External meter cupboard on the garage wall.

29 Jan 2010
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United Kingdom
Meter cupboard is mounted on the external garage wall 100amp fused and rather than have the CU in the garage I would prefer it to be at a sensible central position in the house.
Am I correct in thinking that ----
From the meter, short 25mm tails to an 80amp DP fused breaker and then in plastic trunking using 15mtrs of 25mm tails to the CU, 16mm earthing cable to run alongside.
Is it in order to run the cable in plastic trunking through the connecting house cavity wall, are there any regulatory obstacles.

Cheers Mick.
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I'd definatly use a BS1361/BS88 switchfuse rather than a DP MCB, otherwise you might encounter problems with discrimination with final circuit breakers, you could even go to 100A.... there is little reason why you have to ensure discrimination with the service cut out.

While you could use DI tails to run within the house, I think I'd probably use 3 core SWA if I was doing it (or possibly split con - but thats not seen that often around here!)

Someone (lucia?) told me that architects these days try and avoid placing switchgear under stairs/central in domestics to try and keep it out of fire escape routes, I must admit I'd not heard that one before, so we'll leave it here and see if anyone picks up on it and elaborates!

Are you aware of the building regs concerning this work?
And have you thought about the following:

How you'll isolate the supply?

How you'll extend any final circuits you need to?

How you'll carry out all of the testing required before and after re-energising the installation?
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Hi Steve.
Thanks for the response, while cost is not critical, SWA was considerably more expensive when including the glands and a suitable enclosure to terminate the SWA cable.

I considered the DP 80amp fused switch as a means to protect the suppliers fuse.
Speaking to building reg's only drew a comment of 'Speak to your electrician' and having engaged in conversation with several qualified electricians I'm not convinced given the variety of replies which is the best way forward.
Some saying 2 core SWA and use the armour as the earth to others who call for 3 core.

Hello BAS.
Appreciate your picking up on this, isolation would be close to the meter box through the DP fused switch, virtually as the tails come into the garage.
I noted on previous posts that some suppliers don't mind the isolating switch being in the external cabinet but I would rather it was on the opposite side of the wall, internal so no clever so and so could easily put us in darkness. Meter cupboards are not exactly secure.

Cheers Mick.
Speaking to building reg's only drew a comment of 'Speak to your electrician'.
Well they aren't going to do electrical design work for you.

What Adam meant (I think) was are you aware of the Building Regulations which apply to what you propose to do, specifically Part P of Schedule 1 (there might be others as well) and the notification requirements in Regulations 12, 13 & 14?
Hello BAS.
Appreciate your picking up on this, isolation would be close to the meter box through the DP fused switch, virtually as the tails come into the garage.

.... so how will you isolate the supply to make it safe to fit your switchfuse?
So no supply yet, no CU and final circuits to move? Makes life easier...

You need to check with your DNO what they want you to do regarding the extending of their meter tails, rather than find out via a refusal to supply that you didn't get it right.

Who is doing the design, construction and testing of the installation?
Are my initial train of thoughts correct ?

I am to say the least hacked off up to press at the blatant attempts (while I appear to be laid back) to make capital out of my wish not to be overly involved and consider me as some sort of gravy train, to that end I am seeking sound advice drawn from certain people that have given what appears to be reliable and credible advice without £ signs uppermost in their minds, I need a background and feel as to how others would approach it so I can have the benefit of some knowledge before I engage Bob Sparky and not Bob Sharky.

I am BAS to say the least suprised at the initial liberal attitude of the DNO's whichever you approach, it seems they want you as a customer first.

Cheers Mick.
If using SWA, it is highly unlikely the DNO will accept a 2 core cable using the armour as the only CPC.

Although the armour can be used as the cpc in many instances, the equivalent cross sectional area of the armour will be significantly smaller than the inner conductors.
The armour on a 2 core 25mm SWA is typically around 42mm, however as this is steel, it is the equivalent of a copper cpc of only 5 or 6mm.

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