Discolored/Burned? Boxes


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Old 01-31-14, 02:51 PM
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Discolored/Burned? Boxes

Have you ever seen a portion of the entire of a metal electrical box that is discolored?

I found one old ceiling box (circa 1950's) that a portion of the interior is discolored, kind of looks blackened or like maybe some soot or dirt. Theres some rust portion in it too. I cant tell if its discolored from age, moisture/cold from attic above or if its burn.

The connections appear sound and no problems to speak of. Although the wires are obviously old. The neutrals have some dirt blackening of the insulation too.... but up towards where it exits the conduit. 6 inches from there they appear normal color where the wirenut connections are? I even see a little of the rust leaching onto the insulation of some of the wires. So this one I was thinking maybe old age?

But then I find another box in the basement with a similar discolorization. However, this one might have been an arc at some point as a portion of hickey that connects the conduit to the box might have a very small arc weld on it. Like someone shorted the box at some point.

So I don't know really what to think. Any ideas or suggestions welcomed.
 
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Old 01-31-14, 03:54 PM
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Yep, seen it. Second time I seen it the landlord gave the tenant his walking papers. Old house where the receptacles spidered out from the overhead light. First time it happened I warned him to plug the electric space heater only into the dedicated 120v window A/C receptacle about three feet from the receptacle he'd used. Landlord was not happy the second time he had to pay me to go back to fix it because the tenant kept using the GP receptacle.

Not saying that is your problem but old cloth insulation, heat from an oversize incandescent bulb and to much load can equal black. Problem may well have been fixed a long time ago. I didn't clean the box mentioned above. I just fixed it.
 
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Old 01-31-14, 06:13 PM
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(circa 1950's)
I've seen some old boxes that appeared that they may have been black when new.
 
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Old 02-01-14, 04:03 PM
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Is there anything I should do to assure this is safe/OK?
 
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Old 02-01-14, 05:50 PM
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You could call a licensed electrician to do an inspection.
 
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Old 02-02-14, 12:51 PM
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CasualJoe

You could call a licensed electrician to do an inspection. .

Thanks , I had that much figured out though.........

Before I go down that road though, some ideas of related problems/symptoms to look for might help?
 
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Old 02-02-14, 01:20 PM
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It sounds to me, without seeing pictures of what you have, that what you're seeing is most likely old dust that's been baked and/or aged onto the boxes.

If everything looks like it's electrically and mechanically OK now I'd leave it alone. No point in fixing what ain't broke.
 
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Old 02-02-14, 01:25 PM
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thank you. That could be the case.

I was kinda of thinking along the lines if this was a case of an old fixture burning the box, overwattage. What signs would I look for that I would have a dangerous situation. Melted insulation? Exposed copper? Flcikering light, tripping breakers?

When conductors are damaged in this manner, what are the warning signs?

Is it common for 50 year old wiring to show such signs? I know its not new, but it aint knob and tube either.... (I realize this is vague)
 
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Old 02-02-14, 03:44 PM
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I was kinda of thinking along the lines if this was a case of an old fixture burning the box, overwattage. What signs would I look for that I would have a dangerous situation. Melted insulation?
Yes. Probably more baked and crumbly than melted.
Exposed copper?
Yes.
Flcikering light, tripping breakers?
Only if there's been severe and prolonged overheating.

When conductors are damaged in this manner, what are the warning signs?
None. You find it when you drop the fixture. The thing to look for and correct is a flush-mounted fixture that has, or that you know has had, an incandescent bulb larger than 60W installed in it. I would drop those and check the house conductors.

Is it common for 50 year old wiring to show such signs? I know its not new, but it aint knob and tube either....
No. I've successfully kept K&T in service as part of a renovation, Always gave the inspector a personal tour of the work, and it always passed.

The damage results from overlamping a close-fitted fixture, and only from that. Chandeliers and other pendant fixtures can't put enough heat on the house conductors to damage the insulation.
 
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Old 02-02-14, 04:38 PM
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Often , with a fixture that has been run with over wattage lamps , the insulation on the wire has been " cooked " . If you bend / move the wires ( may be very stiff ) , the insulation will crack and break / fall off .

If the insulation is better / OK , up close to where the cable enters the box , I have repaired the bad insulation by buying a package of assorted colors of heat shrink .

Slidie the heat shrink over the wires . Trying for a color on each wire that is appropriate for its function ( hot , neutral , switch leg , etc. ) .

The old wiring likely does not have any earth grounds . But if it does , you can legally leave them bare , if they are not going to get into anything hot . Or sleeve the earth grounds with green heat shrink .

God bless
wyr
 
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Old 02-02-14, 08:32 PM
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I have some NOS boxes that are painted black from the factory.
 
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Old 02-03-14, 08:21 AM
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CasualJoe

You could call a licensed electrician to do an inspection. .
Thanks , I had that much figured out though.........

Before I go down that road though, some ideas of related problems/symptoms to look for might help?
If you really think you might possibly have a problem, someone qualified needs to look at it or at the very least you could post some pictures of what you are seeing. At this point, all you have is a lot of guesses.
 
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Old 02-14-14, 10:24 AM
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Update on this one.

I replaced the fixture that was on this box and was able togain access to the discolored wire. With my finger nail I scraped the black right off the wires in question. It was its normal white color under it.

That leads me to believe its dirt? Burn wouldn't come off correct?
 
 

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