[VAC] Re: aluminum wiring

[Dr. Gerald N. Johnson, electrical engineer]

Copper in branch circuits can be a pain. A trailer (as in mobile home)
is generally made of thin lightweight wood panels that practically
explode when ignited. The flame advance rate down a hall way is faster
than a sprinter. That generally means that there's little for the fire
company to do if everybody got out because there's little left but the
metal frame and some ashes in very few minutes.

In that situation aluminum wire would get a bad rap because it will melt
in a wood fire and so appear to leave evidence of damage by arcing. Its
very hard to visually tell the difference between fire melting and arc
melting. Even copper which generally takes a strong forced draft with
wood to melt will sometimes leave confusing signs by being dissolved in
molten zinc from box fittings. I have collected a number of pictures of
such things over the past 30 years. I prefer to not do fire
investigations, especially not mobile homes and automobiles, but I've
done about 200 (mostly not mobile homes or cars). Those two are nearly
impossible to find a source based on what was heated hottest or longest.
There's nothing left but copper and steel. And its too expensive to cut
a cross section from each wire and examine the crystalline structure to
see if the wire was heated internally or externally.

Gerald J.



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