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Posted By Topic: supply to shop next door

miquel
May 28 2017 12:44

Hi all. The owner of shop A has bought shop B next door. Wants to save on electricity costs and wants 1 ICP instead of 2. Proposes to feed through the wall from main board in shop A to shop B as a sub board. Apart from not good practise and nuisance I can't find anything in the Act/Regs/3000 to back me up on. Any ideas? Thanks
   

gregmcc
May 28 2017 14:06

How about maximum demand and the mains size?, at a very rough guess you would be doubling the load, can the existing mains safely supply the load? Supply fuses?
   

AlecK
May 29 2017 08:39

nothing wrong with the concept from Regs perspective. Any number of old installations from Power Board days that used to have separate supplies (on grounds of good engineering) have been amalgamated now that fixed charges based on available supply are such a big part of the cost.
But as gregmcc says there are practical issues to be worked through.


   

miquel
Jun 01 2017 17:34

What about 3.9.8.2 ? I know it used to be common practise but can you do it now?
   

AlecK
Jun 01 2017 22:14

If you feed one from the other, they will no longer be separate / different installations.
   

miquel
Jun 02 2017 17:21

Thanks Alec, that makes sense
What is your view on the situation where there is a block of flats with 1 common meter board say at the front, and submains to distribution boards at the back but the submains of the back flats are going through the roof space of front ones?
   

AlecK
Jun 03 2017 06:43

If - as stated - they are submains to each from common point, electrically they are all parts of same installation. No different from any other MSB supplying several DBs, the submains have to pass through other parts of the installation to get to where they are wanted. Simply not an issue.

The only restriction in wiring Rules comes if the flats / shops / whatever are separate installations. Remembering that separate metering and even separate ICPs have NO bearing on whether they are separate installations; that's simply down to the definition of "electrical installation", which depends largely on "point of supply".

Even for separate installations, as long as they are separate cables and not in same wiring enclosure [3.9.8.2], there's no compliance issue. In new edition this rule will change to also prohibit same (closed) duct - which will be a pain for short ducts eg crossing under driveways will need a separate duct for each. Mainly aimed at u/g cabling, to reduce risk of people cutting into cable / conduit when some wiring inside is still alive.

The idea that cables that are part of one installation should not pass through another is a myth, and no different electrically from cables supplied by one DB passing through an area mostly supplied by another DB (or the MSB).

There could be a civil issue, but that depends on who owns what. For example, where o/h supply for one installation crosses the neighbouring property, it's called "aerial trespass".
For u/g supply, if the several separate properties each own a narrow strip of shared driveway, their mains can't even be in common trench but each must instead run through their own strip of drive - unless some sort of cross-lease or easement is in place.
So if your flats are on unit titles, with no common area for cables to run through, there could be a civil issue.