Breaker Immediately Trips, Need Help Troubleshooting Why

Question

I installed 4 Lithonia LED recessed lights on my living room 15 amp circuit. Everything was working great yesterday when doing final testing. I left the breaker off overnight as I was planning to do final closing of junction boxes and drywall patching today.

Last night at 2am the fire alarm connected to my inactive ADT home security panel starts chirping. I go to the ADT motherboard in our coat closet and start disconnecting the low voltage wires attached to the motherboard trying to get the thing to shut up. It ended up being a stupid battery problem on the fire alarm unit itself...but I realized the wires going to the ADT motherboard are hot as a red and black touched and gave a spark, so I leave them disconnected and wire nut them all off. It was 2am and I didn't think much of it.

Today for final install of the LEDs I stupidly forego one last test (because I did it yesterday and everything worked great) and push them all up into the drywall using the spring clamps. When I go to turn on the breaker it immediately trips upon multiple attempts.

I have tried the following which have not fixed the problem of the breaker immediately tripping:

• turned off and back on all breakers for the house...Nope!

• unplugged all appliances and turned off all light switches on that circuit and retried breaker...Nope!

• reset GFCI on a different circuit that may be in between breaker and the tripped circuit...Nope!

• unplugged and wire nutted off all low voltage wires going into the ADT motherboard...Nope!

These are some potential variables that may or may not be relevant:

• The 4 LEDs are connected to a Lutron Maestro low voltage dimmer switch. It is not a traditional on/off knob but a flat low profile click if that makes sense. To be considered 'off' do I need to disconnect the wires going into it? Anything else about the switch that might affect my attempt to reset a short circuit? The wires are all intact and no burning or discoloration.

• There is a motion detector and a door contact in the room with the LEDs that are wired back to the ADT motherboard in a different part of the house. I assumed since I disconnected all those wires from the motherboard this would eliminate this from being a factor?

Any tips or things I can do to narrow this down is much appreciated!!!

Answer 1

Shared Circuit

Assuming this isn't just some crazy coincidence, I'd bet on:

• The alarm and the lights are on the same breaker
• When you left the breaker off for an extended period of time, the battery on the alarm started to get low, which caused the chirping as a (correct) warning
• Red and black on the alarm are battery connections and not incoming AC power. A typical alarm system has a converter (either a wall wart or built in to the main alarm panel) to convert from 120V AC to 6V or 12V DC. That AC wiring will, in the US, almost always be black & white (hot & neutral). Black & red is, however, typical for battery power. A battery, even when relatively low, can make quite a spark when shorted.
• Sensors, bells, etc. connected to the alarm have nothing to do with the current (pun intended) problem.

So what is going on? Anything is possible. But since the breaker is tripping immediately, the likely scenarios are:

• Something came loose & shorted when you put the new wires, dimmer, etc. back in the box. To test this, open up the box and disconnect the hot & neutral from the dimmer and see if the breaker can be reset. If so, you know the problem is somewhere in: dimmer, lights, connections between dimmer & lights.
• Something came loose & shorted when you messed with the alarm. Not on the low voltage side. You need to find the incoming power - either to a wall wart or into the main alarm panel - and disconnect it and then try resetting the breaker.

If you can't find the problem in one of those two places then you have to disconnect each light or receptacle on the circuit until you find the problem. There is a small but non-zero possibility that somewhere in the circuit something else (e.g., a bad backstab connection) went bad coincidentally with the new work.