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Very long meter tails - is this proposed arrangement OK?

Chris Kessell

I would be grateful if someone could give this a sanity check...

We live in a bungalow, and the electricity meter and consumer unit are currently located side-by-side in an internal cupboard.  The DNO (Western Power) service cable to the house runs from an overhead line to the gable end of the bungalow and then around the external walls and into the back of this meter/CU cupboard. 

However, we're planning an extension which will require the service cable to be relocated because part of the wall it runs along is to be demolished.  A team from the DNO has visited to discuss the matter.  

We had hoped they might be able to simply reroute their service cable through the loft space to the existing meter location, but this isn't permitted.  However, they explained that the meter tails are our responsibility and hence could be run through the loft.  Hence their proposed solution is to fit an external meter box to the gable end wall of the house, relocate the meter into that, and run the meter tails through the loft space to the CU.  The distance from meter to CU would then be about 15m.

This arrangement was proposed by the DNO so I assume it's OK, but I have read (including in the DNO's own guidance literature) that meter tails should be no more than 2-3m long.  Ours would be at least 15m long!  So does their proposed solution sound reasonable?  Are there any potential issues I ought to be aware of?

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  • 0

    You need to ensure that the tails are suitably protected (e.g. upfront RCD and/or mechanical protection) if they run in places where they might get damaged, e.g. buried in plaster less than 50mm deep.

  • 0 in reply to wallywombat

    And in lofts get attacked by vermin such as mice, rats or squirrels.

    Z.

  • 0 in reply to wallywombat

    An upfront single R.C.D. may cause total loss of an electrical supply. Not a good design in my opinion.

    314.1.

    Z.

  • 0 in reply to Zoomup

    in a TT system, an upfront RCD of some sort is unavoidable though. Even if its a 100mA S type or 300mA S type or what ever the case might be.

  • 0 in reply to tattyinengland

    and that is the sort of thing that really will only trip when you need it to. 

    You could argue the same single point of failure about the 100A supply fuse.Very few folk argue for its omission - well perhaps those wiring up dope farms ;-)

    A row of 300mA delay RCDs one  per SWA submain out, is actually quite a sensible and common TT arrangement for rural factories farms etc.
    Mike

  • 0 in reply to mapj1

    You would surely agree Mike that a 100 Amp cartridge fuse is not as sensitive as an R.C.D., and liable to disconnect for numerous, (not always identifiable) reasons. Even time delayed "S" types can disconnect for no apparent reason.

    I had an upfront 100mA "S" type R.C.D. trip off when supplying several R.C.B.Os in a new consumer unit in a modest bungalow. I never found out why. It got changed to a 100 Amp. D.P. switch after the installation was converted to P.M.E. earthing.

    Z.

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  • 0 in reply to mapj1

    You would surely agree Mike that a 100 Amp cartridge fuse is not as sensitive as an R.C.D., and liable to disconnect for numerous, (not always identifiable) reasons. Even time delayed "S" types can disconnect for no apparent reason.

    I had an upfront 100mA "S" type R.C.D. trip off when supplying several R.C.B.Os in a new consumer unit in a modest bungalow. I never found out why. It got changed to a 100 Amp. D.P. switch after the installation was converted to P.M.E. earthing.

    Z.

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