AFCI trips before GFCI

C

Chasinmendo

Member
Location
Northern California
Occupation
Builder, Developer, Engineer
I have a circuit that's protected by an AFCI that also has a GFCI included as it's close to the kitchen sink. We are getting ready for final and testing the GFCIs I have one that has three downstream outlets protected by the GFCI. When the tester is plugged all the wiring reads correct but when the GFCI button is depressed the AFCI breaker trips before the GFCI has a chance to. We've checked all the receptacles for loose wiring have no idea why the AFCI trips. It's the only one that does. All the bathroom and other kitchen GFCIs work perfectly but this one circuit does not. Any suggestions appreciated.
 
Is it a combination AFCI/ GFCI breaker?
Sounds like a teeny tiny selective coordination problem, just like big power systems your ground fault is seen by the upstream breaker first. Remove the breaker and install a normal one for testing the GFCI receptacle.
 
CoolWill said:
Press the test button on the GFCI. If it trips, it works. Don't worry beyond that. If someone else is worrying about it, replace the breaker with an AFCI/GFCI combo and put a standard duplex in.
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My thoughts exactly. The plug-in testers actually connect to the ground pin to test the GFCI function. That will produce an arc, which the AFCI is picking up on faster than the GFCI, because the arc signature moves back along the wire at the speed of light to the AFCI breaker, whereas the GFCI has to observe and calculate the differential between Hot and Neutral to determine if there is an imbalance. The difference may only be milliseconds, but once the AFCI starts to open, it wins. The test circuit built into the GFCI outlet puts a resistor in the circuit to create the imbalance, so it will not affect the AFCI breaker.
 
Thanks guys. Appreciate the suggestions. Unfortunately my inspector thinks he's a genius and used the little plug in tester. I have to have the GFCI in the circuit because it's in the kitchen and I have to have a AFCI in the breaker box because it's specified on the drawing. Let me see if I can convince him that if the GFCI test button works it's OK. Thanks again for all your responses, I really appreciate it.
 
Post a photo of the AFCI breaker. Some have LED's that indicate why they tripped it would be interesting to know what the Leds show.
Also I'd be interested to know how many ohms the GFCI tester shows across hot to ground pins with the button pressed and a decent multimeter connected, I' guess around 15k-13k ohms.
If its 4000 ohms or less that would probably trigger the GFPE feature in AFCI's that have it.
 
Is there any reason you can't change the breaker to a combo AFCI-GFCI? Some may not like the inconvenience of having to go to the panel to reset a GFCI, but I have GFCI's all over and they never trip for me. The AFCI's randomly trip occasionally, especially during storms.
 
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