Parallel METER TAILS

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I need to move my Consumer Unit about 8 meters from its present location. This will result in shorter ring mains and lighting circuits. In fact the only circuit 'losing out' is the one that will feed the garage and that runs off a 13A FCU in the lounge at present so a better solution is needed anyway. At the moment there is 1 30A ring main for the whole house, but I am going to have a separate

30A ring for the kitchen , plus a non-rcd radial for the fridge. Existing CU has 16mm sq tails and 60/80 company fuse. I know its now past april 1st but I have 25 meters of black 25mm sq meter tail (=A35 in B&Q), but the only red that seems to be available is 16mm sq. In a past post someone mentioned that running two live cables together from my switch fuse to the new CU is permitted. I.e two runs of 16mm sq red plus 1 run of 25mm sq blck. Is this correct ?, (or does anyone want to swap 12.5 meters of 25mm sq red 6181y for 12.5 meters of my black ?).

PS The meter box is metal and in the hall. I intend to use the existing conduits that take the cooker/ring/lights/immersion to run my sub-main up into the ceiling void above hall but I read somewhere that live and neutral must go through same hole of a metal box else eddy currents would result. This is this correct ?,

Yes I do know about Part P.

Andrew

[Hugh]

30A ring for the kitchen , plus a non-rcd radial for the fridge. Existing CU has 16mm sq tails and 60/80 company fuse. I know its now past april 1st but I have 25 meters of black 25mm sq meter tail (£5 in B&Q), but the only red that seems to be available is 16mm sq. In a past post someone mentioned that running two live cables together from my switch fuse to the new CU is permitted. I.e two runs of 16mm sq red plus 1 run of 25mm sq blck. Is this correct ?, (or does anyone want to swap 12.5 meters of 25mm sq red 6181y for 12.5 meters of my black ?).

PS The meter box is metal and in the hall. I intend to use the existing conduits that take the cooker/ring/lights/immersion to run my sub-main up into the ceiling void above hall but I read somewhere that live and neutral must go through same hole of a metal box else eddy currents would result. This is this correct ?,

Yes I do know about Part P.

Andrew

AFAIK, if the fuseboard is more than one metre away from the meter you need to use armoured cable.

Hugh

[John White]

No this is not safe. One of the two parallel 16mm tails could become disconnected or damaged, throwing the full load on to the remaining one.

A better solution is to cut two lengths of the black 25mm tail and then use brown and blue tape to identify them at both ends. This is much safer and complies with the regulations.

Yes both conductors must pass through the same hole. This also applies to the conduit tubes (which is really a hole in very thick material) if they are metal.

Good!

John

[Andrew Gabriel]

This may be further than your supply network maintainer will allow without fitting an additional switch fuse at the meter.

3m is a typical limit, but it varies by area.

No. (Well, if you can show compliance with the "Conductors in Parallel" part of the regs, it is, but I wouldn't bother.)

Both my meter tails (as fitted by Eastern Electricity) are black, with a ring of red tape round each end of the live one.

Yes, if the metal is magnetic (e.g. steel). Another method is to cut a slot to prevent the eddy currents, but you would need to know where to cut the slot(s) -- that's really only safe when done by the manufacturer.

[tony sayer]

In

Interesting this . A pro electrician, AKA Billy the Kid, did an install like this where we work at sometimes, with all conductors in separate holes, and I can't say I've ever noticed any heat around the holes despite pretty high power consumption....

[John White]

I've never seen things heating up in this way either. Maybe you only get serious heating in certain circumstances.

On the other hand, the OP mentioned Part P, and he may encounter a by-the-book inspector, so it's as well to do it properly.

John

[The Wanderer]

Others have already confirmed that this is the case. Be warned, if you ignore it the consequences could be disastrous!

It was only something I heard about second hand, but a new HV/LV transformer on a business park, I think it was an 800kva[1], so 7 lv single core cables which ran to the customer's main intake position, through a cluster of 4 over 4 pipes installed by the builder, except that they were steel pipes and not earthenware as had been specified. That, together with the fact that the jointer hadn't bonded the armouring on the s.c. cables properly, and the whole lot overheated, and overheated, and overheated because of hysteris currents when the load increased until there was bloody great bang......

[1] Yes I realise we're not talking about demands of several hundred kva, but the story does illustrate that there are reasons why you shouldn't do it!