Inspecting multiwire circuits in the panel

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can someone please spell out for me how this new rule will make thing safer. I know someone mentioned that a "hack" could work on the circuit and cause a dangerous situation. What is the actual possible danger?

Thanks
 
Twoskinsoneman said:
can someone please spell out for me how this new rule will make thing safer. I know someone mentioned that a "hack" could work on the circuit and cause a dangerous situation. What is the actual possible danger?

Thanks
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Well a hack could shut off one of the circuits sharing a neutral and then receive a shock if that neutral were opened without de-energizing the other shared circuit(s).
 
infinity said:
Well a hack could shut off one of the circuits sharing a neutral and then receive a shock if that neutral were opened without de-energizing the other shared circuit(s).
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I agree Trevor...but it also seems to me that we put a rule into 410 to protect people from these when working with ballasted luminaires, which are probably 90% of the energized MWB circuits that are worked on. :( Wasn't that rule enough?
 
ryan_618 said:
I agree Trevor...but it also seems to me that we put a rule into 410 to protect people from these when working with ballasted luminaires, which are probably 90% of the energized MWB circuits that are worked on. :( Wasn't that rule enough?
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My thoughts exactly. I'm all for safety and the ballast disconnect was a good idea. That rule IMO was enough.
 
infinity said:
My thoughts exactly. I'm all for safety and the ballast disconnect was a good idea. That rule IMO was enough.
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I agree as well.

Back to the OPs question, here is a very handy tool for identifying the neutral that goes with a certain circuit conductor.

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It also can be used to check a neutral before opening a splice that might have a load on it.
 
stickboy1375 said:
Too bad they didn't go the extra step and make the jaws wide enough for 4/0 AL... PITA sometimes...
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Can that meter read up to 200 amps?
 
I think that this rule, if enforced, will create situations where much more live work will be the result, IMO.

Also, any switch along the way disconnecting any of the phases would null out the supposed benefits of the section, as a switch could be shut off without shutting off the circuit breaker anyway.

I do not understand why a proposal from a representative of the "American Chemistry Council" was accepted on an electrical work safety issue? There have been work safety issue proposals from people working in the field that have failed with better substantiation than this one. :roll:
 
georgestolz said:
II do not understand why a proposal from a representative of the "American Chemistry Council" was accepted on an electrical work safety issue? There have been work safety issue proposals from people working in the field that have failed with better substantiation than this one. :roll:
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I guess that we'll have to point the finger (pick one, I like the one in the center) at the CMP who accepted this nonsense.
 
ryan_618 said:
There will also be a requirement that you tape (or similiar) the nuetral to the ungrounded conductors of a multiwire circuit in the panel, unless the grouping is obvious. Obvious would include a single cable, or a single MWBC in a raceway.
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Ryan, I think that proposal was rejected in the comments phase, wasn't it? Comment 2-10?
 
ryan_618 said:
In my opinion, it has nothing to do with buying more multipole breakers or handle ties...I think it has everything to do with the copper manufacturers selling more wire because people will stop using MWBCs. There are too many design issues with using them now that this change has passed. I keep thinking about a MWBC feeding 277V troffers. What is that, about 60 lights or so on the MWBC? If that circuit goes down, the designer is going to have an angry client...
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There will be a very very small number of contractors that are currently running MWBCs that will stop using them. . The client will only be angry if the contractor uses multipole breakers. . If singles are used with handle ties, the circuit that trips won't kill the other circuits. . The electrician that comes in to work on the circuit will remove the handle tie and then go about his job the same as he has for years.

By adding the step of removing the handle tie, the person working on the lights takes on more liability. . This will have the effect of making it more likely that the business owner will call an actual electrician to do the work instead of Tennisshoe Ted. . The electrician then has the obligation of reinstalling the handle tie, but I doubt most will get reinstalled on most service jobs.

David
 
georgestolz said:
Ryan, I think that proposal was rejected in the comments phase, wasn't it? Comment 2-10?
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No. Section 210.4(E) was deleted at the comment stage, but 210.4(D) was not. The two were similiar to each other, which is why one was removed and the other stayed.
 
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