My background is in electrical/electronic engineering and I haven't been directly involved in telecoms wiring for 45 years or more.
I thought I might share my thoughts on aluminium wiring as it has affected me.
I believe aluminium wiring was first used during WW2 when large numbers of services camps were built using pre-fabricated methods. Because of the wartime shortages of copper a decision was made to use aluminium for wiring the camps.
The wiring fittings then (as now), used brass tube connections with brass grub-screws to terminate the wiring.
A series of serious fires caused the abandonment of the experiment.
Aluminium is a reactive substance and the reason it doesn't rapidly disappear is that it rapidly forms an oxide layer on it's surface which protects it from further corrosion. This oxide layer has insulating properties and when it is built up by processes such as anodising it can produce a hard surface that is a very good insulator.
A few years ago insulating washers of anodised aluminium were used between semiconductors and their heatsinks and claims of 1000 volt withstand were made. What chance a ADSL signal ?
Aluminium tends to creep much more than copper from under the pressure of a tight connection.
Aluminium is of course used for heavy power distribution cables but where it terminates to copper or brass connections, special bi-metal crimps are used. These have an aluminium socket to crimp onto the cable which is welded in an high-tech factory process to a copper socket or lug for the copper connection. Stranded aluminium with a steel core for strength is used for the Grid & Supergrid lines carried on lattice towers.
Above ground lightning conductors are normally aluminium nowadays but the connection that goes into the earth to the earth rod is always copper with a bi-metal joint just above the ground.
The smallest cable that can be used in a building according to the regs is 16 mm2 and only then if properly terminated.
During the 1970's the African copper crisis caused a shortage of copper and a few new houses were wired with copper-clad aluminium but this caused all sorts of problems because the grub-screw connections broke through the thin copper coating.
Fittings were produced that used a flat claming plate connection like in the original BT linebox A & B line connections.
Unfortunately electricians continued to use the more common fittings.
Hopefully all this copper-clad will have been replaced by now. If they did cause fires they were probably put out by the leaking stainless steel plumbing systems that were installed at the same time.
I know the BT scientists maintain that aluminium wiring doesn't present a problem but unless they use gel filled bi-metal crimps (fitted the correct way around) then I think that aluminium is always going to cause problems.
I don't know what the maximum length of BT undergound cables is but it occurs to me that there must be many joints in the average cable run between exchange and consumer. I would think the worst case scenario would be several changes of material in the run.
I hope that BT desist from installing aluminium in future and feed our broadband and POTS along a nice bit of fibre.
