Fun with multi-wire circuits

[darcyh]

Hi Guys:

I don't often install multi-wire circuits except for split outlets in the kitchen.

I have ALWAYS connected it to a 2 gang breaker.

Is there ever a scenario where a MW could be connected to 2 individual breakers (of course on opposite phases of the panel).

Like this:

Red to breaker 1
Black to breaker 2
Common white

I run this wire to a junction box and connect two 14/2 romex cables. Red to black of cable 1, common white. Black to black cable 2, common white. I then run these branches to various outlets, lights etc.

If cable 1 overloads it should trip breaker 1. The same for cable 2. As there are no 'split' outlets on these two circuits is it necessary for the ganged breaker?

I would never wire this way, but I am trying to conceptualize some the circuits in the house we have.

Thanks as always for your feedback.

Dave

 

[Rob_b]

You could do it that way but why bother? It could be murder to trouble shoot down the road if you have problems, Do it right the first time and it will run trouble free.

 

[ForceFed70]

Hi Guys:

I don't often install multi-wire circuits except for split outlets in the kitchen.

I have ALWAYS connected it to a 2 gang breaker.

Is there ever a scenario where a MW could be connected to 2 individual breakers (of course on opposite phases of the panel).

Like this:

Red to breaker 1
Black to breaker 2
Common white

Dave

Could it be run this way and work - Yes, so long as each breaker is on a different leg. BUT, it would be against code unless there is a breaker tie in there (so that when 1 breaker trips the other breaker trips as well).

 

[pattenp]

MWBC doesn't need to be on a common trip breaker. The handle tie between two single breakers is to provide a common disconnect when servicing the circuit so not to leave one leg of the circuit hot. On an overload one side can trip with out tripping the other side.

 

[darcyh]

Thanks folks.
Another question. On a 2 gang breaker if one side trips, will it disconnect the breaker on the other side of the leg?

 

[MrMark]

MWBC doesn't need to be on a common trip breaker. The handle tie between two single breakers is to provide a common disconnect when servicing the circuit so not to leave one leg of the circuit hot. On an overload one side can trip with out tripping the other side.

That's interesting and I don't doubt it. I have several and I've done it both ways, handle tie between two adjacent breakers and a double pole breaker. I've never had one trip, but you are saying that the handle tie isn't solid enough to trip both at once? There is enough slop there is what you are implying. It seems very possible seeing the cheap nature of most electrical stuff but it would be very dangerous and defeats the code intent behind having common trip as the common neutral is still "hot" if current flows through the other untripped breaker. I'll have to investigate this now. I'm pretty sure you are right on the Square D homeline handle tie as it is as cheap as they come. You could do as well with a nail or screw like the old timers used to use.

 

[MrMark]

Thanks folks.
Another question. On a 2 gang breaker if one side trips, will it disconnect the breaker on the other side of the leg?

Yes, two pole breakers are just two one pole breakers tied together with a rigid handle tie. See my concern above with the handle tie issue.

 

[pattenp]

MWBC are to serve only Line to Neutral loads and the code requirement specifies the disconnection means for such, but does not specify common trip for an overload. The exception is if the MWBC also serves Line to Line loads then the breaker needs to be a common trip on overloads. Also the Line to Line load is allowed if the circuit is only supplying one utilization equipment.

 

[pattenp]

Yes, two pole breakers are just two one pole breakers tied together with a rigid handle tie. See my concern above with the handle tie issue.

Typically double pole breakers are designed to common trip on overload. But two single pole breakers with handle ties are not. I have not tested single poles with a handle tie to see if both trip on an overload. This is just my understanding. I have been wrong before.

 

[Jefe]

I have a circuit(s) designed exactly this way. Two separate breakers installed on opposite sides of the bus. 14-3 runs upstairs to provide power to bedrooms. The only real hassle is finding the right breaker since they not installed adjacent to each. It gets to be even harder to keep straight if you need to swap out for skinny breakers save space in your panel like like I do. I would have much preferred that the electrician just spend the extra 5 minutes and $5 to do another run of 14-2.

The important thing to remember is that even if there are no split outlets, you will have current on the neutral if you don't disconnect both circuits. And it can hurt. Ask me how I know...

 

[Stuart in MN]

To be clear: a multiwire circuit can use two individual single pole circuit breakers, but those two breakers must be next to each other in the panel with a handle tie between them. You can't have one breaker on the left side of the panel and the other on the right side.

Now, this is in the USA. The original poster is in Canada so I can't say for sure, but I assume this rule is the same there.

 

[Charles (in GA)]

As Stuart noted, OP is in Canada.......... Different rules...........

Charles

 

[Rob_b]

Up here in the great white north, we basicly follow the same rules as the NEC with very few exceptions. Use the tie bar if you do go that way. You have to kill all the power in the single 3+1 wire at the feed if one side trips.