uiRe: A Question for Real Electricians ?

[Appin]

The message from "Andrew Mawson" contains these words:

> > > > > > > > > > > >> A /proper/ crimper is the best way to join wires. > > > > > > And a proper crimp for the job. We had a problem on largeish (IIRC > > > aluminium) cables where the crimp was slightly oversize. Crimping > > > stretched the cable leading to early failure. > > > > Crimping Ally is way beyond my expertise except. I would treat ally > > conductors with great respect. > > > > > > -- > > Ed Sirett - Property maintainer and registered gas fitter. > > The FAQ for uk.diy is at > Gas fitting FAQ > Sealed CH FAQ > Choosing a Boiler FAQ > > > Horrid fatigue / work hardening issues with aluminium - lots of > expertise in the US as loads of aluminium wire used during the > Rhodesian coppper crissis. > AWEM

The problems were not only with work hardening but with terminations into fitttings designed for use with copper wire.

To anyone who's not used to the NEMA 5-15 receptacles commonly used in the US, these may come as a bit of a shock (!) anyway. Models of excellent quality do exist, but they aren't what's generally used. And they tend to run VERY hot, because the plug blades carrying a full 15 amps are usually just a flimsy piece of bent brass strip and the socket innards are usually no better.

Because alumin(i)um is very ductile, the combination of poor clamping arrangements for the individual conductors within the receptacle and the consequent restricted contact area led to the metal flowing away from the contact point and the heating becoming even more severe as the contact area lessened and the joint became higher resistance. Quite a number of major fires resulted and receptacles had to be redesigned if they were to be rated for use with alumin(i)um conductors.

Alumin(i)um is now restricted, in the main, to uses where the termination can be very strictly controlled.