Electrical Dimming


We've lived in a home for 20 years that was built in 1970. It has aluminum wiring. Over the years we have a consistent problem with a kitchen light in the middle of the ceiling browning out after we turn it on. It turns on just fine and a few seconds later it dims and then goes back to full light. It might never do it again or it might repeat this. We've been unable to establish a pattern.
We've been all over the house and exterior trying to tie that particular behavior with appliances turning on or off, the washer changing cycles or something and can't. We've had three separate electricians try to diagnose and fix the problem but they keep trying to say that it's a general brownout of the neighborhood when it clearly is not.
We've changed the switches in the kitchen and elsewhere and "pigtailed" the switches. I'm imagining that if there were a danger of fire we would have had one by now so I'm assuming this is not a clearly unsafe condition. One neighbor suggested that if there one non-aluminum line on a circuit that this might be the source. Someone had added some wiring before we bought the house. Does this make any sense or can you suggest another direction to look?
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bardsapprentice wrote:

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Well, if other outlets/lights on the circuit are not affected, and switches/connections to the fixture in question didn't resolve it, it's isolated to either the fixture itself or in the wiring itself between the fixture/switch. I'd start by looking a the connections to the fixture and then suspect the base of the fixture -- bases will oxidize or the base spring relax, etc.
I wouldn't assume because you haven't had a fire yet you wouldn't/won't.
My inclination would be to simply replace the fixture if it's just an ordinary ceiling fixture. If you have a spare or an accessible porcelin bulb base somewhere, substitute it for a few days and see if the problem doesn't go away...
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I concur. Remove the light fixture and put a pigtail socket and bulb there for a few days and see what happens. I recently installed an expensive Italian design light fixture for a customer. While I was there some of the bulbs would go out and come back on a short time later. I tightened the bulbs which seemed to help, but the problem would not go away. Inside the small lamp sockets was a narrow strip of metal on the side that was suppose to come in contact with the shell of the bulb. I bent the strips forward a little on each socket and the problem went away.
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Sounds like a loose connection - but where? The first place I would check is the circuit breaker. Aluminum wiring is well-known as a fire hazard because it's such a good conductor of heat and it expands and contracts so much (compared to copper) that terminations eventually loosen over time and get warm as they do (because of resistance) and as they warm, they expand and then contract when the switch is turned off. Every time the switch cycles (gets turned on and off) the wire warms and cools further loosening the connection until you start having the "brown out" condition you describe. Sometimes there will be an arc in the loose joint and the condition will disappear for a while (the wire actually welds itself) until the heat/cooling cycle builds up enough to break the little weld and you're back to the brown out condition.
Somewhere between the circuit breaker box and your fixture there is a loose connection and I would consider it VERY unsafe and a potential fire hazard. Find a different electrician. No self-respecting electrician would EVER leave a homeowner with the described condition, furthermore if that electrician wants to keep working and avoid having the liability of a fire (and all the consequences that can accompiany that) on his record.
Jeff
bardsapprentice wrote:

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jeffreydesign wrote:

Given that the symptom appears to occur only in one fixture, it would appear localized well beyond the circuit breaker...as I noted in another response, I would venture most likely is the fixture base itself, then the connection _to_ the fixture, then internal in the fixture...after eliminating those possibilities I'd start casting a wider net...
I don't disagree it is a potential hazard...

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Well, they say they've tried three already...agree it would seem they should have been able to isolate something, but this is a little over-the-top on liability -- if they didn't do anything, there's little they can be liable for imo. Inability to find/solve a problem not of their creating isn't an offense that I'm aware of...
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bardsapprentice wrote:

<snip>
I hope you didn't pigtail with purple wirenuts http://www.inspect-ny.com/aluminum/ideal65.htm
This device seems better and is only slighty larger than a 'red' wirenut http://www.kinginnovation.com/products/alumiconn.html I have no ties to King just passing on a _potentially_ better product. There are also special switches and outlets that are designed for use with aluminum wiring.
I agree with most of what has been said. If you are comfortable I would pull the panel cover and check the tightness of the connections in your breaker box. I also have aluminum wiring and tightened all of the screws and less than a year later at least three were loose.
Lights will give you an immediate indication of a problem on a circuit because it is visual. A toaster on the same circuit will give you no indication of the same problem.
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Had a similar problem once but had all copper wire. Power company found a loose connection at the transformer.

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It's down to two likely problems. A poor connection to that lamp somewhere or a floating neutral. Both can be serious and the fact that you home has not burned down yet is not evidence of no problems, in fact you have a known problem and maybe others unknown.
I know you will not like this advice and there will be some who will say I am being over concerned, but if it were my home I would have a qualified electriction go over the whole home and verify that it is all in good shape, not just that light. If not, make sure the batteries are changed in your smoke detectors!
--
Joseph E. Meehan




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