12 AWG Circuit, 14 AWG Cable For The Last Load -- A Switched Light - Electrical - DIY Chatroom Home Improvement Forum
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Old 04-12-2019, 06:14 PM   #1
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12 AWG circuit, 14 AWG cable for the last load -- a switched light


Hi, I have a double ganged light switch+receptacle box on my kitchen counter wall. The light switch is on a 15A living room circuit and controls an overhead kitchen sink light, not GFCI protected. The receptacle is on a 20A kitchen circuit and is GFCI protected. I don't like this setup, because 1) I almost forgot to switch off the living room circuit breaker while working in the box; 2) I'd prefer having the light switch be protected by the GFCI circuit as well since it's close to the sink. I'd like to feed the light through the 20A GFCI circuit instead, and cap off the 15A/14AWG wires. The receptacle is the last one on the GFCI protected 20A/12AWG circuit, is it ok to add the switched light to this last receptacle through the existing 14/2 romex for the light?

What does the current U.S. NEC code say about my situation? thanks


Attached drawing describes the situation.
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Old 04-12-2019, 06:19 PM   #2
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


No. Cable ampacity must be equal or greater than the branch breaker.
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Old 04-12-2019, 06:35 PM   #3
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


OK, thanks. Are switches on kitchen counter walls required to be GFCI protected?
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Old 04-12-2019, 06:35 PM   #4
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


Maybe separate the double box into separate single boxes.
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Old 04-12-2019, 06:44 PM   #5
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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Originally Posted by ElectricIQ View Post
OK, thanks. Are switches on kitchen counter walls required to be GFCI protected?
No they are not.

Quote:
I'd prefer having the light switch be protected by the GFCI circuit as well since it's close to the sink. I'd like to feed the light through the 20A GFCI circuit instead
Can't do that. Kitchen counter receptacle can't have lights on the circuit by code.

Arrange the two breakers so they are beside each other and install a handle tie so they both go off together.
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Old 04-12-2019, 06:46 PM   #6
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


Thank you for the definitive answers. I will just leave it be then.
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Old 04-13-2019, 07:19 AM   #7
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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No. Cable ampacity must be equal or greater than the branch breaker.


So does that mean all the commercial buildings with 14 gauge, 3 wire whips to the lay in fixtures on 20 amp breakers are wrong.


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Old 04-13-2019, 08:03 AM   #8
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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So does that mean all the commercial buildings with 14 gauge, 3 wire whips to the lay in fixtures on 20 amp breakers are wrong.


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As long as the whip was manufactured as part of the fixture it is complaint. It is a listed assembly, no different that a light fixture using 16 gauge wires that connect to a 15 or 20 amp circuit.
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Old 04-13-2019, 09:07 AM   #9
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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As long as the whip was manufactured as part of the fixture it is complaint. It is a listed assembly, no different that a light fixture using 16 gauge wires that connect to a 15 or 20 amp circuit.


So all the fixture whips that are bought or made with 14 gauge wire are wrong if they weren’t supplied with the fixture?


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Old 04-13-2019, 09:48 AM   #10
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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So all the fixture whips that are bought or made with 14 gauge wire are wrong if they weren’t supplied with the fixture?


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Correct, they are not tested as a listed assembly. They can be used on a 15 amp circuit.

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Old 04-13-2019, 01:17 PM   #11
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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Thank you for the definitive answers. I will just leave it be then.

Yes. The way it's wired is exactly the way it's supposed to be wired. Just be careful when working on electricity, and be sure test ALL wires in a box for power before working on anything in that box.
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Old 04-13-2019, 01:55 PM   #12
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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So does that mean all the commercial buildings with 14 gauge, 3 wire whips to the lay in fixtures on 20 amp breakers are wrong.


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There are tap rules for lighting. So you can run a smaller conductor from a junction box to the fixture, even if it isn't part of the listed fixture.

You can't do it from the switch thou.
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Old 04-13-2019, 03:58 PM   #13
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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There are tap rules for lighting. So you can run a smaller conductor from a junction box to the fixture, even if it isn't part of the listed fixture.

You can't do it from the switch thou.
Tap rules are beyond the scope of most DIYers experience and are very easy to misunderstand and misuse. The OPs situation is not within the scope of an allowable tap.
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Old 04-15-2019, 08:10 AM   #14
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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Maybe separate the double box into separate single boxes.
Sounds to me the issue isn't the boxes, it's his brain forgetting that the light and outlet are on separate circuits. Unless you mean to further separate the switch and outlet in some fashion to distinguish one from the other, like actually moving the separate boxes a few inches apart.
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Old 04-15-2019, 12:28 PM   #15
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


Just use a Sharpie and write a note on the yolks of the switch/receptacle, or on the back side of the cover plate that says "2 circuits in this box!" Or label them as "Ckt 1" and "Ckt 2" or whatever
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