I use the simplified chart above to help determine this. The minimum circuit ampacity tells us how big the wire needs to be. These units all have a label applied to them that tells us the minimum circuit ampacity, and the maximum fuse or circuit breaker size. An OCPD is a generic tongue-twister for a circuit breaker or fuse.įor air conditioners and heat pumps, the only thing we need to look at is what’s printed on the compressor unit. Note: while I say circuit breaker throughout this post, what I really mean is the overcurrent protection device, or OCPD. One such place where these rules for circuit breakers or fuses don’t apply is for air conditioners and heat pump circuits. Wires can be larger, but not smaller than this… for the most part. Thankfully, this simplified chart works for most of the stuff I come across as a home inspector. While the true formula for figuring out exactly how much current a wire can carry is fairly complicated, most home inspectors rely on a simplified version of this for branch circuits: Breaker or Fuse (amps)įor the full story, you’d have to start with table 310.15(B) (16) in the National Electric Code, but there are a ton of exceptions that make it challenging to fully figure out the exact answer. Circuit breakers protect the wires from overheating. When a wire is too small for a circuit breaker, you have a potential fire hazard. One of the standard things home inspectors look at while inspecting an electrical panel is comparing wire sizes to circuit breakers sizes.
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