The circuit breaker for our kitchen lights trips instantly when I turn on ANY light switch on that circuit. It is 6-month-old new construction and everything worked just fine until a week ago. And then this behavior suddenly started without us changing anything.
It is a 15A circuit with five switches:
- Switch #1: Lutron Caseta wireless dimmer with 6 LED recessed lights (7.6W each)
- Switch #2: Lutron Caseta wireless dimmer with 8 LED recessed lights (7.6W each)
- Switch #3: Lutron Caseta wireless switch with 4 LED exterior lights (10W each)
- Switch #4: regular toggle switch with exterior motion detecting flood light (36W)
- Switch $5: regular toggle switch for pendant lights but no lights installed yet.
The circuit breaker looks like this: https://www.homedepot.com/p/Square-D-Homeline-15-Amp-Single-Pole-Combination-Arc-Fault-Circuit-Breaker-HOM115CAFIC/202353305?irgwc=1&cm_mmc=afl-ir-27795-483420-&clickid=VB9TeuUQPxyOWTXwUx0Mo34GUki2SIXtR1fETE0
- With no switches on, the breaker remains on.
- If I turn on any of the switches 1-3, the breaker instantly trips.
- If I turn on the switch 4, the breaker trips in about 2 seconds.
- If I turn on the switch 5 (no lights), the breaker doesn't trip.
The breaker has a white "test" button. The test button trips the breaker ok.
Given the fact that breaker trips when turning on ANY switches with lights installed, can this be due to a faulty breaker? But again, it's brand new and I don't know how likely it is.
Or can it be a faulty switch? But the breaker doesn't trip when no switches are on. Can a faulty switch cause other switches to trip the breaker?
Also, I don't know why the breaker trips after 2 seconds with the motion detect light, while it trips immediately with other lights.
What are some possible explanations for this behavior? Is there anything I could try before hiring an electrician?
UPDATE 1: Per @ThreePhaseEel's suggestion, I tried the Square D breaker's built-in diagnostics (holding down the white test button and turing on the breaker), and it tripped immediately. According to the instruction, it means "Fault to ground (arcing to ground, grounded neutral, shared neutral, ground fault)". What can cause this after 6 month of use?
UPDATE 2: I checked the switch wiring. AFAIK, the wiring looked ok. However, switch #5 seemed faulty because my pen-type voltage detector detected voltage from both black wires even when then switch was off. I changed it to a different switch. Switch #4 was backwired but no wire's exposed.
I tried to untangle wires so that no wires/switches are touching anything, but sadly the breaker continued tripping even after that with turning on any of switches #1-#4 (instantly for #1-#3 and in 2 seconds for #4).
Guess it is time to call an electrician, but I'm attaching the pictures of the switch boxes in case anyone can find anything suspicious.
One thing I forgot to mention above was that both switches #1 and #2 are originally wired as 3-way (switch boxes 1 and 2 below), but they are wired as instructed in pages 3-6 in https://www.casetawireless.com/documents/0301710a_caseta%20advanced%20inst.pdf with remotes.