SWA with 7 Cores 1mm blue, 4 cores 2.5 g/y and 1 core brown 10mm ???

26 Sep 2006
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United Kingdom
Never seen this cable before but did an EICR on an apartment today and did a double take when the neutral supply into the CU consisted of 7 1mm singles . Furthermore the Earth was 4 2.5 mm singles. The line conductor was 10mm single. Obvious first reaction was that Sparky had run out of 10 mil for N and E and use the conductors in parallel to make up the CSA of the neutral and earth. What a bodge..... But no - upon further inspection at the services cupboard all seven apartments have been supplied with an SWA thst appears to have this configuration as per my title. Has anyone else seen this or offer an explanation as to why this has been used?


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It’s call split concentric. Or something like that.

Brown in the middle
Blue cores around that
Then CPCs on outside
It’s call split concentric. Or something like that. ... Brown in the middle ... Blue cores around that ... Then CPCs on outside
Indeed - although I think the blues and CPCs are usually 'interleaved' (or, at least, in the same plane) rather than the CPCs being 'outside' the blues.

Kind Regards, John
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Theres no steel in it so its not SWA

Looks like a bit of steel showing near the bottom left of the outer sheath, just above where the brown exits the sheath. The cores have probably been cut back flush with the sheath.
Nothing wrong with split-con... quite common in BNO land.

The way its been installed... thats a different matter! A complete bodge:
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Yes installation Of this cable a complete bodge some sort of large SWA type gland shroud kind of held on with masking tape. Could tell if SWA or just pvc sheath bit still not sure why would be used for supply from switch fuse to CU ... ?
This is known of as "split con", it is used by the DNOs for TN-S supplies. The DNOs presumablly think that neutral is close enough to earth to count as the protective earthed metal layer required for underground wiring.

Under the 16th edition this was a decent choice for submains, cheaper and less termination hassles than SWA and available in larger sizes than T&E.

However (i may be wrong here) my understanding is that under the 17th/18th edition it doesn't comply with the rules for non-RCD protected concealed cables, so it's not such a good choice nowadays.
The only split cons I’ve seen before was as you say for a TN DNO suppies not as meter tails , also never seen insulated singles in this format every day a learning day I guess

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