Q. What is the proper size branch-circuit, short-circuit, ground-fault protective device required for a hermetic compressor with a nameplate rated load of 38A? The branch-circuit selection current on the nameplate is rated at 40A. Note: Do not exceed the values obtained from the lower multiplier.
Explanation: As per 440.22 of the 2005 NEC, you must use a multiplier of 1.75 (175%) for this calculation.
40A x 1.75 = 70A
A check of 240.6 reveals that 70A is a standard size ampere rating for fuses and inverse time circuit breakers.
Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at [email protected].