Using armouring as earth and RCD protection

[Mspark2987]

Hi,

If an SY cable is used to supply a consumer unit, and there isn't a guaranteed depth of 50mm for the wall it is in, would using the braiding as the earth negate the meed for RCD protection of that cable?

Thanks

 

[James]

Not in my opinion.
sy cable is shielded, NOT armoured.

 

[pc1966]

The problem, or at least one of the problems, with SY cable is it is not to an BSI standard, so its use for wiring and in particular "fixed wiring" is strongly discouraged.

In the application you are asking about you would need to know that the braid was able to handle the fault current / energy to open the supply fuse/breaker without allowing the penetrating nail, etc, to become isolated and only in contact the the live conductor. I don't think any SY has such a rating.

If you don't want to use SWA due to its stifness and specific gland requirements then an alternative that is rated for some breaker use (to 20A C-curve I think) if Flexishield cable. it is pretty nice to work with as well as being UV resistant and not often nibbled by rodents.

 

[pc1966]

BS 8436 & IS 273 - Circuit Breakers

BS 8436 & IS 273 - Circuit Breakers

www.flexcables.co.uk

They have a 200A limit so 32A B-curve or 20A C-curve.

In most cases you are better with SWA as more choice and high fault rating as well as reasonable mechanical resistance to damage.

 

[Rockingit]

No, because the braid on SY is only for reasons of electromagnetic shielding and no way goes near the criteria for mechanical protection. And that’s even before we’ve gone to the ‘SY’ conversation.

 

[D Skelton]

No. SY braiding provides no mechanical protection, nor is it rated to carry fault current.