MWBC with AFCI

darekelec said:
if it says on a afci or gfci 2 pole breaker 'to be used on 120/240V circuits' can I use it on 120/208V single phase circuits? in NYC we only have 120/208 single phase for residential.
Click to expand...
At one time I don't believe most AFCI were compatible with 208 volts and MWBC's. I don't know if that is still an issue or not, or which manufacturers it may or may not apply to.

GFCI protection only shouldn't have any problem with this though, all it is looking for is net zero on all protected conductors, what current goes out on one conductor has to return on any other protected conductor of the circuit. So as long as nothing finds a return path that is not through the GFCI it will hold.
 
Quick search and it appears that Siemens, Square D Qo & HOM, Leviton and Eaton BR have 2 pole afci breakers for use on MWBC. Can't speak to how well they all perform but I have had good outcome with the Siemens 2 pole afci breakers. They also were the first to make a 2 pole afci that worked for MWBC, They also have a tandem AFCI. The new Siemens don't even need the load neutral brought to the breaker. Both the PON and pigtail neutral only are present for the electronics of the breaker.
 
The two-pole AFCI breakers (Siemens at least) are pretty expensive, well over $100. Not that much more than two single-pole ones though, I suppose.
 
Fred B said:
Quick search and it appears that Siemens, Square D Qo & HOM, Leviton and Eaton BR have 2 pole afci breakers for use on MWBC. Can't speak to how well they all perform but I have had good outcome with the Siemens 2 pole afci breakers. They also were the first to make a 2 pole afci that worked for MWBC, They also have a tandem AFCI. The new Siemens don't even need the load neutral brought to the breaker. Both the PON and pigtail neutral only are present for the electronics of the breaker.
Click to expand...
I never have a issue with two pole afci breakers , don’t get me wrong I don’t use them often but I do, and at least 7-8 years ago prob more GE designed their CAFCI breakers with no gfp to function using a shared neutral to accommodate MWBC’s, eventually Siemens followed GE’s lead removing GFP from their CAFCI breakers , I can verify two single pole PON Siemens CAFCI breakers with a identified handle tie functions without issue when protecting a 120/240 MWBC, I’ve never attempted with the older Siemens or Siemens with a pigtail
Heres a link for GE
 
I have used ge single pole afci's for a multiwire branch circuit. The neutral from the load goes to one breaker the other is left open.
 
Fred B said:
Quick search and it appears that Siemens, Square D Qo & HOM, Leviton and Eaton BR have 2 pole afci breakers for use on MWBC. Can't speak to how well they all perform but I have had good outcome with the Siemens 2 pole afci breakers. They also were the first to make a 2 pole afci that worked for MWBC, They also have a tandem AFCI. The new Siemens don't even need the load neutral brought to the breaker. Both the PON and pigtail neutral only are present for the electronics of the breaker.
Click to expand...
The question was will they work on a 208/120 MWBC. I don't think some of them worked on this system because the phase angle caused issues with how they operate. They worked fine on 120/240 MWBC's though.

I myself never used a 2 pole AFCI or handle tied two that were capable of operating that way, and only occasionally have come behind someone else that utilized those.
 
I can see some these newer AFCI's from the ones that don't even require landing the load neutral on the breaker not having a problem with MWBC on a 208 supply. They basically are only monitoring activity on the ungrounded conductor and are otherwise two independent breakers.
 
RustyShackleford said:
The two-pole AFCI breakers (Siemens at least) are pretty expensive, well over $100. Not that much more than two single-pole ones though, I suppose.
Click to expand...
Yet, Siemens is one of the companies who has removed the GFP from their AFCIs and you can use two of their single pole AFCIs with a handle tie for a multiwire circuit.
 
kwired said:
I can see some these newer AFCI's from the ones that don't even require landing the load neutral on the breaker not having a problem with MWBC on a 208 supply. They basically are only monitoring activity on the ungrounded conductor and are otherwise two independent breakers.
Click to expand...
The only reason they ever had a load neutral was because of the GFP.
 
kwired said:
The question was will they work on a 208/120 MWBC. I don't think some of them worked on this system because the phase angle caused issues with how they operate. They worked fine on 120/240 MWBC's though.

I myself never used a 2 pole AFCI or handle tied two that were capable of operating that way, and only occasionally have come behind someone else that utilized those.
Click to expand...
The scope of UL 1699 says AFCIs are intended for use in 120 volt 60 hertz AC circuits. I assume that applies only to each individual pole of a two pole device as they see 120 volts line to neutral no matter if they are on a 120/240 volt system or a 208Y/120 volt system.
 
don_resqcapt19 said:
The only reason they ever had a load neutral was because of the GFP.
Click to expand...

Correct me if I’m wrong but GE was the first manufacturer to remove gfp from their single pole CAFCI breakers in the link below to MWBC’s allowing two single pole CAFCI breakers with identified handle tie as the MWBC disconnecting means in compliance with 240.15(b)(1) and as far as I know these GE removed gfp from these single pole CAFCI breakers 8-9 years ago so they’ve been available for a while , and Siemens followed suit removing GFP from single pole CAFCI breakers



Sent from my iPhone using Tapatalk
 
Jaybone812 said:
www.homedepot.com

Siemens Handle tie ( 10 Per Pack) US2:ECQTH3P - The Home Depot

Get the Siemens Industry Inc Breaker Tie ECQTH3P, ul listed switch breaker handles that are adjacent to each other from The Home Depot
www.homedepot.com
Click to expand...
Maybe we're going in circles here, but I still wonder if these will work with their AFCI breakers. Here's a pic of one (righthand pic), notice the handle is somewhat different than on a regualr Siemens one-pole breaker (lefthand pic).
 

Attachments

  • Screenshot 2025-05-17 at 2.12.24 PM.png
    Screenshot 2025-05-17 at 2.12.24 PM.png
    641.8 KB · Views: 2
  • Screenshot 2025-05-17 at 2.07.11 PM.png
    Screenshot 2025-05-17 at 2.07.11 PM.png
    712.9 KB · Views: 2
RustyShackleford said:
Maybe we're going in circles here, but I still wonder if these will work with their AFCI breakers. Here's a pic of one (righthand pic), notice the handle is somewhat different than on a regualr Siemens one-pole breaker (lefthand pic).
Click to expand...
I just read that you cannot use 2 sp siemen afci on a multiwire branch circuit. I see, also, that they make dp afci breakers. Ge does not make dp afci's
 
You must log in or register to reply here.
Top