text: Where are you using the circuit breaker ?\nin a house panel the circuit breaker is max sized by the wire and mim sized by the load at 100%. Unless the load is a motor then the c/b is oversized 115% or 125%.  the reason is the starting current of the motor and if it has a 60 or 90 C rating. Please read the (Nationa Electrical Code 2005) for more information.