Odd residential tied-breaker setup for 120v branch circuits

[asavage]

I'm DIY but worked Facilities for about a decade and am a relatively experienced DIYer WRT residential and 1-phase commercial, up through 277v lighting.

I'm helping a friend with his house today, and while I located a failed "back stab" receptacle wiring connection, I ran into something I've not seen before and don't understand: His panel has three handle-tied breakers (ie 240v type) that are feeding a LOT of 120v single gang receptacles and a few overhead lighting cans. I see six circuits that have breakers that are handle-tied (see pics). I do not find a sub-panel where these would be split out to individual branch circuits, and the longest run from these breakers to the end of a branch is less than 70'.

Panel is in an attached garage, one of these handle-tied breaker circuits is literally the garage receptacles! So I don't think there's a sub-panel.

Can somebody explain why someone would set up 120v branch circuits with handle-tied breakers as shown? The panel wiring is tidy, but to me, this looks wrong.

Panel is a C-H/Eaton W-7830; house is 1990s construction.

 

[Afjes]

More than likely they are MWBCs (Multi Wire Branch Circuits). Do some Googling for a more in depth understanding of how MWBCs work and you will quickly understand why 120v branch circuits for receptacles and lighting are connected to 2 pole breakers.

Two individual 120v circuits share the same neutral. The neutral does not overload in this case because the 2 hots are on opposite legs of the service.

 

[Sponsor]

 

[asavage]

Thanks, that's the answer I needed. I've put some time in reading on MWBCs and now understand what I'm looking at.

Thanks, again.

 

[Reach4]

Branch Circuits Not Over 1000 Volts AC, 1500 Volts DC, Nominal | UpCodes

Explore a searchable database of US construction and building code. Code regulations are consolidated by state and city for easier navigation.

up.codes

210.4(B) Disconnecting Means
Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.
Informational Note: See 240.15(B) for information on the use of single-pole circuit breakers as the disconnecting means.

 

[Afjes]

Thanks, that's the answer I needed. I've put some time in reading on MWBCs and now understand what I'm looking at.

Thanks, again.

I'm glad my response helped.
I personally am not in favor of MWBCs. Tends to complicate troubleshooting etc. Also, some electricians will utilize a MWBC to save on wire. Instead of running two individual branch circuits of 120v for example: 15 amp 14/2 they have to use two sets of 14/2 cable, installing MWBC they only have to install a single 14/3 cable. The "kicker" is depending on the code cycle that premise/property is on of the NEC or the AHJ (Authority Having Jurisdiction) AFCI breakers may be in order or the inspection will fail. If the electrician installed MWBCs and AFCI protection is required there are no 2 pole AFCI breakers available.

Also most DIYers with half somewhat knowledge of 120v circuits such as general lighting or receptacle and have an issue the first thing they will target in troubleshooting is a single pole 120v breaker (such as yourself) not knowing about MWBCs. Retired now, but when ever I did wire a house I never used MWBCs. Some Canada codes require a MWBC such as the SABCs for a kitchen, where the countertop receptacles are split receptacles; top of the receptacle on one circuit and the bottom on another circuit. I believe that may even still be code for Canada..

Not that MWBCs are dangerous (if installed properly) just a hassle to deal with sometimes and home owners get confused dealing with them.

 

[WorthFlorida]

I was replacing corroded outlets at my parents condo in Maui. Right on the ocean all things turn green from the salt air. I was getting a tickle from one outlet. It was a multiwire and the other circuit was on and the tickle was from the shared common. Fortunately only the microwave was on the other circuit powering on the display.

 

[wwhitney]

If the electrician installed MWBCs and AFCI protection is required there are no 2 pole AFCI breakers available.

This used to be an impediment, but now several manufacturers have removed all neutral monitoring from their AFCIs, so you can just use two single pole AFCIs on an MWBC

Cheers, Wayne

 

[Afjes]

This used to be an impediment, but now several manufacturers have removed all neutral monitoring from their AFCIs, so you can just use two single pole AFCIs on an MWBC

Cheers, Wayne

Oh, was not aware of that fact. Thanks for the update - nice to know.
Is there a list of the manufacturers that have done this?

 

[wwhitney]

Is there a list of the manufacturers that have done this?

Not sure. Siemens definitely (just checked), maybe GE, I think Cutler Hammer (but maybe only one of CH and BR, not sure), pretty sure not QO or Homeline, don't know about Leviton.

Cheers, Wayne