In 2017, I had a new 20 amp circuit (with dedicated GFCI outlet and AFCI breaker) installed by an electrician, which is right below my then two-year-old Square D electrical panel box (with aluminum bus). I run my .62 amp air purifier 24/7. But often, I also run my 1/2 amp fan and my 12 amp space heater at the same time. I have the space heater plugged directly into the outlet, while the other two appliances are plugged into a 3 in 1. The space heater runs for no longer than two hours at a time. But I would leave the fan on for hours.

Lately, this circuit has tripped twice. I don’t believe I’m overloading the circuit. And appliances with a ground fault would trip the circuit immediately upon being plugged in. So I’m wondering if it’s an arc fault trip. How can I tell the difference between a real arc fault trip and a nuisance arc fault trip? Also, could the aluminum bus circuit breaker be a factor (as opposed to a copper bus)?

  • 2
    “Appliances with a ground fault will trip immediately” - not true it may only trip when that faulty circuit or function is used.
    – Solar Mike
    Feb 14, 2020 at 7:59
  • Have you run the trip diagnostics on the breaker yet? That'll tell you if it's an overload/short (traditional breaker trip), a straight arc fault trip, or an arc-to-ground (gross ground fault)... Feb 14, 2020 at 12:44
  • What color is the test button on this breaker? Feb 14, 2020 at 12:49
  • Did your breaker trip the last two times all of your equipment was running or does it trip at random times throughout a period of time? Feb 14, 2020 at 14:08
  • Did you change anything since your question about this circuit not tripping? Feb 14, 2020 at 18:40

1 Answer 1


Since you said the breaker is AFCI and the breaker is now tripping I would guess the controls in the air purifier or the heater control contacts are getting dirty. When contacts get dirty or pitted they arc more than new and will trip AFCI circuits. I love square d but AFCI and GFCI breaker troubleshooting stinks as they don’t have the indicators that other brands have to show what the trip was caused from.

I agree that you probably were not overloading the circuit and that it has recently started tripping can show some arcing in the contacts.

AFCI protection is there to detect wiring problems, being right at the panel and in your garage I would eliminate the AFCI it is not required but the GFCI is required. Some might say it is protecting the home but a UL listed air purifier and space heater may keep tripping the breaker (the breaker could also be going bad). I have had many problems with AFCI breakers tripping on circuits that have speed control or ballasts all electronics no contacts so my state allows them to be removed with problem equipment.

  • There is no ballast on this circuit but all three of the appliances I mentioned have speed controls on them. Your answer seems pretty reasonable so far. I don’t know how old the fan is. But the air purifier is only two years old and the space heater is only four years old.
    – user62948
    Feb 15, 2020 at 1:35
  • I was trying to give the reasons I have had issues with. The additional info may help someone else.
    – Ed Beal
    Feb 15, 2020 at 1:55
  • I just found out that the fan is “at least six or seven years old” from the guy that gave it to me.
    – user62948
    Feb 15, 2020 at 1:55
  • I might try figuring out if it has oil ports or oil light bearings, both can be revived in most cases with a few drops of any standard motor oil.
    – Ed Beal
    Feb 15, 2020 at 3:11
  • “Oil ports”/“oil light bearings”/using motor oil… I’m not tracking what you mean by this. Are you referring to cleaning the contacts to the controls of the air purifier and the space heater?
    – user62948
    Feb 18, 2020 at 22:20

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