Re: [TCML] primary tubing - now Aluminum wiring failures

["Quarkster" <quarkster@xxxxxxx>]

Jim -

The terminations of the aluminum wire become oxidized, develop some 
resistance across the termination, and eventually overheat.

There are several contributing factors:
1. Aluminum exposed to air immediately develops a high-resistance oxide 
film;
2. Aluminum wire is quite soft and "cold-flows" under pressure;
3. Aluminum's high rate of thermal expansion can cause a "self-degenerating" 
thermal-cycling problem where a small amount of resistance creates localized 
heating, which causes the wire (and any clamped connections) to expand. When 
the electrical load on that circuit is removed, everything cools off, and if 
the aluminum has cold-flowed, there is now less clamping pressure, which 
allows further oxidation in the connection, which creates more resistance, 
which gets hotter the next time the circuit is loaded, etc, etc.

I've personally seen wire-nuts on aluminum wiring that got so hot that the 
plastic wire-nut body completely melted away, leaving only the conical steel 
spring from inside the wire-nut holding the wires together.

Aluminum house wiring was a cost-saving measure that was implemented without 
adequate testing, and turned out to be a complete disaster, a great example 
of shoddy Engineering.

Regards,
Herr Zapp


----- Original Message ----- 
From: "Jim Mora" <wavetuner@xxxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Wednesday, November 11, 2009 11:19 AM
Subject: RE: [TCML] primary tubing - now Aluminum wiring failures


Hi,

This is certainly not my bailey wick; but, what are the failures? Is it 
metal to dissimilar metal connections?
(snip) 

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