When *should* an AFCI trip?

M

ModbusMan

Senior Member
Location
Cleveland, OH
Occupation
Building Automation Engineer
Putting this here for "me" education ;) Just now, wifey called me over to the master bedroom because the lights were "acting weird." Come in and they're flickering a little, with buzzing coming from the switch. Seems pretty obvious if you ask me, but Mr. QO220CAFCI was perfectly content to let things go as they were? So when are these things supposed to trip? Am I misunderstanding something fundamental to how these things operate, or is the breaker itself faulty and needs replaced (along with the switch, nat)?
 
ptonsparky said:
They should trip when you press the Test button, other than that, who knows.
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Welp, the test button worked perfectly normally, so don's probably correct that there's a minimum current necessary for the series arc detection chip to work, and I just wasn't anywhere near that level.

electrofelon said:
UL supposedly has a test they put an afci breaker through, but it seems to be a national secret what that test setup consists of.
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I wonder if it's anything like the Navy's salt fog tests for electronic assemblies. In more ways than one... towards the beginning of the MIL-STD that defines it, there was a line that essentially read "This test is pretty much useless, but it's tradition, and we've always done it, so keep doing it!"

ELA said:
Many years back when AFCi's were still relatively new I did an experiment that demonstrated a component failure that generated a small flame but did not trip an upstream AFCI. here:
https://forums.mikeholt.com/threads/experiments-with-afcis-and-gfcis.53582/
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I'll have to check that out :)
 
electrofelon said:
UL supposedly has a test they put an afci breaker through, but it seems to be a national secret what that test setup consists of.
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Those tests are specified in UL 1699, and you can view the UL standards using the same non-user-friendly viewing system that the NFPA uses for the free viewing of their codes. Just like with the NFPA, you have to register with an email address.
 
don_resqcapt19 said:
Those tests are specified in UL 1699, and you can view the UL standards using the same non-user-friendly viewing system that the NFPA uses for the free viewing of their codes. Just like with the NFPA, you have to register with an email address.
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Don
Can you list the website you are describing please.
I tried a few weeks back, I believe was UL solutions and they are asking for a business name, phone number, name, address, etc…all mandatory entries.
 
don_resqcapt19 said:
Those tests are specified in UL 1699, and you can view the UL standards using the same non-user-friendly viewing system that the NFPA uses for the free viewing of their codes. Just like with the NFPA, you have to register with an email address.
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I believe I looked into that awhile back and it was very vague about what the arc test was and was not specific about what the apparatus was to create the arc to test the breaker with
 
electrofelon said:
I believe I looked into that awhile back and it was very vague about what the arc test was and was not specific about what the apparatus was to create the arc to test the breaker with
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Don't you remember the test setup with the neon sign transformer, razor blade that cut into a piece of zip cord which was wrapped in some kind of flammable sleeve? Yup, we saw it.

-Hal
 
hbiss said:
Don't you remember the test setup with the neon sign transformer, razor blade that cut into a piece of zip cord which was wrapped in some kind of flammable sleeve? Yup, we saw it.

-Hal
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Standard QO115 and 120 breakers for years before AFCI came along would usually trip if you cut into a piece of zip cord with a razor blade. Their lower magnetic trip setting than most competitive breakers was the reason, and they did not cost $50-$80 and have a bunch of electronics that might not really have much real purpose.
 
MyCleveland said:
Don
Can you list the website you are describing please.
I tried a few weeks back, I believe was UL solutions and they are asking for a business name, phone number, name, address, etc…all mandatory entries.
Click to expand...
I registered a long time ago, it appears that they have changed the requirements, but there is still an option for an individual to register, and I doubt that they check anything other than the email address, so just provide random information for the other fields :)
 
ModbusMan said:
Putting this here for "me" education ;) Just now, wifey called me over to the master bedroom because the lights were "acting weird." Come in and they're flickering a little, with buzzing coming from the switch. Seems pretty obvious if you ask me, but Mr. QO220CAFCI was perfectly content to let things go as they were? So when are these things supposed to trip? Am I misunderstanding something fundamental to how these things operate, or is the breaker itself faulty and needs replaced (along with the switch, nat)?
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Other than the buzzing from your switch it's sounds like the drivers for the led's are giving up the ghost. Did you try incandescent instead?
 
qcroanoke said:
Other than the buzzing from your switch it's sounds like the drivers for the led's are giving up the ghost. Did you try incandescent instead?
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Not sure these little guys even have drivers (or if they do, they're a *lot* smaller than the usual A19 bases)... but the buzz was definitely from the switch. It's already been replaced and I'm back to normal lights and silence.
 
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