Multiwire BC and AFCI

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olly

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Location
Berthoud, Colorado
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Master Electrician
This is probably the dumbest Q I have asked in a while, but here goes.... Is there a AFCI out there that will work for a multi-wire branch circuit w/ a shared nuetral? Im doing a weird Terra dome house thats all in conduit. I would think if you put a beaker tie on say two single AFCI's it would trip them right away with a shared nueteral.
 

GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
But unlike most GFCI breakers they are not allowed for use on a "partial MWBC" in an apartment building or other location that uses two lines of a 208Y/120 three phase four wire service. You would have to use a three pole AFCI (if available) in those cases.
 

JFletcher

Senior Member
Location
Williamsburg, VA
But unlike most GFCI breakers they are not allowed for use on a "partial MWBC" in an apartment building or other location that uses two lines of a 208Y/120 three phase four wire service. You would have to use a three pole AFCI (if available) in those cases.

Yep. Most of the ones Ive seen say 'use only on 120/240V systems'.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
This is probably the dumbest Q I have asked in a while, but here goes.... Is there a AFCI out there that will work for a multi-wire branch circuit w/ a shared nuetral? Im doing a weird Terra dome house thats all in conduit. I would think if you put a beaker tie on say two single AFCI's it would trip them right away with a shared nueteral.

If there is any way you can use the GE combination AFCI, that is the way I'd go. A very versatile solution. You can mix and match single pole AFCIs to the needs of the multiwire branch circuit and only use a handle tie.

The neutral goes to one or the other breaker. Doesn't matter which.

You can even have a 15 A on one leg and a 20 A on the other leg. Very versatile.
 
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