220V dryer sparked on startup (3 wire) What to test?

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On Wed, 20 Nov 2013 14:04:25 -0800, Oren wrote:

The ones that I found on the net from Home Depot seem to be for both copper and aluminum. The only difference, I saw, was the acceptable gauge changes depending on the material.
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This is normal. You might be better off getting the larger barreled variety. The larger ones might allow you to terminate two conductors per lug (size permitting, of course), though this is usually a desperate measure based on not enough terminals. Keep things clean, when you can, then if you need to do maintenance on one item you will not be messing with something else.
There is adequate space in your meter-main to add another neutral bus.
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On Wed, 20 Nov 2013 19:58:37 -0600, Nightcrawler® wrote:

Is the general consensus that lug corrosion is what actually caused the huge wires to overheat?
What would be other reasons? Or, is that the only reason a neutral would overheat, when no other wire appears to be overheated?
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On 11/21/2013 8:45 AM, Danny D'Amico wrote:

Then you have to figure out how to connect the second bus to the first one.

What I remember is the set screw looked like it rusted. That suggests that the screw is steel. Steel has a rather different expansion rate than aluminum, and thermal cycling can cause a loose connection. Was the lug rated for aluminum? Expansion rate is one of the problems with aluminum.
What were the instructions for installing the lug? Did the manufacturer want the wire to be wire brushed and antioxide paste used?
Connections for large aluminum wires are generally reliable if the right lugs are used.
Could be it wasn't tightened adequately.
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Not much of a problem.
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On 11/21/2013 8:19 PM, Nightcrawler® wrote:

How would you suggest Danny connect a second neutral bar?
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A length of appropriately sized wire would likely be my suggestion.
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On 11/22/2013 11:25 AM, Scott Lurndal wrote:

Danny knows what an "appropriately sized wire" is?
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On 11/22/2013 11:25 AM, Scott Lurndal wrote:

Danny knows what an "appropriately sized wire" is?
What I remember is there are a lot of breaker positions in the panel that are not used, and as a result a lot of neutral bar positions not used. I don't remember that a second neutral bar is necessary.
It is easy to add a ground bar - there should be a SquareD ground bar on the label that can be used.
Adding a neutral bar is not nearly as easy. Does SquareD list one on the label? Can you find a UL listed one? How to connect it?
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What you see on the lug might be heat related. With heating and cooling of a circuit, sometimes they work their way loose.
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On Thu, 21 Nov 2013 09:23:51 -0600, bud-- wrote:

This is what it looks like: http://www.flickr.com/photos/98287134@N02/10953807416/

If it's as simple as a loose connection, once I replace the lug, it's *still* going to be steel on aluminum, right?
If so, the simple answer seems, to me, to be that I should tighten the lugs once a year (or so).
Does that seem viable?
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On 11/21/2013 10:35 AM, Danny D'Amico wrote:

I think the yearly torque and tighten is totally excellent idea. I've gone down the row with screw driver in others power panels, and found loose lugs.
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Any new panel I enter gets everything tightened. Period.
With service contracts we would check all connections on an annual basis.
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On Thu, 21 Nov 2013 13:53:55 -0500, Stormin Mormon wrote:

I turned off the power, and tightened *every* lug on every panel!
Who would have known that's part of normal yearly homeowner maintenance.
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On 11/22/2013 2:32 AM, Danny D'Amico wrote:

Pretty much no one would know.
As to the lug that's rusty, I'd take that screw and wire out, and wire brush the wire and the lug. Might need to go to the plumbing department and buy a 1/2 inch fitting brush. Smaller fitting brush if they sell em.
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On Thu, 21 Nov 2013 09:14:57 -0800, Oren wrote:

The funny thing is that this web site says the aluminum wiring was used in the 70s, but my home was built in the 80s and it has aluminum feeder wires.
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On 11/22/2013 1:34 AM, Danny D'Amico wrote:

Because of high copper prices, starting about 1965 and going through the early 1970s aluminum was used for 15 and 20 amp branch circuits. There were problems with both the wire and devices (switches, receptacles). There were fires, and as a result there were changes in the UL standards, twice. The link is about 15 and 20 amp branch circuits. The recommendations for making connections that are there somewhere, abrade surface of the wire and apply antioxide paste, are relevant to all aluminum connections.
Aluminum has been used for higher current circuits before that, and is often used now. The connections for 15 and 20 amp branch circuits are much different than for higher current circuits. Aluminum is quite reliable in the heavier circuits, like what you have.
I suspect the failed lug was not rated for aluminum, or was not tightened enough.
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On 11/22/13 4:12 PM, Oren wrote:

There are certain fittings to use with aluminum wire. Add those and you should be good to go. We use AL wire regularly due to the lengths we need. Sizes range from #4 to 350 MCM. This is outside where condensation and dirt can be problems. We seldom have problems with the terminations.
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On Thu, 21 Nov 2013 09:23:51 -0600, bud-- wrote:

I turned off the power today, and tightened them all. They were all pretty tight. Only a couple would turn even a fraction of a turn. Specifically, the rusted & burned one was tight.
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On Friday, November 15, 2013 5:21:18 PM UTC-5, Danny D. wrote:

Wrong. The two hots are out of phase by 180.

Wrong. Any two of a 3 phase system are out of phase by 120. But what comes into your house originates from just one of those via a center tap transformer.

Current from the unbalanced portion of the load flows in the neutral. As others have pointe out, in the case of your dryer that could be things like the timer, the light, etc.

It's both.

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