Tap a tile from the legend below, then tap the board slot it belongs in (or drag it, if you'd rather). Assemble a transformer, main breaker, feeder, and panel loads — the diagram updates live as you build, and the right combination is recognized as a real assembly class, the same way the BOM Generator recognizes a part's components in reverse.
This is a learning tool, not a substitute for a licensed engineer's short-circuit, coordination, or code-compliance study. It assumes a single-voltage radial system, an infinite utility source, and ignores feeder impedance in the fault-current estimate — the same simplifications used by the Fault Current Estimate calculator.
Place a transformer, main OCPD, conductor, and length tile, then click “Check My Design”.
No. The sandbox uses simplified, infinite-source, single-voltage-level formulas — the same methods used in the Engineering Calculators page — for learning and first-pass checks only. Always use a licensed engineer's full study for actual design or code compliance sign-off.
Standard K-factor voltage drop, kVA/FLA sizing, and infinite-source fault current formulas, plus commonly published NEC Table 310.16 75°C copper/aluminum ampacities. The same formulas power VOLTFIELD's Engineering Calculators page.
Yes — it's free, runs entirely in your browser, and needs no signup. Nothing you enter is sent anywhere.
Seven more calculators for cable sizing, BESS, solar strings, PF correction, and unit conversion.