running 2 circuits off 14/3 wire

2mshepherd · 06-14-2010, 08:12 PM

I have a 14/3 wire that is hooked up to two 15amp breakers. the red goes to one breaker and the black to the other (obviously). i'm honestly not sure what the whole rig was for exactly, but the black powers all the lights and outlets in my bathroom.

so, i have the red circuit doing nothing, and i need to run power to some outlets in a room i'm renovating. can i just use the red to power those outlets?

since it is 14/3 wire, each the red and the black hot lines can obviously handle the 15 amps that the breakers will allow. my concern though is the white wire. isn't this wire effectively being loaded to a max of 30 amps (assuming you load each of the circuits to their max capacity)? and since the white is only 14 gauge like the rest, doesn't this mean it's handling twice it's rated load?

my main concern is whether this configuration would be to code or not. it seems like it wouldn't be, but then again if this is how you create a 220V circuit then isn't the white handling 30 amps in that case also? so it must be to code, no?

i've been googling for answers and found plenty of threads that seem to cover similar topics, but i need an answer in plain english.

any help is appreciated.

kbsparky · 06-14-2010, 08:56 PM

As long as the red and black wires are connected to opposite legs of the incoming service, the white (neutral) will carry the difference of the loads, not the sum.

Therefore, the maximum amount possible would be 15 Amps, if one circuit was fully loaded, and the other one off.

You should measure the voltage between the black and red lines with both breakers on, to ensure they are indeed connected to opposite legs. You should see a 240 Volt potential difference there.

The best way is to use a double-pole breaker.

Using a so-called tandem breaker is not a double-pole, but a "twin" set of single poles connected to the same leg of your panel. Be sure you can tell the difference here.

Scuba_Dave · 06-14-2010, 09:02 PM

Where are you located ?

US requires 20a in the bathroom & GFCI
Bedrooms & most other rooms now require AFCI

secutanudu · 06-15-2010, 01:16 AM

This type of setup (done properly) is called a Multi-Wire Branch Circuit (MWBC).

06-14-2010, 08:12 PM	#1
2mshepherd Newbie Join Date: Jun 2010 Posts: 1	running 2 circuits off 14/3 wire I have a 14/3 wire that is hooked up to two 15amp breakers. the red goes to one breaker and the black to the other (obviously). i'm honestly not sure what the whole rig was for exactly, but the black powers all the lights and outlets in my bathroom. so, i have the red circuit doing nothing, and i need to run power to some outlets in a room i'm renovating. can i just use the red to power those outlets? since it is 14/3 wire, each the red and the black hot lines can obviously handle the 15 amps that the breakers will allow. my concern though is the white wire. isn't this wire effectively being loaded to a max of 30 amps (assuming you load each of the circuits to their max capacity)? and since the white is only 14 gauge like the rest, doesn't this mean it's handling twice it's rated load? my main concern is whether this configuration would be to code or not. it seems like it wouldn't be, but then again if this is how you create a 220V circuit then isn't the white handling 30 amps in that case also? so it must be to code, no? i've been googling for answers and found plenty of threads that seem to cover similar topics, but i need an answer in plain english. any help is appreciated.

06-14-2010, 08:56 PM	#2
kbsparky Electrical Contractor Join Date: Sep 2008 Location: Delmarva Posts: 3,148	running 2 circuits off 14/3 wire As long as the red and black wires are connected to opposite legs of the incoming service, the white (neutral) will carry the difference of the loads, not the sum. Therefore, the maximum amount possible would be 15 Amps, if one circuit was fully loaded, and the other one off. You should measure the voltage between the black and red lines with both breakers on, to ensure they are indeed connected to opposite legs. You should see a 240 Volt potential difference there. The best way is to use a double-pole breaker. Using a so-called tandem breaker is not a double-pole, but a "twin" set of single poles connected to the same leg of your panel. Be sure you can tell the difference here. __________________ -KB Life is uncertain -- eat dessert first!! To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

06-14-2010, 09:02 PM	#3
Scuba_Dave Xtreme DIY'r Join Date: Jan 2009 Location: South of Boston, MA Posts: 17,248	running 2 circuits off 14/3 wire Where are you located ? US requires 20a in the bathroom & GFCI Bedrooms & most other rooms now require AFCI

06-15-2010, 01:16 AM	#4
secutanudu Just call me Andrew Join Date: Mar 2009 Location: Albany, NY Posts: 2,247	running 2 circuits off 14/3 wire This type of setup (done properly) is called a Multi-Wire Branch Circuit (MWBC). __________________ Andrew

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running 2 circuits off 14/3 wire