bothched circuit

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  #1  
Old 05-01-14, 04:35 PM
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bothched circuit

My wife had an electrician wanting to run a separate neutral and turn a MWBC into 2 standard circuits. They did not run the additional neutral to the point where the neutral splits for both legs of the mwbc. Instead as seen in the diagram below they added a second, redundant neutral to the shared neutral.

That obviously is wrong correct? And why is it wrong? And the diagram shows below, that's still a MWBC despite now having 2 neutral and 2 ungrounded conductors in the same raceway (ie in the panel)

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  #2  
Old 05-01-14, 04:46 PM
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It is perfectly okay for a multiwire branch circuit to leave the panel and, some distance away/downstream, split into two regular circuits (with separate neutrals).

If the neutral is split in two up in the house before the red and black hot wires physically separate, then all 120 volt subbranches and taps and devices must be connected to the neutral that goes with the corresponding hot being used.

Also, regular subcircuits may branch off from one side (one hot and neutral) of an MWBC here and there.

Back at the panel, the neutral of the MWBC correctly continues to the neutral bar undoubled.
 
  #3  
Old 05-01-14, 04:54 PM
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Im talking about that splice closest to the panel in the diagram. Eventhough there are two neutrals at that point, they are in parallel and are redundant correct?

In other words... that's still a multiwire circuit in the diagram.
 
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Old 05-01-14, 05:03 PM
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If the multiwire branch circuit leaving the panel goes to a junction box nearby where splicing or branching occurs, you do not run a second neutral from there back to the panel while just one shared neutral continues onward from there any distance. The original single neutral from the panel is sufficient.

So long as there is any length of shared neutral, the red and black hot wires must still be on opposite legs of the 120/240 volt service.

Why is it (what your electrician did) wrong?

When two separate circuits come into the same junction box up in the house (okay in itself), neither their hots nor their neutrals may be interconnected there. So you may never have two circuits (with separate neutrals) leave the panel and power up an MWBC at a junction box.
 

Last edited by AllanJ; 05-01-14 at 05:18 PM.
  #5  
Old 05-01-14, 05:26 PM
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Are you saying that 2 neutrals splice to one and then split into two again? Are the breakers on opposite legs of the panel?
 
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Old 05-01-14, 05:37 PM
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Fixing it is easy. Turn off the power and unhook the second neutral that goes back to the panel.

Cap (or tape) it off, curl it up and put it back into the box.
 
  #7  
Old 05-01-14, 05:42 PM
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Are you saying that 2 neutrals splice to one and then split into two again? Are the breakers on opposite legs of the panel?
Exactly,

2 neutrals are on the busbar and are on the same pipe with the two hots. The two neutrals splice with the lone neutrals (at this point its 3 wire) until it gets into a device box where the neutrals split again for each side of the MWBC. The two ungrounded conductors are on breakers that are stacked on top of each other (on opposite legs).

So the fix then is to simply remove one of the neutrals on the busbar and make that first neutral splice just two wires not 3.
 
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Old 05-01-14, 05:51 PM
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The neutral can be shared, but it cannot be paralleled at the panel end.
 
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Old 05-01-14, 06:03 PM
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but it cannot be paralleled at the panel end.
It can be paralleled if the wires are able to carry the entire load by themselves. Although it does make things confusing.
 
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Old 05-01-14, 06:18 PM
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The wires are not large enough to be paralleled, nor are they correctly paralleled.
 
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Old 05-01-14, 06:34 PM
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Note: I see my info about paralleling conductors was eliminated in 2008. Disregard my previous post.

I would just add another neutral wire and separate the neutrals. Then it will no longer be a multi-wire circuit and each hot will have its own neutral.
 
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Old 05-01-14, 06:37 PM
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That sounds like the best solution, especially since it can be pulled in the conduit.
 
  #13  
Old 05-02-14, 05:05 AM
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Pulling a separate neutral to make it two circuits is not so easy... that's why it got screwed up to begin with. The installer (Im guessing) knew he wouldn't be able to pull the neutral thru 3 boxes and then go upstairs and hunt for the box where the neutrals actually split and instead gave up and half assed it.

What was done to correct, the neutral at the first box where its spliced was removed from the busbar, raceway and the first homerun where it was spliced.

My point in asking here was I wanted to assure the way it was wired (as in the diagram) wasn't a valid method ... as in by removing the redundant wire, the circuit isn't botched it up further.
 
  #14  
Old 05-02-14, 06:58 AM
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There is no compelling need for the circuit as it leaves the panel not to be a multiwire branch circuit. No changes at the panel were needed.
 
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Old 05-02-14, 07:14 AM
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There is no compelling need for the circuit as it leaves the panel not to be a multiwire branch circuit. No changes at the panel were needed.
Not in relation to functionality, but technically another person servicing those circuits may have opened the panel and saw 2 neutrals for 2 circuits. There is no handletied breaker either so it would deceive that person into thinking he is working on 2 separate circuits instead of mwbc.
 
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