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'Dissimilar metals'
1999\09\24@174935 by Robert A. LaBudde

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At 11:27 AM 9/24/99 -0500, Martin wrote:
>        On the topic of dissimilar metals which has also appeared in
>this thread, I remember the big scare over aluminum house wiring which
>occurred in the United States during the seventies or so.  Lots of
>houses were wired with this stuff and they began to burn down after
>people incorrectly installed fixtures rated for copper wiring on the
>aluminum cables.  The gauge of the wire was slightly larger to begin
>with and so it didn't fit well under the screw.  A little thermal
>cycling and electrolysis of the aluminum/brass junction would create a
>resistance heater which would one day get red hot and start a fire if
>someone connected anything substantial to that outlet.

I'm one of those unfortunate individuals who lives in a house with aluminum
wiring.

Normal use causes the aluminum to loosen at all connections due to thermal
contractions and expansions at the joints. Then the resistance increases,
which increases heat, which loosens further. Eventually it can cause a fire
in the wall (which a neighbor had). You have to have an electrician
retighten all connections every 5-10 years.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: spam_OUTralTakeThisOuTspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

1999\09\25@091126 by Updraft942

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In a message dated 9/24/99 4:56:26 PM, .....ralKILLspamspam@spam@LCFLTD.COM writes:

<< Normal use causes the aluminum to loosen at all connections due to thermal
contractions and expansions at the joints. >>

Aluminum is one of those materials that "cold flows".  If anyone ever tinned
a stranded copper wire and put it under a screw terminal, they know about
loose connections and cold flow.  It WILL get loose, no matter what the
fixtures were designed for.

1999\09\26@185119 by Dennis Plunkett

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At 08:59 25/09/99 EDT, you wrote:
>In a message dated 9/24/99 4:56:26 PM, ralspamKILLspamLCFLTD.COM writes:
>
><< Normal use causes the aluminum to loosen at all connections due to thermal
>contractions and expansions at the joints. >>
>
>Aluminum is one of those materials that "cold flows".  If anyone ever tinned
>a stranded copper wire and put it under a screw terminal, they know about
>loose connections and cold flow.  It WILL get loose, no matter what the
>fixtures were designed for.
>
>

That is only one form of cold flow. The other from is when a wire is
strained hard over an edge, which can cause the insulation to be eaten
through.
Foergive my dislexix fingers, I have spent the weekend dinging a trench for
our new storm water drain (Some 90feet by 2 to 3feet deep (Got it and the
plumbing done, and filled in! wow!)

Dennis

1999\09\26@192725 by Wagner Lipnharski

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> Normal use causes the aluminum to loosen at all connections due to
> thermal contractions and expansions at the joints.
>
> Aluminum is one of those materials that "cold flows".  If anyone ever
> tinned a stranded copper wire and put it under a screw terminal, they
> know about loose connections and cold flow.  It WILL get loose, no
> matter what the fixtures were designed for.

This should be why in USA they use screw and spring connections at the
power outlets. At the first time I saw a solid wire just inserted into
the spring blade contact I thought it was just a faster way to do the
wiring, even representing a very weak contact compared to what could be
if using the screw just aside the same power outlet.

It is some kind of a double fork where the solid wire enters but can not
gets out, it keeps a spring pressure electric contact to the wire.

Of course the screw connection would be much stronger, but... probably
for aluminum wire this is the answer.

Some of my house's power outlets (w/aprox 8 amps consume) needed to be
replaced right after 6 years of use, at the new ones I used the screws.
The previous wires got superheated and the isolation burnt at that
spring loaded contact...

By the way, some experiences with transformers using aluminum wire?  :)

Wagner.

1999\09\26@194347 by Dennis Plunkett

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At 19:26 26/09/99 -0400, you wrote:
{Quote hidden}

It seems that you are suffering under the guize of Eddisons total lack of
forsight. Pathetic 120V distrobution, at least we got that right, and we
have the oldest power plug standard in the world. To think that some idiots
where thinking of forcing us to change to your quazi standard! Thank Andy's
g-d that, that didn't happen!

As of aluminuim cable, well we use T.P.S. and it only comes in copper, I
can recall some articals on the use od Au, but it was rejected due to the
cost of retraining electricans, and all the aterations that would be
required for fittings, and then there was the wire cost, very little
difference. The drop wire (Or feeder into the house is Au, and so too are
most power cables)

(I am waiting for all the comebacks on 11kV 22kV 220kV distrobuition and
500kV 1 and 2 and 5 MegV stuff, then 1500V DC and 600VDC, come on I can
take it <G>)


Dennis

1999\09\26@195008 by Richard Prosser

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Swap you Cu for Au anyday!

Not Cu for Al though!

Richard

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