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Author Topic: There, I fixed it  (Read 240 times)

Perd Hapley

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There, I fixed it
« on: January 14, 2022, 01:55:43 PM »

Iíve run into something I hadnít seen before, and Iíd like to know if any of you chaps had run into similar. As you may know, weíre staying in a rental house until our domicile is repaired from fire damage. One of the fixtures in the basement of our temporary house is the porcelain, pull-chain type. There was no bulb in it when we moved in, so I put in one of the LEDs I already had. The bulb was flashing on and off, so I tried another one, with the same result.

To make a long story short, I was about to disconnect the fixture when I found a lot of black gunk inside the wire nuts. I keep one of the gun-cleaning wire tooth-brushes in my tool bag, and I didnít think it would make any difference, but I used it to clean up the outside of the twisted wires. Problem solved. I put on a new pair of (non-gunked) wire nuts.

It seems strange to me, since all I did was clean up the outside of the wires. It seems like the connection between the wires should be exactly the same as before, especially since there were no wire nuts in place (which would create an additional path between the wires) when I first turned the fixture back on. But I just cleaned what I could easily reach, and it worked.

Not that Iím complaining.
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cordex

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Re: There, I fixed it
« Reply #1 on: January 14, 2022, 02:02:13 PM »

Maybe during the cleaning you happened to rub the wires together enough to create a better connection?

K Frame

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Re: There, I fixed it
« Reply #2 on: January 14, 2022, 02:10:01 PM »

Black gunk...

Adhesive from old electrical tape from an old fixture?
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Brad Johnson

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Re: There, I fixed it
« Reply #3 on: January 14, 2022, 02:12:40 PM »

Maybe during the cleaning you happened to rub the wires together enough to create a better connection?

This, mostly likely. The relatively low draw of LED lamps can make minor surface corrosion more an issue than higher-amp incandescent lamps.

The addition of the new wire nuts just sealed the deal.

Brad
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lee n. field

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Re: There, I fixed it
« Reply #4 on: January 14, 2022, 03:15:17 PM »

Quote
black gunk

Anti-oxidizing goop.  You wires are copper, right?


This, mostly likely. The relatively low draw of LED lamps can make minor surface corrosion more an issue than higher-amp incandescent lamps.

The addition of the new wire nuts just sealed the deal.

Brad

I wonder if that's whats going on in our bathroom.  LED bulbs don't want to work.  Incandescents (out of my hoarded stash) do.
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Brad Johnson

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Re: There, I fixed it
« Reply #5 on: January 14, 2022, 03:28:25 PM »

I wonder if that's whats going on in our bathroom.  LED bulbs don't want to work.  Incandescents (out of my hoarded stash) do.

Are they on a dimmer, by chance?

Brad
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lee n. field

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Re: There, I fixed it
« Reply #6 on: January 14, 2022, 10:22:59 PM »

Are they on a dimmer, by chance?

Brad

No.
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230RN

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Re: There, I fixed it
« Reply #7 on: January 14, 2022, 10:56:26 PM »

I was also heading toward the idea that the original aluminum wiring had been "pigtailed" with copper connections.

I had to do this with every outlet and fixture in an old mobile home I owned for a while.

The process involved attaching a copper stud to the existing aluminum wire with a spring-loaded wire nut, well greased to keep oxygen off the aluminum, then make the copper connection to the fixture in the normal way.

This was a royal pain in the ass, but was designed to prevent fires starting from the aluminum wiring, see NOTE.

I could see the grease applied getting all funky over time and not protecting the aluminum anymore, thus destroying the "goodness" of the Al-to-Cu connection.

Terry, 230RN

NOTE:
 
It took a while to realize this, but house fires had been due to alumimum wiring.

1. Al has a much higher coefficient of expansion than Cu.

2.  Al forms an oxide layer almost instantly, and aluminum oxide is a great insulator.  In fact, aluminum oxide ceramic insulators are used in high-voltage applications.

In the normal Cu wiring, turning down the screws to make the connections is relatively permanent and stable, and since the connection is so good, I2R heating is minimal since R is so low.

But with aluminum under that same screw, any heating results in expansion of the aluminum, and with cooling after the appliance is shut off, the aluminum contracts, reducing the dimensions of the aluminum and therefore loosening the "goodness" of the connection and allowing oxygen to contact the aluminum and form an insulating layer.  Not much, but it's there.

This can result in a runaway condition, where every time the appliance is turned on and off, the situation gets worse. Not catastrophically and suddenly, but gradually over long periods.  Ultimately, in some cases causing sparking or overheating and possibly a fire. 

It took a long time and a lot of fires for this to finally come to light

The "fix' was to use a spring-loaded wire nut between the Al wiring and a short copper stub going under the appliance  screws.  The spring loading  compensated for the expansion/contraction, and heavy greasing kept the oxygen off the aluminum portion of the connection.

That's the way I understand it, but I've heard of various alternate explanations for the aluminum-wired house fires.

« Last Edit: January 14, 2022, 11:28:14 PM by 230RN »
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zxcvbob

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Re: There, I fixed it
« Reply #8 on: January 14, 2022, 11:02:30 PM »

I was also heading toward the idea that the original aluminum wiring had been "pigtailed" with copper connections.

I had todo this ewith every outet and fixture in an old mobile home I owned for a while.

The process involved attaching a copper stud to the existing aluminum wire with a spring-loaded wire nut, well greased to keep oxygen off the aluminum, then make the copper connection to the fixture.

This was a royal pan in the ass, but was designed to prevent fires starting from the aluminum wiring, see NOTE.

I could see the grease applied getting all funky over time and not protecting the aluminum anymore, thus destroying the "goodness" of the Al-to-Cu connection.

Terry, 230RN

NOTE:  Under construction.

Or they used the wrong kind of connectors.  Most wire nuts are not rated for AL/CU connections.  (I think the current ones are purple)
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230RN

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Re: There, I fixed it
« Reply #9 on: January 14, 2022, 11:33:51 PM »

Yes.  Note the "fix" required "spring-loaded" connections.

(You may wish to reload my quote since typographical corrections were made in the interim.)
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zxcvbob

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Re: There, I fixed it
« Reply #10 on: January 15, 2022, 02:35:01 AM »

Yes.  Note the "fix" required "spring-loaded" connections.

(You may wish to reload my quote since typographical corrections were made in the interim.)

You explanation was fine, both before and after you added additional details.  I just wanted to point out that not all spring-loaded wirenuts are listed for mixing aluminum and copper.  (perhaps they work fine and CPSC or UL just didn't test them) =)

BTW, I am a fan of aluminum wiring, but only for circuits 40A and up, and with proper devices.  There aren't that many circuits in a house that large; service entrance cables, electric range, and feeders for subpanels are about it.  I think electric water heaters are typically 30A.
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K Frame

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Re: There, I fixed it
« Reply #11 on: January 15, 2022, 08:29:17 AM »

"Anti-oxidizing goop.  You wires are copper, right?"

You mean dielectric grease?

I've never seen any that's black. Every kind I've ever used has been clear.
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Brad Johnson

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Re: There, I fixed it
« Reply #12 on: January 15, 2022, 10:53:42 AM »

Maybe possible someone used Liquid Tape?

Brad
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RocketMan

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Re: There, I fixed it
« Reply #13 on: January 15, 2022, 12:02:15 PM »

Maybe possible someone used Liquid Tape?

Brad

Now that's a possibility.  I've used that type of product from 3M, and it might break down over time and leave a black gooey residue.
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K Frame

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Re: There, I fixed it
« Reply #14 on: January 15, 2022, 12:05:53 PM »

Maybe possible someone used Liquid Tape?

Brad

Oh, wow! I'd not thought of that! Yes!
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RoadKingLarry

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Re: There, I fixed it
« Reply #15 on: January 15, 2022, 12:43:35 PM »

"Anti-oxidizing goop.  You wires are copper, right?"

You mean dielectric grease?

I've never seen any that's black. Every kind I've ever used has been clear.

The stuff AT&T used for power connections in the CO when I was there was brown.

https://www.amazon.com/NO-OX-ID-Special-Electrical-Contact-Corrosion/dp/B00HDF9EXE/ref=sr_1_1?keywords=no-ox&qid=1642268525&sr=8-1

I used it when I re-worked all the battery connections on my sailboat.
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