Multi-wire circuits and AFCI protection

[danschweitzer]

Hey guys. My question is about Multi-wire branch circuits and AFCI protection. According to the 2014 NEC pretty much every 15 and 20 amp 120 volt branch circuit has to be AFCI protected. Is it possible to use 2 AFCI breakers for a Multi-wire circuit and tie their handles together or will the AFCI not work correctly in that configuration? Or do they make 2-pole breakers with AFCI protection? Thanks for any info you can give.

Dan

 

[augie47]

A double pole AFCI would be required for MWBCs and they are manufactured]
(example Siemens Q220AFCP.. "big box" price $85).

 

[danschweitzer]

Double pole AFCI

Double pole AFCI

Thank you for the info!

Dan

 

[mbrooke]

GE makes on without 30ma GFP so a handle tie will work.

 

[Dennis Alwon]

Ge has designed their afci so that you can use 2 sp afci breakers with a handle tie for a multiwire branch circuit.

 

[augie47]

Interesting ! Looks like the ole fart is behind the times AGAIN

 

[jap]

Ge has designed their afci so that you can use 2 sp afci breakers with a handle tie for a multiwire branch circuit.

So what senses the fault on the on B phase breaker since the load neutral connected to the A phase breaker only ?

 

[GoldDigger]

So what senses the fault on the on B phase breaker since the load neutral connected to the A phase breaker only ?

The breaker on the B phase senses the fault.
Unlike a GFCI, the AFCI does not rely on matching signals on hot and neutral.
The sensitivity of the B breaker may be somewhat lower for line to neutral arcs, but a line to ground arc would not show an arc signature on the neutral anyway.

Now a line to neutral arc from the B phase might trip the A breaker too through the arc signature on the neutral.

 

[danschweitzer]

Square D

Square D

Have any of you seen one from square D yet? Specifically their Homeline brand?

Dan

 

[Dennis Alwon]

Have any of you seen one from square D yet? Specifically their Homeline brand?

Dan

One what?? DP AFCI breaker? Years ago I called and the homeline brand did not have one but I don't know about the present day.

 

[danschweitzer]

Square D

Square D

Would 2 single pole AFCI breakers tired together work with that type of square D produc?

Dan

 

[Dennis Alwon]

Would 2 single pole AFCI breakers tired together work with that type of square D produc?

Dan

No-- GE's unit is made this way but I am unaware of any other manufacturer who has done that. I have heard that Seimens has taken the GFP out of their AFCI breakers but I don't know if they followed suit with GE.

 

[kwired]

Would 2 single pole AFCI breakers tired together work with that type of square D produc?

Dan

Bottom line is if the breaker has any level of GFP it needs all ungrounded and grounded circuit conductors run through the breaker, anything that leaves via the GFP CT monitor must also return through the CT monitor or it will trip on ground fault. As mentioned GE is the only one that doesn't include GFP in their AFCI's and possibly Siemens.

It is possible the diagram Dennis posted "works" even if the neutral is landed on the neutral bus instead of the neutral terminal of the breaker.