12 AWG Circuit, 14 AWG Cable For The Last Load -- A Switched Light - Electrical - Page 2 - DIY Chatroom Home Improvement Forum
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Old 04-17-2019, 12:18 PM   #16
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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 huesmann View Post
Sounds to me the issue isn't the boxes, it's his brain forgetting that the light and outlet are on separate circuits.
His memory shouldn't enter into it. It's a good idea to make sure no conductors in the box have power before working in it. I learned that the hard way.

After almost 40 years of building and remodeling my own houses (including installing two full services and moving one circuit breaker panel), as well as being an electronic technician and engineer, I turned the circuit breaker off to an outlet, opened the box, started pulling out the wires and ZAP!

After some head scratching I realized that the original electrician had pulled 12-3 cable into the box. Each supply wire was attached to an adjacent circuit breaker in the panel (opposite polarities) and when they got to that first box he broke them out into two separate runs. Doing so saved him a couple of dollars in wire and reduced the crowding in the wall above the CB panel.

I looked carefully into the CB panel and found that he had done this with quite a few circuits and sure enough, I found a couple more of those junction boxes during the remodel. But I had learned my lesson. Just because the power goes off to the outlet, doesn't mean all of the wires in the box are shut off. Test everything. It's easy to do with one of those proximity testers.
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Old 04-17-2019, 12:30 PM   #17
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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?
There wouldn't be much point. The reason outlets near a sink are required to be protected isn't that you might touch the outlet and the sink at the same time. It is because something you plug in may in some way conduct electricity into your body while you are touching the plumbing. Plumbing is often a very good ground and the combination could kill you. The authorities cannot predict what you might plug into an outlet or how you might use it, so they try to cover you by requiring a GFCI outlet or circuit near a sink.

Touching a light switch, even with dripping wet hands, isn't likely to put you into contact with electricity. And if water did somehow get all the way in to a supply wire, fresh water isn't very conductive. The only part of a properly installed light circuit where the user is at all exposed to electricity is in the light socket itself. Yeah, if you stick your finger all the way into it and contact the little button at the bottom, you will be exposed to 120V. But at that point you are probably on a stool or ladder and couldn't reach the sink, anyway. So practically speaking, there wouldn't be anything for a GFCI to protect you from.
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Old 04-17-2019, 01:07 PM   #18
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


You could install a 15 amp ground fault only device on the light circuit, but that would mean installing a second box for it. Same with a fan in a bathroom, where the lights are fed by a separate 14 gauge 15 AMP circuit from the receptacles which are 20 amp 12 gage. Or you could try finding someone that makes a switch only with GFCI. Last year when I searched I couldn't find one, so used the GFCI stand alone only.
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Old 04-17-2019, 01:45 PM   #19
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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The authorities cannot predict what you might plug into an outlet or how you might use it, so they try to cover you by requiring a GFCI outlet or circuit near a sink.
GFCI protection is required on all kitchen countertop receptacles. The sink doesn’t make a damn bit of difference.

If you think about it, every metallic appliance in your kitchen (large or small) is a pretty good ground (assuming an EGC and 3 prong plug). You get caught between a hot leg and almost any metallic surface in the kitchen, and you are talking about a phase to ground short with you in the center of it.
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Old 04-17-2019, 03:59 PM   #20
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


I agree. But also the code requires GFCI for any device that is within a specified distance of water or water pipes. Like a fan above a shower, or within a minimum distance to a shower. There is probably a code requirement for light fixtures installed above sinks how much distance between metal and light. Probably about the arm span of a person. Also, I wonder if there is a different code requirement for plastic interior piping. I don't have plastic, so I don't look for it.
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Old 04-17-2019, 04:18 PM   #21
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


Also, some sinks are metal, and any porcelain sink can be removed and a metal one installed. So a sinks/faucets are like appliances. Outlets wires...etc are considered permanent.
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Old 04-17-2019, 04:25 PM   #22
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


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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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You could install a 15 amp ground fault only device on the light circuit, but that would mean installing a second box for it. Same with a fan in a bathroom, where the lights are fed by a separate 14 gauge 15 AMP circuit from the receptacles which are 20 amp 12 gage. Or you could try finding someone that makes a switch only with GFCI. Last year when I searched I couldn't find one, so used the GFCI stand alone only.
If you are saying you can tap a 20 amp circuit by using a 15 amp GFCI and #14 wire, that is absolutely wrong.

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Old 04-17-2019, 05:14 PM   #23
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


No, I'm saying add it to the 15 amp circuit.
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Old 04-17-2019, 05:24 PM   #24
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


The reason why individual loads can have lower rated wires (for example a lamp can have a 16 gauge wire instead of 14) is because the device has it's own protection in it.

Even incandescent light bulbs have protection.

Most quality appliances have a fuse or mini-breaker.

---------
In the end, you should have a separate box for the 15 amp circuit.
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Old 04-17-2019, 06:05 PM   #25
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


Interesting point. I've noticed LED fixtures rated for 15 amp circuits generally only pull about 4 amps, and have very small gage stranded lead wire. These wires must always be contained in the fixture/receptacle to contain any hot metal from igniting a fire, if for some unforeseen reason the wires short.

So ya, I still agree it's best to keep the 15 amp branch wiring separate from the 20 amp circuit, regardless of what device is installed.
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Old 04-17-2019, 06:22 PM   #26
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Re: 12 AWG circuit, 14 AWG cable for the last load -- a switched light


Theoretically you are safe and fine. However the code doesn't allow for theoretical situations that might change in the future, so it's not allowed.
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Old 04-17-2019, 07:49 PM   #27
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Originally Posted by user_12345a View Post
The reason why individual loads can have lower rated wires (for example a lamp can have a 16 gauge wire instead of 14) is because the device has it's own protection in it.

Even incandescent light bulbs have protection.

Most quality appliances have a fuse or mini-breaker.

---------
In the end, you should have a separate box for the 15 amp circuit.
Rarely would you find overcurrent protection built into a fixture of appliance. The load is known so the wires can be smaller than the house wiring. The house wiring needs to be sized for the entire load of the circuit.
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Old 04-17-2019, 07:53 PM   #28
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I agree. But also the code requires GFCI for any device that is within a specified distance of water or water pipes. Like a fan above a shower, or within a minimum distance to a shower. There is probably a code requirement for light fixtures installed above sinks how much distance between metal and light. Probably about the arm span of a person. Also, I wonder if there is a different code requirement for plastic interior piping. I don't have plastic, so I don't look for it.
There is no code requirement for GFI protection for a light fixture over a sink or separation from a metal surface.
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Old 04-17-2019, 08:19 PM   #29
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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 Jim Port View Post
Rarely would you find overcurrent protection built into a fixture of appliance. The load is known so the wires can be smaller than the house wiring. The house wiring needs to be sized for the entire load of the circuit.
Many do.

I have a window fan with a 3 amp fuse built right into the socket in addition to motor thermal protection.

Electric stoves have separate protection devices for each element, as well as oven and outlet. With a regular outlet the load won't be more than 15 amp, 20 amp appliances have a modified socket.

I've seen mini-breaker for protection in mixers, microwave always has a fuse.

Decent computer power supplies have a fuse or other form of protection.

There may be cheap junk designed without over-current device.

There's known load but in the event of a fault, the current can exceed what the internal wires/components can take but still be insufficient to trip a 15 amp breaker.
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Old 04-18-2019, 09:05 AM   #30
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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 Oso954 View Post
GFCI protection is required on all kitchen countertop receptacles. The sink doesn’t make a damn bit of difference.

If you think about it, every metallic appliance in your kitchen (large or small) is a pretty good ground (assuming an EGC and 3 prong plug). You get caught between a hot leg and almost any metallic surface in the kitchen, and you are talking about a phase to ground short with you in the center of it.

It certainly does matter. This is why GFCI are required in bathrooms, garages and exterior locations as well - potential wet areas. There are no "metallic appliances" expected to be on your back deck or bathroom, for example. Now it just might be that if there were some strange room in houses that had a lot of "metallic appliances" but no wet area for some reason, that the code would require a GFCI there too, but since there is no such thing, the "raison d'etre" for GFCI is the presence of water. Water is a pretty decent conductor of electricity, and that's the bottom line w.r.t. the code.
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