Harry Muscle wrote:

Newsgroups: misc.consumers.house
From: Mark Fineman
Date: Wed, 10 Aug 2005 21:30:08 -0400
Local: Wed, Aug 10 2005 9:30 pm
Subject: Info to backup safety of aluminum wiring?

Does anyone know if using (and regularly testing) AFCI (Arc Fault
Circuit Interrupers) increases reliability aluminium wiring to
that of copper wiring when the current connection mechanisms are used?

***

A very good question. I'd love to know the answer too.

Thanks,
Harry


Tests show that failure in wire nuts result from no contact between the
wires because of oxide on the aluminum. The steel spring breaks through
the oxide to make contact with the aluminum conductors. This means all
the current is going through the spring. A CPSC report at
http://www.inspect-ny.com/aluminum/pl2p2.htm
shows a 2 volt drop across the wire nut at 17 amps. This is only about
0.1 ohm resistance but is a 34 watt heater. At this current level the
spring is red hot. This destroys the insulation on the wires and the
wire nut and can start a fire. But the voltage drop is low and constant
so lights are not dim and do not flicker. Since there is no arc, there
is nothing for the AFCI to see.

Later in the deterioration the the connection can totally fail, possibly
with arcing that generates a lot more heat. Arcing here would be picked
up by an AFCI.

(The link above is part of a slide show that goes forward and back.)

http://www.inspect-ny.com/aluminum.htm links to this site and others
of interest.

Bud--