AFCI question

Yesterdays warranty inspection had two ACFI breakers that were about 40 degrees hotter than the average breaker temp in the panel, they were just over 100 degree and the average temp was around 58 - 60. There was no significant load on these bedroom circuits at the time of inspection, bedroom clocks, etc.

The homeowner reported that if they plug the vaccuum into any of the bedroom outlets, they trip immediately, everytime. They have already had the builder out to look at them. The builder apparently checked the plugs in the rooms and looked in the panel. Nothing was replaced. They ended by telling the homeowner to plug the vaccuum into the hall outlet.

Do to the temperature differential alone I was recommended having these AFCIs checked.

Any thoughts on this problem? Is it a problem? I did suggest maybe something is wrong with their vaccuum?

What was the brand and model number of the AFCI breaker and panel?

Did you try plugging anything else into those outlets? I would think that outlets are not a problem if the vacuum works in the hall.

A 40 degree temperature difference indicates a problem. I would definetly document it. Sounds like the builder is trying to brush over a problem.

Brian is asking for the brand and model number because some of the AFCIS have been recalled.

Not with AFCI breakers. They run hot.

I would not be concerned with this. . .

I’ll bet that the power is on to the vacuum when they plug it in, which would create the same “arc” that the AFCI is designed to prevent.

Otherwise, there is likely some other problem, perhaps in the cord, causing the AFCI to function as it is intended.

What Jeff said!

The vacuum has a motor that has brushes in it. They arc as the armature turns, and tripping the breaker as it is designed to do.

A fan will do the same thing.

Hope this helps


Thanks for the info gent’s…always a pleasure to learn from the best!

I assumed it works in the hall because it is not an AFCI.

I know AFCI run hotter, but I always go on and have found around a 20 - 25 degree difference. Somedays in Texas 100 degree readins fall well within that range. But it was a very chilly 48 or so degree morning and all of the other breakers were in the 58-62 degree range. The third AFCI in the panel was also in what I consider the normal range around 80.

They were not Square D’s.

As I said I did suggest to the homeowner that the problem may lie in their vaccuum. Unfortunately I do not carry one in the truck to test it for them.

I know about the vaccuum motors tripping AFCIs when plug is operated with unit on. In fact that is the most common example I give to the average client to explain what an AFCI does and why it trips.

Report is sent. I recommended that it be looked at because I felt the temp dif. was out of line, and am comfortable with that position. If a sparky or the builder overrules that and is willing to back it up, fine by me. They are the experts/specialists - the sparkys anyways.

My question would be, “what do consider to be normal (in-line), and why?”

I’m certainly not picking on you Kevin, but I would like to hear your justification for making the recommendation (as a learning tool for all of us).

If your answer is - “it just didn’t seem right to me” - I will accept that, but I’d be more interested in hearing something with some substance, or some mitigating factors (i.e. scorched wires, evidence of overheating, buzzing or hissing, etc.).

Personally, I wouldn’t be inclined to recommend service based simply on a “hot” breaker, especially an AFCI breaker. In fact, I won’t typically check breaker temps unless I find other issues first.

That’s my protocol. I’d like to hear from others as well.

Hmmm, I know you aren’t picking Jeff, it is a valid question.

Honestly i would have to answer with “it didnt feel right” in this case. There were no visible cues. I cannot say that I have any concrete data that I based that on. But I do generally run the ir thermometer over breakers, and most lf the time the temps are in pretty consistant ranges. Yes, AFCI are always higher. Breakers that have high load are higher, and no I cannot always comment on what has been going on with the breaker just before I tested it. So I understand it is not an exact science.

This one was outside of the range that my personal experience says is typical. That does not mean necessarily that it is broken. But common sense makes me question why a circuit that is not in use, that the homeowner is present and states that nothing unusual has been plugged in that morning, that is that much hotter than the rest of the breakers seems odd to me. Does it mean that I have detailed knowledge of every breaker type and brand and their operating temps? No. Based on the information I had at the time, it didn’t feel right.

Part of what I feel we do is offer the experience of the fact that we look at so many houses. I do not claim to have the most experience in my area, on this board, far from it I am sure, but it is what I have to go on. I am careful not to be alarmist and say “this is a fire hazard!! Shut it down and get an expert out here today!” But I think stating that this is not typical in my experience and may warrant further investigation by an expert seems a reasonable course of action and reasonable to say in our position. If I am wrong hopefully, I will find out and learn from the experience. If I am right, maybe I saved them some trouble down the road.

I have a comment in for the 2008 NEC about heat and AFCIs. Lets see what NFPA says

What’s your comment Greg? You can’t expect us to wait now that you’ve let the cat out :smiley:


I spoke with someone on the NFPA Board the other day and I was explaining the PROPER way AFCI’s need to be done in bedrooms and we started chatting about the heat build up. ( I get advice calls all the time from AHJ’s )

He is also on the NFPA board and he said they had a independent review board look at the heat issue on AFCI’s grouped and he said they found no problems with it…the heat build up was negatible in association they said to the warm and hot point of causing the breakers any problems…super nice guy…

Also he said the largest argument was that the local builders and contractors would cause so much problems with the increased cost that it would caused the local AHJ’s to mandate their own rulings regardless of the NEC and have the locality adopt local rules…and overide the all 15A & 20A AFCI proposal if it happens to make it through…but he also did not think it would be accepted the next cycle anyway…

Just some info from a previous chat…

Square D has responded to some customers claiming the same problem.$file/VacuumFAQ0502homeowner.pdf



Jeff I just asked the same question Paul addressed. How will grouping a dozen or more AFCIs affect heat in a panel. After all most breakers are calibrated at 40c and that is not really hot around here for a panel in a garage (no A/C). Add the heat load of a bunch of AFCIs and we may have problems

That was the “In the KNOW” response from the NFPA guys…my personaly opinion is like the NEC always does…they TRY something and if it becomes a problem then they change it…lol…so who knows.


I know that AFCI’s will run hot, but isnt a 40 degree differential a but much??

Possibly, but not absolute.

There are several considerations to be taken in, such as the circuit load, but more so in the breakers themselves.

If there is a lone AFCI breaker surrounded by standard breakers, it’s not likely it will get “too” hot. As you increase the number of AFCI breakers, side by side, the heat will multiply as well, and the middle breaker(s) will generally have the greatest temp.

I’ve seen as many as 8 AFCI breakers “stacked” and in contact with eachother and you could literally feel the heat coming off of them. Although there are no provisions that set a maximum number for these breakers, some manufacturers suggest that no more than three be in direct contact because of the excessive heat build-up.

As Greg pointed out, there are upcoming codes that may require all circuits to be AFCI protected. What do you expect the temperature difference to be when there are 40 AFCI breakers stacked in a single panel?

This is how I stated it in my report. I did not state definatively that it was faulty. i simply pointed out that this temperature differential seemed high and IN MY OPINION it should be further investigated by an expert. Particularly because I could confirm with the homeowner, this was a warranty inspection, that the only thing on this circuit in the identified bedroom was an alarm clock.

I still think it was a reasonable opinion to render. It may ultimately end up being wrong and an expert may say it is fine. But I am comfortable with pointing it out in this situation. I will follow up with the homeowner next week and see what has come from it.


The point will really be in what the Manufacturers say even if adopted by the NEC. If the manufacturers put a requirement on spacing yet the NEC were to adopt the provision it is looking at…who would overrule…well it would be the Manufacturer…THEN what…anyway should be an interesting debate and I am along with GREG on THIS side of the electrical fence awaiting how the two sides plan on forming a MARRIAGE together over this…should be interesting…