Clarification Sought

[rbmontgomery]

I am seeking clarification of 2008 NEC article 210.4(B). Is this saying that anytime two or more hot wires share one grounded wire - feeding for instance multiple duplex receptacles in various locations - that the circuit breakers feeding this "multiwire" branch circuit have to have a handle tie so all poles open at the same time.
If my interpretation is correct while I see the safety aspect it doesn't seem practical from the aspect that to service any portion of the circuit would affect power to twice as much.

 

[Poolside]

Welcome to the forum!

You are reading it correctly and I agree that it doesn't make it very practical either. Better stock up on 2 and 3 pole breakers.

- Greg

 

[BackInTheHabit]

Welcome to the forum.

You interpret it correctly.

I believe, however, that it is practical. We commonly wire a dishwasher and disposal circuit with 14/3 or 12/3 from the panel. We are and have been required to have a 2-pole breaker as the OCPD. If you only had a single pole breaker installed and had to service the disposal or dishwasher, the other ciruit would still have power and would be a safety issue.

 

[ibew441dc]

90.1(A), (B), & (C) are very vital in building a solid foundation in the NEC. Read these sections over and over again and after a million years it will be easy to digest sections that don't make sense.

 

[quogueelectric]

90.1(A), (B), & (C) are very vital in building a solid foundation in the NEC. Read these sections over and over again and after a million years it will be easy to digest sections that don't make sense.

What I think they are trying to eliminate is that some electricians will wire mwbcs with oddball ckt numbers. For example ckts 1,16,23 are perfectly safe to share a neutral on a 4 wire ckt but it becomes confusing to some and to make it safer for those that cannot figure it out the easiest solution is to require all mwbcs to be on the same breaker It will make it 1,3,5 or 2,4,6 etc easier for the less knowlegable to figure out.

 

[jerm]

Welcome to the forums!

There are a few dozen (+/-) threads on this topic, search for "MWBC and Handle".

Read "[im]proper mwbcs", starting at post 14, or "handle ties" from post 12, or "multiwire branch circuits" from post 2, "multi-wire branch circuits / neutral Q" from post 4, "Inspecting multiwire circuits in the panel" from the beginning.


And remember to post early and post often!

 

[ibew441dc]

What I think they are trying to eliminate is that some electricians will wire mwbcs with oddball ckt numbers.

They are not trying....its done the new requirements in 2008 make it clear.
210.4(B)

For example ckts 1,16,23 are perfectly safe to share a neutral on a 4 wire ckt

They are perfectly safe until an electrician that is unaware of this configuration shuts off one of the ungrounded conductors and assumes that the neutral conductor is no longer carrying current.

but it becomes confusing to some

90.1(A),(B),&(C)

and to make it safer for those that cannot figure it out the easiest solution is to require all mwbcs to be on the same breaker It will make it 1,3,5 or 2,4,6 etc easier for the less knowlegable to figure out.

It will be easier for all of us with the new requirement in 2008.

 

[jerm]

end your quote with [/quote]

 

[Poolside]

It will be easier for all of us with the new requirement in 2008.

Safer?- Yes. Easier? I don't necessarily think so. I guess that depends on what I was doing. What if I have to change out a light switch and want to de-energize just the one circuit, but now may have to de-energize all three circuits due to a common handle tie? There is a good chance in that scenario, I'm changing the switch either hot or in the dark.

- Greg

 

[jerm]

Safer?- Yes.

I disagree. It will be less safe because more of us will work it hot. It may be safer for the untrained, who shouldn't be in the mwbc in the first place.

But we've gone over all this before...

 

[ibew441dc]

Safer?- Yes. Easier? I don't necessarily think so. I guess that depends on what I was doing. What if I have to change out a light switch and want to de-energize just the one circuit, but now may have to de-energize all three circuits due to a common handle tie? There is a good chance in that scenario, I'm changing the switch either hot or in the dark.

- Greg

Are you trying to suggest that you could somehow de-energize the circuit your working on and the light will magically stay on.

 

[quogueelectric]

What I think they are trying to eliminate is that some electricians will wire mwbcs with oddball ckt numbers.

They are not trying....its done the new requirements in 2008 make it clear.
210.4(B)

For example ckts 1,16,23 are perfectly safe to share a neutral on a 4 wire ckt

They are perfectly safe until an electrician that is unaware of this configuration shuts off one of the ungrounded conductors and assumes that the neutral conductor is no longer carrying current.

but it becomes confusing to some

90.1(A),(B),&(C)

and to make it safer for those that cannot figure it out the easiest solution is to require all mwbcs to be on the same breaker It will make it 1,3,5 or 2,4,6 etc easier for the less knowlegable to figure out.

It will be easier for all of us with the new requirement in 2008.

You must be an aprentice.

 

[jerm]

Are you trying to suggest that you could somehow de-energize the circuit your working on and the light will magically stay on.

Daniel,

Imagine a hypothetical room with three rows of strip lights. Each row is tied to a difference phase, they share a neutral. You need to change one switch, or one ballast for the first row. You can now turn off all three and work it in the dark (because of the handle tie on all three lighting circuits), drag in temp lights, or just work it hot. He's saying there would have otherwise been more lighting circuits in the room to work by, but now we have to turn off all three instead of just the one. In many retail situations this will not be acceptable. Real world stuff here. Stuff we've all gone over in the past...

Jeremy

 

[quogueelectric]

Daniel,

Imagine a hypothetical room with three rows of strip lights. Each row is tied to a difference phase, they share a neutral. You need to change one switch, or one ballast for the first row. You can now turn off all three and work it in the dark (because of the handle tie on all three lighting circuits), drag in temp lights, or just work it hot. He's saying there would have otherwise been more lighting circuits in the room to work by, but now we have to turn off all three instead of just the one. In many retail situations this will not be acceptable. Real world stuff here. Stuff we've all gone over in the past...

Jeremy

He is obviously an apprentice.

 

[jerm]

They are perfectly safe until an electrician that is unaware of this configuration shuts off one of the ungrounded conductors and assumes that the neutral conductor is no longer carrying current.

But any competent electrician would be well aware of the situation. An apprentice, handyman, DIYer would have trouble with it. This is just dumbing down the code to the lowest common denominator.

 

[ibew441dc]

You must be an aprentice.

And you must be an english teacher.

 

[jerm]

And you must be an english teacher.

Actually, my first degree is in English Lit. Try to make a living with that paper...

 

[quogueelectric]

And you must be an english teacher.

Yes we will distract attention to you dont know electrical work.

 

[ibew441dc]

Yes we will distract attention to you dont know electrical work.

It is obvious to me that your own personal experience with MWBCs has made you somewhat emotional and unable to change with the next generation. You will be weeded out like all bad habits. Again I will state code reference to you. Article 90.1(A)(B)&(C) were written so that people like you do not do things hypothetically and will ensure a safe installation.

 

[jerm]

That's why so many states aren't adopting the 08, or adopting it with major amendments? Have you done much work in the field yet? Are all of your 190 posts this insightful?