Two feeds, 4 core cable

[moosey86]

I was in a pub cellar yesterday and like most it's wired like *****, like the rest of the building. But one thing I noticed was three single phase breakers supplying three 63A single phase rcd iso's. It was done in a 4 core SWA so yep u guessed it the forth core was a shared neutral for the three supplies just looping in and out to the next one!! Disgraceful lol.

So anyway, only two of the supplies were actually being used so I was going to take one of the live legs from the iso not being used and put it into one iso that was being used and change it to a neutral at the main board. Obviously just make the existing neutral the one for the other iso being used.

So the 4core SWA would be carrying two single phase supplies. The earth would have to be shared through an earth tag from the banjo. Do-able?

 

[moosey86]

Id imagine putting them on the same phase would be sensible

 

[moosey86]

Any chance of some suggestions or thoughts from anyone??

 

[Knobhead]

I’ve done it in the past but under M&Q regs.

Would you fancy running two 450M 16mm 2c SWA’s when you’ve found a redundant 16mm 4c not 5M from where you want it? The cores were sleeved correctly and the JB & supply DB had engraved notices in them. You have got to clearly identify neutral 1 & neutral 2.

Don’t know if you can do it under IEE regs.

 

[BlueToBits]

AFIK There is nothing in the regs to prevent you from doing what you suggest. I don't even think you need to mark the 2 neutrals as anything other than neutral. It's what would happen if it was singles a steel conduit using the conduit as the ECC. they don't have to be on the same phase. I would go so far as to say it was more responsible to do what you propose than to strip out the cable and install new. Why generate more waste than is needed?

 

[Guest123]

The only concern I have is would the armouring be sufficient enough to carry the fault currents of both circuits at once.

An adiabatic would confirm. Also what kind of circuit lengths are we talking here???

 

[moosey86]

I didn't think it would be a problem, just never really done it before!! The circuit length is about 15m. I've quoted a fair few things for him there so I wana keep the cost down as much as pos. But fortunately the previous 'sparks' was so bad I think I can get some mileage out of sorting out wrong doings

I quoted a job for him ages ago for some infrared heaters but lost out on price. Now I'm back to sort out the cheap mess that was made. Hehe