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Equipotential bonding dilemma!

geov
I have an issue on which I would value your opinions.

I’ve been conducting EICRs in a building developed over the 16th, 17th and 18th centuries, more castle than domestic dwelling, though it is now providing around 20 flats. The properties were rewired in the early 80’s. I’ve found a number with no MEB to incoming water or gas or both. The issue is that the cut outs and consumer units are, without exception, the opposite end of the properties from where gas and water enter the properties.

It’s a listed building so nothing can be run externally, floors are polished hardwood ( not sure what vintage) and ceilings are ornate plasterwork.

Although all were rewired under one contract, many have had electrical alterations and additions since, except bonding. That said, the typical set up is a MK board with an up front 80A, 30mA rccb with 3871 type 2 mcbs for the domestic circuits, along with a separate off peak board serving storage heating. In the flats which have had gas installed, some of the former off peak circuits are now  radials with socket outlets with no rcd/rcbo protection.

Readings suggest PME/tnc-s supplies, a few have PME stickers.

So, to my question - is there any way I can address the lack of access to install bonds to water gas ( leaving aside ripping up historic floor boards or getting copper services changed to plastic)? Innovative, whacky, off the wall suggestions welcomed as are technically sound, difficult ones!

TIA
  • 0
    If the supplies are metallic, advise that isolating sections need to be inserted where they enter the building. 411.3.1.2
  • 0
    Chris - now why didn’t I think of that??
  • Former Community Member
    0 Former Community Member
    Hi geov, are there any main bonding conductors to the metallic services piping at the main intake position? If there are then you shouldn't need any main bonding conductor in each flat.
  • 0
    Each property has its own incomer, cut out & meter. There are two landlord supplies (agin with their own meters and cut outs) in different parts of the building, but no water/gas services in these locations.
  • 0

    Chris Pearson:

    If the supplies are metallic, advise that isolating sections need to be inserted where they enter the building. 411.3.1.2




    I think that all gas pipes within a building have to be metal Chris. So gas supply pipes run in a floor screed or which are extraneous-conductive-parts will still need to be main bonded. 411.3.1.2.


    Z.

  • 0
    I would make the main visible bonding conductor a "feature". We need an attractive acceptable conductor. Why not make the visible protective bonding conductor a polished lacquered solid copper rod arrangement? 543.2.1 (iv). It could have lovely brass engraved warning notices attached to it at regular intervals warning about its purpose and damage or removal of it will incur the death penalty. You don't want ugly green and yellow insulated cables surface run, that would look awful.


    Z.
  • 0
    I might check that all the extraneous and exposed metalwork throughout the building has continuity and an appropriate earth loop impedance can be obtained at every accessory and socket outlet. If all is acceptable then I might take a veiw....


    Legh
  • 0
    Can you determine the type of supply cabling to the cut outs?

    Readings suggest PME/tnc-s supplies, a few have PME stickers.



    If a few have PME stickers, assume the whole lot is the same.  As for risk I would concentrate on the individual flats and what is likely to introduce a differing potential  into each. So protective bonding on metallic services where they enter the flat or where you can first see it and touch it may well be required. You say some have, some have not. I do not think you need to go from each flat all the way back to where the metallic services enter the main building.  The main/whole building is the landlord bits [ x2 ], technically these could require protective bonding, but where could you simultaneously touch these parts and the exposed conductive parts of the landlords distribution board/ switchgear [ if they are metal ] or exposed conductive parts of the final circuits of the landlords installation? Can you grab both gas and water pipes anywhere in the landlord bit? If so a 10mm or 16mm earth link between would solve that. So the "landlord" bit may not need it, but if each flat has its own bonding internally, this is common with the suppliers earth terminal and the landlords supply should also be common with that. The whole thing is in one building. Perhaps the individual flats that have no protective bonding and it is required, are the ones who are going to have to bite the bullet.
  • 0
    Having re-read, each individual flat has DBs/ cutout  at opposite end to incoming gas/water [ to flats ].

    There may be a wacky solution.... Making an assumption original water service is one incoming pipe then branching to 20 differing locations [ flats ] and it is continuous metal.  Use this as protective bonding conductor for whole building. Somewhere you may be lucky that a cut out position is not too far away from this water pipe, so you you could make a sort of building earth marshaling terminal with a suitably sized earthing conductor, route and aesthetics permitting. Then, with even more luck, the incoming gas and water in each flat are fairly close, so make and bond between water and gas. Non -standard, but a possible solution.
  • 0

    geov:

    Chris - now why didn’t I think of that??




    What you have described is a large building. Why bond each flat separately (arguably supplementary equipotential bonding) when you could bond the whole building?


    Also, bearing in mind the installation in the early 1980s, it may be that the apartments without bonding are appropriate, whereas those with bonding have been over-bonded.

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