29 Apr
2012
29 Apr
'12
7:14 p.m.
On 29 Apr 2012 at 21:02, Steven Hirsch wrote:
Wasn't aluminum house wiring outlawed in the US
during the 70s? I
recall something about a rash of fires due to wiring in device boxes
cracking at the screw terminals.
Outlawed for lighting and receptacle use. The problem is that
aluminum not only oxidizes almost immediately, but that it deforms
(cold-flows) easily. When used in normal lighting and utility
fixtures (i.e. outlets), the aluminum eventually forms a resistive
connection under the binding screw of a switch or outlet. The heat
of such a contact further deforms the aluminum and you get a fire.
Most of the wiring used in that manner was 12-14 AWG, solid strand.
While there were specialty switches and receptacles for use with
aluminum wire, they didn't work very well. A method used to
ameliorate existing situations where aluminum is employed is to use a
special hydraulic tool that crimps a copper pigtail onto the aluminum
wire.
Aluminum is still code for high-current appliance wiring, where multi-
strand cable is used. Indeed, it's still used for power drops in
some locales as well as high-tension power distribution. FWIW, my
house was built in the 1980s. The feed from the transformer sitting
in the front yard going to the distribution panel is aluminum and it
was replaced about 8 years ago. I'd be surprised if there weren't a
fair amount of use of aluminum throughout the world for high-current
distribution.
See for example, IEC 61089.
--Chuck