Another MWBC question

[conmgt]

In general and not specific to another post of mine, does the code allow 240V and 120V loads be served on the same MWBC?
L1, N feeding a 120V load, L2, N feeding a 120V load, L1, L2 feeding a 240V load. Is that any different than a 3w 3ph MWBC or even a 4w 3ph MWBC?

I've always been anti MWBC because it's likely a homeowner or handy dude will come along and disconnect a wire at the neutral bar. And even we could do it by accident.
Dwelling units don't change much but recently I've been doing commercial work and there's a bit of turnover on properties and tenants which requires rewiring to meet a tenant's needs. I'm trying to work with existing conduit and wires as much as possible and feel that MWBCs have a lot to offer in time, material savings so I'm looking to learn what I can.

 

[iwire]

does the code allow 240V and 120V loads be served on the same MWBC?
L1, N feeding a 120V load, L2, N feeding a 120V load, L1, L2 feeding a 240V load.

Absolutely allowed.

It is no different than the MWBC supplying an electric range or dryer.

 

[Twoskinsoneman]

As usual Iwire is correct. Just don't think you can use single pole CBs with handle ties.

Here's some code for ya.

210.4(C) Line-to-Neutral Loads. Multiwire branch circuits
shall supply only line-to-neutral loads.
Exception No. 1: A multiwire branch circuit that supplies
only one utilization equipment.
Exception No. 2: Where all ungrounded conductors of the
multiwire branch circuit are opened simultaneously by the
branch-circuit overcurrent device.

 

[renosteinke]

Something seems both very right and very wrong here.

I did some work in a hotel where the same 240v circuit that powered the baseboard heat also powered the 'window shaker' A/C unit - and the had a combination receptacle that allowed for the use of either 240v or 120v air conditioners (there were other provisions that prevented both heat and cooling from being used at the same time). Since there was a neutral wire, I did not have an issue there.

On another job, I encountered a 240v air conditioner receptacle that had been powered by tieing it into both the convenience receptacle circuit and the lighting circuit. That just didn't seem right.

I think that the key word here is "loads." I don't think a circuit for convenience receptacles counts as a 'load.' Unlike the usual circuit design, we do not consider 'load' when we run residential convenience circuits.

I also believe that this situation is diffeent from the 'split' within various appliances (remember when kitchen ranges had 120v receptacles mounted on them?) in that the appliances are engineered using known loads; the kitchen range receptacles also had their own little fuses.

 

[Dennis Alwon]

On another job, I encountered a 240v air conditioner receptacle that had been powered by tieing it into both the convenience receptacle circuit and the lighting circuit. That just didn't seem right.

I think that the key word here is "loads." I don't think a circuit for convenience receptacles counts as a 'load.' Unlike the usual circuit design, we do not consider 'load' when we run residential convenience circuits.

Not quite sure what you say here but 210.23(A)(1)& (2) explicitly allows what I think you are saying.