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# Wiring gauge or circuit breaker- Which defines the circuit?

#1
10-12-16, 06:25 AM
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Join Date: Feb 2011
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Wiring gauge or circuit breaker- Which defines the circuit?

I think I know the answer, but I would like reassurance. I have a home built in 1988. The home's breaker box contains 15 and 20 amp breakers. About a 50/50 ratio. I am changing some kitchen lighting. In opening the 4" j-box I noted what I think was 12 gauge wire. When I went to the breaker box the circuit breaker was a 15 amp breaker. I thought 12 gauge was normally for 20 amp circuits. I cannot understand why an electrician would use it for a 15A circuit.

Can someone explain?

#2
10-12-16, 07:12 AM
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The minimum gauge for a 20 amp general circuit is #12 and #14 for a 15 amp circuit. Larger csizes of wire can be instaĺled.

Perhaps there is #14 somewhere in the circuit.

#3
10-12-16, 07:13 AM
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When I went to the breaker box the circuit breaker was a 15 amp breaker. I thought 12 gauge was normally for 20 amp circuits.
It is but there is nothing wrong in using a larger size.
I cannot understand why an electrician would use it for a 15A circuit
It is what was on the truck or some sections of the circuit has #14.

#4
10-12-16, 08:45 AM
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...or some sections of the circuit has #14.
Perhaps there is #14 somewhere in the circuit.
Is that allowed by code? It seems misleading to use 12 at the panel, then switch to 14 in a junction box. If I were to make changes downstream I would base my wire & load choices by what I see in the panel.

#5
10-12-16, 09:35 AM
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As long as the smallest conductor is protected it is allowed. It may not be best practice for the reason you stated.

#6
10-14-16, 02:05 AM
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Join Date: Feb 2011
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Posts: 221

So, I think I get it. It was OK for the electrician to use 12 ga wire on a 15A circuit. Some overkill, but OK. I find the stuff stiff and difficult to work with. I don't think I would have used it when it was not required.

More confusing yet. In a couple cases I see both 12ga and 14ga used on the same 15A circuit. Based on comments here it is still OK. Just confusing for a beginner like me.

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