How do I identify multi-wired circuits?

[wyliesdiesels]

If that was the situation, then I would have a potential problem now....generator usage or not. Correct? I think every other breaker uses a different leg.

only if you pulled enough current to overload the neutral...

 

[Norcal]

If those are twin or slim breakers as Norcal pointed out, make sure the MWBCs actually are on different stabs. Seems to me you could get that part wrong.

GE breakers due to the design are rarely a problem with that, GE is the only brand in current production where a twin can be used for 240V, with Siemens QP, SQ D, HOM, & Eaton BR a quad is required for 240V.

 

[sparky 1971]

only if you pulled enough current to overload the neutral...
[/QUOTE]

And what are the odds one neutral from a MWBC is going to get overloaded when running an entire house off a 120 volt 3500 watt genie?

My last house had 18 MWBC'S in it, we lost power for three days due to an ice storm. I grabbed the generator from the shop and made myself a suicide cord, plugged it into a basement receptacle,, stuck a two pole 30 amp breaker in the panel with the poles jumped together, turned off the main and never gave it another thought. I ran the entire house like that. All gas appliances and it was winter so no AC wasnt an issue.

 

[Spacecoastz]

Slim breakers have two breakers per leg. So each pair would be together.

So if you take the right side, top to bottom and number the breakers starting at one, with full size breakers, 1, 3, 5, etc would be on the same leg. With tandem (half size), 1, 2, 5, 6, 9, 10, etc would be on tbe same leg. So a MWBC would need to go on 2 and 3 instead of 1 and 2 or 3 and 4

So if you look at one of my photos, the first breaker (top) on the right side is a 120v feeding the washing machine. The next two down is 240v service for the dryer. Counting the individual wires down the first red wire for 120v is wire number eight...just below the breaker that has a white dot on it. So what positions would the MWBC's be on? Or what would be the first breaker that is a MWBC?

 

[dave*99]

Would this help you? Seems like you are trying to trace out the individual breakers

 

[dogdog]

Looking in my panel the wires are really bundled and tied together. Really hard to see what black/red wires are coming from the same cable. Any other ways to determine what shares the neutral?

It’s super simple to do, dependents on how far each circuit is away from your breakers in your house. And dependents on your comfort level of working the electricals of cause.

MWBC just means the neutral wires are shared supposedly between the L1 and L2.

Just create a spread sheet and shut off main power and use a long extension and multi meter and identify what breaker used what neutral. Log them in spread sheet and sort them. Just becareful not to poke into the incoming large wires that is still live before the main breaker.

 

[AntonLargiader]

If your MWBCs are wired to the same pattern as your 240s are, then obviously you're fine. And it sort of looks like that to me, based on the appearance of the wires, but you're the one that's there.

 

[mike93lx]

So if you look at one of my photos, the first breaker (top) on the right side is a 120v feeding the washing machine. The next two down is 240v service for the dryer. Counting the individual wires down the first red wire for 120v is wire number eight...just below the breaker that has a white dot on it. So what positions would the MWBC's be on? Or what would be the first breaker that is a MWBC?

So that aligns with my post. Combining 2 and 3 gives you 240v.

8 and 9 could be a MWBC. Basically you need an even plus the one next in line. 10 and 11, 12 and 13, etc

On my phone so it's hard to go back and forth from the pic to this post

 

[sparky 1971]

All he has to do is cut a couple of easily replaceable tie wraps and everything will be plain as day.

 

[Spacecoastz]

I'm beginning to wonder if all of my MWBC's are already on the same phase. I say this because wire/breaker #13 (black) and wire/breaker #14 (red) look to be smaller gauge (maybe 14 gauge) whereas the wires above them look to be 12 gauge. You're not going to get a cable with two different size gauge of red and black...right...or can you? And being in position 13/14 would put them on the same leg. It would need to be in position 12/13,or 14/15 to be on different legs. I'm going down a rabbit hole. Looks like I may need to cut the ties and see what I can trace.

 

[wyliesdiesels]

Why don’t you just cut the zip ties and trace the individual conductors back to their entry end of the panel? You’re making this more difficult than it has to be

 

[dogdog]

I'm beginning to wonder if all of my MWBC's are already on the same phase. I say this because wire/breaker #13 (black) and wire/breaker #14 (red) look to be smaller gauge (maybe 14 gauge) whereas the wires above them look to be 12 gauge. You're not going to get a cable with two different size gauge of red and black...right...or can you? And being in position 13/14 would put them on the same leg. It would need to be in position 12/13,or 14/15 to be on different legs. I'm going down a rabbit hole. Looks like I may need to cut the ties and see what I can trace.

You can’t find magic cure over the internet here, only way to find out is to map it out. It’s easier if it is a sub panel and you have reaching distance to alll plugs and switches

 

[sparky 1971]

Why don’t you just cut the zip ties and trace the individual conductors back to their entry end of the panel? You’re making this more difficult than it has to be

Ah, c'mon man. That would way too easy and make way too much sense. This is garage journal, where what seems like the simplest of tasks turn out to be more difficult than moving a mountain with a teaspoon.

An even easier solution would be to not use the toaster and microwave at the same time if it's that big of a concern. But what do I know? I obviously am clueless as to what the ramifications could be. And, as I already stated, it's too effin' easy.

 

[sparky 1971]

I'm beginning to wonder if all of my MWBC's are already on the same phase. I say this because wire/breaker #13 (black) and wire/breaker #14 (red) look to be smaller gauge (maybe 14 gauge) whereas the wires above them look to be 12 gauge. You're not going to get a cable with two different size gauge of red and black...right...or can you? And being in position 13/14 would put them on the same leg. It would need to be in position 12/13,or 14/15 to be on different legs. I'm going down a rabbit hole. Looks like I may need to cut the ties and see what I can trace.

For the sake of all things holy, don't do that. There are a lot of other ways to accomplish the task that will eat up more time and if you do it right, money.

 

[Spacecoastz]

Sparky I appreciate your input....so for now lets put this to rest until I can do some tracing.

 

[dave*99]

Ah, c'mon man. That would way too easy and make way too much sense. This is garage journal, where what seems like the simplest of tasks turn out to be more difficult than moving a mountain with a teaspoon.

An even easier solution would be to not use the toaster and microwave at the same time if it's that big of a concern. But what do I know? I obviously am clueless as to what the ramifications could be. And, as I already stated, it's too effin' easy.

Raising the concern to run the house. The toaster. The microwave. On a 3500 watt generator. Says a better master plan is required. Individual wires are not the main factor.

 

[Spacecoastz]

No one is saying that you run a toaster and microwave at the same time with a small generator. In fact, I would simply turn off the inside frig for whatever time we would need to heat food in the microwave. The microwave is 1,700 watts max. I've done this many times before over the last 20 years using a smaller generator.

 

[sparky 1971]

Raising the concern to run the house. The toaster. The microwave. On a 3500 watt generator. Says a better master plan is required. Individual wires are not the main factor.

It will do it, just need to keep in mind that it's a 3500 watt generator and watch what is running. I've done it for three days with a 3500 watt 120 volt generator. I was single at the time so there no wife and kids doing stupid stuff to worry about, but I did laundry, microwaved dinner, ran the dishwasher, etc. And it was in the middle of winter so the furnace ran a lot.

 

[Spacecoastz]

So I thought I would give a follow-up as to what I found...plus I have a few questions depending upon what I might do. I first validated what each circuit actually powered, top to bottom of the right side of the panel. Actually found a few labeling mistakes which were all within the MWBC's. No big deal. Next I cut the ties and using two zip ties (removed the locking tap) I trace each red wire to the cable, and traced back the black. Every MWBC was arranged exactly as I expected....for example, the microwave and the two outlets below the microwave between the range share the neutral. The refrigerator, and the single outlet next to it share a neutral...and so on. Remember, in my situation every 120v breaker is an individual breaker....no tandems. And in every case for the four MWBC's the black wired circuit is just above the red wired circuit.
But here is what I also found...which I suspected...and that each MWBC is on the same phase. Been that way for 20+ years. So the refrigerator and the 1,500 watt air fryer use the same neutral. The microwave and the 1,000 watt toaster share the same neutral, etc.
So....I need to decide if I 1) do nothing, 2) move those eight breakers up one spot and move something down, or 3) move those eight breakers down and move something up. I think I have enough wire slack for number 3. So here are my questions:

When I move anything, should I leave the wire intact on the breaker and move the entire wire/breaker as a unit...or disconnect each wire and just move wires?

If I find that its best to move the MWBC's up one spot and thus move something down (like the Garage outlet circuit) which requires additional wire to be added, what is code for adding length to a 12 gauge 120v circuit inside a panel?

Is there another option that I not seeing?

Here is what I found:
Also....thank you to whoever suggested using a zip tie to trace the wires....that worked really well.

 

[mike93lx]

You can extend wires in a box without an issue. Wire nut or wago, whichever you prefer.

As long as you keep wire gauge aligned with breaker size, it's up to you on moving wires or breakers.

I'd try to move around as little as possible

 

[dave*99]

So I thought I would give a follow-up as to what I found...plus I have a few questions depending upon what I might do. I first validated what each circuit actually powered, top to bottom of the right side of the panel. Actually found a few labeling mistakes which were all within the MWBC's. No big deal. Next I cut the ties and using two zip ties (removed the locking tap) I trace each red wire to the cable, and traced back the black. Every MWBC was arranged exactly as I expected....for example, the microwave and the two outlets below the microwave between the range share the neutral. The refrigerator, and the single outlet next to it share a neutral...and so on. Remember, in my situation every 120v breaker is an individual breaker....no tandems. And in every case for the four MWBC's the black wired circuit is just above the red wired circuit.
But here is what I also found...which I suspected...and that each MWBC is on the same phase. Been that way for 20+ years. So the refrigerator and the 1,500 watt air fryer use the same neutral. The microwave and the 1,000 watt toaster share the same neutral, etc.
So....I need to decide if I 1) do nothing, 2) move those eight breakers up one spot and move something down, or 3) move those eight breakers down and move something up. I think I have enough wire slack for number 3. So here are my questions:

When I move anything, should I leave the wire intact on the breaker and move the entire wire/breaker as a unit...or disconnect each wire and just move wires?

If I find that its best to move the MWBC's up one spot and thus move something down (like the Garage outlet circuit) which requires additional wire to be added, what is code for adding length to a 12 gauge 120v circuit inside a panel?

Is there another option that I not seeing?

Here is what I found:
Also....thank you to whoever suggested using a zip tie to trace the wires....that worked really well.

It appears your MWBC's are not MWBC's If this is confirmed, I'd open all those boxes and inspect.

 

[AntonLargiader]

But here is what I also found...which I suspected...and that each MWBC is on the same phase.

How did you determine that? When you first posted this I did a brief web search which indicated that the layout of that panel wasn't so intuitive. Did you measure line-to-line on those circuits and you got zero volts? That would indicate that they are indeed on the same phase.

 

[Spacecoastz]

Ok...first of all, the idea of using a generator is not the subject for now...so forget that. What I wanted to know was what circuits share a neutral. I was fairly sure that I knew just from seeing what circuits were near the red wires, but I was not certain. So, I traced every one of them...and if you look at my attachment you can see where they are (with the X's), what they are, and what phase (last column by color code) they are on. I also validated that using my meter those individual MWBC's are not in a 240v position. Each one (one MWBC but two individual circuits) are on the same leg. I know for certain that each one has to move by one space...either all of them up one....or all of them down one in order to put each MWBC on different legs and thus different phase. Again...look at the attachment.

The only thing I'm looking for are regarding my questions.

 

[Spacecoastz]

How did you determine that? When you first posted this I did a brief web search which indicated that the layout of that panel wasn't so intuitive. Did you measure line-to-line on those circuits and you got zero volts? That would indicate that they are indeed on the same phase.

yes......and did that for each MWBC. Each one is in a position of A/B. To get 240V (different phase) each one needs to be in position B/A.
Also, the bottom of my panel on the left side has some empty spaces...and I can physically see how it works in order to get from one leg to the other leg. It always has to be position B/A...or stated another way space 2/3, 4/5, 6/7, 8/9, etc.

 

[Spacecoastz]

The last column shows the circuits that share a neutral along with color denoting which phase. I enhanced on colors on this attachment.

 

[dave*99]

In principle, you could move the 8 wires or breakers up 1 position as you mention. Then move the first circuit from the top of the 8 pack to the bottom of the stack.
But WOW, it's hard to imagine someone was so careful in wiring the panel so neatly and made a major screw up like this.
You really need to open those boxes and inspect the neutrals.

Just to confirm - you went in the kitchen and stabbed your voltmeter probes into the line side of the pairs of outlets and confirmed zero volts? I'd want to be 1000% sure before I moved a wire.

 

[Spacecoastz]

I checked a couple of ways....
1) I installed an extension cord into the frig outlet, and took a reading with the outlet that I thought might share the neutral (which it does based on the tracing that I did later), making sure I went into the hot inputs.....got zero volts.
2) traced the wires to determine what shared the neutral (power was off) and then after turning the power back on took readings with the meter and got zero volts. I kept track of the tracing....plus it turned out how I expected. This is why I suspected that they were on the same phase as I posted a while back...when I was still somewhat confused.
3) looked at it physically...which you can do too. Look at the attachment and look where the 240V breakers are. See the location...its on 2/3 position...which is a B/A position. All the MWBC's are on a A/B position...same phase.

I think what I need to do is remove and disconnect breaker #15 (Bedroom #2) 15 amp....then working from bottom up move each of the breakers/wires from #14 through #6 down one position, then reinstall the #15 breaker into spot #5 along with disconnected Bedroom feed. Part of the problem is that the last MWBC (Family Room) is 15 amps, whereas the kitchen MWBC's are 20amps. I need to keep to same breaker ratings. And the Bedroom breaker is also 15 amps. I can't just move wires.

Because none of these breakers are tandem, I think its an easy mistake for the electrician to make...and the breakers are individual and can go in any spot. Maybe that's why the code was changed to tandem breakers so that this kind of mistake doesn't happen.

 

[mike93lx]

I checked a couple of ways....
1) I installed an extension cord into the frig outlet, and took a reading with the outlet that I thought might share the neutral (which it does based on the tracing that I did later), making sure I went into the hot inputs.....got zero volts.
2) traced the wires to determine what shared the neutral (power was off) and then after turning the power back on took readings with the meter and got zero volts. I kept track of the tracing....plus it turned out how I expected. This is why I suspected that they were on the same phase as I posted a while back...when I was still somewhat confused.
3) looked at it physically...which you can do too. Look at the attachment and look where the 240V breakers are. See the location...its on 2/3 position...which is a B/A position. All the MWBC's are on a A/B position...same phase.

I think what I need to do is remove and disconnect breaker #15 (Bedroom #2) 15 amp....then working from bottom up move each of the breakers/wires from #14 through #6 down one position, then reinstall the #15 breaker into spot #5 along with disconnected Bedroom feed. Part of the problem is that the last MWBC (Family Room) is 15 amps, whereas the kitchen MWBC's are 20amps. I need to keep to same breaker ratings. And the Bedroom breaker is also 15 amps. I can't just move wires.

Because none of these breakers are tandem, I think its an easy mistake for the electrician to make...and the breakers are individual and can go in any spot. Maybe that's why the code was changed to tandem breakers so that this kind of mistake doesn't happen.

Are the wires run on those 15a circuits #12 or #14?

 

[Spacecoastz]

Are the wires run on those 15a circuits #12 or #14?

They look to me as #14. Go back to page 1 and see actual photos....

 

[wyliesdiesels]

whats the model # on your panel? I see that its GE...

 

[Spacecoastz]

TM20EC

 

[dave*99]

Since you will want to have a look at the neutrals in the kitchen junction boxes anyway:
make one final test and measure from red to black and also red to white and black to white in any box that has all 3 just to confirm.

 

[Spacecoastz]

What would I confirm? I confirmed by clearly tracing each individual red wire up to the individual cable that contained its white, black, red, and ground wires. Then I carefully traced the black back down to its breaker/circuit. Each set of MWBC were:
1) black wire/circuit directly above the red wire/circuit in the panel, and
2) each MWBC was exactly wired how I thought it would be based on what the red wired circuits supplied...in other words the black wired circuits were what I expected based on location of what the red circuits powered.
Example: kitchen island outlet and the dishwasher share the same neutral becasue they share the same cable. Why? Because the kitchen island is fed by an under-slab conduit that originates in the wall behind the dishwasher, so it makes sense that the electrician would run those wires in that fashion...feeding the black of the cable to the dishwasher and using the red to power the kitchen island outlet. Simular situation for the other three MWBC's. Each one is close together in location.

So far the only possible over-loading would be using the toaster (1,000 watts max, with all slots being used) at the same time as the microwave (1,700 watts at full power) is being used, which is fairly unusual and would not last very long. Nonetheless, I still want to correct the wiring because I don't like it being incorrect.

 

[wyliesdiesels]

TM20EC

that is the front cover part number.... but regardless, based on several panel labels ive seen with the same cover, you are correct in that an AB arrangement for 2 breakers feeding a MWBC or 240v load will not have 240v potential as they both connect to the same bus.

in order to get 240v potential you need to do the BA arrangement...

 

[wyliesdiesels]

But WOW, it's hard to imagine someone was so careful in wiring the panel so neatly and made a major screw up like this.

You really need to open those boxes and inspect the neutrals.

Just to confirm - you went in the kitchen and stabbed your voltmeter probes into the line side of the pairs of outlets and confirmed zero volts? I'd want to be 1000% sure before I moved a wire.

its actually easy to do on a GE panel. on other panel brands, they dont have AB arrangements like GE does. so the busses alternate in each breaker space. with GE's AB breaker arrangement, both A and B position on each circuit # connect to the same buss. its because GE has slim half space breakers.... so whoever wired this panel wasnt paying attention...

 

[Spacecoastz]

Thanks for checking on my panel. I had a suspicion that they were on the same buss...and confirmed by tracing and taking meter readings. Also the lower left section of my panel is unused...so with the cover off and can see how the physical buss/breaker attachment points work.

 

[Spacecoastz]

I wonder if I could get a new blank panel label? I'll need one.

 

[mike93lx]

I wonder if I could get a new blank panel label? I'll need one.

Make a label up in excel. You can buy adhesive sheets at places like Staples, or just print and tape it on the inside of the cover

 

[dave*99]

New blank panel labels are available for the write in section.
I found an excel template online for my Eaton panel.
I typed all the circuit names in, printed it and used spray label adhesive to attach. It fits exactly and covers the old handwritten info perfectly.

 

[dave*99]

What would I confirm? I confirmed by clearly tracing each individual red wire up to the individual cable that contained its white, black, red, and ground wires. Then I carefully traced the black back down to its breaker/circuit. Each set of MWBC were:
1) black wire/circuit directly above the red wire/circuit in the panel, and
2) each MWBC was exactly wired how I thought it would be based on what the red wired circuits supplied...in other words the black wired circuits were what I expected based on location of what the red circuits powered.
Example: kitchen island outlet and the dishwasher share the same neutral becasue they share the same cable. Why? Because the kitchen island is fed by an under-slab conduit that originates in the wall behind the dishwasher, so it makes sense that the electrician would run those wires in that fashion...feeding the black of the cable to the dishwasher and using the red to power the kitchen island outlet. Simular situation for the other three MWBC's. Each one is close together in location.

So far the only possible over-loading would be using the toaster (1,000 watts max, with all slots being used) at the same time as the microwave (1,700 watts at full power) is being used, which is fairly unusual and would not last very long. Nonetheless, I still want to correct the wiring because I don't like it being incorrect.

Somewhere around post 10 you expressed concern about overloading the neutrals in your MWBC's if you were to use a 120V generator. As others have said - a 3500W generator with a few loads connected does not leave a lot of headroom to run a toaster and a microwave too. I think those were the loads you were worried about.

Long term use of the miswired circuit from the utility supply provides a greater opportunity to overload the neutrals. So I assumed you would have an even greater concern. Hence my suggestion to inspect once you learned of the miswiring. If I was therefore inspecting, it would be a simple matter to double check at the receptacle end.