What is the maximum allowable circuit breaker ampacity for use with 8 AWG copper NM-B cable supplying a range?

When selecting the maximum allowable circuit breaker ampacity for an 8 AWG copper NM-B cable, it’s important to reference the National Electrical Code (NEC) guidelines. An 8 AWG copper conductor is typically rated for a continuous load of 40 amperes. Therefore, for a circuit breaker that protects this size conductor, the appropriate maximum ampacity is indeed 40 amperes.

This rating ensures that the circuit breaker will trip at a point that protects the wire from overheating and potential fire hazards. The 40-amp rating aligns with commonly accepted practices for residential applications involving ranges and similar devices, which often draw significant power.

For these reasons, the correct answer is that the maximum allowable circuit breaker ampacity for use with 8 AWG copper NM-B cable supplying a range is 40 amperes. The other options either exceed this safe limit or do not align with standard electrical practices for such setups.