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Preparing a flat for renting

Harry Macdonald
Hi all,

I would be very grateful for some advice. 

My daughter is having her Edinburgh 1st floor flat prepared for renting and it needs some work highlighted by an electrical safety report. Some things have been noted as requiring remedial work that seem odd to me:
  • Two sockets are noted as being wired in Aluminium Twin & Earth cable. Is this likely? It looks to me like stranded copper.  Would it need replacing even if it is as this would be a pig of a job as the wiring is under a laminate floor.

  • The electrician has quoted for adding rubber grommets to all socket back boxes. I know that this is good practice but is it necessary before a property can be rented.?

  • The gas meter is plastic with metal pipes in and out. It is in the ground at the front of the house. Immediately through the wall is the termination point for the DNO supply with a big earth terminal with the rising (copper) gas pipe a few inches away. The Electrician says that the incoming gas supply must be bonded to the Flat main earth point, i.e. up the stairs and across a doorway and not the the building main earth point. Is he correct?


I have a photo but I can't work out how to upload it. It says drag but that doesn't seem to work.
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    The electrician is misguided, there must be a bonding conductor of min 10mmsq on each service in each dwelling to create a equipotential zone at the point of entry and after the meter.  Furthermore at the point of entry in the intake and after an isolator of the building there must be a bonding conductor with a size meeting the incomer.


    Regards, UKPNZap
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    I read the original post as saying the meter for the flat is in a Semi concealed meter box


    Now I have to recall what I learnt in a JP earthing and bonding masterclass
  • 0
    Each flat is an installation so requires bonding where the pipe work enters the flat.

    Isn't BS 7671 a bit agnostic on that point? Especially if the DNO supply arrives at a single point for the entire building. If the designer was to say that the installation covered the entire building and supplies to individual flats were just distribution circuits of the larger installation and any bonding within each flat was merely supplementary building, what regulation(s) say otherwise? Physically bonding once at the intake would be exactly what would be required if it were one large house that hadn't been subdivided into flats or were say a hotel with just the same number of rooms - so where's the actual danger if individual flats don't duplicate main bonding? These days with DNO abdicating responsibility for building networks, it's likely BS 7671 applies between the intake an individual flats anyway.


    I agree the T&E sounds more like imperial sized copper - copper conductors were originally tinned to prevent a reaction with compounds in rubber insulation, but the practice continued into the early days of PVC. A quick file on the end of a conductor should show up the copper underneath.


       - Andy.
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    Well what is it! Air B and B?!

    Regards, UKPNZap
  • 0
    Thanks all.

    The gas meter is in a semi buried box against the front wall of the building and immediately through the wall is the DNO incomer with the copper gas pipe to the flat above very close. The boiler is directly above supplied by a 2.5mmsq 16A supply.

    The CU for the flat is in the middle of the building surrounded by laminate flooring so it would be a pig of a job to get a 10mmsq wire from the CU to the boiler.

    My question is therefore is it acceptable to bond the gas pipe to the DNO earth terminal, which is presumeably connected to the CU earth, or does it have to be direct from the CU? If so, which reg says so.

    I'll try again with the photo of the 2.5mmsq cable254c4b84c2d0b8517f7826954a587354-original-20200730_141505.jpg
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    The bond has to be connected to the MET, which is the first point where the earthing conductor can start splitting. At the moment it sounds like your MET is the CU earth bar, but there's no reason why the MET can't be moved to be next to DNO cutout - but use a separate MET bar rather than directly using the DNO's earth terminal as the MET.
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    Thanks Wallywombat. The problem with this is that there is no good route for a new cable from the DNO incomer, at the front at ground level, to the CU, in the middle of the building at first floor level.

    As I understand your proposal, a new cable would need to run between these points and the existing cable armour cannot be used, even though it is clearly adequate other wise the whole installation is not earthed.

    The electrician is proposing running a 10mmsq up the skirting board along side the stairs and over a couple of doorways.
  • 0
    Harry Macdonald:

    254c4b84c2d0b8517f7826954a587354-original-20200730_141505.jpg




    From looking at the picture I would say that’s tinned copper and I am  99.9% certain I can see the yellow of the copper showing through the tin.


     If you are there scratch some of the tin off to be absolutely 100% sure, you know what copper looks like.


    Andy Betteridge 


  • 0
    seconded fort that being tinned copper - as well as the visible gold flash at the neutral tips,  if you try and  twist ally like that it snaps.

    I presume your inspecting sparks is young and keen, but has not had much to do with real installations - there must be thousands of miles of this still in service, which makes you  wonder about his other comments..


    (tinning was originally  because the sulpher in vulcanized rubber tarnishes the copper quite quickly  - and when PVC cable first came in, it was a direct copy of the existing rubber.

    Now there is almost no rubber left in service that is not obsolete, the need to tin coat has disappeared except in cables for use hostile atmospheres, or w here even a little corrosion would be catastrophic, like very thin wires..)
  • 0
    Harry Macdonald:

    Thanks Wallywombat. The problem with this is that there is no good route for a new cable from the DNO incomer, at the front at ground level, to the CU, in the middle of the building at first floor level.

    As I understand your proposal, a new cable would need to run between these points and the existing cable armour cannot be used, even though it is clearly adequate other wise the whole installation is not earthed.

    The electrician is proposing running a 10mmsq up the skirting board along side the stairs and over a couple of doorways.


    Your description has completely lost me I'm afraid. Your original question seemed to be whether you could terminate the bonding at the cut out rather than at the CU, and I was answering with a qualified "yes"


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