Strange Cable

[davetheglitz]

Came to connect up what I thought was a 16mm 3C SWA cable - but instead of the steel wire it was 1mm copper strands. Has anyone come across this this type of cable?

I'm a bit concerned as it feeds a large barn approx 50m from the house and it has all been buried. Arguably as it has an earthed sheath so if struck it would blow the fuse - but although it's a really chunky thick sheathed cable it isn't armoured.

Apparently the cable was put in place by the ex brother in law who worked for the DNO.

Hope someone can shed some light on this!

 

[Andy™]

straight con, or split con is some of the outer strands are insulated

 

[Andy™]

also, are the phase conductors ali? most DNO's use straight con with copper outer conductors & ali inner conductors. probably cheaper

 

[Sidewinder]

Not "officially" recognised by BS7671 in either straight, or split con.

 

[Steve3948]

Made for DNO like the 16mm

 

[Sidewinder]

Well, meter to db is under 7671 so how does this comply?...

 

[NozSpark]

I had someone ask me to connect up a garage with sone Alu core straight con that they had installed... I refused as if you connect the sheath to the earth you have no neutral and if you connect to the sheath to the neutral you dont have an earth..

The only other option was to PNB it which as we know needs Home Office approval

 

[Andy™]

I had someone ask me to connect up a garage with sone Alu core straight con that they had installed... I refused as if you connect the sheath to the earth you have no neutral and if you connect to the sheath to the neutral you dont have an earth..The only other option was to PNB it which as we know needs Home Office approval

if its 3c concentric, it could be used for single phase with the sheath used as earth only

also, the outer copper is not insulated, only sheathed, so cant be used as a neutral

 

[Steve3948]

I cannot remember the date now of install but I think it was 1985.

Its the first time I've seen it ever, during a EICR last month, cable was in cavity with a 16mm

 

[davetheglitz]

Thanks for the excellent replies!

Reckon this must be a straight concentric 3C cable - cores were stranded - not solid. As I'm not using it as a 3 phase installation I can make the copper surround a cpc and leave one redundant core - so as such not a safety issue.

Suspect the cable came off the back of a lorry!

 

[Andy™]

Thanks for the excellent replies!Reckon this must be a straight concentric 3C cable - cores were stranded - not solid. As I'm not using it as a 3 phase installation I can make the copper surround a cpc and leave one redundant core - so as such not a safety issue.

Suspect the cable came off the back of a lorry!

why leave a core redundant? for how much extra hassle it would be, might aswell connect it to earth along with outer

 

[davetheglitz]

As I'm TTing the barn I didn't see any advantage.

 

[Sidewinder]

Reducing efli on the sub main would be a major advantage IMHO!

 

[davetheglitz]

You've got a point there!

 

[apprentice87]

Hi All,

The cable is obviously stolen from the DNO...

It is what they call "Hybrid" concentric service cable. The usual three phase stuff [for up to 100A supplies] is 35mm three core, with solid aluminium conductors and the copper concentric combined neutral and earth. This is presumably what this cable is...

My opinion???? Well, you CANNOT use it as it is intended to be used, as you CANNOT have TNC as part of your installation wiring, as it is banned by the ESQCR so far as i know...

Likewise, if you just want to use it for single phase and just use the internal cores, you are still in trouble.... For a start off it is NOT armoured, so it would have to be in a duct or have sufficient additional mechanical protection, and secondly, how you going to terminate it??? A "normal" gland grips the steel armour, always remembering that, although you might not be using the "armour" [for want of a better term] for a CPC, a joint has to have sufficient MECHANICAL properties, as well as electrical ones.....

So, throw it in the bin and start again....

P.S. The word "Barn" gives it all away.....

john...

 

[steptoe]

yea, bin it, do you want me to come down and take it away for you Dave, save you getting a skip like.

 

[binky]

Sod off I'm nearer :

If you want a second opinion I'll pop over Dave

---------- Post Auto-Merged at 22:50 ---------- Previous post was made at 22:46 ----------

Cost you more in diesel than it's worth steps

 

[steptoe]

but I get to see Dave performing, and have a beer, .

 

[davetheglitz]

but I get to see Dave performing, and have a beer, .

Decade 5 playing here!

Tavisrock N' Blues Fest | Rock Chicken

---------- Post Auto-Merged at 23:25 ---------- Previous post was made at 23:11 ----------

Hi All,The cable is obviously stolen from the DNO...

...

Likewise, if you just want to use it for single phase and just use the internal cores, you are still in trouble.... For a start off it is NOT armoured, so it would have to be in a duct or have sufficient additional mechanical protection, and secondly, how you going to terminate it??? A "normal" gland grips the steel armour, always remembering that, although you might not be using the "armour" [for want of a better term] for a CPC, a joint has to have sufficient MECHANICAL properties, as well as electrical ones.....

See your point re mechanical properties - however if the cable is clipped/secured at the termination, the outer conductors are gathered together and the whole lot terminated in a fixed adaptable box the mechanical problems disappear. Fortunately the cable has been installed in a flexible duct - so I still think this is a goer.

Alternatively they might want to dob the ex brother in law...

 

[Andy™]

and secondly, how you going to terminate it??? A "normal" gland grips the steel armour, always remembering that, although you might not be using the "armour" [for want of a better term] for a CPC, a joint has to have sufficient MECHANICAL properties, as well as electrical ones.....

have you ever used the stuff? like split con, its fairly easy to terminate. not far from T&E or flex actually. nothing wrong with using split con, and straight con could be used providing there is enough cores to use one of them as a neutral instead of the sheath