Multiwire branch circiuts

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I suspect that 2011 or at the latest 2014 will require AFCI on non-dwelling circuits also. If that is the case, either multi-pole AFCI breakers will be available or MWBC's will be a memory. I don't believe that AFCI's are going to go away or be restricited to dwellings just because many of us are not happy about them. I was in the car business in the early 80's when computers were first installed in cars. Most mechanics were not happy about it and wished they would go away - didn't happen, did it? I see AFCI as the beginning of a similar revolution in the electrical industry. Once we install "electronics" in equipment or devices, there is almost no limit as to what you can do with it.
 
Yet the MWBC is still a controversy..I also agree with the AFCI's are here to stay..I still think the manufacturer can give better trouble shooting technical or even a computer hook up to diagnose the error on the AFCI..would it not be easier to know you are looking for a GFCI occurrence, a parallel arc or a series arc..would that not make trouble shooting easier..knowing the duration of the event will also help..They need to make it happen..they have the technology to do it..they do it now in the research labs..
 
cschmid said:
Yet the MWBC is still a controversy..I also agree with the AFCI's are here to stay..I still think the manufacturer can give better trouble shooting technical or even a computer hook up to diagnose the error on the AFCI..would it not be easier to know you are looking for a GFCI occurrence, a parallel arc or a series arc..would that not make trouble shooting easier..knowing the duration of the event will also help..They need to make it happen..they have the technology to do it..they do it now in the research labs..
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"looking for a GFCI occurrence, a parallel arc or a series arc"
Seimens claims their combos do just that.

They also need the R+D $ which I believe that they are now getting with the new Jan 1st combo requirement and the big increase in AFCI required circuits. . With only 3 manufacturers on board [only, SquareD, Seimens , + Eaton, according to the Seimens guy] they should be able to set aside some R+D cash and 1st, make sure all of the bugs are worked out. . And second, make them able to talk to a computer. . I think Seimens is already pretty close. . They have different lights to indicate different events. . They have their AFCIs record specifics about events with a one month memory [according to the Seimens rep].
 
I read that but I believe you reset it by reseting the cb and the memory goes by by..lights are nice but still iffy if you want my opion..Even if you don't I am giving it...:grin:

I don't see the AFCI involved in conduit territories but I can see it every where NM is run..
 
roger said:
Buck, they have been available for ages.

Roger
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And to think I have been ruining perfectly good two pole breakers. Just to rob the handle ties. Because I need breakers of a different ampacity.
That's why I carry 5 minute epoxy on the truck.
It helps hold the breaker lockouts on . too.
The handel ties to create two single pole breakers in to a double, I don't think that is code compliant for a true double pole.

It probably is for the 08 multi wire (neutral sharing) circuit disconnect.
 
buckofdurham said:
The handel ties to create two single pole breakers in to a double, I don't think that is code compliant for a true double pole.
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It's compliant for simultaneous manual operation, but not for internal common-trip.
 
Buck, as Larry says, there is a difference between where a "common trip" breaker and disconnecting more than one breaker at a time is required.


For example

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1099596895_2.jpg



Roger
 
mdshunk said:
In resi, MWBC's are going to pretty much disappear anyhow. For non-dwelling work, I'll be interested to see what installation standard develops in the industry. I'm not sure many commercial property owners and tenants would tolerate simultaneous disconnection, so a neutral for every conductor might be a more tolerable (if not more expensive) solution.
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Why do you think MWBC's will disappear in resi work? AFCI's??
 
dnem said:
We'll also have to see how common it will be for those servicing the lights after occupancy to just pop off the handle ties. . Alot with be based on the exact manufacturing technique. . Will the handle ties pop off easily or will it be a big project ? . If quick pop off handle ties become standard procedure, we'll see MWBC remain common place.
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I don't be suprised when that happend and in fact i did see few place some mantanice dolts done that they cut off the handle ties off.

That is automatic red flag to me when i see the handle tie cutted off.

Merci,Marc
 
frenchelectrican said:
I don't be suprised when that happend and in fact i did see few place some mantanice dolts done that they cut off the handle ties off.

That is automatic red flag to me when i see the handle tie cutted off.

Merci,Marc
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Alot of guys are used to playing the cat and mouse game with the inspector so much that they lose focus on the real issue, liability. . You can cut all of the handle ties off all of the breakers one minute after you get your final occupancy certificate and I'm out of the picture. . There won't be a red tag. . It's none of my business what anybody does after occupancy. . But there's liability. . If somebody gets killed, questions will be asked.

If someone really wants to remove a handle tie and work on a live neutral, what is the reason for not reinstalling the handle tie after they're done. . Taking responsibility/liability for yourself is one thing. . If a person is confident in their knowledge, ability, and craftsmanship, that's great. . But it doesn't explain leaving the job without the same required safety devices that were there when they got there.
 
Now were are talking about the bad manipulation of a MWBC..that is what this is all about..the whole issue is the negative side of the MWBC and that is working live..I can see no way to fix the issue so I can see were the code will head to abolishment of it..the code is not about cost it is about safety..If someone removes the handle tie and gets hurt the NEC will vote on the elimination of the MWBC..
 
cschmid said:
If someone removes the handle tie and gets hurt the NEC will vote on the elimination of the MWBC..
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They might vote to eliminate the handle tie option. . Then the only options will be multipole breakers or dedicated neutrals.
 
dnem said:
They might vote to eliminate the handle tie option. . Then the only options will be multipole breakers or dedicated neutrals.
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That will simply cause more people to work on hot circuits.

You could also install switches upstream of where the circuit splits, then you can carry on like nothing has changed.


Roger
 
roger said:
That will simply cause more people to work on hot circuits.

You could also install switches upstream of where the circuit splits, then you can carry on like nothing has changed.


Roger
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I'm just picturing some of these installations that shoot out across the hard ceiling under the drop tile ceiling and hit junction boxes at 100 and 1 different places thruout the building. . That hard ceiling jbox is the end of the shared neutral HR.

So do you mount switches on raised covers on those jboxes sprinkled thruout the ceiling ? . Moving your ladder around and pooping open tiles just to find the switch would be a big project.

Do you add MC switch legs and put the switches at a easier to find and more accessible location ? . By the time you get done doing that, wouldn't it have been easier to pull the additional neutral HRs ?
 
dnem said:
Do you add MC switch legs and put the switches at a easier to find and more accessible location ? . By the time you get done doing that, wouldn't it have been easier to pull the additional neutral HRs ?
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I would put switch banks in the electrical closet immediatly after leaving the panel.

In reality, it will be as I said before, there will be alot of hot work taking place.

Roger
 
I think the mandate for AFCIs coming from the AFCI manufacturers is more likely to spell the death of the MWBC than anything else. I fully expect them to get all residential circuits under AFCI "protection" eventually, and start to work on commercial and industrial next.
 
petersonra said:
I think the mandate for AFCIs coming from the AFCI manufacturers is more likely to spell the death of the MWBC than anything else......
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For a few dollars more you could use a 2 pole AFCI breaker ,....I wonder what the cost difference is between using a 2p AFCI and running a 14/2/2 vs. 14/3 in residential??
 
M. D. said:
For a few dollars more you could use a 2 pole AFCI breaker ,....
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According to Seimens, none of the 3 current manufacturers of combo AFCIs make a combo that will tolerate unbalanced current on the neutral. . I'm not sure of availability of 2pole AFCI combos that would serve only a 240volt [208v] load that would not have 120v current flow/neutral current flow.
 
I have seen so many butchered MWBC that I will not design with them unless specifically requested to do so..it really has not affect us by not using them..I just do not see any thing but up front cost savings with MWBC..after the upfront cost savings it is all down hill from there..Why do you think the ballast disconnect came to be..so janitors can change ballast in box stores..these are the same people that screw up MWBC and are normally the ones getting hurt..We are not going to change the mentality of businesses that are cutting costs by having the under qualified doing electrical work..MWBC are dangerous to their health..

I agree they have no business doing electrical work but if you have a program to change the way it works let me know, if it is good I will get on board..I know from living in rural setting that political repercussions are very severe..
 
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