On 12/30/2010 4:08 PM, Rik van Riel wrote:
> On 12/30/2010 03:45 PM, Kevin Normoyle wrote:
>> If you're going Al to Cu, I would think for our purposes waterproofing the
>> think will prevent any corrosion issues. (for the lifetimes we deal with)
> I go Al to Cu to get from my 80m loop to my balun. I want some
> flexibility in the wire that goes to the balun, so I use 14ga
> stranded THHN copper for the final foot or so (a loop from the
> center insulator to the balun).
> The procedure I use for connecting Al to Cu is as follows:
> 1) tin the copper so none of it is directly exposed, as a
> side benefit this results in the end of the copper wire
> acting as solid not stranded
> 2) use some fine sand paper to remove the inevitable oxide
> from the end of the aluminum wire
You can remove gross oxide, but not the actual coating of Al oxide. Al
oxidizes almost instantly and certainly before you could remove the sand
paper and add the connection. It's this coating of oxide that protects Al.
When making connections the pressure cuts through the very thin oxide
layer to make the connection.
As these are not high current connections outdoors, I don't know why
"wire nuts" wouldn't work just fine as long as there is little or no
tension on them.and the elements are kept out.
> 3) coat both wire ends in NoAlox
> 4) stick each end of the wire into another side of one of
> the blocks from a european style terminal strip, like:
Al wires should really overlap, but outside that probably would not be a
problem as long as it's weatherproofed.
> 5) tighten both screws on both wires, they are now very firmly
> connected to each other and to the terminal strip connector
The biggest problem making connections with Al is the expansion and
contraction, particularly with compression connectors.
At one time there was a big push to use aluminum wiring in new homes,
but that expansion and contraction was causing poor connections with the
resulting fires is why Al wiring is now banned although as I said
before, except between the meter and breaker box. Even with 4 ought,
you have to retighten the big connections at the top yearly for the
first 3 to 5 years. I use a long extension on the handle of the large
allen wrench, a wee bit pf either noalox or never-seeze and really reef
it down. This is not a job for the Novice, As they say on the TV
programs, "Do not try this at home", but I've done it hot as well as
watching electricians do it hot. If you ever short out that 220 line
where the only fuse is at the transformer on the pole you will be lucky
to survive and not burn the house down. That transformer in my case is
supplying three 200 amp services. I once saw one of the plant
electricians slip and stick a LARGE screwdriver into an overhead buss
with that kind of capacity. There was a loud bang and then that whole
buss was slowly burning back like a fuse while growling like a D7 Cat.
Man, but that sucker was noisy, but at least I wasn't up there on the
step ladder with the electrician. <:-)) No he didn't get hurt...except
for maybe his nerves.
Their boss wasn't exactly happy either as he shut that whole room full
of production equipment down which probably ran at least several hundred
thousand dollars loss.
> 6) wrap the connection in coax seal
> I have had no problems with connections like this. They are
> easy to make and appear to be rock solid.
> I'd be interested in any opinions on my method, especially ways
> to improve it :)
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