How to mitigate 12 AWG to 14 AWG transition at GFCI

Question

Was it ever acceptable in the past to use 20A breakers with 14 AWG wire?
1960 house I'm working on has 20A breaker and 12 AWG terminating at a GFCI receptacle  in a box in the garage. The breaker is dedicated to the garage. On the GFCI load side 12 AWG
goes to the outlets and 14 AWG goes to two LED sensor lights.  The 14 gauge is more than 10 feet.
Is the GFCI outlet sufficient here or should I change out the breaker to 15A?

nobody · Answer

You should change the breaker to 15A, or replace the wire. It is not OK to have 14 Ga wire on a 20A breaker like that.
The GFCI is not an over current protection device and does not help you here. It will happily let 20A through and light the 14 Ga wire on fire as long as there’s no imbalance between hot and neutral.

Harper - Reinstate Monica · Answer

GFCI receps do not provide over current protection at all. Much the opposite, UL White Book rules absolutely require all duplex 15A receptacles to safely tolerate 20A of pass-through! Because of this rule:

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The only way to protect #14 wire is a 15A breaker.

How to mitigate 12 AWG to 14 AWG transition at GFCI

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