AFCI protection for multiwire branch circuits

[luiscarlos]

Will AFCI protection work on multiwire branch circuits.This is an existing house that the main service disconnect was replaced and branch circuits were extended more than 6ft . Several branch circuits are sharing the neutral conductor.
NEC 210.12(B) branch circuit extension or modifications .

 

[infinity]

Will a AFCI 2-pole breaker work?

 

[ModbusMan]

Will a AFCI 2-pole breaker work?

Not any better/worse than an AFCI 1-pole breaker :snicker:

But despite Mr. QO220CAFCI not being upset with my failing light switch, its coworker did correctly identify a floating ground on an unused receptacle, so not entirely useless, I suppose?

 

[ramsy]

branch circuits were extended more than 6ft.. NEC 210.12(B)

If new panel wasn't moved > 6ft, 210.12(D)(2) will work regardless of panel brand.

If panel was extended, then AFCI breakers on MWBC is brand dependent.

 

[CoolWill]

I hate this AFCI stuff so much. I'm dealing with it right now where a new toaster oven trips Square D AFCI breakers. It doesn't trip Eaton or Siemens AFCI breakers. Customers don't understand all this and think you're lying when you say there is nothing you can do about it. There is a final inspection coming up and as soon as that is done, I'm sticking a regular breaker in and moving on.

 

[ramsy]

There is a final inspection coming up and as soon as that is done, I'm sticking a regular breaker in and moving on.

There is no reward for being good, unless everybody else is bad, and ugly.

 

[ramsy]

new toaster oven trips Square D AFCI breakers. It doesn't trip Eaton or Siemens

When idols fall, new deities may be considered, or the offending appliance may be bannished.

 

[ramsy]

Customers don't understand all this and think you're lying when you say there is nothing you can do about it.

Show them a listed appliance that works fine, and you demonstrate good warning against unlisted junk sold on Amazon.

 

[electrofelon]

Will a AFCI 2-pole breaker work?

Not any better/worse than an AFCI 1-pole breaker :snicker:

 

[CoolWill]

Show them a listed appliance that works fine, and you demonstrate good warning against unlisted junk sold on Amazon.

It isn't the appliance. It's the UL listed junk breaker sold by Square D. We've been dealing with these mysteries since AFCIs came out. It has occasionally been the appliance and occasionally an errant staple or ground neutral short, but it has very very rarely ever been an actual arcing fault, and is far more likely to be a quirky breaker.

 

[electrofelon]

There is no reward

Disagree. The mental satisfaction of hearing an AFCI breaker hit the bottom of a nice empty 10 yard dumpster is nearly priceless . I often will sit there for a moment after the ringing and echoing stops. I imagine it's final journey down the highway. It's final movements for eons when it is dumped into the landfill. One last moment of light as the days final sun rays turn to orange and then red. Here comes the bulldozer with the daily landfill cover. It's nearly over now....there it's is, it's over, eternal silence.

 

[ramsy]

far more likely to be a quirky breaker.

One mans’ quirky nuisance trip is another’s treasured lesson.

 

[ramsy]

The mental satisfaction of hearing an AFCI breaker hit the bottom of a nice empty 10 yard dumpster is nearly priceless

LMAOL, missed that option, too cheap not to try somewhere else to charge for it.

 

[don_resqcapt19]

It isn't the appliance. It's the UL listed junk breaker sold by Square D. We've been dealing with these mysteries since AFCIs came out. It has occasionally been the appliance and occasionally an errant staple or ground neutral short, but it has very very rarely ever been an actual arcing fault, and is far more likely to be a quirky breaker.

All of the arc signature algorithms are propitiatory, so differences in operation between brands is to be expected.

The real issue is that the manufacturers want us to believe that their algorithms know the normal operating arc signatures of all existing appliances and all appliances that will come into being over the life of the AFCI....not even remotely possible.

 

[CoolWill]

All of the arc signature algorithms are propitiatory, so differences in operation between brands is to be expected.

The real issue is that the manufacturers want us to believe that their algorithms know the normal operating arc signatures of all existing appliances and all appliances that will come into being over the life of the AFCI....not even remotely possible.

The most effective component of the AFCI was the ground fault sensing, but they removed that. Did it ever come back? I haven't been keeping up. If they wanted to truly make a difference, that is what they would have done from the beginning instead of the voodoo bunk that is AFCI. The toaster oven I'm dealing with is a quality unit. I've monitored it in action and it is PWM'ing rapidly to get the right temperature, so that is likely what the breaker is sensing as adding.

GFP would actually work since a real arcing fault, or worse, a glowing connection, would rapidly lead to a ground fault before much damage could be done.

 

[curt swartz]

The most effective component of the AFCI was the ground fault sensing, but they removed that. Did it ever come back?

Square D QO/HOM and Eaton CH still have GF detection in their breakers. I believe Siemens NON PoN AFCI's still do too but the PoN breakers don't.

You mentioned having a problem with the toaster oven connected to a Square D AFCI but not when its connected to a Eaton or Siemens. Are you sure the appliance or branch circuit doesn't have a ground fault? The Square D would sense that but not the Eaton or Siemens.

 

[CoolWill]

Square D QO/HOM and Eaton CH still have GF detection in their breakers. I believe Siemens NON PoN AFCI's still do too but the PoN breakers don't.

You mentioned having a problem with the toaster oven connected to a Square D AFCI but not when its connected to a Eaton or Siemens. Are you sure the appliance or branch circuit doesn't have a ground fault? The Square D would sense that but not the Eaton or Siemens.

Yeah, no ground fault. I plugged it in elsewhere and it tripped the AFCI anywhere it went. To appease the customer, I ran a dedicated circuit just for it, and it tripped the new AFCI. I meggered the circuit just to be sure and it was good. I plugged in an Eaton BR AFCI in the HOM panel and it worked fine, and tried it with a Siemens just for the fun of it and it worked.

 

[don_resqcapt19]

The most effective component of the AFCI was the ground fault sensing, but they removed that. Did it ever come back? I haven't been keeping up. If they wanted to truly make a difference, that is what they would have done from the beginning instead of the voodoo bunk that is AFCI. The toaster oven I'm dealing with is a quality unit. I've monitored it in action and it is PWM'ing rapidly to get the right temperature, so that is likely what the breaker is sensing as adding.

GFP would actually work since a real arcing fault, or worse, a glowing connection, would rapidly lead to a ground fault before much damage could be done.

When they first stated making the branch circuit/feeder AFCIs (the original ones), the only way that they could pass the testing required by UL 1699 was to use ground fault detection. Over time, starting with GE, the manufactures found ways to pass all of the testing without using and ground fault sensing.

I agree that it was the most effective part of the AFCI and even got one applications engineer to agree, but it becomes a cost issue and if they can eliminate costs and still meet the requirements of UL 1669, they will.

GE did it because that would let you use single pole AFCI breakers with a handle tie to supply multiwire circuits. No need for a two pole AFCI. Now with many installers using dual function AFCI/GFCI breakers, you need a two pole one for a multiwire circuit.