arc fault breaker trips off of different circuit

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rllevine

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Alameda, CA
Has anyone ever seen this? Turning on a light is causing an arc fault breaker to trip. The catch is that the light is not on the circuit that is connected to the arc fault. How can this be?
 
I thought about that. The lighting circuits exits the panel going up. It's Romex. And it powers a total of 3 lights. The arc fault circuit exits the panel going down. It's MC cable. It powers receptacles in two bedrooms and lighting in a finished basement space. I have checked and double checked in the panel to make sure the neutrals aren't crossed. And I have opened up and checked every receptacle and switch box to make sure the splices are sound.
 
As long as enough current is flowing through the AFCI to meet the series arc threshold it is possible that there is a source of an arc fault signature on the one circuit that is being leaked onto the other circuit.
But it is far and away more likely that you are seeing a GF trip, hence the suggestion of a shared neutral.
See whether the breaker indicates which kind of trip, AF or GF, is happening. Your troubleshooting will be very different depending on the kind of trip.
 
Yes these things do happen, when current levels meet levels required for arc fault detection on Afci breakers they all see signatures (or interferences coming from other circuits ) as they all tie to the buss bar (usually on the same phase).

Since you say there are only 3 lights on this particular circuit and if they happen to be LED, then this circuit is not drawing enough current for the afci to detect arc fault but other circuits that are already loaded may see the problem. If it truly is a problem or just something with the LED driver inducing interference.

For afci to detect series arc it must have a minimum 5 amp draw, for parallel arc detection spiking currents of 75 amps must be present. As I understand it.
 
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