Switch & fixture getting HOT

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  #1  
Old 10-07-06, 02:51 PM
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Switch & fixture getting HOT

I'm having a problem with a light switch and the ceiling fixture it controls. Sometimes after the light has been on a short time, maybe 15 minutes, the switch gets hot and the bulbs start pinging like they're heating up. The drywall for 2' around the fixture is warm. Up in the attic, the junction box itself radiates heat and even the ceiling joists are warm. And I'm talking about HEAT, not a little warmth like bulbs normally generate. The attic insulation actually turned black.

I had an electrician come out and replace the switch, fixture, and a few other outlets, switches & fixtures on the same circuit that had also been giving me trouble. He said everything looked fine except for old worn-out outlets & switches. Things seemed fine for 2 weeks but now this one switch/fixture is getting hot again. I'm afraid of a fire starting. What can be causing this?
 
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Old 10-07-06, 03:06 PM
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1st; is the light bulb no bigger than the max rated in the fixture?

next; is this circuit part of a multiwire branch circuit? If so and the neutral became disconnected, it could allow up to 240 volts across the bulb and switch. Check the voltage at the fixture to determine that it is correct.


Is the fixture vented properly if required? (is ther insulation against the fixture where ther shouldn;t be)

any other info you could add may be helpful.
 
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Old 10-08-06, 03:29 PM
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"1st; is the light bulb no bigger than the max rated in the fixture?"

Yes.

"Is the fixture vented properly if required? (is ther insulation against the fixture where ther shouldn;t be)"

This is ok too.

"next; is this circuit part of a multiwire branch circuit? If so and the neutral became disconnected, it could allow up to 240 volts across the bulb and switch. Check the voltage at the fixture to determine that it is correct."

I believe this IS a multiwire branch circuit. I heard the electricians talking about 2 curcuits sharing a neutral. I'm not the electrical DIYer in this house - a friend helps me with it but he's not available today. When he gets back I'll ask him to check the voltage.

"any other info you could add may be helpful."

The house was built in the 50's with several amateur remodels through the years. Some of the electrical was VERY scary -like masking tape used instead of electrical tape- but we thought we got rid of all the dangrous things. Maybe not.

Another thing that happened was the ceiling plate on the bathroom overhead fixtures discolored. This is on the same circuit as the problematic kitchen ceiling fixture. It looked to me like heat caused it, but the electricians found no evidence of the wires heating up or any problem at all in that section of wiring. I had them replace the fixtures anyway.

Around the same time the coffeepot broke (also this same circuit). The on/off switch was so hot it burned my hand.

I have 3 other outlets on the same circuit that have been working fine. One is in between 2 that went bad, the others are after those.

The start of this problem coincides with mice moving into my attic, so if there was a loose wire they may have knocked it out of place.
 
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Old 10-08-06, 03:57 PM
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Glad to see you back. I though maybe the house had burned down and all advice was moot.


"I believe this IS a multiwire branch circuit. I heard the electricians talking about 2 circuits sharing a neutral."

Yes, that would be a MWBS. Due to the physics involved, if the neutral became detached or even partially detached, this could cause the voltage to increase (in certain circumstances) and cause just about everything you mention as being a problem.

Actually any loose connection can cause heat but with the lamp getting hot as well, I would look towards the neutral situation.


It's time for your friend to be taken out to dinner. His task at this time is to find the loose/broken neutral and fix it.


Until then, if it is as bad as it sounds in your posts, I would seriously consider not using the lights involved unless you have really good insurance and were thinking of a VERY complete redecorating job.
 
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Old 10-08-06, 04:06 PM
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Thanks for the advice. My gut is telling me this is a serious problem but the electrician was trying to tell me it's not, since it wasn't happening the day he was here. Of course not, it's like the car never makes that noise when the mechanic is listening.

"Until then, if it is as bad as it sounds in your posts, I would seriously consider not using the lights involved unless you have really good insurance and were thinking of a VERY complete redecorating job."

No, I really don't want to redecorate right now. So should I avoid using everything on this circuit, which is most of the kitchen & bath, or is it ok to just avoid this one fixture/switch which is currentty a problem? I think you're going to tell me to avoid them all.
 
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Old 10-08-06, 04:49 PM
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It would be best to avoid all usage if possible but I too live in a real world. The lights are generally the biggest concern because they get turned on and then are left on ofr extended periods of time. Most plug in appliances are short term usage.

I would not use anything that is set and forget. Also realize that if the neutral situatoin is the true situation, any appliance plugged in may experience over voltage and be damaged. Also realize that if what you see is getting hot. it is very possible those little wires in the wall are getting heated a bit too.

Tell the electrician he is an idiot. Anytime you have enough heat to blacken anything around it, there is a serious problem.

When you do get this figured out and fixed, please post back. We all like to hear how the story ends.
 
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