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-   -   2 circuits on a 3 wire (http://www.houserepairtalk.com/f9/2-circuits-3-wire-6362/)

vdotmatrix 03-30-2009 07:10 AM

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?

kok328 03-30-2009 08:18 AM

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

This is OK right? YES

triple D 03-31-2009 12:12 AM

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

KEITH 03-31-2009 06:06 AM

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

triple D 04-01-2009 11:16 PM

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.

vdotmatrix 04-02-2009 08:33 PM

Quote:

Originally Posted by triple D (Post 28944)
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:)

vdotmatrix 04-02-2009 08:35 PM

Quote:

Originally Posted by KEITH (Post 28948)
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:)

vdotmatrix 04-02-2009 08:37 PM

Quote:

Originally Posted by triple D (Post 28988)
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.:)

vdotmatrix 04-02-2009 08:52 PM

1 Attachment(s)
Quote:

Originally Posted by KEITH (Post 28948)
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

Attachment 1141

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

kok328 04-02-2009 09:10 PM

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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