Just moved into a new house that has a bunch of AFCI circuits. I've done a bunch of remodel wiring in the past without issues but this one has me stumped.

I've been in the house for 4 days. Today I installed a dimmer on the family room lights. It was fine for several hours but when we sat down to watch TV, the AFCI breaker tripped a few minutes after I turned on the A/V system. I reset it, it tripped again. I shut the lights off and it was fine. As soon as I turned the dimmer on it tripped again a few minutes later. I took the dimmer out and installed a single pole Decora switch (it was easier because I didn't have to swap out the new Decora-style faceplate). It's very simple. 2 wires and a ground. It does the same thing. All that's left to do is install the original, single pole switch that was in there but I don't see how that would help. There doesn't seem to be anything special about it - your basic single-pole switch.

It's definitely related to the lights I messed with. If I leave them off everything is fine.

Any idea what I might have done?

 

Check the connections at the lights.

 

Thanks for your reply. I should have mentioned that there were no issues with the circuit before I messed with the switch. Spent 4 days and 3 nights here with those lights on - no problem. I swap out the switch and now I have this problem.

 

But sometimes it is what you least expect. First try with the switch pulled out, wires carefully separated. If you still have a problem try with the light pulled out, wires separated.

 

I'll have to try that. Strange, but it's fine this morning. i'm now starting to wonder if it's a legitimate overload versus an AFCI thing. It's not likely but I can't imaging what else it would be. I found that the hot water heater (gas, Power Vent) is on the same circuit. Looking at the motor it only draws 2.3 amps. My AV system is on the same circuit, but it doesn't draw much. And then there's the lights - 4 65 Watt PAR30 bulbs. All on a 15 amp circuit. It should be fine.

I have everything turned on now, like last night, and just put on a hot washing machine load. I'm waiting to see what happens when the hot water heater fires up.....

Thanks!

 

So it's been fine all day with the same electrical loads as last night. The lights or light switch was definitely the culprit, but I can't explain it. Everything was fine until I turned them on. I find it hard to believe that the problem fixed itself, but it's all good for now....

 

A typical fault issue is caused by neutral touching ground. It won't show up as any kind of short that you can test for easily but it is technically an arc fault short.

 

I thought I'd follow-up with the resolution of this issue. Long story short, the AFCI tripping after the light switch replacement was a coincidence. It turns out that the breaker was indeed tripping because of an overload situation. I neglected to realize until this past weekend when the lights went out again that a wine fridge is also on that circuit. It takes a combination of the wine fridge running, A/V system on, the XBOX on and the hot water heater firing up (gas, but a Power Vent) to trip the breaker. I'm going to run a dedicated circuit to the HW heater in the basement. They tapped into the family room circuit for convenience I guess since it's directly above the HW heater.

 

Did you check the load on that circuit with an Amprobe to be sure it was overloaded?

 

My guess is actually the igniter or flame sensor on the HE gas water heater.

 

I'd agree with Ben on the igniter..... the water heater should not be on an arc fault breaker.