One neutral, two different loadcenters

[grasfulls]

I have been "fixing" a modular lighting system and in one of the module enclosures were several 14/3 NMS cables leaving the enclosure. Pulling everything apart we found a 14/2 from one loadcenter feeding one leg going out (straight through the panel, no connection to any module output). The neutrals were also tied together with a jumper to one of the neutral bars for modules. The other feed out was fed by an output on a module, the input coming from a different load center. The loads feeding straight through are for constant power to 1/2 of duplex receptacles in rooms. The loads feeding from modules are for the switched half. We disconnected the jumpers to module neutral bars and lost power to plugs.
We checked with a volt meter and there was still power but no neutral. We opened the panels, one with breakers for house loads (P1), one with breakers for lighting modules (P2). A side point here is that the phasing of A and B is different for both panels so there is 240 vac potential from phase A to phase A and Phase B to phase B.
We found three neutrals not connected in P1. Checking voltage from disconnected neutral to the associated breaker showed 240 volts, so we knew there was back-feed from a breaker on the other phase. It turned out to be the breaker feeding the module inputs that in turn fed the switched half of the receptacles. They are on the same phase if you just go A, B, A ,B etc, that is when we noticed the inverted phasing. So, the switched half has its own breaker from P2, and the constant power its own breaker form from P1, but with the 14/3 going out to the areas, there is really only one neutral. We wanted to land all of the neutrals so we made sure everything was phased the same (no 240 from from two different panels in a box), but now we are potentially loading up the neutral. We have suggested to the owner to drop the circuit from P1 and feed all of the plugs with one breaker so as to insure no overloading the neutral.
What are your thoughts?
1) Keep one breaker from each panel but on different phases and there is now 240 under the yoke of the receptacle but a balanced neutral?
2) Put the two breakers in one panel and use a tied 2-pole breaker?
3) Abandon one breaker and feed both halves of the receptacle with one breaker?
4) Leave the panel's opposite phasing alone (should not have been an issue if wired properly)

I think I will make a little drawing because this is very weird.

thanks!
gare

 

[grasfulls]

Made a drawing

Made a drawing

Attachment: 2 panels one plug.pdf
It may not be beautiful, but you can see a little better what I tried to relay in writing.

 

[JFletcher]

Having a hard time understanding your described install, but a MWBC has to originate from one panel. Having one hot leg power the receptacles while the other powers the switched half is okay. If that neutral serves more than 2 circuits you need to eliminate the double fed circuits. It is impossible to overload the neutral on a properly wired MWBC. Whatever panel the 14/3 comes in, I would make the appropriate connections there and eliminate the split circuit between the two panels.

 

[Smart $]

Run all circuit conductors from one panel. Whether a 1-pole 2-wire circuit, or a 2-pole or (2) 1-pole handle-tied 3-wire circuit does not matter per se under the NEC.

An alternative is separate the noodles all the way through the circuits.

 

[grasfulls]

Hard to understand

Hard to understand

Having a hard time understanding your described install, but a MWBC has to originate from one panel. Having one hot leg power the receptacles while the other powers the switched half is okay. If that neutral serves more than 2 circuits you need to eliminate the double fed circuits. It is impossible to overload the neutral on a properly wired MWBC. Whatever panel the 14/3 comes in, I would make the appropriate connections there and eliminate the split circuit between the two panels.

Sorry, it was/is hard for me to explain. I think I will draw it completely. I agree, eliminating one circuit at this stage is the quickest fix. Thank you for taking the time to try and understand it.

 

[grasfulls]

Drop a circuit or split up neutrals

Drop a circuit or split up neutrals

Run all circuit conductors from one panel. Whether a 1-pole 2-wire circuit, or a 2-pole or (2) 1-pole handle-tied 3-wire circuit does not matter per se under the NEC.

An alternative is separate the noodles all the way through the circuits.

Exactly, how on earth did you figure out what i said (rhetorical)? Neutrals all the way through would be optimum but with everything closed up, that would be intrusive and costly.
Thank you for the input. I envision a "discussion" between the owner, the original installer, and myself and wanted to have some back-up as to what is in error with the installation. It is a rather convoluted install and I hate getting involved in heated discussions. The moral thing would be for the installer to make the necessary "fixes" and not encumber the homeowner with further costs. If they had run two 14/2's out to the plugs and broke the tab on the neutral side, and phased things properly, this would be a non-issue.

 

[grasfulls]

Redrawn - asfound, asmodified,optimum, settleon

Redrawn - asfound, asmodified,optimum, settleon

Sorry, it was/is hard for me to explain. I think I will draw it completely. I agree, eliminating one circuit at this stage is the quickest fix. Thank you for taking the time to try and understand it.

I have to upload the last one in another message, i hit the limit

 

[grasfulls]

Settle on

Settle on

Sorry, it was/is hard for me to explain. I think I will draw it completely. I agree, eliminating one circuit at this stage is the quickest fix. Thank you for taking the time to try and understand it.

This is what will probably end up being what is done

 

[Ponchik]

IMO, your solution is one MWBC from one panel.

You can not share the neutral from another panel, if you have separate legs/phases on the same device they have to disconnect at the same time, and you can not do that if you have two separate circuit s from two different panels.

 

[grasfulls]

IMHO: Absolutely correct

IMHO: Absolutely correct

IMO, your solution is one MWBC from one panel.

You can not share the neutral from another panel, if you have separate legs/phases on the same device they have to disconnect at the same time, and you can not do that if you have two separate circuit s from two different panels.

This seems the best solution. Thank you everyone for replying, I have sent the client a link so they can see I am not making up solutions. Awesome electricians in here!

 

[iwire]

You have at least a few code sections to make the customer aware of.

First all conductors of a MWBC must originate in the same panel

210.4 Multiwire Branch Circuits.
(A) General. Branch circuits recognized by this article shall
be permitted as multiwire circuits. A multi wire circuit shall be
permitted to be considered as multiple circuits. All conductors
of a multi wire branch circuit shall originate from the same
panelboard or similar distribution equipment.

Second, MWBC is going to require a common means of disconnection

210.4 Multiwire Branch Circuits.
(B) Disconnecting Means. Each multiwire branch circuit
shall be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where
the branch circuit originates.

Now lets say you decide to rip up some walls and run separate neutrals, this will also be a problem with two circuits landing on a single yoke.

210.7 Multiple Branch Circuits. Where two or more
branch circuits supply devices or equipment on the same
yoke or mounting strap, a means to simultaneously disconnect
the ungrounded conductors supplying those devices
shall be provided at the point at which the branch circuits
originate.

Good luck.

 

[grasfulls]

Code Infractions

Code Infractions

You have at least a few code sections to make the customer aware of.

First all conductors of a MWBC must originate in the same panel
Second, MWBC is going to require a common means of disconnection
Now lets say you decide to rip up some walls and run separate neutrals, this will also be a problem with two circuits landing on a single yoke.
Good luck.

Thank you for the code references. Now, IF I am forced to deal with the installers, I believe all that is necessary has been compiled and I truly have unbiased opinions - relative to anyone knowing another, and biased with respect to code compliance and safety.