Smoking light switch...short circuit?

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  #1  
Old 07-19-03, 09:40 AM
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dhusband
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Smoking light switch...short circuit?

Hi. Hours before going out of town for the weekend, my wife noticed a light switch in our kitchen that was VERY hot and sparked when she turned it on.

I immediately took the cover plate off and noticed one of the wires glowing red/white with fire and emitting a small amount of smoke. Naturally, I quickly turned off the circuit. Upon inspection and disassembly, here is what I found.

1) The switch is a 3-way switch which controls a ceiling light in the kitchen. There is another switch on the other side of the room that also controls that light. The switch in question is mounted in the same box as another 3-way switch which controls another (hallway) light.

2) The wire that was glowing and smoking is a black wire connected to the lower terminal on the right-hand side of the switch. There is another black wire jumpered from that terminal to the same terminal on the other switch in the box that controls the other (hallway) light. At the time of the incident, that jumper wire was actually so melted, that is was no longer connected to the terminal on the kitchen light switch. The black wire that was smoking/glowing was still connected.

3) After removing the switch from the circuit, I noticed the lower right-hand terminal to be charred and the jumper wire to the other switch to be melted and disconnected. Both the jumper wire and the smoking/glowing wire had about a half inch of melted insulation.

4) The red wire and its terminal (upper right-hand) do not appear to be damaged. Neither does the white wire and its terminal (upper left-hand).

QUESTIONS:

1) After removing the fried switch from the circuit, the other (hallway) light no longer works. Is this circuit dependant on that jumper? Note: Yes, I have turned the circuit breaker back on after removing the bad switch and wrapping the exposed wires.

2) The kitchen light no longer comes on when using the other switch on the other side of the room. Is this kitchen light circuit completely disabled by removing the one switch from the circuit?

3) Is my problem most likely just a failed (short-circuited) switch that will be rectified upon insalling a new switch?

4) Why did the circuit breaker not trip, thereby cutting the power BEFORE the wires and insulation melted?

5) Is there some other trouble-shooting that should be accomplished before just replacing the bad switch?

Since a picture is worth a thousand words, I am attaching a photo with labels. Thanks in advance for any information and advise you may have on this issue.

Regards,
Dave
 
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  #2  
Old 07-19-03, 10:13 AM
Join Date: Feb 2003
Location: Indiana
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1 yes it sounds like the jumper was the feed for that switch.

2 Yes if you disconnect a switch from a three way circuit the circuit is not going to work properly or at all

3 Not sure need more info for that diagnossis (However it may just have been a loose connection at the switch especially if there were two wires under the same screw on that switch.)

4 Not a high enough current draw for the breaker to trip. if the wire was loose and arcing, the problem and heat were isolated. If it was a short to ground or the neutral then the breaker should have tripped.

5 Probably not. Repair the burned wiring and pig tail the two black wires (Install a 4-6" piece of wire on each switch _The old one for the hall and the new 3-way_and splice them to the black wire that was origionaly glowing using a wire nut) and then install the other two wires on the new switch as well.


Now these repairs are assuming that your origional problem was a loose connection that arced and got hot. So when you put this switch back into service there should be some testing done to determine the amperage of this circuit to make sure there is no short circuit or overload condition. The best way to do this is with a clamp-on amp-meter.

Let us know if you have access to one and also let s know what is on this switch how many lights and what wattage.
 
  #3  
Old 07-19-03, 02:42 PM
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dhusband
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No...I don't have access to a clamp-on amp meter. I DID replace the burnt switch, following your suggestions regarding the pigtailing of new wires. Operational check is good, and I "observed" the switches with the cover off for a while to make sure there was no adverse conditions.

The only draw on the circuit (15amp switch) is one light fixture with three 75-watt bulbs.

Thanks again for your advise. I have also checked all other "double switches" in the house and configured them all so that there are no switches with dual wires under one screw.
 
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