Split concentric submains

[Silly Sausage]

543.4 refers to PEN conductors, split con is under discussion here.


addition:

543.4.7 because Earth would be disconnected.

 

[Guest55]

hmm , getting warmer with this debate now ;-)

following on from tonys post ,

pvc concentric cable was indeed developed for use by the dno's as it is lighter and cheaper than swa , flexible in the cold , and can be worked on live fairly easily as you know the live core is in the centre of the cable , making stripping it back alot safer with the power on.

which all means its great for the dnos.

the issues i have with its general use in buildings wiring is that the neutral conductors are not afforded the same level of insulation and protection as the live.
and as the earth conductors are bare anyway , it wouldnt take much in the way of abuse before you start getting crappy ins. res. readings between N & E.

all things considered though , its good stuff but its applications must be selected carefully.

 

[Knobhead]

Biff, nail on head!

Split concentric is for post DNO termination, concentric pre termination.

Handled and terminated right, its excellent cable. I’d much rather work with a 25mm S/C than the equivalent SWA.

I took a piece of DNO concentric and put a 1KV test on it. It took seven good clouts with a 2Lb hammer for it to even start breaking down. Not very scientific I know, normal test methods for me.

 

[Andy78]

Biff, nail on head!

Split concentric is for post DNO termination, concentric pre termination.

Handled and terminated right, its excellent cable. I’d much rather work with a 25mm S/C than the equivalent SWA.

I took a piece of DNO concentric and put a 1KV test on it. It took seven good clouts with a 2Lb hammer for it to even start breaking down. Not very scientific I know, normal test methods for me.

That'll do for me.
I first saw the durability of MI shown to me in this way. A live piece of 2L1.5 with a lamp attached and lit was pounded with a lump hammer on an anvil. Was flattened to about an inch wide before the cable failed.

 

[tbs1983]

we use split con in my job on street lighting. we get a lot of neutral-earth faults with it. mostly dead shorts. Tend to use SWA as much as possible now on new installs & rewires as we find it a lot more reliable.

 

[Knobhead]

we use split con in my job on street lighting. we get a lot of neutral-earth faults with it. mostly dead shorts. Tend to use SWA as much as possible now on new installs & rewires as we find it a lot more reliable.

Faults are mainly due to incorrect termination, I’ll guarantee it.

 

[Rockingit]

Never having terminated split-con or that I can recall, ever having seen it demonstrated, what is the correct/preferred method?

 

[Rockingit]

the issues i have with its general use in buildings wiring is that the neutral conductors are not afforded the same level of insulation and protection as the live.

Apart from the obvious one of the live being itself 'protected' by N & E, I can't see how that really stacks up? You've a 7 stranded core covered in one layer of insulation, and a N of 7 x singles (or small stranded) all individually wrapped to produce the same csa - so on aggregate that's far more PVC covering the N than the L!

 

[Knobhead]

Split Concentric Cable to BS 4553-1 and BS 7870-3.20 | Eland

 

[Silly Sausage]

From the previous link, note...
"Other applications include sub main connections within high rise buildings"

 

[Guest55]

Apart from the obvious one of the live being itself 'protected' by N & E, I can't see how that really stacks up? You've a 7 stranded core covered in one layer of insulation, and a N of 7 x singles (or small stranded) all individually wrapped to produce the same csa - so on aggregate that's far more PVC covering the N than the L!

because the insulation covering the neutral strands is a quarter of the thickness of the live core and can be stripped off with a nothing more than a fingernail - ie , its very thin & weak in comparison.

get a piece and strip it as youve never terminated the stuff. ;-)

 

[Rockingit]

because the insulation covering the neutral strands is a quarter of the thickness of the live core and can be stripped off with a nothing more than a fingernail - ie , its very thin & weak in comparison.

get a piece and strip it as youve never terminated the stuff. ;-)

OK, I will! If someone would like to give written instructions on how it should be done, I'll happily get the bits in to do it, give it a first go with pics, and you can all peer review!! See.....got big ones, me.

 

[Guest55]

its a doddle.....


strip back outer pvc and inner clear selophane wrapping to reveal thus.........



twist together neutrals into 1 bundle & sleeving over earth strands
heat shrink pvc boot can be inserted over the base of cores if youre feeling flash
and cable entry is nothing more extravagant than an IP stuffing gland & shroud.

;-)

 

[Rockingit]

its a doddle.....


strip back outer pvc and inner clear selophane wrapping to reveal thus.........

View attachment 21198

twist together neutrals into 1 bundle & sleeving over earth strands
heat shrink pvc boot can be inserted over the base of cores if youre feeling flash
and cable entry is nothing more extravagant than an IP stuffing gland & shroud.

;-)

LOL - and here was me thinking I'd be needing to get the spanners out!! In which case, I think I got it covered. :cowboy:

 

[Guest55]

i'd have finished and gone home while you went for the spanners

 

[netblindpaul]

OK, I am too busy to try to find the reference, & thus I will give in, and apologise & say that I can't find the reference to limit the use of split con, but I thought it had come in recently with the last red or green books.
SORRY, it looks like I was wrong, as my memory has failed me, again.

I only have the latest book in electronic format to run a search on, but, if it came in on the red it should still be there.

So, I'll say I was wrong to say it CAN'T be used, but, I will not back down on it being treated as flex, as it does not have an earthed outer, thus it cannot be used in the same manner as SWA.

SO, if you are going to use it in an area where an earthed outer is required to negate RCD protection for example, then you can't, as the N cores are wrapped around under the sheath and are still classed as live conductors, so you can't bury it in walls for example and say that you don't need an RCD in the same way you can with conventional SWA.
The N cores do not have an earthed outer to protect them.

IF I can find the reference(s) I was hoping to, IF I ever have time, I will try, to remember to post it/them.

Sorry.

 

[Knobhead]

its a doddle.....


strip back outer pvc and inner clear selophane wrapping to reveal thus.........

View attachment 21198

twist together neutrals into 1 bundle & sleeving over earth strands
heat shrink pvc boot can be inserted over the base of cores if youre feeling flash
and cable entry is nothing more extravagant than an IP stuffing gland & shroud.

;-)

Personally I would have put a heat shrink on the both the CPC and neutrals, then tightly bind the crutch with amalgamating tape.

To tape the crutch properly the CPC and neutral have to first be layed at 90° to the line conductor. Each set of conductors twisted to the natural lay of the cable and then heat shrink applied. It’s a good idea to also heat shrink the line. Tape up using ½ lap to form a tight seal.
Looks mint and is a dammed site smaller than a heat shrink boot.

 

[Engineer54]

its a doddle.....


strip back outer pvc and inner clear selophane wrapping to reveal thus.........

View attachment 21198

twist together neutrals into 1 bundle & sleeving over earth strands
heat shrink pvc boot can be inserted over the base of cores if youre feeling flash
and cable entry is nothing more extravagant than an IP stuffing gland & shroud.

;-)

All looks so easy and simple to terminate when shown like this... In reality, in tight locations, and it can be anything but easy and simple. As i say, most of the final terminations to this type of cable that i've seen, have been a real pig's ear!!

Oh and personally i'd never even contemplate using any unarmoured concentric cable in a direct burial installation, only when ducted!!

 

[Silly Sausage]

As i say, most of the final terminations to this type of cable that i've seen, have been a real pig's ear!!

You've got to stop working with amateurs Eng! :smilielol5:

 

[Knobhead]

All looks so easy and simple to terminate when shown like this... In reality, in tight locations, and it can be anything but easy and simple. As i say, most of the final terminations to this type of cable that i've seen, have been a real pig's ear!!

Oh and personally i'd never even contemplate using any unarmoured concentric cable in a direct burial installation, only when ducted!!

Where did direct burial come from?

As far as a remember we are talking of internal wiring with sufficient depth to negate RCD protection.

Regarding making off in a restricted space, it’s no worse than SWA.

Going back to DNO concentric, I’d pit it against a SWA when attacked with a pick and shovel.