swa cable colours

[tedsacre]

Hi everybody
I am doing the ground works on a renovation project and would like to run a swa cable in a trench at the same time.. The meter box is 8M from the consumer unit. Now I understand that the cable needs to be 25mm but can I use 2 core in brown /blue and use the shield for earth. because the only 3 core I have seen is in 3 phase colours. we have a multi point earth system, with the earth and neutral connected together. I am not an electrician. Cheers Ted.

 

[flameport]

Whether 25mm / 2 core / 3 core or whatever is suitable depends on several other factors.

The best option will be to install some 50mm ducting (or larger) with a draw rope inside, so the correct cable can be installed later.

 

[PrenticeBoyofDerry]

I normally run three core using both armour of cable and one core as the CPC/connection to earth and identify the cable colour cores accordingly at all terminations.
So if you have
Black
Grey
Brown
I would sleeve them
Blue
Green/Yellow
and leave Brown as Phase.

 

[ricicle]

Hi everybody
I am doing the ground works on a renovation project and would like to run a swa cable in a trench at the same time.. The meter box is 8M from the consumer unit. Now I understand that the cable needs to be 25mm but can I use 2 core in brown /blue and use the shield for earth. because the only 3 core I have seen is in 3 phase colours. we have a multi point earth system, with the earth and neutral connected together. I am not an electrician. Cheers Ted.

As per flameport - please just install a duct at a suitable depth with a draw rope in it. You are asking too many questions to be able to carry out the electrical work yourself, leave that to a competant professional.
It would be best getting them on board from the off with regard to the ducting size, depth and route.

 

[JohnW2]

So if you have Black, Grey, Brown, I would sleeve them Blue, Green/Yellow, and leave Brown as Phase.

If you mean 'respectively', I thought the usual convention was to blue sleeve the grey and G/Y sleeve the black - the reasoning being a desire to distance oneself from the 'old' association between black and neutral?

Kind Regards, John.

 

[tedsacre]

many thanks I think a duct is the best idea then the contractor can put in what he is happy with. Cheers Ted.

 

[Paul_C]

If you mean 'respectively', I thought the usual convention was to blue sleeve the grey and G/Y sleeve the black - the reasoning being a desire to distance oneself from the 'old' association between black and neutral?

That's been promoted by certain organizations, but as has been discussed here in the past, it's not an absolute. When the new cables first appeared there were certainly suggestions to do it the other way. Either way is acceptable as far as BS7671 is concerned, and both seem to be used quite widely.

 

[JohnW2]

That's been promoted by certain organizations, but as has been discussed here in the past, it's not an absolute. When the new cables first appeared there were certainly suggestions to do it the other way. Either way is acceptable as far as BS7671 is concerned, and both seem to be used quite widely.

Sure, I wasn't suggesting that it was any sense 'compulsory' - merely that I thought it was 'the usual convention'. However, from what you say, it is perhaps not quite as 'usual' as I had thought. Thanks.

Kind Regards, John.

 

[ban-all-sheds]

The best option will be to install some 50mm ducting (or larger) with a draw rope inside, so the correct cable can be installed later.

I'd install 2, side by side, so that you have the option of also running phone/data cables out there.

 

[Paul_C]

Sure, I wasn't suggesting that it was any sense 'compulsory' - merely that I thought it was 'the usual convention'. However, from what you say, it is perhaps not quite as 'usual' as I had thought.

Certainly nowhere near as "usual" as sleeving yellow to green/yellow and blue to black was with the old cables.

//www.diynot.com/forums/viewtopic.php?t=216257&start=0

 

[JohnW2]

I'd install 2, side by side, so that you have the option of also running phone/data cables out there.

The OP wasn't totally clear, but it almost sounded as if the SWA was to run from the meter box to the main consumer unit. If that were the case, then it's presumably unlikely that phone/data cables would ever be a requirement.

Kind Regards, John.

 

[JohnW2]

Certainly nowhere near as "usual" as sleeving yellow to green/yellow and blue to black was with the old cables.

Fair enough, but that was a bit different, since there was no old/new colours potential confusion at the time.

Kind Regards, John.

 

[Paul_C]

Fair enough, but that was a bit different, since there was no old/new colours potential confusion at the time.

Plus other long-standing factors which played a part. From circa 1970 onward we had brown/blue in flex, so there was a natural association of blue-to-black there, plus the obvious association of yellow already being "halfway there" when green/yellow for earth became common.

But the blue association goes back earlier than that. Under the 13th edition, when using a 3-core flexible cable with red/white/blue cores for a single-phase application, the specified method was to use white sleeved green for E and blue for N, with no sleeving necessary on the latter (and red for L, of course). Similarly, for a 3-wire d.c. or a.c. circuit the standard allowed the blue in a 3-core red/white/blue cable to be used unsleeved as the neutral.

 

[ban-all-sheds]

The OP wasn't totally clear, but it almost sounded as if the SWA was to run from the meter box to the main consumer unit. If that were the case, then it's presumably unlikely that phone/data cables would ever be a requirement.

FGS - why didn't you tell me I had to read the original post properly?

 

[JohnW2]

FGS - why didn't you tell me I had to read the original post properly?

I don't imagine you read the OP any less properly than I did - but, as I said, it wasn't totally clear. The OP didn't tell us where the SWA was going to/from, but his mention of the distance from meter box to CU might be a clue

Kind Regards, John.