36
Chapter 3
VII.
Fuse and Circuit Breaker
Sizing
The following information applies to Compressor
Motor - Branch Circuit, Short Circuit and Ground
Fault Protection only.
A. NEC Article 440
Hermetic compressors should be protected in accor-
dance with Article 440 of the National Electric
Code which calls for substantially larger circuit
breakers than are required for open type motors.
B. Maximum Size
The maximum size of the fuse or circuit breaker
used to protect against short circuit and/or ground
fault of a unit utilizing a hermetic compressor shall
be no more than the sum of 225% of the compressor
Related Load Amps (RLA) as marked on the system
serial label, plus the RLA values of each of the other
motors which use the same branch circuit.
C. Minimum Size
The minimum value of the fuse or circuit breaker
shall be no less than 175% of the RLA of the com-
pressor.
The interpretations and directions given above apply
only to single branch power supplies, and do NOT
pertain to any plug-in type of appliances. Also, see
“PSC Motor Starting” on page 18.
