Questions tagged [mwbc]

Use this tag for questions about Multi-Wire Branch Circuits, sometimes called "Edison circuits".

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Sharing Neutrals - How To Correct?

I have a 12/3 NM cable landing on two separate 20 amp breakers sharing a neutral between the two. They are landing on a Dishwasher/Garbage Disposal outlet. I understand this is NOT to code since there ...
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  • 344
2 votes
3 answers
1k views

Is this MWBC setup allowed?

I'm continuing to fix the issue introduced by someone else (Why run the same phase twice to a series of outlet?). The other room they did has this setup: a 3-conductors cable brings the same phase ...
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  • 1,649
2 votes
2 answers
243 views

Replacing single duplex outlet on MWBC with two of them in kitchen?

My kitchen has a single duplex outlet (so two devices can be plugged in) on a multiwire branch circuit. I'd like to tear that out, replace it with a larger box and install two GFCI duplex outlets. ...
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  • 5,539
0 votes
2 answers
64 views

Changing Tandem Breakers with Potential Unmarked MWBC

I have two adjacent 20A tandem breakers in my panel. I need to change one of the breakers on each tandem to 15A (in order to protect 14 gauge wires on the respective circuits). The possibility exists ...
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  • 41
7 votes
1 answer
645 views

House Wired Incorrectly? - MWBC [duplicate]

I am working on finishing my basement. In my basement there is 3 junction boxes fed by 12/3 wire. Each junction box feeds a single 12/2 line (White-White, Black-Black, Ground-Ground, Red-Nothing). My ...
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  • 71
4 votes
4 answers
1k views

Is a 120V/208V MWBC good enough for 240V loads?

As detailed in a previous post, I was planning to use the dryer circuit in my condo as a MWBC. A 120V/20A outlet between one of the two hot conductors and neutral would power my small washer and dryer ...
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  • 151
2 votes
1 answer
120 views

Replacing receptacle & switch on a MWBC in kitchen

Background: The house was built in 1983. Previous owner(s) have been creative on some DIY projects around the house. The receptacle was wired half direct & half sideways. Problems: The switch on ...
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  • 23
0 votes
3 answers
226 views

How can I safely utilize a dryer outlet to power 100V and 220V loads?

In my house there is a dryer outlet that, even though inconvenient to me (my dryer is 120V), I don't want to eliminate for house reselling reasons. As it was until now a 3 prong outlet, I have been ...
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  • 151
0 votes
1 answer
136 views

Shared neutral on two circuits using a single-pole tandem breaker

I just looked inside of my sub-panel for the first time, which has ten single-pole tandem breakers. They all have two black wires connected, except for one breaker, which has a black wire and a red ...
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  • 315
5 votes
1 answer
368 views

MWBC with both circuits on the same bus -- any easy fixes?

While moving some wires around in my garage (to make space for attic storage), I discovered an electrical issue that might be concerning: In my garage there are two circuits delivered as a MWBC, but ...
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  • 153
4 votes
2 answers
882 views

Is this a bunch of wrong MWBCs?

I've just opened up my main panel with the plan of adding a new circuit, but have temporarily aborted that idea after squinting for a while, followed by getting worried. I put some pictures from more ...
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  • 73
2 votes
1 answer
213 views

Wiring for switched NEMA 6-20R and 5-20R in same box in garage

My goal is to have 20A receptacles in a particular spot in my garage dedicated to power tools (such as saws) whose motors can be configured for either 240V or 120V, with a switch as a handy second ...
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6 votes
2 answers
2k views

Look over father's plan to fix outdoor electrical circuit

So to begin with, I am not a DIY'er when it comes to electricity. I prefer to allow the professionals to handle these matters as it's not something I'm confident in and not too knowledgeable about... ...
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8 votes
3 answers
3k views

Splitting 240V into two 120V Circuits

I think I have this figured out for the most part but looking for validation from expert strangers on the internet. Renovated the kitchen in this 1960's house. I think it probably has been renovated ...
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2 votes
1 answer
120 views

GFCI breaker on a MWBC (Shared common)

We are doing kitchen reno. We had to replace the main breaker panel. Local code requires we use arc fault breakers. This is not an issue for most of the project, however, the inspector is insisting ...
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0 votes
2 answers
224 views

GFCI receptacle connected to Multi-Wire Branch Circuit

I have a Multi-wire branch circuit & would like to connect GFCI receptacles. The MWBC currently powers dimmable LED lights in basement. In process of finishing basement. I would like to extend ...
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0 votes
2 answers
103 views

Identifying what receptacles and fixtures are on each branch of a MWBC

How should I safely identify which breaker controls which fixtures & receptacles in a Multi-Wire Branch Circuit? There is intentionally a handle tie for the MWBC in my panel which must be kept to ...
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  • 95
2 votes
3 answers
140 views

Disposal Circuit Update

I moved to a house built in 1995 and want to update the disposal connection, but found some conflicting rules that I don't know how best to comply with. The existing connection is a 14-2 NM cable run ...
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0 votes
2 answers
98 views

3 phase MWBC - 2 pole breaker with shared neutral

I’ve searched around and can’t quite find an answer to my question. I understand that you can share a neutral on a 3 phase panel if you use a 3 pole breaker. But can you still share a neutral on a 3 ...
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  • 1
4 votes
3 answers
553 views

MWBC exists, use for bathroom?

I am finishing my basement. The previous owner had ran a MWBC to the area that will be the bathroom. In the panel it is two 1-pole 20amp breakers. My questions are: First to confirm, it seems I ...
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  • 43
2 votes
2 answers
228 views

MWBC for split kitchen receptacle

When installing a split receptacle in a kitchen, where the top and bottom are each their own circuit, is there any way you can use an MWBC, or is your only option to run two normal circuits with two ...
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2 votes
2 answers
216 views

Can I have an MWBC plus another circuit in the same junction box?

The conduit coming in on the left carries a 15 A MWBC. In this junction box, it splits to the brown-to-black wire for the furnace, and the orange wires to some basement lights (top) and an upstairs ...
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  • 848
4 votes
3 answers
2k views

Two Circuits on a Single 12/3 - Shared Neutral

I was recently trying to upgrade a 20A breaker supplying outlets in my kitchen and dining room to a CAFCI breaker. When I opened my breaker box I saw that the neutral on this circuit was shared with ...
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5 votes
3 answers
539 views

Multi-Wire Branch Circuit on wrong breakers

My electrical panel has a double-pole breaker that looks like it's for a MWBC, but actually the attached wires are from different cables. In the below picture the black wire with the yellow rubber ...
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5 votes
2 answers
1k views

In a multiwire branch circuit, can the two hots be connected to the same phase?

This may be an obvious question, but I haven't been able to find a direct answer. I believe I have a MWBC - I have two hot wires connected to two separate circuit breakers, sharing a neutral and ...
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  • 51
2 votes
2 answers
211 views

Is this a weird or very problematic shared neutral?

I will try to explain it and I made a drawing that give an idea of what it seems to look like. I just had some work done on my house (built in 1967) and the electrician found this weird connection. I ...
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  • 175
8 votes
3 answers
980 views

Neutral pigtails on MWBC

I've recently moved into a new home with a few outbuildings. Due to the property being in rural unincorporated area, no inspections or permitting was required on the outbuildings when they were built ...
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  • 715
2 votes
1 answer
454 views

2 independent GFCI (or 2-pole GFCI) outlet in 1-gang box. Does that exist?

I have a 1-gang duplex outlet under the sink in my kitchen. The two outlets are on separate phases of a single MWBC circuit. One of them powers the garbage disposal, and is controlled by a switch. The ...
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  • 251
3 votes
2 answers
657 views

Is it possible to wire 2 GFCI receptacles on 2 circuits with 12/3 wire shared neutral?

I am planning to run a few needed 20amp outdoor receptacles (and therefore want GFCI). My plan was to run 12/3 wire from 2 separate circuits in the panel to a double gang weatherproof box with 2 gfci ...
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3 votes
1 answer
92 views

MWBC and very low power factors

The principle of an MWBC is that two hots can share a neutral if they're on opposite phases, since the current on the neutral will cancel instead of adding. But isn't this only true for loads with ...
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0 votes
1 answer
221 views

Diagnosing a suspected multi wire branch circuit

Last week I lost power to my new garbage disposal. I opened the box to find this: There are three cables coming in from the bottom. Two of these are somewhere downstream from the Panel, not too sure. ...
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0 votes
2 answers
159 views

Convert MWBC to single 240V receptacle

I currently have a 20 amp double pole breaker supplying a multi-wire branch circuit for two 120v receptacles in a double gang box. I'd like to remove the 120v receptacles and install a 240v receptacle....
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  • 1
1 vote
1 answer
160 views

Is this a MWBC?

I think I have some MWBCs that are not handle tied. Can you tell from this picture if the bottom red breakers and top blue breakers are MWBCs? I can't trace back to the conduit and they supply "...
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  • 11
2 votes
1 answer
74 views

Can I serve mwbc 110v from 220v circuit?

If I have a 240v 20a circuit serving a single 240v 20a receptacle (12/3) can I leave the 240v receptacle in service then branch two 120v 20a circuits from it?
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  • 8,677
4 votes
2 answers
507 views

Shop Electrical - MWBC Serving 240V and 120V Outlets

I've seen this setup in use in other shops and am interested in using the technique myself. However, the mere mention of it seems to incite rabid pandemonium rather than civil discourse. I'd very ...
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1 vote
2 answers
192 views

Overloaded circuit on ungrounded outlets

So I've stumped/annoyed most of the internet with this one. I hope there might be someone who can point me in a different direction.. I have a house built in 55 with ungrounded outlets. A space ...
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  • 11
1 vote
2 answers
1k views

Connecting 120/240 receptacles on the same circuit breaker

I want to add a branch circuit to the control panel using 12/3 wire and protected by 20 amp double pole circuit breaker. Is it safe to connect multiple duplex receptacles 120 volts and 240 volts on ...
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0 votes
2 answers
301 views

MWBC for Fridge and Microwave

I've recently learned about Multi-Wire Branch Circuits and intend to use one to provide dedicated circuits for both my built-in microwave and refrigerator. I understand the requirements around handle ...
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  • 356
4 votes
2 answers
369 views

Possible to ground-fault protect both legs of a MWBC with two single-pole breakers?

To get a MWBC working, with both legs GF protected, I installed 2 Single Pole GFI breakers, on adjacent slots, with a handle-tie. Since there are 2 lugs for Neutral wires, and only one neutral coming ...
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  • 81
4 votes
2 answers
506 views

is this the right way to ground fault protect both sides of an mwbc?

is this the correct way to ground fault-protect both sides of an mwbc? pigtail the (line) neutral to two separate gfci outlets, and pigtail the (load) neutrals to the neutral that's going outside.
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  • 81
0 votes
1 answer
258 views

Microwave on 220 volt branch

A friend has a microwave on the same circuit as electric stove. Independently they work fine but if an element on the stove is on and the microwave is turned on the breaker goes off. An electrician ...
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4 votes
2 answers
9k views

Understanding the wiring of 2-Pole Quad Circuit Breakers

I only want to understand the concept, so you dont have to address if my panel accepts tandem breakers or a certain brand of breakers. I will also omit any reference to ground wires for clarity. I ...
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  • 75
6 votes
1 answer
4k views

Why are tandem breakers on shared neutral (MWBC) problematic?

I hear that shared-neutral or multi-wire branch circuits (MWBC) can have issues when used with tandem breakers (also called duplex, twin, cheater or double-stuff breakers). What is the issue there? ...
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0 votes
3 answers
199 views

2 breakers - should they work as one?

I have a circuit with 2 15 amp breakers. They don’t act, individually they both have to be shut off to shut off the circuits. Am I looking for an outlet with two devices? Example switch and outlet? ...
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1 vote
1 answer
633 views

Can I use a two-pole single handle breaker for mwbc?

I have a mwbc with two 20A breakers with their handles clipped for common trip. Can I replace this ensemble with a single two-pole 20A breaker with just one handle? New panel in CA. I'm unsure ...
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  • 8,677
0 votes
2 answers
2k views

Best way to get both 120V and 220V from existing multiwire branch circuit (MWBC)

I have a double pole 20A breaker feeding a 120V MWBC with 12/3 with ground, romex that goes up three levels to two separate 120V duplex GFCI receptacles with common neutral. I want to have both 120V ...
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  • 56
4 votes
2 answers
2k views

MWBC (Multi-Wire-Branched-Circuit) w/out joined breakers, how best to fix?

I was trying to replace a fan/light in my living room with a new led light, and have found that the living room branch circuit (lights and outlets) is actually fed by a Multi Wire Branch Circuit (14-3)...
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5 votes
2 answers
5k views

Change from 240V to 120V

I did quite a bit of research including on this forum but wanted to double check if I got things right. On the outside of our home there is a standard electrical box (guessing about 3"x5") to install ...
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  • 51
1 vote
1 answer
85 views

MBWC using two twin breakers with middle handles tied

My question is whether overload protection will work for the two handle tied circuits described below: Four separate circuits are involved. These are in a residence, feeding outlets and lights, ...
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0 votes
2 answers
138 views

Separate Phases for Residential Wiring

I am trying to find out if I can use a 14/3 cable to power two separate circuits, and to do that I know I must use two separate phases, but I am not sure how to do that.
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