Can you use two three cores for three circuits?

[JohnW2]

Try saying that to the person tasked with providing the 1200A 3 ph feed for a chiller on the roof from the switch room at the other end of the building 10 floors below.

I reckon that probably qualifies as pretty rare - although I concede that it may be much more common in what I would call 'heavy industrial situations' in which the currents are very high and single conductors large enough to support those currents would be enormous, very heavy, and very difficult to handle.

However, needless to say, those are situations of which I have zero experience. I think people sometimes forget that this is a 'DIY' forum

Kind Regards, John

 

[Jackrae]

For such circuits is helps greatly if you put good labels on each end of each core and a circuit sketch within each terminal box - though someone's bound to say it's a fire risk - which it isn't

 

[Harry Bloomfield]

It would presumably be very rare that there was a particularly good 'excuse' (apart from laziness and cost), since it would virtually always be possible to find a larger cable that would be adequate on its own.

It will not bother then, telling you about the number of times I have had to parallel feeds up to big equipment in power stations and similar large equipment situations.

 

[EFLImpudence]

I may have missed a bit but - what is the problem?

 

[JohnW2]

It will not bother then, telling you about the number of times I have had to parallel feeds up to big equipment in power stations and similar large equipment situations.

As youy will have seen that I wrote in response to a similar comment from SUNRAY...

I reckon that probably qualifies as pretty rare - although I concede that it may be much more common in what I would call 'heavy industrial situations' in which the currents are very high and single conductors large enough to support those currents would be enormous, very heavy, and very difficult to handle.
However, needless to say, those are situations of which I have zero experience. I think people sometimes forget that this is a 'DIY' forum

Kind Regards, John

 

[JohnW2]

I may have missed a bit but - what is the problem?

As has been more recently discussed, I don't think that there is even a theoretically problem provided that each 3-core cable contains switched lives plus the neutral to the lights supplied by those S/Ls. In other words, as has been said, two 3-core cables could service 4 lights - with two S/Ls and the corresponding N in each cable.

If one wants to avoid the 'theoretical problem', the only thing one has to avoid is any cross-connection (at the downstream end) between the two neutrals.

Kind Regards, John

 

[EFLImpudence]

...

I misread your post.

 

[pedr0]

Yes, thank you all. Definitely happy now that I can have my three (four!) switched lives.

 

[SUNRAY]

Does this help?

I've shown the earths linked, in reality all 6 wired should fit in a single connector block

 

[pedr0]

Yes. That's great. Got it straight in my mind now.

The one thing that I find strange though is how the original electrician left the grey PVC cable coming out of the wall into the garden. It emerges from the wall and then goes into a wiska box after about 50cm. He'd slipped some metal Flexicon conduit over it, but there arent any glands or anything actually connecting the conduit to the wiska box.

How should that first bit of grey pvc cable be protected before it gets to the wiska box?

 

[pedr0]

Here's a photo. Landscaper must have taken the flexicon off today. Not sure why.

Edit : none of these cables are live. They are yet to be connected.