Journeyman Electrician Exam (NEC)Equipment and DevicesHard
A journeyman electrician is calculating the minimum required feeder size for a commercial kitchen with multiple 120-volt, 20-ampere general-purpose receptacle branch circuits. According to the National Electrical Code, what is the demand factor that can be applied to the portion of the receptacle load exceeding 10 kVA for a non-dwelling unit?
- A100%
- B80%
- C75%
- D50%
Show answer & explanationAnswer & explanation
Correct answer: D. 50%
According to NEC 220.42(B) for non-dwelling units, the demand factor for general-purpose receptacle loads is 100% for the first 10 kVA, and 50% for the remainder over 10 kVA. This allows for a reduction in the calculated load for the feeder since not all receptacles will be used simultaneously at full capacity.
Why the other options are wrong
- A. This is applied to the first 10 kVA of the load, not the portion exceeding 10 kVA.
- B. This is typically a continuous load derating factor, not a general receptacle demand factor.
- C. This demand factor is not specified for general-purpose receptacles in non-dwelling units in this context.
Receptacle Demand Load (Non-Dwelling)
For non-dwelling units, the demand load for general-purpose receptacles is calculated using a demand factor of 100% for the first 10 kVA, and 50% for the load exceeding 10 kVA, as per NEC 220.42(B).
- NEC 220.42(B) applies to non-dwelling units.
- First 10 kVA of receptacle load is at 100% demand.
- Load exceeding 10 kVA is at 50% demand.
- This reduces the calculated load for feeder and service sizing.
Memory trick: Commercial plugs: first 10k is full, rest is half.