Circuits sharing a neutral......

[MichaelGP3]

Greetings. I'm curious to hear if there are any code references or installation/labeling conventions regarding which circuits in a circuit breaker panel share a particular neutral (without pulling the dead front off and looking) to facilitate LOTO all breakers that are 'related' before working on a single circuit. Thanks in advance.....

 

[480sparky]

210.4 is about all there is in the NEC. Not sure about any other references.

 

[don_resqcapt19]

The 2008 code will address this issue by requiring handle ties on the breakers that feed multiwire branch circuits
Don

 

[realolman]

I think that is an excellent idea. Apparently, I mistakenly thought you already had to use the ties. It certainly seems that you should. It makes sure the two circuits are on different phases, and that there is no current on the neutral if one is shut off.

Ahead of my time again.:smile: It's hard to be humble.

 

[RichyL]

I think that is an excellent idea. Apparently, I mistakenly thought you already had to use the ties. It certainly seems that you should. It makes sure the two circuits are on different phases, and that there is no current on the neutral if one is shut off.

Ahead of my time again.:smile: It's hard to be humble.

Only required if you have 2 seperate circuits on the same device, such as a duplex receptacle with the top being one circuit and the bottom the other. But I agree with you, this is an important amendment...

 

[celtic]

Only required if you have 2 seperate circuits on the same device, such as a duplex receptacle with the top being one circuit and the bottom the other. But I agree with you, this is an important amendment...

The '08 NEC has addressed the MWBC issue in 210.4(B) ...and it says a lot more than 2 circuits on the same yoke...

 

[iwire]

I think it is a terribly short sighted change.

IMO it will result in people working on live circuits more often due to the fact they will have to shut down two or three circuits as opposed to one.

It is also further code to make things safer for the unqualified to be poking around inside electrical enclosures.

 

[brian john]

I agree with Bob 100% make that 200%. Are we preparing the future with NEC to allow for less than qualified electricians.....

 

[roger]

I agree with Bob and Brian 300%.

Roger

 

[infinity]

I agree with Bob, Brian and Roger 400%. I hate this new requirement. If your not properly trained to work on MWBC's then you should be fooling around with them in the first place.

 

[realolman]

I agree with Bob, Brian and Roger 400%. I hate this new requirement. If your not properly trained to work on MWBC's then you should be fooling around with them in the first place.

I don't understand why you would feel so strongly against this. It seems like a good idea to me.

 

[iwire]

I don't understand why you would feel so strongly against this. It seems like a good idea to me.

Forgetting about any other reasons I will just repeat this one.

The new requirement is likely to result in not turning the power off as now it will be killing power to circuits that are both in use and not going to be touched anyway.

 

[infinity]

I don't understand why you would feel so strongly against this. It seems like a good idea to me.

For one Bob has it right. We do a large amount of commercial work and shutting off three circuits to work on one will cause major disruptions. So the next choice is to shutdown no circuits and work on it live. Kind of defeats the purpose of the requirement.

Besides many times you will on a portion of a MWBC circuit that is unaffected by the shared neutral. So turning off all three circuits of the MWBC will have zero affect on what you're doing. In that scenario it would be better to simply turn off the one circuit perform the task and turn it back on. By requiring all three circuits (or two) to be de-energized it may be simpler to just work on it live. Not a great idea especially with 277 volt lighting.

 

[roger]

I would add that if the handle ties can be removed, they will be gone shortly after the initial installation.

Roger

 

[realolman]

I am very hesitant to pursue this, as I feel that I am going to be made into mince meat by some of the most knowlegable electrical people I have ever encountered... but...

It seems to me that if all the breakers associated with the MWBC are not turned off, the circuit is in fact, energized.

 

[roger]

I am very hesitant to pursue this, as I feel that I am going to be made into mince meat by some of the most knowlegable electrical people I have ever encountered... but...

It seems to me that if all the breakers associated with the MWBC are not turned off, the circuit is in fact, energized.

Part of the circuit is, but after splitting into two wire componets of the circuit there is no need to disconnect the other parts to work on an isolated part of the circuit.

The same scenario exist when working on any disconnected two wire circuit where the neutral conductor is still landed on the neutral bar in the panel.

Roger

 

[realolman]

Part of the circuit is, but after splitting into two wire componets of the circuit there is no need to disconnect the other parts to work on an isolated part of the circuit.

The same scenario exist when working on any disconnected two wire circuit where the neutral conductor is still landed on the neutral bar in the panel.



Roger

The neutral would have to be in the same cable or conduit, and boxes as the phase conductors... otherwise it would not be a MWBC. I don't see at what point you would be splitting into two wire components without undoing the neutral splice to some extent. You don't have to undo all the neutrals to work on one in a panel.

 

[iwire]

The neutral would have to be in the same cable or conduit, and boxes as the phase conductors... otherwise it would not be a MWBC.

Not so at all.

I often run a 12/4 or 10/4 from the panel out to a central location. From the central location I will run three 12/2s in different directions. One might be supplying a number of outlets, another might be feeding lighting and the third might be supplying a single outlet for fixed appliance.

Any point after I split out at the central point is just a two wire circuit and can be safely worked on with the other legs on.

So now if I come to serve that one fixed appliance I also have to shut off lights and plugs.

Now of course I can change my methods to all two wire circuits but they use more copper and waste more electricity. Whats the point of that?

 

[realolman]

Not so at all.

I often run a 12/4 or 10/4 from the panel out to a central location. From the central location I will run three 12/2s in different directions. One might be supplying a number of outlets, another might be feeding lighting and the third might be supplying a single outlet for fixed appliance.

Any point after I split out at the central point is just a two wire circuit and can be safely worked on with the other legs on.

I wouldn't think the two wire circuits to be MWBC. would I be thinking wrong?

I gotta say I don't like your wiring methods.

 

[roger]

I wouldn't think the two wire circuits to be MWBC. would I be thinking wrong?

I gotta say I don't like your wiring methods.

Realolman, this a very common wiring method and is used industry wide.

Think of supplying a sub-panel at a central location, it is the same case scenario except you would be putting OCPD's at the split point.

In large buildings it would be extremely wasteful to pull two wire circuits to long distances where one MWBC could be pulled to a central location and the two wire extensions of the MWBC could continue from there.

Roger