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01-10-2012, 06:52 PM   #1
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## Romex 12/3 or 12/4

If you are running a length of Romex 12/3 the black and red of which are the Hs from two different CBs, can you use the same white wire for the N for both circuits?

Basically can you use 12/3 for two CBs using the same white wire for the N for both circuits?

01-10-2012, 06:53 PM   #2
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Quote:
 Originally Posted by highdeserthome If you are running a length of Romex 12/3 the black and red of which are the Hs from two different CBs, can you use the same white wire for the N for both circuits? Basically can you use 12/3 for two CBs using the same white wire for the N for both circuits?
Yes. This is known as a multiwire branch circuit.

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01-10-2012, 06:59 PM   #3
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Quote:
 Originally Posted by highdeserthome If you are running a length of Romex 12/3 the black and red of which are the Hs from two different CBs, can you use the same white wire for the N for both circuits? Basically can you use 12/3 for two CBs using the same white wire for the N for both circuits?
Yes, its called a Multi-wire Branch Circuit (MWBC). It has been covered on this site quite a bit.

1. The two circuits have to be on opposite phases of each other so the power on the neutral will not be cumulative.
2. The circuit breakers (depending on location, but always recommended) need to have a handle tie, so that one cannot be shut off independently from the other circuit.
3. The neutral wires at the receptacles must be pig-tailed before attaching to the receptacle.
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Last edited by <*(((><; 01-10-2012 at 07:02 PM.

01-10-2012, 07:07 PM   #4
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Quote:
 Originally Posted by <*(((>< Yes, its called a Multi-wire Branch Circuit (MWBC). It has been covered on this site quite a bit. 1. The two circuits have to be on opposite phases of each other so the power on the neutral will not be cumulative. 2. The circuit breakers (depending on location, but always recommended) need to have a handle tie, so that one cannot be shut off independently from the other circuit. 3. The neutral wires at the receptacles must be pig-tailed before attaching to the receptacle.

If I put the two leads of my multimeter on the hots, if it reads 240 then they are opposite phases? Usually for CB immediate next to each other or odd and even location will be opposite phase? Is this true even for the Pushmatic Bulldog?

 01-10-2012, 07:10 PM #5 Member   Join Date: Jan 2012 Posts: 84 Rewards Points: 75 "The two circuits have to be on opposite phases of each other so the power on the neutral will not be cumulative." Thanks This info really answered my question. I wondered about the load on the N for this setup.
01-10-2012, 07:11 PM   #6
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Quote:
 Originally Posted by highdeserthome Basically can you use 12/3 for two CBs using the same white wire for the N for both circuits?
If the wire isn't already installed... try to avoid putting a MWBC in.
If it is installed... be careful of how the rest is done.

01-10-2012, 09:04 PM   #7
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Quote:
 Originally Posted by highdeserthome If I put the two leads of my multimeter on the hots, if it reads 240 then they are opposite phases? Usually for CB immediate next to each other or odd and even location will be opposite phase? Is this true even for the Pushmatic Bulldog?
Bulldog breakers are a different animal. Be sure to use a double-pole breaker, where both sides are connected with a top piece.

And yes, when you have properly connected it up, you will measure 240 Volts between the black and red conductors.

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