[RE-wrenches] Aluminum wire failure

[Steve Johnson]

Bob,

I assume you are talking about feeders.
Although most people are against aluminum
wire it is really quite safe for feeders if installed properly.
To do this the lugs should all be retorqued after one year.
Aluminum "flows" under pressure, that is the steady pressure
at the lug slowly squeezes the soft metal into the corners of the lug
over time.  This leaves the lug not quite snug enough and a candidate for heat build up and eventually arcing.  When the lug is torqued after a year the flow to corners is done and it's good.  Disney was originally wired this way and the contact stipulated every feeder lug in the place was to be retorqued after 1yr under supervision of Disney engineers.
I guess these days nobody wants to go back in a year so we pay for copper,certainly the best conductor of the two.

Steve Johnson
LightWave Solar

On Aug 21, 2010, at 11:23 PM, "re-wrenches-request at lists.re-wrenches.org<mailto:re-wrenches-request at lists.re-wrenches.org>"<re-wrenches-request at lists.re-wrenches.org<mailto:re-wrenches-request at lists.re-wrenches.org>> wrote:

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We don't often get to take picture, as the point of failure is hard to find, and the entire underground line is just abandoned and a new cable is installed.
Most failures I've seen (not actually seen) were on improperly installed runs, done by DIYers.
On the other hand, the majority of underground service in New Mexico is done with direct burial Aluminum, and if done correctly (buried deep enough, bedded in sand, no rocks), it's not so bad.
My regular suppliers don't even carry big copper, as the Al is so much cheaper, and comes in triplex, and 4 plex cables, but it's dry there.
In Hawaii, you see much more copper, so I think it all depends on the conditions, both above and below the ground.

R. Walters
<mailto:ray at solarray.com>ray at solarray.com<mailto:ray at solarray.com>
Solar Engineer




On Aug 21, 2010, at 2:48 AM, bob wrote:

Does anyone have any photos of aluminum wire that has failed? Failures from nicked insulation and such would help.
I have a debate going with a customer who does not believe that it could cause a failure.

If you have any digital pics please send them to my address, <mailto:reellison at gmail.com> reellison at gmail.com<mailto:reellison at gmail.com> instead of to the list.
I know there are some out there somewhere….

Thanks,
Bob Ellison

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