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enter image description hereenter image description hereI'm installing a new dedicated 20 amp circuit for an existing bathroom (new fixture). NEC recommends 12 AWG wiring. But ALL the wires (regardless of amperage) in the main service panel are a much heavier gauge (I'd say in the neighborhood of 6 or 8 AWG). In comparison, my 12 AWG looks pretty small when wired to the 20 amp breaker. Should I be using a different (lower) gauge in the main service panel (to match the others) and then change to 12 AWG in a junction box?

The two photos (one, a closeup) shows the difference.

Dave De Seguirant
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  • Post a picture of this service panel (open.) – Ecnerwal Jun 25 '17 at 13:08
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    What size is written on the sheath of those other cables? Reason I ask is that *insulation* diameter has nothing to do with *wire* diameter. Also do those cables do anything weird? E.g. If 11 of them all ran up the same raceway together for more than 24", they would have to bump up 4 sizes. – Harper - Reinstate Monica Jun 25 '17 at 15:29
  • I hadn't considered that; thanks! I think you're dead on about the run. My circuit is hardly even 30', so I think I'm ok from one of the other responses. Thanks so much! – Dave De Seguirant Jun 25 '17 at 17:35

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Code requires a minimum 12 AWG wire for a 20-amp breaker. You are fine with #12 wire. I have wired quite a few homes where the owners wanted 10-gauge wiring. 10-gauge can carry more current but is not needed unless it is a very long run: over 100 feet. Just to give an idea, #12 is rated for 40 amps with THHN but residential is limited to 20 amps for safety.

ThreePhaseEel
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Ed Beal
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  • Great! Yeah; mine's a very short (~30'), so I should be ok. It just caused me to question myself when I saw those other diameters. I appreciate your answer! – Dave De Seguirant Jun 25 '17 at 17:37
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What you are seeing is actually the insulation not the size of the conductor. To determine that you would have to read the writing on the wire itself or remove a wire and check it with a wire gauge.

That wire is definitely not #6 or #8 believe me. The insulation thickness has deceived you.

TW or THW type insulation from older wire was thicker than modern day THHN/THWN.

Your installation is just fine.

ArchonOSX
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