[TowerTalk] [TOWERTALK] INSTALLING SURGE ARRESTOR ON A COPPER PLATE

[jimlux]

On 4/3/19 1:24 PM, john at kk9a.com wrote:
> Aluminum and copper are not real apart on the galvanic table. Stainless
> steel and aluminum are a much worse combination. I would use conductive
> grease such as Penetrox between the Array Solutions device and your
> plate and simply bolt them together. I have copper and aluminum
> connected together in my ground system and I have not seen any issues.
> 

Not to mention millions of electrical connections in standard electrical 
wiring. The ground/neutral bar in the circuit breaker box is usually 
alumimum, and there's all those copper wires clamped in it. And, using 
wire-nuts or crimped connections to join copper and aluminum wires.


The key thing is to avoid something where temperature cycling causes it 
to loosen - you need enough clamping force that when they grow and 
shrink, they stay together.

The bad thing about aluminum wiring in houses was the cost driven change 
to steel terminal screws (from brass) at the same time as aluminum was 
rolled out for the wiring.

CTE (ppm/C)
Steel	11-12
Aluminum 21-23
Copper 16-17
Brass 18-19

So, with either a copper or aluminum wire under a brass screw, the CTEs 
aren't too far different, but going to an aluminum wire under a steel 
screw, you've got a much larger range. and if the steel screw isn't 
super tight, when things shrink, the aluminum shrinks more than the 
steel and the contact gets loose.

You *can* do steel to clamp aluminum and/or copper - You just need to 
have enough force that in the cold state, there's still contact (you're 
relying on the stretchyness in the bolt and the squishyness of the 
copper or aluminum.  A large high strength stiff bolt is exactly the 
wrong thing here.