  K = 12.9 Cu | 21.2 Al

              Conduit: 40% fill, NEC Ch.9 Table 1  |  OCPD: NEC 240.4 & 430.52  |  EGC: NEC 250.122
            


            

              

                
                
              

              

                
                
              

              

                
                
              

            


            

              

                
                
              

              

                
                
              

              

                
                
              

            


            

              

                
                
              

              

                
                
              

              

                
                
              

            


            

              

                
                
              

              

                
                
              

              

                
                
              

            


            
            
            

          

        


        

          
NEC 310.16 — Ampacity Reference (75°C Column, Copper & Aluminum)

          

            
ⓘ 75°C column used per NEC 110.14(C). Conductors in conduit in free air, not more than 3 CCC, 30°C ambient. Apply temperature correction (NEC 310.15(B)(2)(a)) and conduit fill derating (NEC 310.15(B)(3)(a)) as needed.

            

              

                
                  

                    Size
                    Cu 75°C (A)
                    Al 75°C (A)
                    THHN Area (in²)
                    Circular Mils
                  

                
                
                  
14 AWG15—0.00974,110

                  
12 AWG20150.01336,530

                  
10 AWG30250.021110,380

                  
8 AWG50400.036616,510

                  
6 AWG65500.050726,240

                  
4 AWG85650.082441,740

                  
3 AWG100750.097352,620

                  
2 AWG115900.115866,360

                  
1 AWG1301000.156283,690

                  
1/0 AWG1501200.1855105,600

                  
2/0 AWG1751350.2223133,100

                  
3/0 AWG2001550.2660167,800

                  
4/0 AWG2301800.3237211,600

                  
250 kcmil2552050.3970250,000

                  
300 kcmil2852300.4608300,000

                  
350 kcmil3102500.5281350,000

                  
400 kcmil3352700.5958400,000

                  
500 kcmil3803100.7073500,000

                  
600 kcmil4203400.8676600,000

                  
700 kcmil4603750.9887700,000

                  
750 kcmil4753851.0496750,000

                  
800 kcmil4903951.1085800,000

                  
1000 kcmil5454451.34781,000,000

                
              

            

          

        


      

    


    
    

      

        
🗂️ Panel Schedule Load Analyzer

        
Photograph two views — the schedule/directory card and the breaker dead-front — then review on-device OCR. The breaker photo sizes the table. Manual entry still works without a photo.

        

          ℹ More Info — Panel Schedule Load Analyzer
          

            Photograph the printed circuit directory / schedule and the dead-front breaker row (cover on). Take or upload each view. Never open a live panel or touch anything inside to get this photo. On-device Tesseract.js is the default. Optional Enhance with AI on the tool page can draft a two-up directory from a rotated or glare-heavy photo — still a draft, not an AI electrician. The photos stay on this device unless you turn that toggle on and click Read both views.


            OCR is a draft. Correct every circuit row before using the estimates. Connected-breaker totals above the main rating are common and are not a demand-load calculation or a finding that the panel is unsafe. Informational estimate, not an electrical inspection. Any safety concern goes to a licensed electrician. Directory marking is NEC 408.4; a real load calculation is Article 220.
          

        

      

      

        

          
Panel Schedule Tool

          

            
This browser-only workspace OCRs a panel image, suggests load categories from descriptions, then lets you correct circuits and calculate estimated kVA, current, diversity, and available capacity.

            

              Open Panel Schedule Load Analyzer
            

          

        

      

    


    
    

      

        
📊 Panel Schedule Power Study

        
Extract panel schedule data from a photo, manually correct every field, then run a full demand/diversity/capacity study.

        

          ℹ More Info — Panel Schedule Power Study
          

            This browser-only tool uses on-device Tesseract.js by default. Optional Enhance with AI can draft a two-up directory from a messy photo. You can manually edit panel metadata and every circuit row, including breaker series, circuit class, and positions used, then print a clean panel schedule or save the reviewed data to JSON.
            


            The study view reports connected load, adjusted demand, coincident demand, calculated demand/diversity factors, and estimated room for expansion based on entered main rating and voltage.
          

        

      

      

        

          
Panel Power Study Tool

          

            
Start with OCR extraction from an image, manually correct any mistakes, then generate a printable clean schedule with a full panel demand/capacity study.

            

              Open Panel Schedule Power Study
            

          

        

      

    


    
    

      

        
🧪 Megger TDR Trace Analyzer

        
OCR a Megger TDR500 screen, identify open/short reflections, and recompute distance live when the technician adjusts VF.

        

          ℹ More Info — Megger TDR Trace Analyzer
          

            This analyzer reads the TDR LCD image with a vision model, extracts the on-screen Velocity Factor, Range, and Impedance, and labels the visible reflections. Phone photos are uprighted before upload. Upward / positive reflections generally indicate an open or higher-impedance discontinuity; downward / negative reflections generally indicate a short or lower-impedance discontinuity. Choosing a photo does not upload it — Analyze Trace does.
          

        

      

      

        

          
Upload TDR Screen

          

            
Privacy: choosing a TDR photo does not upload it. The image stays in this browser until you click Analyze Trace. Then it is sent upright to the Beckify vision API (or a HTTPS endpoint you configure). The photo is not saved after you leave or reset.

            

              
📷

              

                Drag and drop a Megger TDR500 photo here

                Choosing a file does not upload it. Analyze Trace sends an upright copy.
              

              
              
            


            

              
No image loaded yet.

              Megger TDR screen preview
            


            

              

                
                
No file selected

              

              

                
                
Ready for a TDR image.

              

            


            

              

                

              

              0%
            


            

              
              
            

          

        


        

          
Trace Controls

          

            

              Distance = base distance × VF ratio × range ratio

              Upward pulse = open | Downward pulse = short
            

            

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

            

            

              Detected settings:

              VF 0.66 | Range 1000 ft | Impedance 75 Ω

              Current VF 0.66 | Current Range 1000 ft | Current Impedance 75 Ω

              Distance scale 1.000×
            

            
          

        


        

          
Detected Fault Events

          

            

          

        


        

          
Feynman-Style Reflection Physics

          

            

              Think of the TDR pulse like a tiny fast-moving ball rolling down a cable. If the cable suddenly changes impedance, some of the pulse energy comes back. When the cable opens up or the impedance increases, the reflected wave rides upward. When the cable pinches down into a short or lower impedance, the reflected wave flips downward. The farther the mismatch sits from the launch point, the longer the round trip takes, so the analyzer converts that time delay into distance using the displayed VF.
            

            

              Use the VF slider when the cable spec is known better than the screen OCR. The fault distances re-scale instantly so the repair callout stays usable in the field.
            

          

        

      

    


    
    

      

        
Look Check

        
Take a camera photo of a person, then get lighting / framing / expression scores and a brief how-you-look summary. Entertainment only — not medical advice, not dating advice, and not a beauty contest.

        

          ℹ More Info — Look Check
          

            This is a bonus vision tool. It rates lighting, angle, expression, sharpness, and framing — not your worth.
            Anyone who appears under 18 is not rated. Cloud-only: there is no on-device Tesseract path.
            Taking or choosing a photo does not upload it. Analyze Look sends an upright copy to a HTTPS vision endpoint.
          

        

      

      

        

          
Take or choose a photo

          

            
Privacy: this tool is cloud-only. Taking or choosing a photo does not upload it. The image leaves this device only when you click Analyze Look. The photo is not saved after you leave or reset. Anyone who appears under 18 is not rated.

            
Entertainment only. Kind-honest notes about light, angle, and the shot — not medical, dating, or beauty authority. Do not use this on photos of children.

            

              
Optional custom HTTPS endpoint. A personal API key stays in this tab only (sessionStorage) and is never sent to Beckify. The Beckify proxy may forward the photo to OpenAI and/or Anthropic. Production can use the Beckify proxy from TDR_API_BASE_URL / beckify-api-base-url → /api/analyze-look.

              

                

                  
                  
                

                

                  
                  
                

              

              
No custom URL yet. Analyze Look uses the Beckify API on this site when available.

            

            

              
📷

              

                Take a photo, drop a file, or choose one

                Taking or choosing a photo does not upload it.
              

              
              
              

                
                
              

            


            

              
No image loaded yet.

              Look Check photo preview
            


            

              

                
                
No file selected

              

              

                
                
Ready for a camera photo or a file. Taking or choosing a photo does not upload it.

              

            


            

              

                

              

              0%
            


            

              
              
            

          

        


        

          
Verdict

          

            
            

              Kind-honest, not cruel. If the model declines, that is the right answer — especially for anyone who looks under 18.
            

          

        

      

    


    
    

      

        
New Glenn Runner

        
The launch arcade lives with the other games so this toolbox stays calculators and references.

      

      

        
Play on the games page

        

          
KID, CADET, and PAD RAT difficulty are still on the start screen. Scores stay in this browser.

          
Play New Glenn Runner

        

      

    



    
    

      

        
⚡ LSI Breaker Settings Visualizer

        
Enter Long-time, Short-time, and Instantaneous pickup/delay settings to visualize a simplified TCC curve on a log-log scale.

        

          ℹ More Info — LSI Breaker Settings
          

            LSI (Long-Short-Instantaneous) refers to the three protection regions of an electronic trip circuit breaker. Each region handles a different fault current level:


            
  • Long-time (L): Overload protection — trips slowly at currents above the pickup (e.g., 1.05–1.2×). Delay mimics motor starting/inrush tolerance.
  • Short-time (S): High overcurrent — trips faster at moderate fault levels. A time delay allows upstream coordination.
  • Instantaneous (I): Bolted fault protection — trips with no intentional delay at very high current (e.g., 8–15× rated). No delay for severe faults.

            Time-Current Curve (TCC): The log-log plot shows trip time vs. fault current. Proper coordination ensures the nearest upstream device trips first, minimizing outage scope.
          

        

      

      


        

          
Breaker Settings

          

            

              L = Long-time region  |  S = Short-time region  |  I = Instantaneous region
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

            

            
            

          

        


        

          
TCC Curve (Log-Log)

          

            
            

              ⓘ The curve shows the three protection regions: Long-time (L), Short-time (S), and Instantaneous (I). Axes are logarithmic. Vertical axis = time (s), Horizontal axis = current (A).
            

          

        


      

    


    
    

      

        
🔋 BESS Peak-Shave Optimizer

        
Estimate peak-shave battery capacity, then use linear programming to select the highest-priority loads that can be served by available battery and solar power.

        

          ℹ More Info — BESS Peak-Shave
          

            Battery Energy Storage System (BESS) Peak-Shaving uses available battery and solar power to serve the most critical loads during a grid outage or demand-charge event.


            
  • Objective: Maximize total priority score of loads served without exceeding available capacity
  • Method: Integer linear programming (ILP) via the javascript-lp-solver library — each load is either fully included or excluded (binary decision)
  • Priority 10: Must-serve loads (life-safety, critical process) — priority 1: low-importance loads
  • Typical use: Emergency power planning, microgrid operations, demand charge avoidance

            Enter available battery kW and solar kW, then assign each load a kW value and priority 1–10.
          

        

      

      


        

          
Peak-Shave Capacity Quick Sizer

          

            

              Required usable energy = (Facility Peak − Target Limit) × Peak Window Hours

              Installed capacity = Usable energy ÷ DoD
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            
            

          

        


        

          
Available Capacity

          

            

              Available Power = Battery Capacity + Solar Generation  |  Maximize: Σ Priority Score of selected loads  |  Subject to: Σ Load (kW) ≤ Available Power
            

            

              

                
                
              

              

                
                
              

            

          

        


        

          
Facility Loads

          

            

              

              

              

            

            

              

              

              

            

            

              

              

              

            

            

              

              

              

            

            

              

              

              

            

            

              

              

              

            

            
            

          

        


      

    


    
    

      

        
🔌 Transformer Tap-Changer Calculator

        
For 23 kV to 480 V transformers. Calculate the recommended tap setting to bring secondary voltage closer to 480 V nominal.

        

          ℹ More Info — Tap-Changer Calculator
          

            De-energized Tap Changers (DETC) adjust the transformer turns ratio to compensate for primary voltage variations and maintain correct secondary voltage.


            
  • Tap positions: Typically ±2.5% and ±5% on the primary winding — a total of 5 tap positions
  • Rule: If secondary voltage is LOW → use a lower (more negative) tap % to raise it. If HIGH → use a more positive tap.
  • Procedure: Measure actual secondary voltage under load, enter it along with the current tap position, and the tool recommends the tap closest to 480 V nominal

            Important: DETC must be changed de-energized. Consult the transformer nameplate and manufacturer instructions. Verify with a qualified electrician.
          

        

      

      


        

          
Tap Setting Calculator

          

            

              Turns Ratio = Vprimary / Vsecondary  |  Tap adjusts primary turns  | 
              Vsec,new = Vpri / (Nominal Ratio × (1 + Tap%/100))
            

            

              

                
                
              

              

                
                
              

            

            
            

          

        


        

          
Tap Setting Reference — 23 kV / 480 V

          

            

              Nominal Ratio: 23,000 / 480 = 47.917


              Tap positions (primary side):

              −5.0% tap → Lower primary turns → Higher secondary V

              −2.5% tap → Slightly higher secondary V

                0.0% tap → Nominal 480 V output

              +2.5% tap → Slightly lower secondary V

              +5.0% tap → Higher primary turns → Lower secondary V


              Rule: If secondary is low, use a lower (more negative) tap.
              If secondary is high, use a higher (more positive) tap.
            

            

              ⓘ Actual tap positions vary by transformer manufacturer. Always verify with nameplate data. Common de-energized tap changer (DETC) steps are ±2.5% and ±5%.
            

          

        


      

    


    
    

      

        
⚠ Hazardous Area Material Lookup (NEC 500)

        
Select a common launch pad / industrial substance to retrieve NEC 500 Class, Division, Group, and T-Code classification.

        

          ℹ More Info — NEC 500 Hazardous Area Classification
          

            NEC Article 500 classifies hazardous (classified) locations by the type of flammable material present and the likelihood of an ignitable concentration forming:


            
    
              
  • Class I: Flammable gases or vapors (e.g., hydrogen, RP-1, methane)
    • 
              
  • Class II: Combustible dusts (e.g., aluminum dust, grain dust)
    • 
              
  • Class III: Ignitable fibers/flyings (e.g., cotton lint)
    • 
              
  • Division 1: Ignitable concentrations exist under normal operating conditions
    • 
              
  • Division 2: Ignitable concentrations exist only under abnormal conditions (e.g., container failure)
    • 
              
  • Group A–G: Identifies the specific gas or dust family for selecting listed equipment
    • 
              
  • T-Code (T1–T6): Maximum surface temperature of listed equipment — must be below auto-ignition temperature of the substance
    • 
            

            Note: This tool provides typical classifications. Always verify with the current NEC edition, SDS/safety data sheets, and a licensed professional for final design.
          

        

      

      


        

          
Substance Lookup

          

            

              NEC 500 — Class / Division / Group / T-Code for common launch pad substances
            

            

              

                
                
              

            

            
            

          

        


        

          
NEC 500 Classification Reference

          

            

              Groups (Class I — Gases/Vapors):

              A: Acetylene

              B: Hydrogen & gases with >30% H₂

              C: Ethylene, propylene oxide, cyclopropane

              D: Propane, methane, butane, gasoline, RP-1


              T-Code Max Surface Temp:

              T1 = 450°C  |  T2 = 300°C  |  T3 = 200°C

              T4 = 135°C  |  T5 = 100°C  |  T6 = 85°C


              Division 1: Hazard present during normal ops

              Division 2: Hazard only if equipment fails
            

            
ⓘ NEC 505 (Zone 0/1/2) is an alternative classification method based on IEC standards. Some facilities use both systems. Always check AHJ requirements.

          

        


      

    


    
    

      

        
💡 Lighting Load & Voltage Drop Optimizer

        
Use linear programming to find the minimum-cost wire size that meets a voltage drop constraint for a lighting circuit.

        

          ℹ More Info — Lighting VD Optimizer
          

            This tool applies linear programming (LP) to select the most cost-effective conductor size for a lighting branch circuit while keeping voltage drop at or below the target (typically 3%).


            How it works:
    
              
  • Total Load: Luminaire count × watts/fixture gives total connected load in watts
    • 
              
  • Current: I = Total Watts / Supply Voltage (120 V assumed single-phase)
    • 
              
  • Objective: Minimize relative wire cost (smaller wire = lower cost)
    • 
              
  • Constraint: VD% = (2 × K × I × L) / (CM × V) × 100 ≤ target VD%
    • 
              
  • LP Solver: javascript-lp-solver (loaded from CDN) evaluates all standard AWG sizes and returns the smallest passing size
    • 
            

            NEC guidance: NEC 210.19 recommends ≤3% VD on branch circuits. Use 120 V for typical lighting; 277 V for fluorescent/LED in commercial.
          

        

      

      


        

          
Lighting Circuit Parameters

          

            

              I = (Fixtures × W/fixture) / Vsupply  |  VD% = (2KIL) / (CM × V) × 100

              LP: minimize cost index subject to VD% ≤ target
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            
            

          

        


        

          
Optimization Reference

          

            

              Voltage Drop (single-phase):

              VD = (2 × K × I × L) / CM

              VD% = VD / Vsupply × 100


              K constants:

              Copper: K = 12.9  |  Aluminum: K = 21.2


              Relative cost index (smaller = cheaper):

              14 AWG = 1.0  |  12 = 1.5  |  10 = 2.5

              8 = 4.0  |  6 = 6.0  |  4 = 9.5  |  2 = 14.5

              1 = 18.0  |  1/0 = 24  |  2/0 = 30


              NEC minimum: 14 AWG Cu for 15A branch circuits
            

            
ⓘ The LP solver selects the minimum-cost wire size that satisfies the VD constraint. If no standard size passes, it recommends the largest available size and flags the exceedance.

          

        


      

    


    
    

      

        
Load Calculation Worksheet

        
Row-based feeder / service worksheet. Connected VA, 220-style demand you can see and edit, phase amps, unbalance, and a spare/future adder. Design aid — not a PE service calculation. Old slugs building-load and this page are the same job.

        

          ℹ More Info — articles actually coded
          

            Only these NEC 220 pieces are implemented — nothing else is implied:
    
              
  • 220.42 — general lighting demand-factor table (dwelling / hospital / hotel / warehouse / all others). Factors are shown and each row can override them.
    • 
              
  • 220.52 — dwelling standard method: kitchen / small-appliance and receptacle rows ride with lighting through 220.42.
    • 
              
  • 220.53 — dwelling: 75% on four or more other / appliance rows.
    • 
              
  • 220.54 — dryer rows use the VA you enter (enter the larger of 5 kW or nameplate).
    • 
              
  • 220.82 — optional dwelling: 100% of the first 10 kVA of general loads + 40% of the remainder; HVAC stays at 100% of entered VA.
    • 
            

            Continuous-type rows apply a 125% sizing check so you can see it. Demand / diversity / growth from measured kVA still lives on Demand, Diversity & Growth — this is not a third peer calculator. Last sheet is stored in localStorage on this device. No customer workbook rows are preloaded.
          

        

      

      

        

          
Sheet settings

          

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

              

                
                
              

            

          

        


        

          
Load rows

          

            
Description, type, qty, VA / W / A, phase (A/B/C or 1Ø/3Ø), optional demand-factor override (enter 0.35 or 35). DF override wins over the coded 220 factor for that row.

            

            

              
              
              
              
            

          

        


        

          
Results and math

          

            

          

        


        

          
Optional VA/ft² seed (does not replace the sheet)

          

            
Adds lighting and receptacle rows from area and outlet count. Not a 220.12 / 220.14 service calculation by itself.

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            
            
            

          

        

      

    


    
    

      

        
📊 Demand, Diversity & Growth Planner

        
Turn connected load, measured demand, and an explicit growth assumption into transparent planning factors and a capacity forecast. For a row-based NEC 220 sheet, use the Load Calculation Worksheet — this is the same job family, not a third peer.

        

          ℹ Definitions and what to enter
          

            
    
              
  • Demand factor = maximum demand ÷ connected load. It describes how much of the installed load is expected to run together.
    • 
              
  • Diversity factor = sum of individual maximum demands ÷ maximum system demand. It is normally 1.00 or greater because loads peak at different times.
    • 
              
  • Coincidence factor = maximum system demand ÷ sum of individual maximum demands (the inverse of diversity).
    • 
              
  • Load factor = average demand ÷ maximum demand over the same interval. Use utility, BMS, or logger data for the interval you are studying.
    • 
              
  • Capacity utilization = maximum demand ÷ available capacity. It is a planning check, not an equipment rating or code calculation.
    • 
            

            If a value is unknown, leave it blank. The tool will show what can be calculated and point to the record that normally supplies it. It never invents an NEC demand factor; verify the applicable code method and equipment data before design or protection decisions.
          

        

      

      

        

          
Known load data

          

            

              

              

            

            

              

              

            

            

            

              

              

            

            
            

          

        

        

          
When information is missing

          

            
Demand factor = Peak ÷ Connected
Diversity factor = Σ individual peaks ÷ System peak
Load factor = Average ÷ Peak
Capacity margin = Capacity − Peak

            
Growth forecast: projected demand = today's peak × (1 + annual growth)years. Enter a documented growth case, then compare it with usable—not merely nameplate—capacity.

            
No connected load? Start with nameplates, schedules, and panel directories. Do not substitute breaker ratings for actual load without marking it as an estimate.

            
No peak demand? Export the highest matching-interval kW/kVA from a utility meter, BMS, power logger, or demand controller. Use the same interval for average demand.

            
No diversity data? Group loads by operating schedule, collect individual peaks, and use 1.00 until documented diversity exists. A number above 1.00 needs a defensible simultaneous-load basis.

          

        

      

    


    
    

      

        
🔓 Intrinsically Safe Loop Verifier

        
Verify entity parameter compatibility between a Zener barrier and a field device for use in classified (hazardous) areas.

        

          ℹ More Info — Intrinsically Safe Loops
          

            Intrinsic Safety (IS) limits electrical energy in a circuit to levels too low to ignite a hazardous atmosphere, even under fault conditions. Governed by ANSI/ISA-60079-11 and NEC Article 504.


            Entity Parameters:
    
              
  • Barrier Voc: Maximum open-circuit voltage the barrier can deliver to the field (V)
    • 
              
  • Barrier Isc: Maximum short-circuit current the barrier can deliver (mA)
    • 
              
  • Barrier Ca: Maximum allowable capacitance the barrier can drive (µF)
    • 
              
  • Barrier La: Maximum allowable inductance the barrier can drive (mH)
    • 
              
  • Device Vmax: Maximum voltage the field device can withstand (V)
    • 
              
  • Device Imax: Maximum current the field device can withstand (mA)
    • 
              
  • Device Ci: Internal capacitance of the field device (µF)
    • 
              
  • Device Li: Internal inductance of the field device (mH)
    • 
            

            Pass criteria (entity concept): Voc ≤ Vmax, Isc ≤ Imax, Ca ≥ Ci, La ≥ Li

            Note: Always verify with the manufacturer's control drawings and a certified IS assessor.
          

        

      

      


        

          
Barrier Parameters (Safe Area Side)

          

            

              Barrier output parameters — what the barrier can deliver to the field
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

          

        


        

          
Field Device Parameters (Hazardous Area Side)

          

            

              Field device entity parameters — what the device requires and contains
            

            

              

                
                
              

              

                
                
              

            

            

              

                
                
              

              

                
                
              

            

            
            

          

        


        

          
IS Entity Concept Reference

          

            

              PASS conditions (all must be true):

              Voc ≤ Vmax    (voltage compatibility)

              Isc ≤ Imax    (current compatibility)

              Ca ≥ Ci      (capacitance: barrier can absorb device C)

              La ≥ Li      (inductance: barrier can absorb device L)


              Cable parameters:

              Add cable C and L to field device C/L

              Cc (pF/ft) + Ci ≤ Ca

              Lc (µH/ft) + Li ≤ La


              Standards:

              ANSI/ISA-60079-11  |  NEC Art. 504

              IEC 60079-25 (IS systems)
            

            
ⓘ Cable capacitance and inductance must be included in the verification. Typical IS cable: 30–60 pF/ft (C), 0.2–0.5 µH/ft (L). Consult the barrier and device control drawings.

          

        


      

    


    
    

      

        
🛡 IP Rating Chart (IEC 60529)

        
Ingress Protection ratings for electrical enclosures — solid particle and liquid protection.

        

          ℹ More Info — IP Ratings
          

            IP (Ingress Protection) ratings per IEC 60529 indicate protection against solid particles (first digit) and liquids (second digit).


            Format: IP XY where X = solid protection (0–6), Y = liquid protection (0–9K).

            Common ratings for facilities: IP54 (dust-protected, splash), IP65 (dust-tight, water jets), IP67 (immersion), IP68 (continuous immersion), IP69K (high-pressure steam cleaning).
          

        

      

      


        
        
Source: IEC 60529 — IP XY, first digit solid-particle protection (0–6), second digit liquid protection (0–9K).



          
First Digit — Solid Particle Protection

          

            

              

                
DigitProtection LevelDescription

                
                  
0NoneNo protection

                  
1>50 mmLarge body parts (back of hand)

                  
2>12.5 mmFingers or similar objects

                  
3>2.5 mmTools, thick wires

                  
4>1 mmMost wires, screws, ants

                  
5Dust-ProtectedDust ingress limited (no harmful deposit)

                  
6Dust-TightNo dust ingress whatsoever

                
              

            

          

        


        

          
Second Digit — Liquid Ingress Protection

          

            

              

                
DigitProtection LevelDescription

                
                  
0NoneNo protection

                  
1Dripping waterVertical drips (1 mm/min)

                  
2Dripping (15°)Drips up to 15° tilt

                  
3Spraying waterUp to 60° from vertical

                  
4SplashingAll directions

                  
5Water jets6.3 mm nozzle, any direction

                  
6Powerful jets12.5 mm nozzle, any direction

                  
7Immersion (1 m)Up to 1 m depth, 30 min

                  
8Immersion (deep)Manufacturer specified depth >1 m

                  
9KHigh-pressure steamClose-range high-pressure/high-temp jets

                
              

            

          

        


        

          
Common IP Ratings in Facilities

          

            

              

                
IP RatingTypical ApplicationNEMA Equiv (approx)

                
                  
IP20Indoor, clean environments (panelboards)NEMA 1

                  
IP44Outdoor, splash-protectedNEMA 3

                  
IP54Dusty/splash environments (HVAC)NEMA 3S

                  
IP55General outdoor (motors, drives)NEMA 3R (close)

                  
IP65Dust-tight + water jets (washdown)NEMA 4 (close)

                  
IP66Heavy water jets (outdoor panels)NEMA 4

                  
IP67Temporary immersion (portable equip)NEMA 6

                  
IP68Continuous submersionNEMA 6P

                  
IP69KHigh-pressure steam cleaning (food mfg)—

                
              

            

            
NEMA and IP ratings are not directly equivalent. Verify both standards when specifying equipment for regulated environments (food processing, pharma, hazardous locations).

          

        


      

    


    
    

      

        
🗄 NEMA Enclosure Types (NEMA 250)

        
Enclosure ratings for electrical equipment — environmental and safety protection levels.

        

          ℹ More Info — NEMA Enclosures
          

            NEMA 250 defines enclosure types for electrical equipment. Types are selected based on environment (indoor/outdoor), hazards (dust, water, corrosion), and agency requirements.


            Types 7, 9 are for hazardous locations (NEC Articles 500–501). Type 4X is the most common for corrosive/washdown environments. Type 12 is the indoor industrial workhorse.
          

        

      

      


        

          
NEMA Enclosure Type Reference

          

            

              

                
                  

                    Type
                    Indoor/ Outdoor
                    Description
                    Corrosion Resist.
                    IP Equiv (approx)
                  

                
                
                  
1IndoorGeneral purpose — dirt, light dust, indirect contactNoIP20

                  
2IndoorType 1 + drip-proof (limited condensate)NoIP31

                  
3OutdoorRainproof, sleet-resistant, windblown dustNoIP54

                  
3ROutdoorRain/sleet resistant (no dust protection)NoIP32

                  
3SOutdoorType 3 + external ice formation on mechanismNoIP54

                  
3XOutdoorType 3 + corrosion resistantYesIP54

                  
4In/OutWatertight — hosedown, windblown rain/dust/sleetNoIP66

                  
4XIn/OutType 4 + corrosion resistant (SS/FRP)YesIP66

                  
5IndoorDust-tight (lint, fibers), drip-proofNoIP52

                  
6In/OutSubmersible — temporary, occasionalNoIP67

                  
6PIn/OutSubmersible — prolonged depthYesIP68

                  
7IndoorClass I, Div 1, Groups A–D (explosion-proof)No—

                  
9IndoorClass II, Div 1, Groups E, F, G (dust-ignitionproof)No—

                  
12IndoorIndustrial — dust, dripping non-corrosive liquidsNoIP54

                  
12KIndoorType 12 with knockoutsNoIP54

                  
13IndoorOil-tight, dust-tight — oil mist, lint, seepageNoIP54

                
              

            

            
NEMA types 7 and 9 are for hazardous locations per NEC 500. For corrosive environments (chemical plants, coastal), specify Type 3X or 4X. Type 4X in 316 stainless steel is standard for food/pharma.

          

        


        

          
Quick Selection Guide

          

            

              Office / Control Room: Type 1 or 12

              Industrial Plant (dry): Type 12 or 4

              Outdoor (non-corrosive): Type 3R or 4

              Outdoor (corrosive/coastal): Type 3X or 4X

              Washdown / Food Processing: Type 4X (SS)

              Wet Locations (pools, car wash): Type 4 or 4X

              Explosion-proof (Class I gas): Type 7

              Dust-ignitionproof (Class II): Type 9

              Submersible (pump stations): Type 6 or 6P

              High-pressure wash (IP69K equiv): Verify mfr rating — NEMA does not define IP69K
            

            
Always verify the enclosure rating against the actual environmental conditions and applicable codes (NEC, OSHA, FDA, etc.). IP and NEMA ratings test different characteristics and are not fully interchangeable.

          

        


      

    

    
    

      

        
NEMA Wiring Configurations & Color Codes

        
Receptacle-face SVG diagrams and US color notes. Neutral and grounding colors cite the NEC. Hot colors are industry convention unless a specific article says otherwise.

        

          ℹ More Info — Code vs convention
          

            Diagrams are the receptacle face (looking at the wall or device), not the plug. Confirm the marking on the device in the field.


            NEC 200.6 requires a grounded (neutral) conductor to be identified white or gray. NEC 250.119 requires an equipment grounding conductor to be green, green with a yellow stripe, or bare. Those two rules are code.


            Ungrounded (hot) colors in the tables below are industry convention, not an NEC requirement. Do not treat the whole table as code-mandated. The exception is the high-leg: NEC 110.15 requires the high-leg of a 4-wire delta to be identified orange (or by other effective means).
          

        

      

      
Field-scan: tap a configuration once. Diagrams are large on purpose for one-handed phone use. This page is a visual reference, not a calculator.

      

        

          
Common NEMA configurations

          

            
            
            

          

        

        

          
Receptacle face

          

            

            

          

        

        

          
Which blade is which conductor

          

        

      

      

        
US conductor color notes

        
White/gray and green are code. Hot colors are convention except the 110.15 high-leg.

      

      

    


    
    

      

        
Torque Lookup

        
Panel-shop and field lookup: typical terminal / lug tightening torque from published UL 486A-B tables, plus a SAE / metric fastener chart. Manufacturer marking on the device wins. Not a calibrated torque-tool substitute.

        

          ℹ More Info — sources and limits
          

            Terminal / lug: typical values vs conductor size and screw type reprinted from UL 486A-B (the same tables appear as NEC Informative Annex I). Column B–style pocket-ref numbers when the lug is unmarked. in·lb and N·m.


            Fastener: typical handbook SAE grade / metric class vs size, dry vs lubricated (lubed shown at 75% of dry). A lookup, not a clamp-load study or FEA.


            If the device, lug, or joint spec is marked, use that value.
          

        

      

      

        

          
          
        

        

          

            

              
Look up a conductor

              

                

                  

                    
                    
                    
                      
                      
                      
                      
                      
                      
                      
                      
                      
                    
                  

                  

                    
                    
                  

                

                

                  
                  
                

                

                
Cite UL 486A-B. Manufacturer marking on the device wins. These are typical when the lug is unmarked.

              

            

            

              
UL 486A-B typical table (search)

              

                

                  

                    
                    
                  

                

                

                
Narrow slot = #10 and larger, slot ≤ 0.047 in wide and ≤ 0.25 in long. Wide slot = larger slot. Hex / split-bolt / other follow the published typical columns.

              

            

            

              
Hex socket by size (UL 486A-B connecting hardware)

              

                

              

            

          

        

        

          

            

              
SAE and metric typicals

              

                
                
Typical handbook values. Not a calibrated torque-tool substitute and not a FEA or clamp-load calculation.

                
SAE coarse (ft·lb)

                

                
Metric coarse (N·m)

                

              

            

          

        

      

    


    
    

      

        
Wire colors (NEC / UL 508A)

        
Phone-friendly color reference. CODE rows cite NEC identification rules. Hot colors are industry convention unless a row says otherwise. UL 508A is industrial control panel practice — not NEC-mandated hot colors, and not a substitute for the standard.

        

          ℹ More Info — code vs convention
          

            CODE: white / gray grounded (200.6); green / green-yellow / bare EGC (250.119); orange high-leg (110.15); 210.5(C) identification of ungrounded conductors where more than one nominal voltage system is present.


            CONVENTION, not code: black / red / blue on 208Y/120; brown / orange / yellow on 480Y/277; and other “typical” hot colors. The NEC does not assign those hot colors.
          

        

      

      

        

          
          
        

        

          

            

              
Articles actually cited

              

            

            

              
System color charts

              

            

          

        

        

          

            

              
UL 508A industrial control panel — internal wiring

              

                
UL 508A 3rd Edition, sections 66.5 (power circuits) and 66.9 (control circuits), including the April 2020 color-coding revision. Yellow / orange foreign-voltage identification is a safety callout: that circuit may be live when the disconnect is off. This is not NEC-mandated hot colors and is not a substitute for the standard.

                

              

            

          

        

      

    


    
    

      

        
💡 Photometrics Calculator

        
Illuminance, lux/foot-candle converter, inverse square law, and lighting level references.

        

          ℹ More Info — Photometrics
          

            Zonal Cavity / Lumen Method: FC = (Lumens × Fixtures × CU × MF) / Area

            CU = Coefficient of Utilization (0.5–0.75 typical), MF = Maintenance Factor / LLF (0.6–0.9)


            Inverse Square Law: E = I / d² (candela, meters) or E = I / d² × 10.76 (foot-candles)


            Units: 1 foot-candle (fc) = 10.764 lux (lx)  |  1 lux = 1 lm/m²
          

        

      


      

        

          
          
          
        


        

          

            

              
Lumen / Zonal Cavity Method

              

                
FC = (Lumens × Fixtures × CU × MF) / Area_ft²
Lux = FC × 10.764

                

                  

                  

                

                

                  

                  

                

                

                  

                

                
                

              

            

            

              
Lux ↔ Foot-candle Converter

              

                
1 fc = 10.764 lux  |  1 lux = 0.09290 fc

                

                  

                  

                    
                    
                  

                

                
                

              

            

          

        


        

          

            

              
Inverse Square Law

              

                
E = I / d²
E in lux (cd, meters) or fc (cd, feet)
Double the distance → ¼ the illuminance

                

                  

                  

                

                

                  

                    
                    
                  

                

                
                

              

            

            

              
Inverse Square Law Reference

              

                

                  Point Source:

                  E (lux) = I (cd) / d² (m²)

                  E (fc)  = I (cd) / d² (ft²)


                  Cosine Law (oblique angles):

                  E = (I × cos θ) / d²


                  Typical Luminous Intensity:

                  LED retrofit lamp: ~800 cd

                  High-bay fixture: 5,000–30,000 cd

                  HID street lamp: 10,000–50,000 cd
                

              

            

          

        


        

          

            

              
Recommended Illuminance Levels (IES/IESNA)

              

                

                  

                    
Space / TaskFoot-candles (fc)Lux (lx)Notes

                    
                      
Parking Lot (open)1–5 fc10–50 lxIES RP-20

                      
Building Exterior2–5 fc20–50 lxFacade lighting

                      
Warehouse (bulk storage)10–30 fc100–300 lxIES RP-29

                      
Warehouse (order picking)30–50 fc300–500 lxTask-level

                      
Corridor / Hallway10–20 fc100–200 lxIES HB-10

                      
Open Office30–50 fc300–500 lxIECC / ASHRAE 90.1

                      
Private Office / Lab50 fc500 lxTask area standard

                      
Conference Room30–50 fc300–500 lx

                      
Classroom30–50 fc300–500 lxIES RP-3

                      
Manufacturing (general)30–50 fc300–500 lxIES RP-7

                      
Manufacturing (precision)50–100 fc500–1000 lxFine assembly

                      
Electrical Room / MCC50 fc500 lxNEC 110.26(D)

                      
Stairway / Egress10 fc100 lxIBC / Life Safety

                      
Emergency Egress Min.1 fc avg / 0.1 fc min10/1 lxNFPA 101 7.9

                    
                  

                

                
Values are typical design targets. Verify with applicable codes (IES, IECC, OSHA 29 CFR 1926, local authority having jurisdiction). AGI32 or DIALux for detailed photometric modeling.

              

            

          

        


      

    


    
    

      

        
〜 Harmonics Tool

        
Identify harmonic sources, compute %THD, and reference IEEE 519 limits.

        

          ℹ More Info — Harmonics
          

            Harmonics are voltages or currents at integer multiples of the fundamental (60 Hz). Non-linear loads generate harmonic currents that cause overheating, neutral overloads, resonance, and equipment malfunction.


            THD (Total Harmonic Distortion): %THD = (√Σh²ₙ / I₁) × 100, where hₙ = harmonic component magnitudes


            IEEE 519-2022: Sets harmonic current limits based on ISC/IL ratio at the point of common coupling (PCC).
          

        

      


      

        

          
          
          
        


        

          

            

              
Harmonic Source Identifier

              

                

                  

                    
                    
                  

                

                
                

              

            

            

              
Harmonic Order Reference

              

                

                  

                    
Order (h)Freq (60 Hz base)TypePrimary Source

                    
                      
2nd120 HzEvenArc furnaces, asymmetric loads

                      
3rd180 HzTriplen (Zero-seq)SMPS, fluorescent, single-phase NL loads

                      
4th240 HzEvenArc furnaces (minor)

                      
5th300 HzNegative-seqVFD 6-pulse, most 3Ø NL loads

                      
6th360 HzEvenRarely significant

                      
7th420 HzPositive-seqVFD 6-pulse

                      
9th540 HzTriplen (Zero-seq)SMPS, UPS, saturation

                      
11th660 HzNegative-seqVFD 6-pulse, 12-pulse

                      
13th780 HzPositive-seqVFD 6-pulse, 12-pulse

                      
23rd, 25th1380/1500 HzNeg/Pos-seq12-pulse drives only

                    
                  

                

              

            

          

        


        

          

            

              
%THD Calculator

              

                
%THD = (√(I₂²+I₃²+I₄²+…) / I₁) × 100

                

                  

                  

                

                

                  

                  

                

                

                  

                  

                

                

                  

                  

                

                
Enter harmonic magnitudes in Amps. Or enter as percentage of I₁ — use the same unit for all fields.

                
                

              

            

            

              
Filter Recommendations

              

                

                  Passive Tuned Filter:

                  Targets a specific harmonic (e.g. 5th)

                  Low cost; risk of resonance with system

                  Typical for VFD 6-pulse (5th, 7th)


                  Active Harmonic Filter (AHF):

                  Broadband correction, real-time injection

                  Reduces THD to <5%; no resonance risk

                  Best for SMPS-heavy loads (datacenters)


                  12-Pulse / 18-Pulse Drive:

                  Phase-shifting transformer cancels 5th, 7th

                  Large drives (>100 HP) with predictable loads


                  3rd Harmonic Blocking Filter:

                  Zero-sequence blocking transformer (ZSB)

                  Prevents triplen harmonic neutral overloads
                

              

            

          

        


        

          

            

              
IEEE 519-2022 Current Harmonic Limits (at PCC)

              

                

                  

                    
                      

                        I_SC / I_L Ratio
                        h < 11
                        11 ≤ h < 17
                        17 ≤ h < 23
                        23 ≤ h < 35
                        TDD (%)
                      

                    
                    
                      
<204.0%2.0%1.5%0.6%5.0%

                      
20–507.0%3.5%2.5%1.0%8.0%

                      
50–10010.0%4.5%4.0%1.5%12.0%

                      
100–100012.0%5.5%5.0%2.0%15.0%

                      
>100015.0%7.0%6.0%2.5%20.0%

                    
                  

                

                
I_SC = available short-circuit current at PCC. I_L = maximum demand load current (fundamental). TDD = Total Demand Distortion (referenced to I_L, not I₁). Even harmonics limited to 25% of odd harmonic limits. DC offset not permitted.

              

            

            

              
Harmonic Effects Reference

              

                

                  Transformers:

                  Increased eddy current losses → K-factor rating needed

                  K-4: general NL loads  |  K-13: VFD-heavy  |  K-20: SMPS


                  Neutral Conductors:

                  Triplens (3rd, 9th, 15th) are zero-sequence — add in neutral

                  3Ø 4-wire: neutral may carry 173% of phase current

                  Solution: double neutral conductor or 4-wire feeder


                  Capacitor Banks (PFC):

                  Capacitors amplify harmonics at resonant frequency

                  f_res = f₁ × √(kVA_SC / kVAR_cap) — avoid tuning to 5th/7th


                  Motors:

                  Negative-sequence (5th) produces counter-torque → heating

                  Use NEMA MG1 derating for high-THD supplies
                

              

            

          

        


      

    




    
    

      

        
🗂 Saved Jobs & Settings

        
Calculation runs you have saved, grouped by job. Everything is stored on this device and works offline.

        

          ℹ More Info — How saving works
          

            Every calculator has a 🗂 Save to job button beside its results. Saving records the inputs, the results, and the calculator's own deep link, so reopening a run puts the calculator back exactly as it was rather than showing a static copy of the numbers.


            Where it lives. Saved work is written to this browser's IndexedDB. There is no account and nothing is uploaded — which also means saved jobs do not follow you to another browser or another device, and clearing site data deletes them. Export a PDF submittal for anything you need to keep off-device.


            Offline. Because storage is local, saving, loading and deleting all work with no network connection.
          

        

      


      


        

          
Saved Jobs

          

            
            

            

          

        


        

          
Preferences

          

            

              

                
                
              

            

            

              The calculators work in the units the NEC tables are published in, so this setting converts
              lengths and areas for display and leaves the code tables themselves alone.
            

          

        


        

          
Game Statistics