Phase Academy Interactive Power Systems Lab

Panelboard & Feeder Load Calculation

NEC ART. 220 · ART. 430
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For education only · Verify against codes NEC adoption and amendments vary by jurisdiction. Section numbers here are paraphrased navigation aids, not code text — verify every result against the adopted NEC edition, your AHJ, and qualified engineering judgment. This tool does not certify permit-readiness.
Connected
0 kVA
All nameplates (present)
Demand
0 kVA
After demand factors
Demand Factor
—
Demand ÷ Connected
Sizing Basis
0 kVA
Demand + continuous
Sizing Current
0 A
At system L-L V
Min Std Rating
—
Candidate only — not final
Connected vs. Demand by Category
Connected Demand (reduced) Demand > connected (adder)
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Add loads
Demand Load Composition
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Add loads
Sizing Current vs. Bus
0 A of — A bus
Set bus rating for utilization check
Demand vs. Connected (per category)

Light blue = connected nameplate. Navy = demand after factors. Amber = categories where demand exceeds connected (e.g., motor 125% adder).

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Add loads

Step-by-Step Calculation Trace

Each category's demand path, then feeder totals, continuous sizing, and current. Values in kVA unless noted; motor steps show amperes.

Add loads to generate a trace.

Method & Assumptions

    Connected
    0 kVA
    Demand
    0 kVA
    Demand Factor
    —
    Demand Current
    0 A
    Sizing Current
    0 A

    Demand by Category

    CategoryRef (paraphrased)ConnectedDemandDFΔ vs conn.

    Δ: green = reduction (savings); amber = increase/adder (demand > connected).

    Sizing & OCPD

    Add loads to see sizing.

    🎯 Design Challenge

    Estimate the sizing parameters for the loads you entered, then check against the tool's calculation. This is a learning aid — not a substitute for a stamped calculation.

    How Scoring Works

    Demand within ±5% and sizing current within ±10% earn full marks. The ampere-rating answer should equal the minimum standard rating ≥ the sizing current (240.6(A)). Real conductor/OCPD selection also depends on ampacity, terminations, corrections, listing, and the next-size rule — not scored here.

    NEC References 2023

    Paraphrased section pointers for the selected edition. Not code text — consult the adopted NEC and AHJ.

    Edition Notes

    Engine Self-Test

    Deterministic unit tests run against the pure calculation engine (same engine the UI uses). Results also print to the browser console.

    What This Tool Does — and Does Not Do

    This tool estimates feeder/panelboard demand load (Article 220 standard method, with Article 430 for motors) and a sizing basis that adds the continuous-load factor. It is a calculation aid and teaching tool.

    Outside or only partially inside this tool (you must handle these separately): conductor ampacity & sizing, voltage drop, SCCR/AIC and available fault current, selective coordination, terminal temperature ratings, ambient/bundling corrections, neutral (grounded-conductor) sizing, grounding/bonding, motor branch-circuit SCGF protection, hermetic-compressor (Art. 440) largest-motor interaction, dwelling range/dryer methods (220.55/220.54), optional/standby methods, local amendments, and AHJ interpretation.
    Demand kVA (what the load is estimated to draw) is reported separately from Sizing kVA/current (what conductors/OCPD are sized to). Do not confuse them. All inputs are apparent power in kVA — kW ≈ kVA only at unity power factor.

    Corrected Concepts

    • Lighting is not "10 kVA/50%". General-lighting demand factors are occupancy-specific (dwelling, hospital, hotel, warehouse, or "all others" at 100%).
    • Receptacle 10 kVA/50% applies to non-dwelling receptacle loads only, not to lighting or dwelling receptacles.
    • 75% fixed-appliance factor is dwelling-only, needs 4+ qualifying fastened-in-place appliances, and excludes ranges, dryers, space heating, and A/C.
    • Kitchen demand is never less than the two largest pieces of equipment.
    • Motors increase the load. 125% of the largest FLC is an adder, not a reduction; use table FLC, not nameplate.
    • Noncoincident heating vs cooling: include only the larger.
    • A/C & heat-pump compressors are motors (Art. 440). On a feeder that also carries other motors they belong in the 430.24 largest-motor determination — this tool does not do that and warns instead.

    Common Mistakes This Tool Guards Against

    • Applying a universal lighting reduction.
    • Using dwelling appliance factors on commercial feeders.
    • Treating nameplate kVA as motor FLC without a warning.
    • Double-counting heating and cooling.
    • Trusting feeder sizing on mixed HVAC + motor feeders without an Art. 440 check.
    • Calling a design "compliant" from bus utilization alone.
    • Reporting demand > connected as green "savings".
    Disclaimer: Educational and calculation-support tool only. Not a substitute for engineering judgment, a licensed professional's stamped calculation, plan review, or AHJ interpretation. The NEC is a minimum standard; local amendments may apply. Verify against the adopted edition and coordinate with the AHJ. Section numbers are paraphrased pointers, not quoted code.