Master Electrician Exam (NEC)Load CalculationsEasy
A single-family dwelling unit has a 240V, 50A electric vehicle supply equipment (EVSE) installed. What is the minimum demand load that must be included for this EVSE in the service load calculation, according to NEC 220.57?
- A75A
- B62.5A
- C50A
- D40A
Show answer & explanationAnswer & explanation
Correct answer: C. 50A
According to NEC 220.57, the demand load for electric vehicle supply equipment shall be the maximum nameplate rating of the EVSE. In this case, the nameplate rating is 50A. Therefore, the minimum demand load is 50A.
Why the other options are wrong
- A. Incorrect. This value is too high and does not align with NEC 220.57.
- B. Incorrect. This would imply a 125% continuous load factor on a 50A load, but 220.57 specifies nameplate rating directly.
- D. Incorrect. This might be a common EVSE rating, but not the specific rating for this installation.
EVSE Demand Load (NEC 220.57)
The demand load for electric vehicle supply equipment (EVSE) is taken at its maximum nameplate rating, as per NEC 220.57, without applying additional demand factors unless specified elsewhere.
- NEC 220.57 specifically addresses EVSE load calculations.
- The demand load is the EVSE's maximum nameplate rating.
- This rating is typically continuous, but 220.57 supersedes the general 125% rule for this specific equipment.
- The provision simplifies load calculation for EV charging.
Memory trick: EVSE's Exact Value: Take the nameplate, it's the demand you'll use.