On 1/7/2017 10:24 PM, isw wrote:
In article ,

The only aluminum wire is used as power lead-ins to houses, as it is much
cheaper than copper. They did use aluminum wire INSIDE houses in the US
around 1966-1968, and it burned a lot of houses down, due to the cold flow
of aluminum weakening the contact force.

ISTR that the problem was mostly that electricians couldn't be bothered
to learn the new techniques and so on that were mandatory to install the
stuff safely. It was only when it was installed just like Cu that it was
prone to overheating.

The problem is only for 15 and 20 amp branch circuits. Larger wire is
used often without problems.

Around 1965 the price of copper went through the roof and aluminum
started to be used on 15 and 20A circuits. Failed connections and fires
resulted, and in 1971 UL pulled the listing on that aluminum wire and
the aluminum rating for devices like switches and receptacles. New
standards soon followed. The new aluminum wire was harder, and devices
had a CO/ALR (Revised) rating.

The CPSC had extensive testing done on aluminum connections. That
testing found that the aluminum oxide surface insulating layer caused
much of the problem - the actual metal-metal contact could be quite
small. Installations done "properly" could still fail. The probability
of a failure was just higher for aluminum than copper. Even though
there is a new alloy, most of the wire actually installed is the "old
technology" stuff. "Backstab" device connections were never listed for
use with aluminum.

If someone is working with this 15 & 20A wire there is a good paper on
connections at:
http://www.kinginnovation.com/pdfs/R...Fire070706.pdf
It is written by the engineer that supervised the testing for the CPSC.
Use of antioxide pastes is generally recommended.

The best connectors are
http://www.kinginnovation.com/produc...cts/alumiconn/
They have a screw connection that likely breaks through surface oxides.
(Connections for large wires also deform the wire.)