Why STEEL in SWA?

Alternatively, you can put the gland on the cable before you thread it into the difficult access position

Undoubtedly better planning would have helped (as ever) but it was one of those situations where the original plans changed over the year. In the final case the SWA had to terminate into  wiska box with threaded entries, so glanding to the cable first wouldn't have worked ?

i am thinking if you replace the steel with copper having the same CCC then the resultant cable would be similar to braided sheath cable. On the other hand if you replace the steel with copper having the same tensile strength (or rather yield strength) the copper content would mostly be in the sheath and would be horrendously expensive given the price of copper at the moment

I was thinking of same size c.p.c/armour as the cores (or as per table 54.7 for larger sizes) - so probably a bit more substantial than “braid” - more like the outer of ordinary concentric cables (e.g.  

) but 2-core rather than single core (or 4 rather than 3 core).

I just wondering why we continue to use steel when others (e.g. DNOs) seem to have moved away from that and are having an easier life as a result.

    - Andy.

AJJewsbury: 
 

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. 

     

Hi Andy, you can run unarmoured cables underground if they are in a duct that provides normal mechanical protection, ie the duct is at an appropriate depth to any expected stress.

If the concern is offering additional protection to anyone who may mechanically stress a buried cable system then the additional protection should be via a 30mA RCD?

Weirdbeard: 
 

AJJewsbury: 
 

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. 

     

Hi Andy, you can run unarmoured cables underground if they are in a duct that provides normal mechanical protection, ie the duct is at an appropriate depth to any expected stress.

 

If the concern is offering additional protection to anyone who may mechanically stress a buried cable system then the additional protection should be via a 30mA RCD?

 

That must be Reg. 522.8.10 then. What is “equivalent protection?”

Z.

Zoomup: 
 

Weirdbeard: 
 

AJJewsbury: 
 

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. 

     

Hi Andy, you can run unarmoured cables underground if they are in a duct that provides normal mechanical protection, ie the duct is at an appropriate depth to any expected stress.

 

If the concern is offering additional protection to anyone who may mechanically stress a buried cable system then the additional protection should be via a 30mA RCD?

 

That must be Reg. 522.8.10 then. What is “equivalent protection?”

 

Z.

Any duct or conduit that is installed underground to contain a wiring system in accordance with BS7671.

AJJewsbury: 
 

. . . just wondering why we continue to use steel when others (e.g. DNOs) seem to have moved away from that and are having an easier life as a result.

I think you will find the rules are different. For DNOs, the Supply Regulations require all live conductors to be enclosed by a metallic screen, at or about earth potential. Either an earth or System Neutral will satisfy the requirement. 

Regards,

Alan. 

Weirdbeard: 
 

Zoomup: 
 

Weirdbeard: 
 

AJJewsbury: 
 

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. 

     

Hi Andy, you can run unarmoured cables underground if they are in a duct that provides normal mechanical protection, ie the duct is at an appropriate depth to any expected stress.

 

If the concern is offering additional protection to anyone who may mechanically stress a buried cable system then the additional protection should be via a 30mA RCD?

 

That must be Reg. 522.8.10 then. What is “equivalent protection?”

 

Z.

Any duct or conduit that is installed underground to contain a wiring system in accordance with BS7671.

“Equivalent” to what exactly?

Z.

I think you will find the rules are different. For DNOs, the Supply Regulations require all live conductors to be enclosed by a metallic screen, at or about earth potential. Either an earth or System Neutral will satisfy the requirement. 

I quite agree the DNO's rules require an earthed(ish) screen - effectively BS 7671 does too  for buried or likely to be damaged cables (if anything more strictly as it must be PE not N) - my question was if the DNO's can achieve that with copper instead of steel these days, why can't we?

   - Andy.

“Equivalent” to what exactly?

To my mind, to provide the same safety in the same circumstances - if an armoured cable remain ‘safe’ when hit by a spake/fork/mattock/pick/mechanical excavator bucket (by virtue of ADS) - the same attack on the duct/conduit system should be no less safe (e.g. if not by ADS then by some other means such as preventing the damage getting through to the cable).

To my mind a bit of plastic “twinwall” duct doesn't quite do that - at least in uncontrolled environments.

    - Andy.

AJJewsbury: 
 

“Equivalent” to what exactly?

To my mind, to provide the same safety in the same circumstances - if an armoured cable remain ‘safe’ when hit by a spake/fork/mattock/pick/mechanical excavator bucket (by virtue of ADS) - the same attack on the duct/conduit system should be no less safe (e.g. if not by ADS then by some other means such as preventing the damage getting through to the cable).

To my mind a bit of plastic “twinwall” duct doesn't quite do that - at least in uncontrolled environments.

   

It sounds like you are installing a wiring system with the anictipation that the mechanical protection is likely to be compromised? Have you complied with BS7671?

It sounds like you are installing a wiring system with the anictipation that the mechanical protection is likely to be compromised?

That's always a risk with hidden cables in situations where digging/nailing/drilling is to be anticipated - I don't know of any wiring or containment system that would mechanically resist that. Hence BS 7671's requirements for concentric c.p.c.s or (for internal situations) additional protection by 30mA RCD.

   - Andy.