Aluminum Wires - Burnt Recepticles, and Photographs!

[electricalperson]

is aluminum wiring actually a problem or is it just the person installing it the problem?

 

[Anthony Cox]

Aluminum Wiring and Photographs!

Aluminum Wiring and Photographs!

This is 3, not 4 10 gauge aluminum hot wires I found in one wire nut.

It looks like 4, because one wire was stripped in the middle, and bent so it looked like there were 4 wires in it.

Maybe someone bent a rule about no more than 3 wires in one wire nut here....

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Here is a close up of the 4 10 gauge aluminum neutral wires going into one wire nut. What you cannot see, is that one of the neutrals, had the insulation split and peeled off, just beyond he nut, for about 3 inches, all the way to about 1/4 inche where it left the box.

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Whoever said, tighting all the screws was correct. One screw was a full 2 turns loose. But strangely, it showed no outward signs of overheating or anything wrong.

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This screw had the loop in the wrong direction, and insulation under the screw, but showed there were no other indications of a problem with it.

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Only 2 wires were in this wire nut, one copper and one aluminum.
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[Anthony Cox]

Thanks, that did it!

 

[LarryFine]

Whoever said, tighting all the screws was correct.

I cannot tell a lie; it was I. :smile:

One screw was a full 2 turns loose. But strangely, it showed no outward signs of overheating or anything wrong.

Except for this:

I noticed that the light switches in the greatroom ... has a wallplate that gets noticably warm to the touch when the lights have been own for about 30 minutes... Hmmm, a warning sign.

As Monk would say, here's what happend:

Being softer, and having a larger coefficient of expansion, than the terminal components, the aluminum flattens under the screwhead from heat, and when it cools, is slightly looser than before.

The next current warms it up more, it expands and flattens more, and gets looser still. It's cycling of power, rather than steady current, that causes aluminum wires to get loose under screwheads.


Years ago, I did a troubleshoot for an addition on a house that loat power. I finally found that the entire addition was supplied from an existing circuit by adding it to an existing receptacle.

I found the original wires, fed from above, to be completely bare, so I opened the wall (with permission) and the three conductors were completely bare for about 30" above the box.

The three wires were perfectly parallel, as if encased in invisible insulation and sheath, even through the staple above the box. The wires were clean, shiny, and bright, showing no sign of heat.

Added: That no fire occured is amazing.

 

[don_resqcapt19]

The CO/ALR devices came into the market in the mid 70's, and at the same time a new alloy of aluminum was produced. There are not too many more failures of that combination of items than with an all copper system, assuming everything was installed correctly. You do have to be a lot more careful with aluminum than copper to insure a safe installation. Bending the conductor back and putting in the wirenut with other conductors is the likely cause of the poor connection. That would not permit the wire nut spring to put the proper pressure on the conductors.

 

[don_resqcapt19]

Being softer, and having a larger coefficient of expansion, than the terminal components, the aluminum flattens under the screwhead from heat, and when it cools, is slightly looser than before.
The next current warms it up more, it expands and flattens more, and gets looser still. It's cycling of power, rather than steady current, that causes aluminum wires to get loose under screwheads.

Larry,
That is why the screws and back plates on the CO/ALR devices are an aluminum alloy. The coefficient of expansion of the screws and the wire are very very close to the same when you use the new alloy aluminum wire with a CO/ALR device.

 

[vinster888]

id love it more if it didnt have the wet burnt smell

 

[Anthony Cox]

That sounds illogical

FACT:
1. Aluminum expands at a different rate than copper.
2. Aluminum expands at a different rate than the screws and backplates of outlets designed for copper wire.
3. The different rate of expansion causes the screw to loosen eventually through repeated power on/off cycles.

Correllary:
A. Aluminum wires in CU only devices will all loosen eventually.
B. Aluminum wires in CO-ALR devices do not loosen from this effect.
C. Backwire devices using spring tension against the wires will not have this issue.
D. Copper wires in CO-ALR devices, will expand at a different rate, and will loosen eventually also for the same reason.

Deduction: Miniature space aliens live in aluminum wires, and they hate screws...

 

[Dnkldorf]

Anthony, I believe I read somewhere that thermal expansion of metals has something to do with it's length, not it's circumference.

I am probably not explaining this correctly, but.....if a length of wire is heated, it expands length wise, not so much outwards.


Anyone?

 

[iwire]

Same expansion in all directions, just much more noticeable when there is more material.

 

[don_resqcapt19]

That sounds illogical

FACT:
1. Aluminum expands at a different rate than copper.
2. Aluminum expands at a different rate than the screws and backplates of outlets designed for copper wire.
3. The different rate of expansion causes the screw to loosen eventually through repeated power on/off cycles.

Actually the screw does not loosen. When the conductor expands it puts pressure on the screw and that causes "cold flow" on the conductor and flattens it out somewhat. This flattened wire does not change back to round wire when it cools and that results in a very small space being created between the screw and the conductor. Over time this space gets larger and you can turn the screw making it appear that the screw loosened when in fact it did not...the wire got smaller.
This is the same issue as we have with re-torquing of mechanical wire terminations.

 

[Anthony Cox]

I heard that if you have a metal plate that expands when heated, and this plate has a 1cm circular hole in it, and you heat it evenly, the metal will plate will expand in all outward directions, but the diameter of the hole will increase. If you have a 1cm diameter metal rod of the same metal, if heated identically to the plate, it will expand in diameter at the same rate as the hole.

 

[LarryFine]

Actually the screw does not loosen.

I thought I said that.

 

[LarryFine]

If you have a 1cm diameter metal rod of the same metal, if heated identically to the plate, it will expand in diameter at the same rate as the hole.

So, one could conclude that air and metal expand at the same rate. :grin:

 

[mxslick]

***THREAD JACK***

How's this, this is where I went today.....

Another fine example of why I don't like the idea of panels in bedrooms..How would you like to have THAT happening while you were sleeping?

Back on topic, I have only once run into an aluminum-wired house. They were very lucky, as they had regular copper-only rated devices in the kitchen (which surprisingly weren't damaged after several years of use) and a Zinsco panel.

I have run into a lot of homes here in So Cali with the old tinned copper wire, which can fool you if you're not looking close enough. Always wondered why they made tinned copper wire anyways..anyone got an "idear"?

 

[al hildenbrand]

Always wondered why they made tinned copper wire anyways..anyone got an "idear"?

The coating was generally a zinc layer to isolate the composition rubber insulation from direct contact to the copper. The copper would degrade the insulation.

 

[iwire]

Another fine example of why I don't like the idea of panels in bedrooms..How would you like to have THAT happening while you were sleeping?

About the same as I would like that in my basement, kitchen or utility room. :grin:

Seriously I don't see the difference if I am asleep.

Back on topic, I have only once run into an aluminum-wired house.

The home I lived in from 12 to 18 was all AL NM, back stabbed into the devices and protected by an FPE 'Stab-Loc' panel. A true safety trifecta. :grin:

The refrigerator would kick on and the TV would dim out for a moment. :roll:

 

[Anthony Cox]

Thanks, everything is tight now.

I put in two new switches.

I fixed the aluminum to copper connections in the wire nuts so they are far better than before.

I replaced the twelve 150 watt floodlamps with twelve 23 watt (120 watt equivilant) bulbs. Not quite as bright, but I feel a heck of a lot safer with less load on that circuit.

The 2 gang box is way too tight for all those wires, 4 light circuits connected to 2 switches on 1 circuit breaker.

God Bless Everyone!

 

[Doug S.]

I heard that if you have a metal plate that expands when heated, and this plate has a 1cm circular hole in it, and you heat it evenly, the metal will plate will expand in all outward directions, but the diameter of the hole will increase.

This idear is commonly used when fitting "press fit" items. They even make little ovens for bearings. =) Heat it up, "slide" it on, let 'er cool.

 

[mxslick]

The coating was generally a zinc layer to isolate the composition rubber insulation from direct contact to the copper. The copper would degrade the insulation.

Thanks Al, that makes sense.

About the same as I would like that in my basement, kitchen or utility room. :grin:

Seriously I don't see the difference if I am asleep.



The home I lived in from 12 to 18 was all AL NM, back stabbed into the devices and protected by an FPE 'Stab-Loc' panel. A true safety trifecta. :grin:

The refrigerator would kick on and the TV would dim out for a moment. :roll:

Well it would make a heck of a wake-up call for sure. :grin:

Yikes..AL, backstabbing and FPE? Bet that house's wiring wouldn't hold up with today's heavier uses of electricity.

This idear is commonly used when fitting "press fit" items. They even make little ovens for bearings. =) Heat it up, "slide" it on, let 'er cool.

See what I started now? Who's idear was that anyways? :grin: