Inspecting multiwire circuits in the panel

[infinity]

David I agree with your thoughts but it is odd (at least to me) that one of the groups pushing for this handle tie requirement was the IBEW.

It seems to me they sell themselves on being better trained but at the same time want to 'dumb things down'

I would guess that those guys typically work on 277 volt lighting in large office buildings where there is pressure to not shut down half of the floor to work on something. I'm sure that many electrical shocks are from working on an energized MWBC neutral with only one branch circuit de-energized. IMO the requirement would have been better if it was limited to commercial buildings. Handle ties for a three wire circuit in a one family home are not needed.

 

[iwire]

I would guess that those guys typically work on 277 volt lighting in large office buildings where there is pressure to not shut down half of the floor to work on something.

Are you saying they do not have the ability to say no?

 

[cschmid]

roger to answer your first question with a question..

What would you call a lighting circuit that shares a neutral if not a MWBC? Than what would you call it if they shared a neutral and were sorted to the same phase? I thought the code was very specific on MWBC they must disconnect all conductors sharing the same nuetral...Am I mistaken here?

Okay would someone explain how you get multiple quotes on a reply for me? LOL

Why would this be different in present code using an MWBC? After it splits it is just two wire circuitry.

I don't understand your question? the circuit never splits.. the neutral and both hots are always present in the j-box's.. MWBC are not a problem on ballast only work.. it becomes a problem on light fixture removal and installs...

Bob you are correct the office managers do not want the lights off.. they move offices around and cram work spaces as they remodel part of the floor and then rearrange the floor and do another part..

We wire it so we do not have to work on live circuits. We also wire it so when we come back and see a bunch of new lights that we did not install we have a clue as to how they are wired because we left them only one way to do it... We do not do the ballasts in lights as owner normally does them.. we don't have the say on what owner does. It is not illegal unless you can catch them in the act, it is only an assumption..We know what the code says but there is really no way to enforce codes unless the inspector catches them in the act..here the inspectors barely keep up with there work load and maybe don't, they have large physical areas to cover. Yet the inspectors still do catch some owners in the act...So the best we can do is work with our customers to encourage them to be safe and call us first. There is also laws in our state that limit everyone except HO from doing electrical work on their premises. But how do you enforce them... I remember being called to a local motel they have a problem with a tripping breaker...after researching the problem...found the problem was their maintenance had installed a new pop machine outlet and tapped into the nearest j-box and just spliced into a hot and neutral. He had no clue and I bet he did it live but that is only an assumption, If he would of shut it off he would of known what it was tied too..it happened to be a lighting circuit to the pool room...LOL they call us now...we treated them nice and have a new customer..

Yes roger the amount of cost difference on 100,000 ft of pipe is significant and on them jobs an engineer has set the rules and they are followed completely to the tee... we will get the work either changing it or adding another..So by adding all the extra pipes you also burn up natural resources so either way it costs when you are into large amounts of conduit...

So is MWBC really a savings when one maintenance person is electrocuted because he did not understand them while he was doing his job.....I don't agree with them doing electrical work while unqualified yet I can not stop them either..

 

[roger]

roger to answer your first question with a question..

What would you call a lighting circuit that shares a neutral if not a MWBC? Than what would you call it if they shared a neutral and were sorted to the same phase?

Cschmid, let's start with the definition;

Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.

If two circuits from the same leg or phase are present they will not have voltage between them, so it can not be a MWBC

I thought the code was very specific on MWBC they must disconnect all conductors sharing the same nuetral...Am I mistaken here?

You are mistaken, in present code only a MWBC supplying a device on a common yoke must disconnect all conductors at the same time, see 210.4(B) otherwise single breakers (with out handle ties) are allowed.

Why would this be different in present code using an MWBC? After it splits it is just two wire circuitry.

I don't understand your question? the circuit never splits.. the neutral and both hots are always present in the j-box's.. MWBC are not a problem on ballast only work.. it becomes a problem on light fixture removal and installs...

If I had multiple rows of fixtures to feed I would drop off the unnecessary circuit conductors at some point closer to the panel, there would be no reason to carry all the conductors to every row.

Bob you are correct the office managers do not want the lights off.. they move offices around and cram work spaces as they remodel part of the floor and then rearrange the floor and do another part..

And in most cases there would be no reason to turn off circuits that are not being worked on

Yes roger the amount of cost difference on 100,000 ft of pipe is significant and on them jobs an engineer has set the rules and they are followed completely to the tee... we will get the work either changing it or adding another..So by adding all the extra pipes you also burn up natural resources so either way it costs when you are into large amounts of conduit...

I guess we do things different, I would never expect an engineer to lay out branch circuitry, they may have specific instructions, for instance, they may include a requirement to upsize conductors over x amount of distance, but that is not the same thing. I don't understand what you mean by "adding all the extra pipes" , what extra pipes would this be.

So is MWBC really a savings when one maintenance person is electrocuted because he did not understand them while he was doing his job.....I don't agree with them doing electrical work while unqualified yet I can not stop them either..

All I can say is, this is where the definition of "Qualified Individual" should be inforced

Qualified Person. One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved.

I certainly do not want anyone to get hurt or killed, but a MWBC would be a very small part of what a "Qualified Person" would need to know.

His / Her Meters and Testers are what needs to be understood more than anything else.

It takes a higher intervention than we can install for to save the "Unqualified Person".

Roger

 

[iwire]

What would you call a lighting circuit that shares a neutral if not a MWBC?

It depends on how the hots are connected, if they are all on the same phase it is not a MWBC regardless of sharing a neutral.

I thought the code was very specific on MWBC they must disconnect all conductors sharing the same nuetral...Am I mistaken here?

You are mistaken.

However that will basically be the case starting with the 2008 NEC.

Why would this be different in present code using an MWBC? After it splits it is just two wire circuitry.

I don't understand your question? the circuit never splits.. the neutral and both hots are always present in the j-box's.

It certainly splits before it reaches the ballast.

Bob you are correct the office managers do not want the lights off.. they move offices around and cram work spaces as they remodel part of the floor and then rearrange the floor and do another part..

We wire it so we do not have to work on live circuits. We also wire it so when we come back and see a bunch of new lights that we did not install we have a clue as to how they are wired because we left them only one way to do it...

I really do not understand as I do the same kind of work and do not have any issues working with MWBCs.

So is MWBC really a savings when one maintenance person is electrocuted because he did not understand them while he was doing his job.....I don't agree with them doing electrical work while unqualified yet I can not stop them either..

No one is killed because it was a MWBC, they are killed because they where unqualified to do the work.

 

[cschmid]

I would like to say thank you Roger and Bob very good answers.

I do not expect an engineer to lay out our circuits but we are not big enough to do jobs that require 100,000's of ft of pipe. We normally come in after the big boys from out of town leave and pick up the work or we sub contract to them for some of the projects involved.

On the conduit thing we seem to find the conduits maxed out and end up adding pipe to add additional lights and outlets so we size ourselves up so when we make the next modification we don't have to run new pipe.

Thank you for the clarification on the MWBC..I was under the assumption that sharing a neutral made it a MWBC and sorting the phases was a no no...
I understand the math of it just thought the way the code read it meant that was wrong..

I also know you don't want to see anyone hurt as we don't either...

I also apologize for not explaining with more clarity I will get better at it...

 

[smithacetech]

I think that this rule, if enforced, will create situations where much more live work will be the result, IMO.

Possibly for the untrained or ignorant. I would imagine that temp lighting & power setups would be a way to handle this.

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 agree with this. I can see this being done as a way of trying to get around this new 210.4 requirement to isolate circuits. Although it may also violate 410.73(f)(g) if only using a single pole switch.
As bad as this new 210.4 is, I can see where the safety concerns are, but to make it make sense they should have also made it a violation to install a single pole switch on a mwbc, if to be used for a maintence disconnect.

 

[cschmid]

As bad as this new 210.4 is, I can see where the safety concerns are, but to make it make sense they should have also made it a violation to install a single pole switch on a mwbc, if to be used for a maintence disconnect.

I agree with that thought

 

[George Stolz]

...they should have also made it a violation to install a single pole switch on a mwbc, if to be used for a maintence disconnect.

And what would be the defining difference between a light switch intended for use by the user (to shut off the lights when they leave the room) or by maintenance? Would it matter who the switch was installed for?

I think that this rule, if enforced, will create situations where much more live work will be the result, IMO.

Possibly for the untrained or ignorant.

Don't kid yourself - the pressure to work live is all around us, and few are vigilant about never working hot.

Believe me, I agree that ideally no one should ever work hot, and I'm aware of the OSHA regs regarding this - but what looks great on paper sadly does not have as large an impact in the field. Everybody has to do their part, and it will get better by the day, hopefully.

 

[cowboyjwc]

I could say that as a maintenance electrician that it was the very rare occasion when we turned off the power to change out ballasts in the plant. We would have been very hard pressed to explain to the plant manager why we had to turn off 60+ lights just to change one ballast.

 

[iwire]

I could say that as a maintenance electrician that it was the very rare occasion when we turned off the power to change out ballasts in the plant. We would have been very hard pressed to explain to the plant manager why we had to turn off 60+ lights just to change one ballast.

I understand there is a real world out there and when I got in the trade I was bolting breakers in hot before long.

But times change and even plant managers are starting to hear about the rules from the company safety people.

From last Jan to July I worked as a sub contractor maintenance position in a large factory. We did nothing except trouble shoot hot.

If I had to kill a circuit I either killed it then or it would be done off hours when I could kill it.

Besides being safer it makes for some easy OT.

 

[cowboyjwc]

Besides being safer it makes for some easy OT.

Worked many a late night or very early morning on the bigger $tuff.

 

[cschmid]

Been there done that and the cash is nice.....I to agree more and more managers are understanding the benefits of coordinated shut downs..Workmans comp is big driver on safety issues and coordinated shutdowns are better than the non profitable instant shutdowns when a major problem happens...I too did maintenance for many years 15 plus.

 

[smithacetech]

And what would be the defining difference between a light switch intended for use by the user (to shut off the lights when they leave the room) or by maintenance? Would it matter who the switch was installed for?

Basically any single pole switch could not be used as a maintenance disconnect. Perhaps a label on this switch or proper training.

Don't kid yourself - the pressure to work live is all around us, and few are vigilant about never working hot.

Believe me, I agree that ideally no one should ever work hot, and I'm aware of the OSHA regs regarding this - but what looks great on paper sadly does not have as large an impact in the field. Everybody has to do their part, and it will get better by the day, hopefully.

I fully understand what happens in the real world when it comes to live work. I think part of being a qualified electrician is being able to do live work safely, thats why we get paid the "big" bucks. But, unfortunately I guess there has been alot of so called qualified people that have been hurt enough to make big brother step in & say no more.
When safety is forced upon us by "the man" even for like seat belts, helmets, etc. it can feel like our freedom is being taken or were being told that your not "good" enough at what your doing to be safe. Which is kind of insulting. But, I guess sometimes we need to be protected from our own egos.
All kidding aside, there is nothing funny about someone getting hurt or killed. So safety laws are basically for our own protection, both life & money.
Be safe, turn it off & live to complain about it another day.

 

[George Stolz]

And what would be the defining difference between a light switch intended for use by the user (to shut off the lights when they leave the room) or by maintenance? Would it matter who the switch was installed for? :wink:

Basically any single pole switch could not be used as a maintenance disconnect. Perhaps a label on this switch or proper training.

If you can picture the nature of the requirement you're contemplating, I can't. No offense meant by that, I just don't understand what you're saying.

 

[smithacetech]

If you can picture the nature of the requirement you're contemplating, I can't. No offense meant by that, I just don't understand what you're saying.

Im just refering to 410.73(g) that requires to disconnect all conductors to the ballast, including the grounded conductor. A single pole light switch does not satisfy this. It only disconnects the hot conductor. This single pole switch would also contradict the new 210.4 if used on a mwbc.

 

[George Stolz]

Okay, but what I'm saying is that the requirement is for handle ties at the panel that supplies the MWBC. If that is done, the code is satisfied. If we install a light switch inside a room for end-user control of the outlets, there's no reason the switch can't be turned off to work on the outlet.

(Suppose we're just talking about a MWBC supplying only receptacles, for argument's sake.)

There's no way to prohibit this from happening, IMO. Do you agree?

 

[smithacetech]

Thats what Iam saying. Code wise there is no violation to put a switch after the breaker. But, wouldnt that defeat the purpose of the handle tie on a mwbc?

 

[LarryFine]

If we install a light switch inside a room for end-user control of the outlets, there's no reason the switch can't be turned off to work on the outlet.

There's no way to prohibit this from happening, IMO. Do you agree?

Thats what Iam saying. Code wise there is no violation to put a switch after the breaker. But, wouldnt that defeat the purpose of the handle tie on a mwbc?

Using the switch might "defeat the purpose" of a handle-tie, but we can't omit all switches to force people to use breakers for all de-energization.

 

[smithacetech]

I agree. Im just pointing out a flaw in the new 210.4 code change.