Commercial Service Load Calculations Flashcards

What is the total calculated load for 50 duplex receptacle outlets in a commercial space before applying demand factors?

Answer: 9,000 VA

Each duplex outlet counts as one yoke at 180 VA, so 50 × 180 VA = 9,000 VA per NEC 220.14(I).

Under what condition does NEC 220.87 permit the optional method for determining commercial service capacity?

Answer: Existing service or feeder capacity evaluation using measured demand data

NEC 220.87 is specifically intended for evaluating existing service or feeder capacity using actual demand measurements over time.

A commercial service calculation yields 285,000 VA on a 120/208V, 3-phase system. What minimum service ampacity is required?

Answer: 800A

285,000 VA ÷ (208V × 1.732) ≈ 791A, requiring the next standard size of 800A.

What must an electrical inspector verify about continuous loads in a submitted commercial service calculation?

Answer: Continuous loads are included at 125% of full-load current per NEC 215.2

NEC 215.2(A)(1) requires continuous loads to be calculated at 125% of their full-load current when sizing feeders and services.

When sizing the neutral conductor for a commercial service, which load type carries no neutral current and does not require neutral conductor capacity?

Answer: Balanced 3-phase motor loads

Balanced 3-phase loads such as motors produce no neutral current because the phases cancel each other out.

A commercial warehouse has 200,000 VA of general lighting load. What is the demand load after applying NEC Table 220.42 factors for warehouses?

Answer: 125,000 VA

For 'all other' occupancies: first 50,000 VA × 100% = 50,000 VA, plus 150,000 VA × 50% = 75,000 VA, totaling 125,000 VA.

Per NEC Table 220.55, what is the maximum demand used when a commercial establishment has a single household cooking unit rated 12 kW?

Answer: 8 kW

NEC Table 220.55 permits a maximum demand of 8 kW for a single range rated 12 kW or less.