Connecting 3-wire and 4-wire Romex

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Old 07-19-15, 05:45 PM
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Connecting 3-wire and 4-wire Romex

Hello,

I am finishing our basement and I am stumped at the moment. The folks who lived here before had everything in the basement on one circuit: water heaters, lights, outlets, you name it. Since I'm finishing the basement and putting in a bunch of new circuits, I'm having to disconnect a lot of what they did.

What has me stumped is I found the box (a 2-gang box with light switches) where the power from the breaker came in. Right now, in that box, I have the power coming from the panel (3-wire Romex), the wire going outside to an exterior light right by the door (3-wire Romex), and a wire going to another 2-gang box in the bathroom (4-wire Romex). The bathroom that the 4-wire is going into is finished so I can't just pull that whole wire out without tearing the wall apart. Is there an appropriate way to connect all those wires? What do I do with the red wire? I'd like to connect it since the power to the bathroom is being pulled off that switch - I just don't know how to connect all the wires.

Thanks!
 
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Old 07-19-15, 06:31 PM
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For ease of typing, let's call your cable 12/2, 14/2 or 12/3, 14/3. Grounds will be connected as usual.

Right now as I read it, there's a switch you didn't mention.

(a 2-gang box with light switches) where the power from the breaker came in. Right now, in that box, I have the power coming from the panel (3-wire Romex), the wire going outside to an exterior light right by the door (3-wire Romex), and a wire going to another 2-gang box in the bathroom (4-wire Romex)
In the switch box, you have:
Power from breaker
Exterior light cable
12/3 or 14/3 going to bathroom

- What does other switch in 2-gang box do??

It doesn't make much sense to run 12/3 to bathroom unless you are running 2 separate hot wires, which doesn't sound like the case.

You can run a hot and neutral to the bathroom using the black and white wires of the 3 conductor cable and cap off the red on both ends.

However, I would look at my questions to make sure you are on the right track.
 
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Old 07-19-15, 07:26 PM
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The other switch in the box was originally a 4-way switch. There was a second 14/3 wire that ran into that box from another 2-gang box. So that 14/3 wire and the second 14/3 wire (that I am currently trying to figure out what to do with) were wired to that 4-way switch. I reused the 14/3 wire from the other switch because I put in a 3-way switch there that goes up to a separate circuit of lights. So now I'm left with the one 14/3 wire that goes to the bathroom that had been on the 4-way switch.
 
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Old 07-20-15, 01:33 AM
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Is there an appropriate way to connect all those wires? What do I do with the red wire? I'd like to connect it since the power to the bathroom is being pulled off that switch
You can power the lights but not the receptacles if it is 14-3. Code requires new wiring meet current code. Code for a bath room requires a 20 amp dedicated receptacle circuit. (So long as only one bathroom is on the dedicated circuit the light can also be on the 20 amp circuit.) You could only use the 3-conductor cable for a receptacle feed if it was #12. If it is you could run 12-2 from a dedicated 20 amp breaker to the black and white of the 3-conductor cable in the basement that goes to the bathroom. Red would be capped on both ends and not used. If the 3-conductor cable to the bathroom is 14-3 you are out of luck. It can't be used except for lights.
 
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Old 07-20-15, 04:38 AM
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Thank you for your input. The bathroom has a GFI on its own 20-amp circuit. These wires I am dealing with only go between switches, there are no receptacles on them. Here's what I was thinking of trying and maybe you can tell me if you think this will work.

If I put in a 3-way switch in the box I am currently working in, I can put the black wire going to the exterior light on the black screw, the red wire on one of the brass screws, and wire nut the remaining black wires (black from breaker and from 14/3 wire) and pigtail those on the other brass screw? I only want that switch to control the exterior light but I want the power to get to the bathroom. The other end of the red wire is tied into the switches in the bathroom so I believe that is a hot wire. Do you think this setup would work?
 
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Old 07-20-15, 10:24 AM
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I think you misunderstand what a 3-way switch is. It is for operating a light or other load from two different locations.

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Old 07-20-15, 10:29 AM
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I understand what a 3-way switch is. It's just that whoever wired the basement appears to to have used the switches not just to turn on the lights but to move power from one switch to another. It's probably best if I just call an electrician to sort it all out.
 
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Old 07-20-15, 10:35 AM
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appears to to have used the switches not just to turn on the lights but to move power from one switch to another.
Not true. You are misunderstanding what you are seeing. They used them as splice points. Same can be done with a wire nut.
 
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