S.W.A. Cables in Parallel.

AJJewsbury:

I have a niggling feeling that I have missed something

The only thing that comes to my mind that you haven't mentioned is consideration of faults - e.g. a fault affecting just one of the cables will likely see the majority of the fault current flow along just one of the cores (or armour) rather than being shared equally between two. That said, it's not normally a problem for just two conductors in parallel (after all half size c.p.c.s are pretty common) - but if you had half a dozen conductors in parallel it could well be an issue (as each core would be so much smaller compared to the protective device).


   - Andy.

The armouring is reliably earthed and the cables have a separate core as an additional C.P.C. each as well. The back up fuse is a 60 Amp B.S. 1361/88 or whatever we call them these days. If the cable was spiked the fuse would blow (fault of negligible impedance). The cable route underground is reliably marked, the rest is surface wired.


Z.

I have a niggling feeling that I have missed something

Andy Shepherd:

I don't see an issue with your install. Colour coding is a matter of preference although I personally use black as the CPC as long as you have identified your conductors its fine.

Sounds like you have kept both cables the same length, if I were to do this I would add cable tags on the outer sheath (brass with steel ties) stating that both conductors are part of the same supply.

The cables have exactly the same origin, follow the same route and have the same destination and consumer unit.


Z.

Zoomup:

mapj1:

The only problem with cables in parallel is what happens if the current share is unequal - actually a reasonable length helps here, on a short length the details of termination can be significant. So long as both armours, or more accurately any one would operate  the ADS if either cable was spiked, then it is fine. I'd be inclined to perhaps tie the ends together in some way, so they form a pair at the terminals, but that is only so it does not confuse any future person looking at it.

Actually with 6mm and 60A you can have it quite a long way out of balance before it matters - it is a similar problem to the current share on the ring final, and we do not normally fuse the individual limbs there.

Mike.

The two cables are of exactly equal length and supply a consumer unit. 4D4A does not rate 6.0mm2 anywhere near to 60 Amps.


Z.

I'll just stick with 514.3.2 and Table 51 ebee. It is easy to identify cable cores as:


a, They are oversleeved by the correct colour sleeving, or tagged by numbers or indicated by coloured tape.


b, They are identified by their connections at terminations by observation.


Z.

mapj1:

The only problem with cables in parallel is what happens if the current share is unequal - actually a reasonable length helps here, on a short length the details of termination can be significant. So long as both armours, or more accurately any one would operate  the ADS if either cable was spiked, then it is fine. I'd be inclined to perhaps tie the ends together in some way, so they form a pair at the terminals, but that is only so it does not confuse any future person looking at it.

Actually with 6mm and 60A you can have it quite a long way out of balance before it matters - it is a similar problem to the current share on the ring final, and we do not normally fuse the individual limbs there.

Mike.

The two cables are of exactly equal length and supply a consumer unit. 4D4A does not rate 6.0mm2 anywhere near to 60 Amps.


Z.

alanblaby:

Grey is usually used as neutral, and black as CPC.

Twin 6mm 3 cores?

It would be far easier to run one 2 core 10mm, or even 1 x 2 core 6mm if clipped direct.

This is basic stuff.

Why?


Yes it is the usual Zoom,


One theory is that it is to dissassociate Black from N but in my world if you thing Red Yellow Blue then think Brown Black Grey you`d probably decide for Grey (oversleeved Blue) to be N . In the old R Y B many would use Blue nonsleeved as N because "it is a N colour as in Flexes" but that was a bit nawty not to oversleeve.

In the Br Bk Blu system Black is oft oversleeved Brown as say a switched L with Brown as the Perm L similar to what you`d have done in the R Y B system. (where you be tempted to use Y (oversleeved) as the cpc or in new money the Black as Alan has said