Admittedly I don't make off a lot of SWA, but do occasionally and can usually do a decent job in a reasonable time but the other day I had to terminate a couple of SWAs into an awkward position (back of cupboard, restricted space, having to work left handed, and not quite enough space to get a spanner in and so on) and got to thinking there must be a better way…
Most of the difficulty was around glanding off the actual steel armour - trying to get everything aligned and tightened in a confined space seemed more like the less desirable aspects of being a plumber rather than an electrician. Split-con would have appealed - as then a simple stuffing gland could have been used and the copper outers just pig-tailed into the terminals, but as the cables go underground split-con isn't permitted any more. Which got me thinking - why is the armour in SWA steel? (apart from the name of course) - had it been copper it could be terminated like split-con. The physical robustness of steel seems rather wasted since if the cable is penetrated by something the steel strands are easily displaced (as in the garden fork experiment) - so really it is ADS that the armour gives us in way of safety rather than an impenetrable mechanical barrier - and copper if anything would be better than steel at enabling ADS. The DNOs use concentric cables with just copper “armour”, if as a PEN rather than just PE, but the principle is the same.
So I guess I'm coming around to copper concentric cables, but with an extra core for a separate N - it could still be glanded off using brass glands if you really wanted to, but you'd have the option of just pig-tailing the c.p.c. where that was more appropriate.
That might feel like it's going to be more expensive (copper instead of steel), but as most people use and extra core in SWA for c.p.c. in parallel with the armour, it's really just moving that copper to the armour instead - so really it's a saving of the steel with no extra copper required. So perhaps slightly cheaper and slightly smaller o.d. cables.
Any other takers for “CWA" cables?
- Andy.
