Earthing SWA at both ends

[davesparks]

What PVC?

Yes, not all PVC is the same! The bedding and sheath are both made of PVC, if you have a proper look at it next time you strip some you will notice that it's not the same. The density, strength, flexibility etc are different due to a lower grade (cheaper) being used for the bedding than for the sheath

 

[Deleted member 26818]

but once the faceplate fixing screws are fitted, it then becomes "exposed".

So by using screws which are earthed via the faceplate, the back box becomes exposed requiring a fly lead to connect it to the face plate so it can be earthed?

 

[remer1957]

I always connect the earthing fly lead to back boxes I install, it's easy to do if done before installation of the box, takes 10 seconds and 4 inches (100mm) of earth cable. In fact, I used to carry pre-cut lengths of cable for just this purpose. I also earth both ends of the SWA, it doesn't take long and I think it's good practice.

 

[shanky887614]

I always connect the earthing fly lead to back boxes I install, it's easy to do if done before installation of the box, takes 10 seconds and 4 inches (100mm) of earth cable. In fact, I used to carry pre-cut lengths of cable for just this purpose. I also earth both ends of the SWA, it doesn't take long and I think it's good practice.

thats a good way to do it, earth lead when you first fix i mean

 

[Deleted member 26818]

thats a good way to do it, earth lead when you first fix i mean

Yep, some of the boxes I've been 2nd fixing have 2 or 3 extensions, can't even see the earth lug.

 

[shanky887614]

Yep, some of the boxes I've been 2nd fixing have 2 or 3 extensions, can't even see the earth lug.

lol must have had the same plasterer, ive used 75mm 3.5mm pins and 3/4 extension pins lol

 

[Dave OCD]

lol must have had the same plasterer, ive used 75mm 3.5mm pins and 3/4 extension pins lol

Plenty of wiring space though.

 

[Risteard]

As stated the bedding (although it may be made from insulating material) is not tested as insulation. Likewise the sheath of T&E; flex etc. is not tested as insulation.

That is not its purpose.

Also, in an SWA the bedding is not intended to be used as a sheath, so couldn't be run free as an insulated and sheathed cable, as it isn't and therefore must be within the enclosure if the sheath and armour has been removed.

 

[Big Sausage]

Certain industrial installation designs require that earthing systems are separated from source supplies due to the requirement to maintain a "single point earthing system".
For example some signalling rooms on railway installations are provided with a earth that forms part of the signalling system and is totally separate from the main supply earth.
Typically the design for those installations will specify that the sub-main SWA cable supplying that location is only earthed at the origination of the supply and that the load end is terminated in to a "insulated cable gland".