AFCI and Multi Wire branch circuit

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Greg1707

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Alexandria, VA
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Business owner Electrical contractor
Are AFCI breakers available for a multi wire circuit? I am running 14/3 to an attic addition. Will this work?
 
But some makes of AFCI now omit any ground fault detection, and for those brands two single pole AFCIs with a handle tie can be used for MWBCs.

Cheers, Wayne
 
Yes, unless you need GFCI as well, two-single pole AFCI breakers with a handle tie may work.

But if you want to be safe I recommed running two 14/2 instead.

(Typing at the same time as Wayne.)
 
What about the newer cable that has the extra conductor (white) in the NM cable?
 
wwhitney said:
But some makes of AFCI now omit any ground fault detection, and for those brands two single pole AFCIs with a handle tie can be used for MWBCs.

Cheers, Wayne
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Just asking.
Am I understanding you correctly. You have tied a multi wire branch circuit on two individual AFCI circuit breaker?
I have never tried that.
What's your success rate on nuisance trips?
 
We stopped using /3 wire home runs after AFCI requirements came into existence. Even though they were initially for bedrooms the writing was on the wall they would get expanded. Switched to using /2/2.

I just checked my pricing for "today" 14/2/2 is $.02 more per foot than 2 X 14/2. I will gladly pay the additional $.02/ft to only need 1 cable.
 
Knuckle Dragger said:
Am I understanding you correctly. You have tied a multi wire branch circuit on two individual AFCI circuit breaker?
I have never tried that.
Click to expand...
Not personally, but I have been following what various manufacturers specify. Some of then have eliminated any L-N differential current monitoring from their single pole AFCIs. And those manufacturers specify it's OK to supply to a MWBC from two individual single pole AFCIs.

I think the list of manufacturers is GE, Siemens, and maybe Eaton BR. But don't take my word for it, check the manufacturer's literature.

Cheers, Wayne
 
So... interesting...
I personally just hate MWBC, really, even before AFCI, but I get the cost saving, & box fill.
I am surprised that 14/2/2 is just a pinch more than (2) 14/2. That is good. Nice.
 
curt swartz said:
We stopped using /3 wire home runs after AFCI requirements came into existence. Even though they were initially for bedrooms the writing was on the wall they would get expanded. Switched to using /2/2.

I just checked my pricing for "today" 14/2/2 is $.02 more per foot than 2 X 14/2. I will gladly pay the additional $.02/ft to only need 1 cable.
Click to expand...
There is two factors at play. One is price, but you pointed out labor savings , and I agree. But the other thing about the game is box fill issues possible , although that too can be overcome with planning it out where the split up will occur.
 
wwhitney said:
Some of then have eliminated any L-N differential current monitoring from their single pole AFCIs. And those manufacturers specify it's OK to supply to a MWBC from two individual single pole AFCIs.

I think the list of manufacturers is GE, Siemens, and maybe Eaton BR. But don't take my word for it, check the manufacturer's literature.
Click to expand...

In a previous comment in another thread I gave the link to the GE literature that says you can do this. Here it is again: DET-719.

I have now been searching for literature from Siemens confirming you can use their single-pole AFCIs on MWBCs, and have not been able to find any. But it seems obvious, yes? They don't even have a terminal for the neutral circuit wire.
 
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