Shared neutral on more than one circuit

Speedy Petey

I'll repeat as I have done on many forums. Using MWBC's is NOT always or only about money. That is a knee jerk reaction comment from those that don't know any better.
There are several benefits to MWBC's, of which money is not the most important one.

TO say you should not use them because the neutral might open is like saying you should not have a service to your house because the neutral might open. That's right, the service to your house is one big MWBC.

WIRED PROPERLY they are perfectly safe and efficient. If you don't know what you are doing then stay away from them, or any wiring.

brric

amen.

Hourglass52

Whatever

AllanJ

It is not unusual to run a MWBC to several outlet boxes expecting to alternate A side and B side for the receptacles. But if you need GFCI protection you would need either a GFCI breaker (240 volt double wide) or individual GFCI receptacles at every outlet box where you do not use any load side terminals.

If you connected a GFCI receptacle to a MWBC, the load terminals are not part of the MWBC. A separate "GFCI protected neutral" must accompany the GFCI protected hot wire to any additional parts of the circuit to be protected by that GFCI.

Conduit fill and temperature derating requirements may in some cases allow a MWBC with more amperes compared with circuits with separate hot and neutral.

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lfparker

Hello - I need two dedicated 20 amp 120 volt outlets in my basement shop. One is for a compressor and one is for an air cleaner. I would like to do it with a MWBC using 12-3 romex from the panel to my shop. I understand that I will be good as long as I use a 2-pole breaker back at the panel. Since this is an a work area in my basement, it will need to be GFCI protected. If I terminate each circuit with a single GFCI outlet, will I be good? Thanks.

darren

Yes you can feed two GFI on a multiwire branch circuit. You HAVE to make a joint on the neutral for this to work. On that note you always have to make a joint on the neutral when you are dividing the circuits on a MWBC.

You can not use a 3 wire to come off the line sides of two GFI and share the neutral.

lfparker

Thanks - I understand the theory, but as a practical matter, is my proposed wiring sequence correct?

After running 12-3 romex from a 2-pole 20 amp breaker at the panel, at circuit 1 GFCI receptacle I should:

• connect the black hot wire to the receptacle screw.
• pigtail the white neutral and feed to the 2nd circuit's GFCI receptacle.
• pigtail the ground and feed it also to the 2nd circuit's GFCI receptacle
• splice the red wire with a wirenut to the black wire on another section of 12-2 romex and feed to the 2nd circuit.

Then at the second circuit I terminate the black, white, and ground on the GFCI receptacle.

I think this is correct, is that right or am I offbase? Thanks.

jbfan

Right on the money!

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lfparker

Cool thanks!

AllanJ

You mean load side, no?

Probably not common but you could have a MWBC feed arrive at a square or double gang box where there are two GFCI duplex receptacle units. Pigtail the neutral to the GFI line side neutrals, red wire to one GFCI line side hot and black to the other GFCI line side hot. Continue GFCI protection downstream using 2 wire cable(s) from the load terminals of one or both GFCIs.

__________________
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.

darren

Allan that is what I meant, thanks for correcting that.

skipoff

wow guys ...you might know alot about eletrical but your communications skills need work. I understood what he was talking about in the very first thread. You made it very complicating...he said nothing about 240 volt. Reread his first post and quit being so arragant. He wants to create two outlets on two seperate breakers and he wants to know if he can share the neuteral (white wire....sorry for being a smart ass). This site is to HELP with DIY not make them feel stupid.

skipoff

oops disreagard thte 240 comment....didnt see his second paragraph.

skipoff

Ok, lets see if i can gets a POLITE answer about my question. I am creating a mother inlaw. 50 ft run in 1" plastic conduit. stove and microwave. stove on 50 amp breaker microwave on 20 amp breaker. stove hase 4-8 gauge wires 2 hot/1 neuteral/1ground. microwave using 12 gauge. Question is....can I use the 8 gauge neuteral and ground form the stove to share with the microwave? Now that is as plain and simple of a question as i can possible make it. Thanks and please dont be rude....

stickboy1375

Try starting a new thread...... hope that wasn't rude.

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