I'm rewiring a bathroom, and will install a GFCI receptacle on a 20 amp circuit breaker (dedicated to the bathroom only). I am also going to have a fan and vanity light on the same circuit, downstream of the GFCI outlet (the fan is above the tub, thus requiring GFCI protection). Question: downstream of the GFCI outlet, am I required to continue to use 12 AWG cable for the rest of the circuit, or can I switch to 14 AWG? A code citation would be most helpful along with any rationale for why this allowed/not allowed, whether this is a good idea/ terrible idea, etc.
Electrical – Do all conductors on a 20-amp circuit need to be 12 AWG
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Best Answer
Yes, all conductors protected by a 20 ampere circuit breaker must be at least 12 AWG copper. There are a few exceptions and loop holes, but none of them apply to your situation.
The rationale here, is that 12 AWG copper conductors are rated for 20 amperes, whereas 14 AWG copper conductors are only rated for 15 amperes. So if you put 20 amperes through a 14 AWG conductor, the conductor could heat to dangerous levels.
That would make it a terrible idea to use 14 AWG copper conductors, on a circuit protected by a 20 ampere circuit breaker.