Multiwire Branch Circuits

[ESolar]

I am simply writing to emphasize that MWBC breakers should be adjacent and tied. In my ongoing review of my own home's existing electrical, I initially identified two multiwire branch circuits (MWBC): (1) SABC + Micro, (2) SABC + GD/DW. The breakers were installed adjacent to each other, and I tied them together. All was good. Later I discovered a third MWBC to the laundry room. One hot in the receptacle was not used. The breakers were separated in the panel, although on different bars. I initially had no idea what that other unused breaker was for and where it led to, without examining the wires in the box. Imagine that the next guy gets in there, rearranges incorrectly, and both circuits are being used overloading the neutral. Adjacent and tied fixes that problem.

Also, any ideas as to what to do with that other unused circuit in the laundry room? Maybe split the receptacle to include two 20A - but for what?

 

[ptonsparky]

I am simply writing to emphasize that MWBC breakers should be adjacent and tied. In my ongoing review of my own home's existing electrical, I initially identified two multiwire branch circuits (MWBC): (1) SABC + Micro, (2) SABC + GD/DW. The breakers were installed adjacent to each other, and I tied them together. All was good. Later I discovered a third MWBC to the laundry room. One hot in the receptacle was not used. The breakers were separated in the panel, although on different bars. I initially had no idea what that other unused breaker was for and where it led to, without examining the wires in the box. Imagine that the next guy gets in there, rearranges incorrectly, and both circuits are being used overloading the neutral. Adjacent and tied fixes that problem.

Also, any ideas as to what to do with that other unused circuit in the laundry room? Maybe split the receptacle to include two 20A - but for what?

Handle ties are now required. Have been for some years. Makes it handy, but it's not the end of the world for most older electricians.

WTD?
Tail out both wires to one breaker.
Cut the extra wire off at both ends and install a new duplex. Be aware you now may need to follow AFCI and or GFCI requirements
Label it & Leave it alone.

 

[ActionDave]

I used to bounce my MWBC all over the panel. What matters is that you keep your phasing correct. It's not that hard to do and not that hard to figure out.

 

[Strathead]

I am simply writing to emphasize that MWBC breakers should be adjacent and tied. In my ongoing review of my own home's existing electrical, I initially identified two multiwire branch circuits (MWBC): (1) SABC + Micro, (2) SABC + GD/DW. The breakers were installed adjacent to each other, and I tied them together. All was good. Later I discovered a third MWBC to the laundry room. One hot in the receptacle was not used. The breakers were separated in the panel, although on different bars. I initially had no idea what that other unused breaker was for and where it led to, without examining the wires in the box. Imagine that the next guy gets in there, rearranges incorrectly, and both circuits are being used overloading the neutral. Adjacent and tied fixes that problem.

Also, any ideas as to what to do with that other unused circuit in the laundry room? Maybe split the receptacle to include two 20A - but for what?

When was your house built? The code requirement came about around the early 2000’s.

 

[kwired]

When was your house built? The code requirement came about around the early 2000’s.

IIRC if both ungrounded conductors landed on same device/yoke it did require handle ties before the current handle tie requirements came about.

 

[electrofelon]

I used to bounce my MWBC all over the panel. What matters is that you keep your phasing correct. It's not that hard to do and not that hard to figure out.

I agree. If you don't no what's going on or can't spot a MWBC, you probably shouldn't be doing electrical work. I do not use handle ties if it's not getting inspected. Handle ties are very dangerous IMO. If it's getting inspected, I skip the tie rod and just use the snap on handle tie so that it can be easily removed if need be.

 

[letgomywago]

I agree. If you don't no what's going on or can't spot a MWBC, you probably shouldn't be doing electrical work. I do not use handle ties if it's not getting inspected. Handle ties are very dangerous IMO. If it's getting inspected, I skip the tie rod and just use the snap on handle tie so that it can be easily removed if need be.

I hate the tie rods they tend to get lost when you want them to stay put with and the bigger over the top ties are more obvious anyway.

 

[jaggedben]

I agree. If you don't no what's going on or can't spot a MWBC, you probably shouldn't be doing electrical work. ...

And yet too many people are. Hence the more stringent rules. Hard to spot an MWBC when the guy before you ran one of the hots in a separate cable and put it on a 15A breaker while the other hot was on a 20. He also brought two MWBCs from separate panels to a jbox where he used one neutral for three of the hots. This almost resulted in shocking one of our guys when he was re-wiring one of the subpanels, and after I diagnosed it I realized we'd gotten lucky not frying anything with an open neutral.

My particular pet peeve is where they don't group the neutrals with the hots when bringing multiple circuits in through the same raceway. (Which is broader than MWBCs, but related.)

If the handle tie requirement forces more people to learn what they are doing, I'm for it. It shouldn't be that way, but it is.

 

[kwired]

And yet too many people are. Hence the more stringent rules. Hard to spot an MWBC when the guy before you ran one of the hots in a separate cable and put it on a 15A breaker while the other hot was on a 20. He also brought two MWBCs from separate panels to a jbox where he used one neutral for three of the hots. This almost resulted in shocking one of our guys when he was re-wiring one of the subpanels, and after I diagnosed it I realized we'd gotten lucky not frying anything with an open neutral.

My particular pet peeve is where they don't group the neutrals with the hots when bringing multiple circuits in through the same raceway. (Which is broader than MWBCs, but related.)

If the handle tie requirement forces more people to learn what they are doing, I'm for it. It shouldn't be that way, but it is.

That has been required since I believe maybe either 2008 or 2011 NEC.

 

[jaggedben]

That has been required since I believe maybe either 2008 or 2011 NEC.

Don't I know it. But don't expect the guys who put both hots of an MWBC on the same tandem to remember that.

 

[electrofelon]

If the handle tie requirement forces more people to learn what they are doing, I'm for it. It shouldn't be that way, but it is.

I am absolutely opposed to making requirements that dumb down the trade to accommodate unqualified people doing work. Where does it end if you go with that philosophy?

 

[electrofelon]

Don't I know it. But don't expect the guys who put both hots of an MWBC on the same tandem to remember that.

Are the guys putting both hots on a tandem following code anyway?

 

[jaggedben]

I am absolutely opposed to making requirements that dumb down the trade to accommodate unqualified people doing work. Where does it end if you go with that philosophy?

It's not accomodating them. It's the opposite. It's giving inspectors the tools to force them out of business if they aren't smart enough to learn.

 

[AC\DC]

Why would handle ties be dangerous?

I. Handle ties are very dangerous IMO.

 

[James L]

Seems like a lot of hullabaloo about nothing.

MWBC is totally irrelevant in any opening other than where the home run is. And if you get into that opening, you should see a red wire. Should make you go...hmmm

 

[Sea Nile]

Why would handle ties be dangerous?

I was just asking the same question, you beat me to it.

 

[ActionDave]

Seems like a lot of hullabaloo about nothing.

MWBC is totally irrelevant in any opening other than where the home run is. And if you get into that opening, you should see a red wire. Should make you go...hmmm

Says the guy who knows what he is doing when he pulls out a screwdriver and opens a junction box

 

[mtnelect]

"Old School Wiring" won't make it in the new digital/electronic world.

 

[letgomywago]

And yet too many people are. Hence the more stringent rules. Hard to spot an MWBC when the guy before you ran one of the hots in a separate cable and put it on a 15A breaker while the other hot was on a 20. He also brought two MWBCs from separate panels to a jbox where he used one neutral for three of the hots. This almost resulted in shocking one of our guys when he was re-wiring one of the subpanels, and after I diagnosed it I realized we'd gotten lucky not frying anything with an open neutral.

My particular pet peeve is where they don't group the neutrals with the hots when bringing multiple circuits in through the same raceway. (Which is broader than MWBCs, but related.)

If the handle tie requirement forces more people to learn what they are doing, I'm for it. It shouldn't be that way, but it is.

The forced education of "electricians" from this and from the GFCI/AFCI rules I think forced people pass the constant mixing of neutrals between circuits.

 

[electrofelon]

Why would handle ties be dangerous?

Because you often have to work the circuit hot because you can't turn off a full boat of circuits. The labs I work in it's a nightmare to turn off one circuit let alone 3.