regs on earthing SWA

[james king]

can any one show me a regulation that the SWA stel outcore has to be earthed. i understand if its to a metal box ect. but plastic?

 

[glasgowbiker42]

never said it was paul, but there is still 3 layers of insulation on the cable?

 

[netblindpaul]

Well your post seemed that way.
However, IMHO and I believe I can back this up with manuf' data, you are still incorrect.
Outside in you have:
Sheath
SWA
Bedding
Insulation

Thus the cable is single insulated.

I will admit that I would have to check the spec on the bedding but, IIRC it is not classed as insulation.

 

[Engineer54]

never said it was paul, but there is still 3 layers of insulation on the cable?

In truth, there is only ''One'' layer of insulation the other layers are basically inner and outer sheath type PVC. But i guess in reality, you could reasonably argue a 3 layer case! ..lol!!!

 

[Knobhead]

I wonder if any of you have come across DWA (double wire armoured). I’ve only worked on a few of them but used to enjoy it. The outer and two inner servings would be tarred jute, these had to have copper whipping around it to stop it falling apart at the gland.

Some of the plants were built in the 1930’s but the cables were still good. We sent samples to BASEC for testing, the report came back saying we could expect another 50 years out of them.

Construction was VIR insulated cores with sisal worming, two layers of cotton tape, tarred jute, armours, tarred jute, armours, and finally more tarred jute. You ended up covered in tar but it was fun to do.

What you’d regard as a 2.5 3 core would be near 35mm thick.