3 core 25mm SWA, not new colours, can it be used for meter <-> cu

[cjard]

I need to run a distance of about 10m from my 2 meters to my 2 CUs. Past advice here recommended use of 3 core 25mm SWA (and this I assume is 25mm csa of each core? What's that approx - as thick as a pencil?) and I do have several metres of such, stripped out of an old industrial installation. The cores are various colours depending on the number, but as far as I can see none are the black/grey/brown/blue colours..

So, am I looking at laying out a few hundred notes on 2 new pieces of cable the current colour, or can the old cores be recoloured (tape? paint?) / have a "mixed colours installation" notice put up? I get the feeling the answer is no, otherwise there's be a much more significant market for old coloured cable, but thought it worth a question if it could potentially save a bit of cash/earth's resources

 

[bernardgreen]

Provided the cores can be identified as to function then all the cores could be black with numbers on.

The only exception is that the earth / ground / CPC / bonding core must be green and yellow AND the green and yellow ( or naked ) conductor must not be used for any other purpose other than as an earth / ground / CPC / bonding conductor.

Local rules or restrictions may apply to some customer's installations.

Cable stripped out from installations needs to be carefully checked for damage, especially if it is to be used in a damp location where a puncture of the outer sheath could allow moisture to reach the SWA and subsequent corrosion of the steel

 

[cjard]

Thanks bernard, I'll check through the cables and see whether any have the relevant colour. I do also have a large amount of very thick earth wire "just on its own" - can that be run side by side with 2 core 25mm swa carrying the line/neutral phases?
For 25mm SWA I should be looking for cable whose core conductor is approx 3mm diameter?

 

[riveralt]

I need to run a distance of about 10m from my 2 meters to my 2 CUs.

You will need to speak to your electricity/meter supplier - most restrict the distance between the main fuse and the CU to 3 metres without a secondary fuse.
Also you cannot legally interfere with the metre.

So, am I looking at laying out a few hundred notes on 2 new pieces of cable the current colour

New cable is around £3.50 per metre - buy it by the metre.

or can the old cores be recoloured (tape? paint?) / have a "mixed colours installation" notice put up? I get the feeling the answer is no, otherwise there's be a much more significant market for old coloured cable, but thought it worth a question if it could potentially save a bit of cash/earth's resources

Nothing to stop you its your property but if you are going to do a job do it properly in the first place.

 

[Taylortwocities]

Thanks bernard, I'll check through the cables and see whether any have the relevant colour. I do also have a large amount of very thick earth wire "just on its own" - can that be run side by side with 2 core 25mm swa carrying the line/neutral phases?
For 25mm SWA I should be looking for cable whose core conductor is approx 3mm diameter?

SWA cable usually has the size of the conductors embossed on the ouside of the outer sheath. The copper of 25mm² cable is around 9mm in diameter. If yours is only 3mm then you have wrong cable. Do not use it!

If you do not know, the 25mm² figure is the cross-sectional area of the copper, not the diameter.

You could run the main earth alongside the SWA but be sure that is also the correct size as detailed in the REGS>

Finally, DNO rule state that 3metres is the max length of runs from the incomer, unless you have a switch/fuse at the incoming point before your 10metre run of SWA. What were you planning to do about that?

 

[cjard]

I need to run a distance of about 10m from my 2 meters to my 2 CUs.

You will need to speak to your electricity/meter supplier - most restrict the distance between the main fuse and the CU to 3 metres without a secondary fuse.
Also you cannot legally interfere with the metre.

Yes, I understand this is something to do with volt drop and some limit that the DNO is willing to let their service head fuses protect the run to the CU. I've no option but to have a longer run than this so I will need something like this on the meter board (i think) - I'll be returning here to seek advice on exactly what I'll need, at some point

So, am I looking at laying out a few hundred notes on 2 new pieces of cable the current colour

New cable is around £3.50 per metre - buy it by the metre.

Funny, I haven't been able to find 25mm 3 core swa less than about £9 a metre - where are you shopping please?

Nothing to stop you its your property but if you are going to do a job do it properly in the first place.

Well, technically my spark could stop me doing it - he's said he's happy to let me first fix so long as he can see everything uncovered before it's boarded and he comes back to second fix. I'm looking to get the right answers and buy the right gear so there isnt a litany of stuff he's unhappy with..

 

[cjard]

SWA cable usually has the size of the conductors embossed on the ouside of the outer sheath. The copper of 25mm² cable is around 9mm in diameter. If yours is only 3mm then you have wrong cable. Do not use it!

If you do not know, the 25mm² figure is the cross-sectional area of the copper, not the diameter.

Yep, i'd just made a typo, sorry.. but thanks for picking it up!

25mm^2 divided by pi is approx 7.95, the square root of which is approx 2.82 -> but that's the raduis, and I wrote diameter..

So I'm expecting a solid core 25mm^2 csa to have a diameter of approx 6mm.. did your 9mm include the insulating sheath?

 

[riveralt]

Funny, I haven't been able to find 25mm 3 core swa less than about £9 a metre - where are you shopping please?

I used this site to get a quote but I have just realised it is for the old colours - which I assume is what you already have.
https://www.tlc-direct.co.uk/Products/SW25slash3.html
New colours from online sites and local trade electrical stores vary around the £6 mark - ask your electrician to get the cable for you if you choose not to use your own.
One other thing, Depending on the age of your property, I will be surprised if the incoming DNO cable is more than 16mm².
In any case either you or your electrician will have to call the DNO to connect the new cable to the meter so you might check with them the size of the cable they want you to use..

 

[westie101]

I will be surprised if the incoming DNO cable is more than 16mm²

Depends on the DNO I would think that less than 10% or ours are below 25mm2,
Even a 16mm2 cable is rated at over 100A on our networks

So using 25mm2 for the tails from the meter to the switchfuse covers all eventualities.

The cable from the switch fuse to the CUs is part of the installation and the DNO is not bothered what size it is.

 

[Taylortwocities]

3 cores swa at £3/metre
But, why are you using SWA. Its a bitch to gland and terminate Why not standard 25mm tails?

 

[riveralt]

The cable from the switch fuse to the CUs is part of the installation and the DNO is not bothered what size it is.

I think the OP is talking about running the new cable from the meter to the CU - are you saying that the DNO are not concerned about that cable size and that they will
fit whatever is offered?

 

[westie101]

The OP was originall talking of running a 10M length of SWA from the meter to the CUs
The 3 m limit has been pointed out so the OP is now talking of fitting a switch fuse at the meter position which he must.
This means the tails are under 3m so that is the only bit the DNO is interested in and I suggest using 25 mm2
After the switch fuse it is part of the internal wiring so of no interest to the DNO

 

[JohnW2]

The cable from the switch fuse to the CUs is part of the installation and the DNO is not bothered what size it is.

I think the OP is talking about running the new cable from the meter to the CU - are you saying that the DNO are not concerned about that cable size and that they will fit whatever is offered?

What westie says seems to make sense to me. I would not have expected the DNO to have any interest in what was downstream of the switch fuse, although you seemingly do. I would have thought that their only concern would relate to tails which were only protected by their service fuse (i.e if there were no switch-fuse, or upstream of a switch-fuse).

Kind Regards, John

 

[EFLImpudence]

3 cores swa at £3/metre
But, why are you using SWA. Its a bitch to gland and terminate Why not standard 25mm tails?

Because, depending on the installation method, they may require RCD protection.

he's said he's happy to let me first fix so long as he can see everything uncovered before it's boarded and he comes back to second fix.

 

[JohnW2]

But, why are you using SWA. Its a bitch to gland and terminate Why not standard 25mm tails?

Because, depending on the installation method, they may require RCD protection.

Yes, quite possibly, but more specifically/pragmatically .....

I need to run a distance of about 10m from my 2 meters to my 2 CUs. Past advice here recommended use of 3 core 25mm SWA

Kind Regards, John