O.K. Here goes… Whenever I’ve found a 14 gauge wire on a 20 amp breaker, I’ve always said it was a safety hazard for reasons we all know. Here’s the tricky part. I spoke with an electrician in the area that told me on older systems, it was fine (but not for new construction). Apparently, a 14 gauge wire can carry 20 amps safely but the “powers-that-be” say it can only carry 15 amps just as a built-in safety measure.
My gut feeling is still call it out as a safety hazard but technically, according to this electrician, it’s O.K.
Short answer electrician is incorrect. There are some instances where it may be permitted (A/C units, motor, etc.) but in general it is not permitted by the NEC. Here’s the relevant NEC section:
In all honesty, the older code was generally more stringent on conductor ampacity. Like all has said, the electrician was dead wrong. I could not tell you how many misinformed or underinformed electricians I have dealt with over the years. Quick reference books are a major contributor to the problem.
Yep, I hear this kinda “crap” all too often - “It used to be ok like this but they changed the code.”