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Working with a wall switch/dimmer and it made a loud POP when I switched on

Working with a wall switch/dimmer and it made a loud POP when I switched on


Old 08-22-05, 03:01 PM
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Working with a wall switch/dimmer and it made a loud POP when I switched on

I've been trying to properly install a dimmer switch in a box that was previously grounded. I didn't know what I was doing at first (and obviously still don't!), and when I initially attempted to install the switch, I cut the ground wire that was going into a ground clip (to ground the metal box), so as to connect the wire to the ground screw on the dimmer. The previous switch did not have a ground screw at all, so only the box was grounded.

Basically, I've kept the switch set up like this until I found out that I should use a pigtail to ground BOTH the box AND the switch. I attempted to do this the other day and then realized that I didn't have another ground clip to use, so when I was putting the switch back into the box, I noticed a good bit more resistance when I was screwing the switch into the wall. All the wires were connected properly and, to my knowledge, no copper wire was exposed (except the wire that was stripped to go into the backwire holes). I got the switch into place, and turned on the breaker.

Everything seemed fine until I flipped the switch on. POP! I heard a loud pop and saw a quick flash of light/spark. I immediately threw the breaker off and started to unscrew the switch. There was a tiny bit of black smoke that was emitted from the switch. I pulled the switch out and it looked like all the wires were still connected properly, but the red (I'm assuming neutral, because the other wire is black and there are only 2 wires and a ground) wire's insulation was a little black near where it is inserted into the backwire hole. I also noticed that there is a tiny rip in the insulation a little bit further down the same wire. You can just barely see the copper wire exposed through the insulation.

So, I'm freaked out and I know how I have to properly ground the switch, but it has worked for the past week or so without any problems before I took the switch out to examine it and figure out how to ground both the switch and the box.

I'm glad I didn't burn the condo down, and I'd appreciate any help you can offer!
Old 08-23-05, 06:41 AM
Join Date: Nov 2004
Location: USA
Posts: 973
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First, you probably fried the dimmer switch, so you'll need to replace it.

Second, the red is NOT a neutral. Regular switches do not need to be connected to a neutral. They connect to a hot wire and a switched hot wire. The hot wire carries power to the switch, and the switched hot wire carries power from the switch to the light or whatever is connected to it. It is more likely that the black is the hot and the red is the switched hot, but that's just a guess. Without seeing what the fixture connects to on the other end, all we can do is guess. You might provide more info as to how many cables enter the box, how many wires are in each cable, and what they connect to. Include any wires that are nutted together and not connected to the switch (I'm guessing you'll see a pair of white wires nutted together, and possibly a pair of blacks + a black pigtail.)

My guess as to what happened: Since you mention the red wire having a bare spot on it where the insulation is damaged, I'd venture to guess that this part of the wire was in contact with the bare ground. When you turned on the switch, you made the red wire hot and, since it was grounded, shorted out the circuit.

I'd advise putting a regular switch in to test with, so you don't blow up an expensive dimmer switch. Hopefully you have some slack in the red wire so you can cut back to the damaged portion. You might have to cut back to it and wirenut a 6" or so new peice of same guage red wire on to fix this.

You do need to ground the box and switch. All the grounds in the box should be connected together, with a pigtail to the box and another pigtail to the switch.

Once you get things straightened out, and know the problem is solved, then you should be able to swap the switch out for another dimmer.

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