IEC Service and Load Calculations 5

Question 1

A 3-phase, 4-wire, 208Y/120V commercial service supplies 15 kW of lighting. Using NEC 220.12 at 3.5 VA/sq ft, the building is approximately how many square feet?

Accepted Answer

4,286 sq ft

Answer

15,000 VA ÷ 3.5 VA/sq ft ≈ 4,286 sq ft for the office/commercial occupancy.

Question 2

Per NEC 230.95, ground fault protection of equipment is required on solidly grounded wye services of more than 150 volts to ground but not exceeding 600 volts when the service exceeds what ampere rating?

Accepted Answer

1,000 amperes

Answer

NEC 230.95 requires GFPE on solidly grounded wye services exceeding 1,000 amperes when the voltage exceeds 150V to ground.

Question 3

What is the calculated load for a 4,000 sq ft commercial office building at 3.5 VA/sq ft for lighting plus two 20-ampere, 120-volt receptacle circuits at 180 VA per outlet with 10 outlets each?

Accepted Answer

17,600 VA

Answer

Lighting: 4,000 × 3.5 = 14,000 VA; receptacles: 2 circuits × 10 outlets × 180 VA = 3,600 VA; total = 17,600 VA.

Question 4

Under NEC 220.82 optional method for a one-family dwelling, electric heating and air conditioning loads at 100% are compared and only the larger is included. This load is then combined with what other loads?

Accepted Answer

First 10 kVA at 100% plus remaining general load at 40%

Answer

NEC 220.82(B) requires the first 10 kVA of all other loads at 100% and the remainder at 40%, then adds the larger of heating or cooling at 100%.

Question 5

A single-phase 120/240V residential service has a calculated load of 23,500 VA. What minimum standard service size in amperes is required?

Accepted Answer

150 amperes

Answer

23,500 VA ÷ 240 V = 97.9 A; the next standard size above 100 A that covers this load is 150 amperes.

IEC - Independent Electrical Contractors Practice Test

IEC - Independent Electrical Contractors Practice Test

IEC Service and Load Calculations 5