Snap switches for Multiwire Branch Circuits

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curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
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Electrical Contractor
Sorry fellas. The code says handle ties on MWBC period. No exceptions for added switches. Don't look for any changes in 2014. The purpose is no current on the neutral. The switch will not prevent this.

Cavie, where is it stated that you can not have individual switches after the branch circuit breaker? If what you are saying is true it would be a violation to have switches in many lighting applications.

210.4(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.

 

infinity

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New Jersey
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I would like to start a pole, how many of you would install snap switches after the handle tie breaker on a multi wire bcs. ??


I wouldn't. I agree that it's a waste of time and money doing the extra work. The next guy can work the circuit hot if he doesn't want to shut down all of the circuits at once.
 

roger

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Fl
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I would like to start a pole, how many of you would install snap switches after the handle tie breaker on a multi wire bcs. ??

I would in certain applications.

Dennis and Cavie, the irony is, rule itself will cause more people to work on hot circuits, installing switches down stream of the OCPD will at least allow someone to turn off a part of the MWBC.

Roger
 

Dennis Alwon

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I would in certain applications.

Dennis and Cavie, the irony is, rule itself will cause more people to work on hot circuits, installing switches down stream of the OCPD will at least allow someone to turn off a part of the MWBC.

Roger

That may be true but we don't really know that for a fact. It will be interesting to see how this plays out.
 

roger

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Fl
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That may be true but we don't really know that for a fact. It will be interesting to see how this plays out.

Dennis, I do know it, we already have guys who are doing this and our safety director is having to keep an eye on it.


Trying to add wording to prohibit downstream switches for this purpose will be impossible.

The switches do not have to be at the panel, I could strategically place switches above ceilings, in cabinets spaced through out the facility, at the entrance to rooms, etc....

Even though it might be defeating the actual purpose, a disconnect for the one leg or phase insight of say fixtures that it serves would actually be code compliant.

The problem I have with this rule is, a qualified person looking in a box with one neutral and more than one ungrounded conductor would have high suspicions that the neutral could very well be carrying current from the ungrounded conductor that is still on and would not open this neutral until he / she was sure that both were shut off.

BTW, I should clarify that we do not do residential and I don't have a problem with the rule in residential settings.


Roger
 

George Stolz

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Windsor, CO NEC: 2017
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I bet they will re-word the code by 2014 to exclude switches being used in this fashion.
How could they? How could it be worded?

brother said:
I would like to start a pole, how many of you would install snap switches after the handle tie breaker on a multi wire bcs. ??
I don't think it would do any good - with all the wonderous variety out there, it's hard to say whether someone would find an application that they would find acceptable, IMO.

Let's face facts - if you have a large area, and the light switch shuts off an entire circuit of lights, then you have just been ordered by the EE to do just that. I see no added safety benefit to adding additional loads to not switch. You know what I mean?
 

Cavie

Senior Member
Location
SW Florida
Cavie, where is it stated that you can not have individual switches after the branch circuit breaker? If what you are saying is true it would be a violation to have switches in many lighting applications.

210.4(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.

I never stated you cannot install switches. What I said was you cannot install the switches and think you do not have to install the two pole breaker on the MWBC. These posts always seem to get away form the OP's questions. Now if you install a 2 poll switch at the panel and run both ckts to it you may be able to convince the inspector you met the intent of the code. But the intent of the code is to turn off BOTH ckts so you wasted time and money on the DP switch.
 
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Cavie

Senior Member
Location
SW Florida
I would in certain applications.

Dennis and Cavie, the irony is, rule itself will cause more people to work on hot circuits, installing switches down stream of the OCPD will at least allow someone to turn off a part of the MWBC.

Roger

Working on a circuit you know is hot is a lot different than working on one you thought you turned off and are not expecting to get bit!
 

charlie b

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Lockport, IL
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I am getting into this one late. So despite the fact that my opinion has already been stated as being other members' opinion, I will state it anyway:
This is a bad, Bad, BAD, BAD idea!
You don't get to work on only one circuit at a time. You have to turn them all off. Anything else is unsafe, no matter how qualified you may be. To create a method to circumvent the rule that makes a MWBC safe, and to do it in the name of expediency, is insanity.

To confirm my opinion, I just drew, once again, a one-line diagram of a 2-pole MWBC. I see where the danger lies; it comes into play when the neutral comes into a box, is connected (using a wire nut) to two or more wires going out of the box in different directions. If you turn off only one leg, and go into that junction box (or outlet box) and remove the wire nut connecting the neutral wires to each other, and then accidently touch one of the neutral wires, then the other leg can send current through its load, and through you. That is why they require us to turn off all ungrounded conductors at the same time.
 

roger

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Fl
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Retired Electrician
To confirm my opinion, I just drew, once again, a one-line diagram of a 2-pole MWBC. I see where the danger lies; it comes into play when the neutral comes into a box, is connected (using a wire nut) to two or more wires going out of the box in different directions.

This is the key, after it becomes a two wire circuit and the leg or phase conductor of this portion of the circuit is off, there is no danger.



Roger
 

iwire

Moderator
Staff member
Location
Massachusetts
Charlie, There are many, many times in the field when we can work on one branch of a MWBC without anymore danger then a two wire circuit. That point is everything beyond the box you describe here.

it comes into play when the neutral comes into a box, is connected (using a wire nut) to two or more wires going out of the box in different directions.

Beyond that box it is now a two wire circuit and will likely feed many outlets (lighting fixtures / ballasts) that could be serviced safely without turning off the other leg(s) of the MWBC.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
I am getting into this one late. So despite the fact that my opinion has already been stated as being other members' opinion, I will state it anyway:
You don't get to work on only one circuit at a time. You have to turn them all off. Anything else is unsafe, no matter how qualified you may be. To create a method to circumvent the rule that makes a MWBC safe, and to do it in the name of expediency, is insanity.

To confirm my opinion, I just drew, once again, a one-line diagram of a 2-pole MWBC. I see where the danger lies; it comes into play when the neutral comes into a box, is connected (using a wire nut) to two or more wires going out of the box in different directions. If you turn off only one leg, and go into that junction box (or outlet box) and remove the wire nut connecting the neutral wires to each other, and then accidently touch one of the neutral wires, then the other leg can send current through its load, and through you. That is why they require us to turn off all ungrounded conductors at the same time.


Yes bad idea but your not the guy in the field working. Try and tell the office or store manager you are shutting off all the light to work on just 1. He will call your boss and if you still want to shut them all off i am sure he will ask you to leave.
 

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
Too long electricians have put themselves in danger needlessly. Guys I know it's difficult to get a handle on how important it is because you can't remember what it was like to be a young tech in the field.

Think about what conditions you might want your son to work in. Say he's just starting out in the field following his dad's footsteps. Sure he is supposed to be "qualified" but sometimes that comes with experience. Do you want him to be bullied by his company to work or live circuits?

I tell you as for myself I'm not going to do it. If I get fired because I refused to work on live circuits I can only hope and help the truth come to light.
 
Yes bad idea but your not the guy in the field working. Try and tell the office or store manager you are shutting off all the light to work on just 1. He will call your boss and if you still want to shut them all off i am sure he will ask you to leave.

I think this is one of the reasons behind it, and also the I suppose on the 'big jobs' this would be more practical especially when this save money overall using multis and just installing the switches and not turning off all 3 circuits or having to always group them in the panel. Maybe on small jobs this would not practical it waits to be seen.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
Too long electricians have put themselves in danger needlessly. Guys I know it's difficult to get a handle on how important it is because you can't remember what it was like to be a young tech in the field.

Think about what conditions you might want your son to work in. Say he's just starting out in the field following his dad's footsteps. Sure he is supposed to be "qualified" but sometimes that comes with experience. Do you want him to be bullied by his company to work or live circuits?

I tell you as for myself I'm not going to do it. If I get fired because I refused to work on live circuits I can only hope and help the truth come to light.

They will not fire you for that reason but you will still be fired
 

iwire

Moderator
Staff member
Location
Massachusetts
Guys I know it's difficult to get a handle on how important it is because you can't remember what it was like to be a young tech in the field.

Who you talking to? :grin:

OK I may not be 'young' but I still work with the tools. At 1AM last night I was in a supermarket hunting down lighting circuits I could tap onto for a few new fixtures.
 

M. D.

Senior Member
Johnny come lately ,...the use of the snap switch after the proper disconnecting is not a violation of the NEC..I'm not sure if this would meet OSHA requirements for working on energized circuits though..

This guy even mentions this idea in his explanation of not supporting the change.. and I see nothing in the NEC prohibiting this practice.



Explanation of Negative:
PURVIS, R.: The new requirement in 410.73(G) of the 2005 code requiring a
disconnect for luminaries that are supplied from a multiwire branch circuit
helps deal with the concerns of the submitter. Also, switches could be installed
in ?warehouse situations?. For maintenance on the ?circuit?, at other locations
a ?qualified? person should be able to deal with the Multiwire issues in the
circuit making it unnecessary to simultaneously disconnect all ungrounded
conductors at the point where the branch circuit originates.
By rejecting this
proposal, the common practice of using SWD breakers on multiwire lighting
circuits would be more practical rather than having to turn off all the lights
with a 3 pole break
 
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