DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Electrical and Wiring > 2 circuits on a 3 wire




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Old 03-30-2009, 08:10 AM  
vdotmatrix
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Default 2 circuits on a 3 wire

BACKGROUND:

* (2) new 20 amp 12/2 circuits (each with own breaker of course), coming from the panel to the switch box in the bathroom.
* New Bathroom exhaust ceiling unit with HEAT, LIGHT, NIGHT LIGHT, and FAN. ( Panasonic FV-11VHL2 )
* (2) 12/3 wire coming from the ceiling unit to the switch box.

* FAN, LIGHT and NIGHT light will share neutral wire from circuit (a) pigtailed in the ceiling unit and in the switch box.
* 4-20A single pole switches in the box will each get their respective BLACK wires from the ceiling unit.

QUESTION:

1. (1) 3-wire cable from ceiling unit back to the box, will control the light (black wire) and night lite(red wire) on circuit (a).
2. the 2nd 3-wire from the ceiling unit will control the FAN (black wire and nuetral from circuit A) and Heat (red wire and neutral from circuit B).

So, if you can follow this narrative, my concern is:

Can I have 2 different circuits within the same 3-wire cable (#2)?

This is OK right?



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Old 03-30-2009, 09:18 AM  
kok328
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Can I have 2 different circuits within the same 3-wire cable (#2)? YES

This is OK right? YES



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Old 03-31-2009, 01:12 AM  
triple D
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Default why two circuits?

If you would like you could scrap one of the twelve threes, and put in a twelve two. The whole unit will run on one circuit. You could have three switch legs for light on the twelve three if you color the white wire black with a sharpie marker. Then the twelve two could be black heater and white neutral. Just a thought, unless its too late......Good luck

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Old 03-31-2009, 07:06 AM  
KEITH
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I may be missing something but the way I read it you have no neutral for the lights.

Why worry about combining circuits? just have power (A) feed switch 1 &2 for the light (black) & night-light (red) and splice the whites. do same on 2nd pair of switches with power(B) for fan and heater

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Old 04-02-2009, 12:16 AM  
triple D
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Default one neutral....

The white wire spoke of in my reply is the neutral for all four switch legs. One power to all four switches and one neutral to fan/heat/lite/night lite.

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Old 04-02-2009, 09:33 PM  
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Quote:
Originally Posted by triple D View Post
If you would like you could scrap one of the twelve threes, and put in a twelve two. The whole unit will run on one circuit. You could have three switch legs for light on the twelve three if you color the white wire black with a sharpie marker. Then the twelve two could be black heater and white neutral. Just a thought, unless its too late......Good luck
Thanks for the reply.
This is a bathroom exhaust with heat. Current NEC codes require dedicated 20A circuit for the heat portion. I ran 2 3-wires. Diagram to follow
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Old 04-02-2009, 09:35 PM  
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Quote:
Originally Posted by KEITH View Post
I may be missing something but the way I read it you have no neutral for the lights.

Why worry about combining circuits? just have power (A) feed switch 1 &2 for the light (black) & night-light (red) and splice the whites. do same on 2nd pair of switches with power(B) for fan and heater
Can't combine circuits. That is the exercise here and my question. diagram to follow thanks
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Old 04-02-2009, 09:37 PM  
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Quote:
Originally Posted by triple D View Post
The white wire spoke of in my reply is the neutral for all four switch legs. One power to all four switches and one neutral to fan/heat/lite/night lite.
The NEC requires an isolated dedicated 20A for the heat, I wanted to completely isolate the heat circuit all the way back to the panel ...I am not sure if this also means the neutral wire.
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Old 04-02-2009, 09:52 PM  
vdotmatrix
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Quote:
Originally Posted by KEITH View Post
I may be missing something but the way I read it you have no neutral for the lights.

Why worry about combining circuits? just have power (A) feed switch 1 &2 for the light (black) & night-light (red) and splice the whites. do same on 2nd pair of switches with power(B) for fan and heater
3_wirePS.bmp

Can't combine circuits. That is the exercise here and my question; neutral wires are pigtailed in the switch box and in the ceiling for the fan,light and night light and are not shown for either circuit in this diagram as well as the ground wire(s).

The HEAT's 12/3 shares nothing with the other circuit except the yellow covering on the cable; the heat 's red and the neutral belong to that 'heat" circuit.

So....I am sorry I didn't return to this forum earlier. I went to city hall and nailed down one of the electrical code enforcement folk and they said I was spot on with my wiring reasoning...I am no pro...

So if were to have pigtailed ALL the neutrals, for all four devices in the switchbox and in the ceiling, would this have been KOSHER?

I know the word neutral means neutral but wouldn't that be mixing stuff across circuits?
ALL devices will have their separate switches.

thanks
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Old 04-02-2009, 10:10 PM  
kok328
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Ok, here's a technique that is not commonly utilized in residential applications but, is still kosher.
You can share a neutral conductor between two individual circuits as long as they are from opposite phases in the load center (i.e.-slots 1&3 are on the same phase whereas, slots 1&2 are on opposite phases). Therefore, being that these are dedicated circuits, it would be safe to use just one neutral out of your 2 12/3 runs, for the entire bathroom.
So depending where you put those (2) 20A breakers in the load center, will depend on whether or not all those neutrals bundled together will be OK or not.



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