Master Electrician Exam (NEC)Load CalculationsMedium
A commercial building has a total of 15 kW of fixed electric space heating and 10 kW of air-conditioning load. According to NEC 220.60, what is the demand load to be used for the feeder and service calculation for these loads?
- A10 kW
- B20 kW
- C15 kW
- D25 kW
Show answer & explanationAnswer & explanation
Correct answer: C. 15 kW
According to NEC 220.60, when both electric space heating and air-conditioning are present, the largest of the loads is taken at 100%, and the smaller load is not added. In this case, the electric space heating is 15 kW and the air-conditioning is 10 kW. The larger load is 15 kW.
Why the other options are wrong
- A. This option incorrectly selects the smaller of the two loads.
- B. This option is incorrect and does not follow the NEC demand factor rules for heating/A/C.
- D. This option incorrectly sums both loads, which is not permitted by NEC 220.60.
Heating & A/C Demand (NEC 220.60)
When calculating feeder or service loads, only the larger of the fixed electric space heating load or the air-conditioning load is considered, not both.
- Applies to fixed electric space heating and air-conditioning.
- Only the larger of the two loads is included in calculations.
- This prevents over-sizing due to non-simultaneous operation.
Memory trick: Heating or Cooling, pick the BIG one, never both!