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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?

  • +1

    Pretty standard arrangement to be honest.  Your electrician will just have to fit a switch fuse in the meter box to protect the tails as the dno don't like it if they are over 3 meters long. Strictly speaking the switch fuse shouldn't be in the meter box however they don't tend to worry about it so long as there is adequate space for all of their own equipment.  It would probably be better run as an SWA cable rather than standard meter tails as well.

    Gary

  • 0 in reply to aligarjon

    That's reassuring, thanks.  I did suggest to the DNO team that an isolation switch may be prudent in the meter box but a switch fuse would be more sensible.  I'm just surprised they didn't insist on it given the cable length. 

  • +1

    Overhead lines? Is the current system TT? (Earthing from your own rod)

    If so, you'd likely need not just a switchfuse but an RCD as well at the meter end - especially if using an earthed wiring system such as SWA.

       - Andy.

  • 0 in reply to AJJewsbury

    Yes, it is TT.

    As it happens the earth rod will also need to be relocated as it lies under the proposed extension; the DNO agent suggested putting the new rod below the new meter box for cabling convenience.   

  • 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 Chris Kessell

    Can't you get the earthing upgraded to P.M.E? Ask for a new P.M.E. earthing terminal if permissible. Around here it is provided for no charge.

    Also, around here (East Anglia) incoming supply cables are run in lofts.

    Z.

  • 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

    The DNO (Western Power) guy insisted it had to remain a TT arrangement.  Not sure why - perhaps something to do with power coming from an overhead pole.

  • 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.

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