Furnace tripping AFCI

[Mdsparky]

Existing residential installation at least 10 years old . At some point the furnace was put on an AFCI maybe a renovation? .Presumably it ran fine for years now it trips the breaker intermittently . This happens in the summer as well the blower runs for cooling . I replaced the breaker (Seimens) twice . It will go months with no issues . The location is Massachusetts. Two questions Is there any relief from the use of AFCI protection. And my thoughts are the blower motor is probably the culprit as it is common to both heating and cooling . Any thoughts ?

 

[ptonsparky]

Hard wire it and take it off the AFCI. Not required. It should be on a separate circuit anyway.

 

[kwired]

Is it on a circuit that supplies other loads?

Is the furnace in a location that 210.12 mentions and therefore is required to be AFCI protected? To comply with other codes a central furnace usually is not in such areas, "unit heaters" however could be about anywhere and if they are 120 volt and in any location mentioned in 210.12 then they require AFCI protection.

 

[Mdsparky]

Mass 210 12 (b). Replace the parent text and list items with the following:
ALL 120 Volt ,single phase, 15 and 20 amp branch circuits supplying outlets or devices installed in dwelling units shall be protected by any of the means described in 210.12(a)(1) through (6).
So in Mass it pretty much does require AFCI protection.

 

[ptonsparky]

Mass 210 12 (b). Replace the parent text and list items with the following:
ALL 120 Volt ,single phase, 15 and 20 amp branch circuits supplying outlets or devices installed in dwelling units shall be protected by any of the means described in 210.12(a)(1) through (6).
So in Mass it pretty much does require AFCI protection.

Not if it was legally installed 10 years ago.
Figure out what happened during that renovation and take it off if possible.

Do the AFCIs have an onboard Troubleshooting indicator? If not, upgrade.

 

[kwired]

Mass 210 12 (b). Replace the parent text and list items with the following:
ALL 120 Volt ,single phase, 15 and 20 amp branch circuits supplying outlets or devices installed in dwelling units shall be protected by any of the means described in 210.12(a)(1) through (6).
So in Mass it pretty much does require AFCI protection.

So MA wants AFCI on all 15/20 amp 120 volt branch circuits in dwellings?

Most furnaces with variable speed blower motors don't play well with AFCI/GFCI's, high frequency capacitive leakage is the main problem. They haven't had any changes in listing standards to force manufacturers to design them to work with AFCI/GFCI's.

 

[curt swartz]

Since you say this unit has worked fine for at least 10 years maybe a intermittent fault has developed in the branch circuit wiring or in the furnace itself. It could be tripping from a ground fault, overload or short circuit. As mentioned are you sure there is nothing else on this circuit?

 

[Mdsparky]

So MA wants AFCI on all 15/20 amp 120 volt branch circuits in dwellings?

Most furnaces with variable speed blower motors don't play well with AFCI/GFCI's, high frequency capacitive leakage is the main problem. They haven't had any changes in listing standards to force manufacturers to design them to work with AFCI/GFCI's.

Not if it was legally installed 10 years ago.
Figure out what happened during that renovation and take it off if possible.

Do the AFCIs have an onboard Troubleshooting indicator? If not, upgrade.

I'm not the electrician who was involved at the time AFCI added . Because this unit worked for years and years without tripping issues I'm very reluctant to remove the protection. If something were to happen after the removal that results in damage ..I can imagine a conversation like this. Powers that be ;" let me get this straight , it was tripping and that tripping became more frequent and you thought it was a good idea to remove the protection ?
Me : well, umm you see umm ..yes .

I have asked a couple of inspectors about relief from the requirement and they are unaware of a legal way . There is , in Mass , a process to remove GFCI protection for incompatibility issues . I asked here too because of the quality and breadth of the members and thought maybe someone might have info . I'm not sure why it was added but my guess is no one involved wanted to put the heat on AFCI though we are getting used to it . My guess is that it was required .

 

[jap]

I'm not the electrician who was involved at the time AFCI added . Because this unit worked for years and years without tripping issues I'm very reluctant to remove the protection. If something were to happen after the removal that results in damage ..I can imagine a conversation like this. Powers that be ;" let me get this straight , it was tripping and that tripping became more frequent and you thought it was a good idea to remove the protection ?
Me : well, umm you see umm ..yes .

I have asked a couple of inspectors about relief from the requirement and they are unaware of a legal way . There is , in Mass , a process to remove GFCI protection for incompatibility issues . I asked here too because of the quality and breadth of the members and thought maybe someone might have info . I'm not sure why it was added but my guess is no one involved wanted to put the heat on AFCI though we are getting used to it . My guess is that it was required .

I think you've pretty much answered your own question.

JAP>

 

[kwired]

I'm not the electrician who was involved at the time AFCI added . Because this unit worked for years and years without tripping issues I'm very reluctant to remove the protection. If something were to happen after the removal that results in damage ..I can imagine a conversation like this. Powers that be ;" let me get this straight , it was tripping and that tripping became more frequent and you thought it was a good idea to remove the protection ?
Me : well, umm you see umm ..yes .

I have asked a couple of inspectors about relief from the requirement and they are unaware of a legal way . There is , in Mass , a process to remove GFCI protection for incompatibility issues . I asked here too because of the quality and breadth of the members and thought maybe someone might have info . I'm not sure why it was added but my guess is no one involved wanted to put the heat on AFCI though we are getting used to it . My guess is that it was required .

So now your job is to find out why it is tripping.

Good luck, especially if it is only intermittent tripping.

 

[Paul_Briganti]

I've been here before... If the furnace is in a conditioned space, basically inside the dwelling unit, AFCI protection is required.
The brushes of either the blower motor or if installed, the inducer motor, are throwing an arc that the AFCI is picking up. Since the furnace is 10 years old, those motors are about to go anyways. I suggest replacing both at the same time, save on the trip charges, and that should take care of your intermittent tripping issues. This worked for me, I am all but certain it will work for you. Best of luck.

 

[ptonsparky]

There are brushes in those motors?

I've been here before... If the furnace is in a conditioned space, basically inside the dwelling unit, AFCI protection is required.
The brushes of either the blower motor or if installed, the inducer motor, are throwing an arc that the AFCI is picking up. Since the furnace is 10 years old, those motors are about to go anyways. I suggest replacing both at the same time, save on the trip charges, and that should take care of your intermittent tripping issues. This worked for me, I am all but certain it will work for you. Best of luck.

 

[curt swartz]

There are brushes in those motors?

I have never seen a furnace that uses motors with brushes.

 

[ActionDave]

If I ever see a motor in a furnace with brushes it will be the first time.

 

[Eddie702]

And what happens if you change the motors and the tripping continues??

I don't see how GFCI/AFCI could be required when it was not required 10 years ago. If someone during remodeling ran a brand new circuit then it would be required. If it is the original circuit, it wouldn't be required.

 

[JohnE]

I'm in MA as well. If this were a new installation, I agree there is no way around the AFCI requirement.

If it is 10 years old I'd have no problem, personally, removing the AFCI breaker, but I understand the reluctance to do so.

 

[kwired]

I've been here before... If the furnace is in a conditioned space, basically inside the dwelling unit, AFCI protection is required.
The brushes of either the blower motor or if installed, the inducer motor, are throwing an arc that the AFCI is picking up. Since the furnace is 10 years old, those motors are about to go anyways. I suggest replacing both at the same time, save on the trip charges, and that should take care of your intermittent tripping issues. This worked for me, I am all but certain it will work for you. Best of luck.

Conditioned space is not a requirement of 210.12. Typical mechanical room where a furnace might be located normally is not a room mentioned in 210.12.

Now place that furnace in a living room, bedroom, laundry room and you need AFCI.

Place a new furnace in one those rooms I just mentioned but build a closet around it, that can't really double as a clothes closet or maybe a pantry, and you made it a "mechanical room", IMO no AFCI required on circuits supplying items in that room.

 

[jap]

Generally with problems like this, eventually you won't be burdened with the issue.

JAP>