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Old 10-23-2008, 09:50 AM   #1
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Do I need 12-3?


I have an electrician coming tomorrow to run dedicated 20A circuits for two bathrooms, a mounted microwave, and maybe a dishwasher. The material costs through the electrician were a little ridiculous last time but I am allowed to provide my own. Do I just need 12-2? I don't need 12-3 for anything do I? The bathrooms each have one GFCI receptacle, one light bar, and a fan.

Other than 3-pole switches, what sorts of things require extra wires?
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Old 10-23-2008, 10:09 AM   #2
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Do I need 12-3?


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I have an electrician coming tomorrow to run dedicated 20A circuits for two bathrooms, a mounted microwave, and maybe a dishwasher. The material costs through the electrician were a little ridiculous last time but I am allowed to provide my own. Do I just need 12-2? I don't need 12-3 for anything do I? The bathrooms each have one GFCI receptacle, one light bar, and a fan.

Other than 3-pole switches, what sorts of things require extra wires?
The things you mention can all be run in 12-2. 12-3 could be used to share between some circuits, but it would require using double pole breakers. That is generally an inconvenience when working on other circuits.

Dryers and ranges also require extra wire.
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Old 10-23-2008, 10:10 AM   #3
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Do I need 12-3?


What about smoke/CO detectors? Are these two wire?
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Old 10-23-2008, 10:15 AM   #4
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Do I need 12-3?


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Originally Posted by jheavner View Post
I have an electrician coming tomorrow to run dedicated 20A circuits for two bathrooms, a mounted microwave, and maybe a dishwasher. The material costs through the electrician were a little ridiculous last time but I am allowed to provide my own. Do I just need 12-2? I don't need 12-3 for anything do I? The bathrooms each have one GFCI receptacle, one light bar, and a fan.

Other than 3-pole switches, what sorts of things require extra wires?
12-2 with ground for the 20A feeds. 12-3 with ground would be for a 20A 240v. Or might be used for a 3 way switch feed (I am still learning exactly the right things to use for 3 way switches, so I am not positive on that.)

If you have no 3 way switches and no 240V appliances. Then the 12-2 will be fine. You need a separate run to each bathroom, each one needs to be on its only circuit with nothing else on it. The GFCI needs to be the first outlet in the series so it will protect the other outlets. The lights do not need gfci protection, and it is generally advised not to protect them as then it is dark if you trip the gfci. You can also use a GFCI breaker instead of the GFCI outlet.

Hope this helps.

I have seen wire prices dropping a little bit. I may have to go buy several pieces of wire today, I think I am going to run out of 14-2 and #6 ground.

Jamie
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Old 10-23-2008, 10:19 AM   #5
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Do I need 12-3?


The lights and receptacle in the bath don't need to be on a separate circuit do they? If they can't be on the same circuit can the lights share a circuit with something else?
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Old 10-23-2008, 10:28 AM   #6
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Do I need 12-3?


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12-2 with ground for the 20A feeds. 12-3 with ground would be for a 20A 240v. Or might be used for a 3 way switch feed (I am still learning exactly the right things to use for 3 way switches, so I am not positive on that.)

If you have no 3 way switches and no 240V appliances. Then the 12-2 will be fine. You need a separate run to each bathroom, each one needs to be on its only circuit with nothing else on it. The GFCI needs to be the first outlet in the series so it will protect the other outlets. The lights do not need gfci protection, and it is generally advised not to protect them as then it is dark if you trip the gfci. You can also use a GFCI breaker instead of the GFCI outlet.

Hope this helps.

I have seen wire prices dropping a little bit. I may have to go buy several pieces of wire today, I think I am going to run out of 14-2 and #6 ground.

Jamie
I know you are eager to help, but this is incorrect information. Three conductor is not used for straight 240V or feeds to switches.

Last edited by jerryh3; 10-23-2008 at 10:33 AM.
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Old 10-23-2008, 10:33 AM   #7
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Do I need 12-3?


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The lights and receptacle in the bath don't need to be on a separate circuit do they? If they can't be on the same circuit can the lights share a circuit with something else?
Everything in the bath can be on one or multiple circuits. But Nothing outside of the bath can be on that circuit.

Option 1:

Circiut A:
Bath Outlets
Bath Lights
Bath Fan

Option 2:

Circuit A:
Bath Outlets

Circiut B:
Bath Fan
Bath Lights



Option 2 would make sense if you have heat lamps (a exhaust fan and dual heat lamp combo for example). 2 500W heat lamps and that fan can draw 15amps. Now if you have some vanity lights, that may draw another 2-4 amp, so right there your 20A is full and you would really need the outlets to be separate. If you don't plan to have any high draw fans, heat lamps, etc, then you can likely put everything together on one circuit.

But think of the bathroom as a little house, (not literally) meaning that you don't tap wires through those outside walls of the bathroom for anything else. A feed come from a circuit for the bathroom directly from the panel, it gets run to outlets, lights, etc, in that bathroom, and then does nothing else outside of the bathroom.

You can group the outlets, fans and lights onto 1 or multiple circuits however you wish, as long as the items are in the bath. I encourage you to think about what you will use and put in the proper level of service now while you doing the work.

Jamie
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Old 10-23-2008, 10:38 AM   #8
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Do I need 12-3?


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What about smoke/CO detectors? Are these two wire?
? I have a co detector that plugs into a 120v outlet. Are you talking about detectors that are part of a system you have?

I think you want to check with the manufacture of the items in question to see what they are looking for power wise.

Jamie
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Old 10-23-2008, 10:43 AM   #9
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Do I need 12-3?


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What about smoke/CO detectors? Are these two wire?
If they are interconnected, then you need 3 wire between them, but only 2 wire to feed the first one.
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Last edited by jbfan; 10-23-2008 at 10:58 AM. Reason: fat finger problems
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Old 10-23-2008, 10:49 AM   #10
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If they are interconnected, then you need 3 wire between them, but only 2 fire to feed the first one.
Ok, that's what I was thinking of. I don't know how they're wired now but I'm just going to assume they are ok and leave them alone.
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Old 10-23-2008, 10:50 AM   #11
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Do I need 12-3?


Quote:
Originally Posted by jamiedolan View Post
Everything in the bath can be on one or multiple circuits. But Nothing outside of the bath can be on that circuit.

Option 1:

Circiut A:
Bath Outlets
Bath Lights
Bath Fan

Option 2:

Circuit A:
Bath Outlets

Circiut B:
Bath Fan
Bath Lights



Option 2 would make sense if you have heat lamps (a exhaust fan and dual heat lamp combo for example). 2 500W heat lamps and that fan can draw 15amps. Now if you have some vanity lights, that may draw another 2-4 amp, so right there your 20A is full and you would really need the outlets to be separate. If you don't plan to have any high draw fans, heat lamps, etc, then you can likely put everything together on one circuit.

But think of the bathroom as a little house, (not literally) meaning that you don't tap wires through those outside walls of the bathroom for anything else. A feed come from a circuit for the bathroom directly from the panel, it gets run to outlets, lights, etc, in that bathroom, and then does nothing else outside of the bathroom.

You can group the outlets, fans and lights onto 1 or multiple circuits however you wish, as long as the items are in the bath. I encourage you to think about what you will use and put in the proper level of service now while you doing the work.

Jamie
Thank you, that was exactly what I needed to see.
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Old 10-23-2008, 11:17 AM   #12
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Do I need 12-3?


Quote:
But think of the bathroom as a little house, (not literally) meaning that you don't tap wires through those outside walls of the bathroom for anything else. A feed come from a circuit for the bathroom directly from the panel, it gets run to outlets, lights, etc, in that bathroom, and then does nothing else outside of the bathroom.
That's true, but not generally true. 210.11(C)(3) states that at least one 20A circuit shall service bathroom receptacle outlet(s), and that such circuits shall have no other outlets. The Exception states that if the 20A circuit services a single bathroom, outlets for other equipment within the same bathroom shall be permitted...

The rule is unclear in that bathroom is not plural, but the exception then implies that multiple bathrooms' receptacle outlets can be served by the 20A circuit, but then no other equipment (lighting, fans, etc) can be serviced by that circuit.

Sooo.. Option 1 is acceptable, given Jamie's house-in-a-house analogy.

In Option 2, assuming Circuit A serves only receptacle outlets, Circuit A could cross into multiple bathrooms. And so could circuit B, unless I'm missing something that prohibits that.
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Old 10-23-2008, 11:22 AM   #13
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Do I need 12-3?


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What about smoke/CO detectors? Are these two wire?
Yes those also require 3 wire, but only when there is more than one. They have to be interconnected, and the red wire provides that.
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Old 10-23-2008, 01:07 PM   #14
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Do I need 12-3?


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Ok, that's what I was thinking of. I don't know how they're wired now but I'm just going to assume they are ok and leave them alone.
Easy way to check is to push the test button on one of the smoke detectors and all of them should go off. I wired in about a half dozen smoke detectors at home, along with a CO detector in the basement near the furnace room. Pushing the test button on any one sets them all off around the house.
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Old 10-23-2008, 01:19 PM   #15
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Do I need 12-3?


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Easy way to check is to push the test button on one of the smoke detectors and all of them should go off. I wired in about a half dozen smoke detectors at home, along with a CO detector in the basement near the furnace room. Pushing the test button on any one sets them all off around the house.
Sorry for the off topic question here, but can you tell me where you get these hard wired smoke detectors and about what they cost? I have not seem them the times I have looked.

Thanks
Jamie
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