# Multiwire branch circuits



## Minuteman (Dec 29, 2007)

2 or 3 pole breakers would have nuisance trip issues, Install single pole breakers with handle ties.


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## Chris Kennedy (Nov 19, 2007)

Welcome to the Forum. You missed 210.4(B) if your under the 08.


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## Chris Kennedy (Nov 19, 2007)

Here.



> 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.


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## RePhase277 (Feb 5, 2008)

Pretty damned stupid rule, in my opinion. But yes, the inspector is right. Looks like the MWBC is a thing of the past. 2- and 3-pole breakers get expensive.


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## perryx5 (Jul 26, 2009)

Yeah, after failing, went to 210.4 and found no exceptions, had to agree that inspector was right, but he also said that handle ties were not a means of simultaneous trip since the trip mechanism in a molded case breaker operates independently of the handle. In other words, it has to be a 2 or 3 pole breaker. I will just start pulling a grounded conductor for every circuit. The extra #12 will still be cheaper than multipole breakers and I can pull 4 circuits per conduit to keep my derate at 70%. I will just run all 1/2" home runs and have to add a couple to each job, no big deal. (It's just money, it's not like we're in a recession or anything) I still could have sworn that in past NECs there was an exception to 210.4 for "qualified personnel".


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## perryx5 (Jul 26, 2009)

The MC cable manufacturers probably don't care for this rule either, because it renders 12/3 and 12/4 useless for anything other than 208 or 480 volt circuits that require a neutral (ovens, dryers, etc.).


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## 480sparky (Sep 20, 2007)

210.4(B) does not make MWBCs obsolete, even in commercial. More expensive, maybe.

But since you're in a restaurant situation, using MWBCs is very difficult when you provide GFI protection as required by 210.8(B)(1) with breakers.

The inspector is _dead wrong_ in saying MWBCs require seperate grounded (neutral) conductors.

Your inspector needs to know the difference between a common-trip breaker and one with handle ties. They (the poles) are not only tied together _externally_ (at the operating toggle), but _internally_ as well. A common trip breaker will turn off all the poles of the breaker if only one trips. 

A set of breakers with handle ties will not cause all the poles to turn off, but will turn them off all at once if you manually turn the breakers 'off'. Handle ties are one method of complying with 210.4(B).


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## RePhase277 (Feb 5, 2008)

It's not any harder to pull another white wire in a pipe. Not to mention the inconvenience of having to turn off other circuits just to work on one.

Just to be on the safe side, the NEC ought to require no more than one circuit per pipe. And multiple circuits shouldn't enter the same box.


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## 480sparky (Sep 20, 2007)

InPhase277 said:


> ..........Just to be on the safe side, the NEC ought to require no more than one circuit per pipe. And multiple circuits shouldn't enter the same box.


I hope you're not serious about that.


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## Minuteman (Dec 29, 2007)

InPhase277 said:


> It's not any harder to pull another white wire in a pipe. Not to mention the inconvenience of having to turn off other circuits just to work on one.
> 
> Just to be on the safe side, the NEC ought to require no more than one circuit per pipe. And multiple circuits shouldn't enter the same box.


Say what??? :blink:


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## Dennis Alwon (May 9, 2009)

Here is one problem with individual neutrals. If you have a pipe run and want to have 3 circuits all with their own neutral then you will have 6 ccc'c instead of 3 in the case of a MWBC. This creates extra heat in the conduit but is certainly legal as long as derating is taken into consideration. 

I don't know about the bolt in type but the plug in style dp breakers don't cost much more than 2 single poles with ties.

Do they make 3 pole handle ties yet. I think I heard that one mfg. was making them but am not sure.


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## drsparky (Nov 13, 2008)

I like the handle tie requirement; it makes it easier to lock out/tag out. 
I would not consider a restaurant a place with qualified personnel. I may be off on this but I have always interpreted this to mean staff electricians. Having a burger flipper resetting breakers is not my idea of qualified.


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## Bob Badger (Apr 19, 2009)

drsparky said:


> I like the handle tie requirement; it makes it easier to lock out/tag out.
> I would not consider a restaurant a place with qualified personnel. I may be off on this but I have always interpreted this to mean staff electricians. Having a burger flipper resetting breakers is not my idea of qualified.


What do qualified personnel have to do with the handle tie requirement?


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## drsparky (Nov 13, 2008)

Bob Badger said:


> What do qualified personnel have to do with the handle tie requirement?


Read the OP.


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## Dennis Alwon (May 9, 2009)

drsparky said:


> Read the OP.


 The op thought there was an exception for qualified personal and handle ties but there is not


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## Bob Badger (Apr 19, 2009)

drsparky said:


> Read the OP.


Oh, now I got it. 



Maybe I should read the entire thread before asking questions. :whistling2::laughing:


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## drsparky (Nov 13, 2008)

perryx5 said:


> I failed an inspection in the city of Atlanta the other day because I pulled some 12/3 MC cable to pick up some circuits I was adding in a small restaurant remodel. Inspector said that multiwire branch circuits required a neutral, or grounded conductor in this case, for each single pole circuit. He said that I would have to use 2 pole breakers on these circuits even though they were supplying receptacles. I have heard of this in residential wiring due to the ability for unskilled homeowners to get zapped by a neutral, but thought that there was an exception in commercial work due to qualified personnel maintaining the wiring. Checked the new code book, and no such exception exists anymore. Is anyone else enforcing this? Basically, in order to pull multiwire branch circuits, you either have to tie receptacle circuits together on a 2 or 3 pole breaker or pull a neutral for each circuit, eating up valuable conduit fill. Any opinions?
> 
> Thanks,
> Jeremy


My point was that I did not think that in any portion of the NEC that have exceptions for qualified maintenance personnel could ever apply to a commercial establishment such as a restaurant. 392.3(B) and 396.10 (B) are an example of an exception granted for qualified persons.


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## Bob Badger (Apr 19, 2009)

InPhase277 said:


> *It's not any harder to pull another white wire in a pipe.* Not to mention the inconvenience of having to turn off other circuits just to work on one.
> 
> Just to be on the safe side, the NEC ought to require no more than one circuit per pipe. And multiple circuits shouldn't enter the same box.


Are you serious or just stirring the pot?

Cause if your serious I want some of what your smoking. :laughing:

Lets say I have to run nine 20 amp 125 volt branch circuits from a 208Y/120 panel to a location 75' away. I will use THHN or THWN-2 in EMT. 

These are all liner loads so I would go with MWBCs (Multi Wire Branch Circuits)

So I would have

9 12 AWG Hots

3 12 AWG Neutrals

1 12 AWG EGC.

That is a total of 9 current carrying conductors which gets a 70% derating.

Still I could run all that in one 3/4" EMT and be 100% code compliant.

Now on the other hand if I used all two wire circuits ..

I would have

9 Hots

9 Neutrals

1 EGC.

Now I have 18 current carrying conductors and the derating hit is 50%.

12 AWG THHN is rated 30 amps in 310.16

30 amps x .5 = 15 amps, now those 12 AWG will need to have 15 amp breakers ........ customer wants 20 amp circuits.

Lets move up to 10 AWG THHN with its rating of 40 amps (T310.16)

40 x .5 = 20 amps so now we know we have to use at least 10 AWG or run more raceways.

So I would have

9 10 AWG Hots

9 10 AWG Neutrals

1 12 AWG EGC.

But wait, 250.122(B) requires the EGC to be also up sized.

So I would have

9 10 AWG Hots

9 10 AWG Neutrals

1 10 AWG EGC.


Now we have nineteen 10 AWG THHN conductors to install ......... that ain't fitting in a 3/4" EMT that will require 1.25" EMT .....much harder to run than .75" EMT.


With MWBCs

75' - 3/4" EMT

975' - 12 AWG THHN


With two wire circuits

75' - 1.25" EMT

1425' - 10 AWG.

Which one is 'easier'


We could also talk about how much less voltage drop there is with balanced MWBCs but just the material and labor savings is enough.


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## Chris Kennedy (Nov 19, 2007)

Bob Badger said:


> I will use THHN or THWN-2 in EMT.
> 
> 
> 1 12 AWG EGC.


Who are you, what have you done with Bob?


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## Bob Badger (Apr 19, 2009)

Chris Kennedy said:


> Who are you, what have you done with Bob?


I was forced to use EMT ...........:laughing:


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## RePhase277 (Feb 5, 2008)

You guys must be coming back from church, and all uptight and serious this morning:laughing:

Of course I was being a smart mouth. I was pointing out the stupid idea that MWBCs are safer on multi-pole breakers, or breakers with handle ties. If that is the case, then it is in the same vein that no box or pipe should have more than one circuit.

Sure there are inherent dangerous possibilities with open neutrals for an MWBC. But this is of no consequence for _real_ electricians. Therefore, the handle tie rule of the '08 Code is pretty dumb and only inconveniences us. Now to turn a circuit off, we have to turn of at least one other circuit, which may be inuse at the time. Pipe fill goes up geometrically if we want to avoid that and use single poles. Etc.

The code making panels are attempting to idiot proof the code. That isn't the answer. Somehow, we need to idiot proof the trade.


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## Magnettica (Jan 23, 2007)

InPhase277 said:


> You guys must be coming back from church, and all uptight and serious this morning:laughing:
> 
> Of course I was being a smart mouth. I was pointing out the stupid idea that MWBCs are safer on multi-pole breakers, or breakers with handle ties. If that is the case, then it is in the same vein that no box or pipe should have more than one circuit.
> 
> ...


I strongly disagree. 

90.1 Purpose. 

(A) Practical Safeguarding. The purpose of this Code is 
the practical safeguarding of persons and property from 
hazards arising from the use of electricity.


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## Bob Badger (Apr 19, 2009)

I think the new rule will lead to more hot work being done, not less.


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## user4818 (Jan 15, 2009)

Bob Badger said:


> I think the new rule will lead to more hot work being done, not less.


Either that, or removal of the multipole devices after the fact.


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## perryx5 (Jul 26, 2009)

I agree that the code is trying to compensate for more unskilled laborers in the workforce. If we properly train the electrician labor force and keep unskilled people from going to Home Depot and listening to a 30 minute "seminar" and deciding to make some "improvements" to their electrical system, we do not need to protect said unskilled individuals from open neutrals. Within the first week of my apprenticeship the dangers of open neutrals were explained to me and at that time, with that level of experience, I knew I had no business working circuits hot. In the IBEW, apprentices are not supposed to work hot circuits until their second year, and even then, under the supervision of a JW. Not that everyone abides by this rule, but a good JW will know when an apprentice has grasped the concept of open neutrals enough to work circuits hot. I'm not trying to demonize Home Depot, but I have heard some of their electrical department personnel giving some downright dangerous advice to unskilled people before.

Jeremy


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## Minuteman (Dec 29, 2007)

perryx5 said:


> I agree that the code is trying to compensate for more unskilled laborers in the workforce. If we properly train the electrician labor force and keep unskilled people from going to Home Depot and listening to a 30 minute "seminar" and deciding to make some "improvements" to their electrical system, we do not need to protect said unskilled individuals from open neutrals. Within the first week of my apprenticeship the dangers of open neutrals were explained to me and at that time, with that level of experience, I knew I had no business working circuits hot. In the IBEW, apprentices are not supposed to work hot circuits until their second year, and even then, under the supervision of a JW. Not that everyone abides by this rule, but a good JW will know when an apprentice has grasped the concept of open neutrals enough to work circuits hot. I'm not trying to demonize Home Depot, but I have heard some of their electrical department personnel giving some downright dangerous advice to unskilled people before.
> 
> Jeremy


Another issue beside the danger to personnel is danger to equipment and property. If a neutral is opened in a energized MWBC, the result could be excessive voltage across the circuit. The magic smoke will leak out.


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## Greg (Aug 1, 2007)

After reading that article several times my question is this; Does the NEC want handle ties or multi-pole breakers? Is the intent to open all poles on a fault or open all pole when turning the circuit off. I realize when you reset the breaker you open all poles first but what does the NEC exactly want.

When they say open all ungrounded conductors simultaneously does that mean on a circuit fault or normal operation?


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## Dennis Alwon (May 9, 2009)

Greg said:


> After reading that article several times my question is this; Does the NEC want handle ties or multi-pole breakers? Is the intent to open all poles on a fault or open all pole when turning the circuit off. I realize when you reset the breaker you open all poles first but what does the NEC exactly want.
> 
> When they say open all ungrounded conductors simultaneously does that mean on a circuit fault or normal operation?


I believe the intent is to open all poles when the circuit needs to be serviced and not on a fault.


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## Bob Badger (Apr 19, 2009)

perryx5 said:


> I agree that the code is trying to compensate for more unskilled laborers in the workforce. If we properly train the electrician labor force and keep unskilled people from going to Home Depot and listening to a 30 minute "seminar" and deciding to make some "improvements" to their electrical system, we do not need to protect said unskilled individuals from open neutrals. Within the first week of my apprenticeship the dangers of open neutrals were explained to me and at that time, with that level of experience, I knew I had no business working circuits hot. In the IBEW, apprentices are not supposed to work hot circuits until their second year, and even then, under the supervision of a JW. Not that everyone abides by this rule, but a good JW will know when an apprentice has grasped the concept of open neutrals enough to work circuits hot. I'm not trying to demonize Home Depot, but I have heard some of their electrical department personnel giving some downright dangerous advice to unskilled people before.
> 
> Jeremy


Jeremy, that is all very interesting guess work but the IBEW was one of the supporters of this change due to 'skilled individuals' being electrocuted on the job.


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## 480sparky (Sep 20, 2007)

Greg said:


> After reading that article several times my question is this; Does the NEC want handle ties or multi-pole breakers? Is the intent to open all poles on a fault or open all pole when turning the circuit off. I realize when you reset the breaker you open all poles first but what does the NEC exactly want.
> 
> When they say open all ungrounded conductors simultaneously does that mean on a circuit fault or normal operation?


Both a multi-pole breaker and a handle tie will satisfy the NEC.

A multi-pole breaker will turn off all poles when there's a fault in just one. A handle-tie doesn't (or at least shouldn't).


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## jfwfmt (Jul 5, 2008)

*From the good book NEC 2008*

The choice of a breaker with simultaneous trip for all poles and for more than one breaker with independent trip and with handle ties is more subtle:

240.15 (B) (1) Multiwire Branch Circuit. Except where limited by 210.4(B), individual single-pole circuit breakers, with or without identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.

This seems to allow single breakers with no handle ties, BUT the reference to 210.4(B) essentially takes that away.

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.

Handle ties suffice for 210.4(B)

210.4(C) Line-to-Neutral Loads. Multiwire branch circuits shall supply only line-to-neutral loads.

This prohibits line-to-line loads on MWBC EXCEPT:

210.4(C) Exception No. 1: A multiwire branch circuit that supplies only one utilization equipment.

MWBCs are allowed to a single piece of equipment (like a heater with heating elements on line-to-line and fan on line-to-neutral)

210.4(C) Exception No. 2: Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device. 

If you want to supply line-to-line load(s) you can do it, if you have SIMULTANEOUS trip on all poles. Handle ties do not suffice.

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

This is not a MWBC rule, but is to require handle ties for more than 1 circuit supplying hots for devices on a single yoke. Note that the circuits need not share a neutral.

300.13(B) Device Removal. In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices 
would interrupt the continuity.

This is another MWBC rule that requires the neutral continuity be preserved when a single device is removed. We normally use wire nuts for splices, but for shared neutrals we use buchanon barrel crimps for splices.

/s/ Jim WIlliams


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## perryx5 (Jul 26, 2009)

Bob, it does not surprise me in the least that the IBEW would support this rule. Good lockout/tagout procedures would make more sense, but then, when has the IBEW ever supported common sense over more regulation. I am neither pro or anti IBEW, I believe there are good and bad electricians both within the IBEW and outside of the IBEW. I received good training from their apprenticeship school, but common sense can't be taught.


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## azca (Aug 2, 2009)

I agree that the Code Making Panels seem to be changing the code for those who are untrained or under educated. The is a serious problem with the lack of training required for electricians, inspectors, engineers and architects across the country. To make matters worse many of the people providing training can be rated as poor at best. Add to this the misconceptions, egos, politics and local amendments to the codes and we have a serious problem.

To understand what the NEC, or any code for that matter, requires you must first understand what the CMP, as well as the people submitting the code change, were looking for or better said, what was the intent. The intent for this section was to provide a greater degree of safety for all individuals servicing equipment by reducing the likely hood of shock by de-energizing all phases that share the grounded conductor. Note I said reduce the chance of a shock, not eliminate it. The only way to be sure you will not receive a shock is to de-energize all equipment on the building/property. Anyone who trusts a breaker or disconnect is too trusting.


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