MWBC with line-neutral AND line-line loads

[rszimm]

Can I put both line-neutral AND line-line loads on a single MWBC. Got a home shop that needs 120V and 240V receptacles throughout. Some of the equipment (e.g. band saws, table saws) runs on 240. Some runs off 120. Generally no two pieces of equipment will be on at the same time. Thinking about putting a single MWBC to power it. 2017 NEC. 210.4.C says "MWBC shall supply only line-neutral loads", but exception 2 says "When all ungrounded conductors of the MWBC are opened simultaneously by the branch-circuit overcurrent device". Given that 210.4.B already requires that all ungrounded conductors be simultaneously disconnected, isn't 210.4.C completely moot/irrelevant?

 

[Sierrasparky]

Maybe it is about common trip and not just handle tie.

 

[david luchini]

Given that 210.4.B already requires that all ungrounded conductors be simultaneously disconnected, isn't 210.4.C completely moot/irrelevant?

Being "disconnected" and being "opened simultaneously by the branch OCD" are different things, so 210.4(C) isn't moot.

Two or three single pole circuit breakers with a handle tie would accomplish the first but not the second.

A two pole or three pole circuit breaker would accomplish both.

Edit: Or what Sierra said

 

[rszimm]

Of course. Great point. OK, so is there anything else in the code that I'm not thinking of that would prevent a mixture of line-line and line-neutral loads on the same MWBC?

 

[dkidd]

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

 

[480sparky]

Even if it's permitted, it sounds like a poor design IMHO.

 

[jap]

Of course. Great point. OK, so is there anything else in the code that I'm not thinking of that would prevent a mixture of line-line and line-neutral loads on the same MWBC?

A mixture of line-line and line -neutral loads occur all the time.

Think of Range or Dryer circuits for example, or, even a 120/240v panel in itself.

Just be careful what you call the circuit and be mindful of the OCPD installed ahead of the conductors.


JAP>

 

[david luchini]

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

:?

2017 NEC. 210.4.C says "MWBC shall supply only line-neutral loads", but exception 2 says "When all ungrounded conductors of the MWBC are opened simultaneously by the branch-circuit overcurrent device".

 

[LarryFine]

:?

Now allowed.

 

[rszimm]

Now allowed.

Why do you say that? It would seem Exception 2 applies here.

 

[infinity]

Why do you say that? It would seem Exception 2 applies here.

It does when you use a mulit-pole circuit breaker.

 

[LarryFine]

Why do you say that? It would seem Exception 2 applies here.

Read the exception again. Only line-to-neutral loads unless protected by a breaker that assures simultaneous opening of all lines.

 

[rszimm]

Yeah, so just a typical 2 pole breaker.

 

[Cow]

I would do everything in my power to talk them into a subpanel, rather than hooking a bunch of 120v and 240v receps to the same circuit.

 

[ptonsparky]

I would do everything in my power to talk them into a subpanel, rather than hooking a bunch of 120v and 240v receps to the same circuit.

What will it add for a 4 circuit main lug panel? Maybe $100? Not worth the time thinking about it.

 

[jap]

There may not be the need to add subpanel.

The OP was simply asking if he could do it.

Heck, for all we know the panel may already be in the garage.

JAP>

 

[kwired]

There may not be the need to add subpanel.

The OP was simply asking if he could do it.

Heck, for all we know the panel may already be in the garage.

JAP>

Exactly, say this is an existing detached garage with just a MWBC supplying it, I'd probably do what OP is asking if the chance of too much load at once isn't very great.