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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
    Hi Geoff,

    Interseting one.

    First thing is to decide what bonding is required to the regs.

    If, as stated, sections of replacment with plastic can mitigate some then good hoh.

    Where you must run a bond then Zoom`s idea of making it a feature has great merit.

    As for listed building status, that must (if it comes down to it) take second place behind safety therefore BS 7671 is paramount (unless you can make an alternative equally as safe (caveat emptor though).

    Work together with rural england or whatever the listers are called but remember that your side takes precedence.

    Good luck and please let us know the outcome.
  • 0
    Well peeps, the view from Gas Safe engineers is that they are not permitted under their Regs to instal a plastic insert to “break” the continuity of the copper gas pipe?.


    We have since found what we believe to be the main gas incomer and a possible route from there to one of the landlords supply intakes. If we manage to bond between these points, do the individual flats with gas still need to be bonded to their local met - I thought they did.

  • Former Community Member
    0 Former Community Member

    geov:

     If we manage to bond between these points, do the individual flats with gas still need to be bonded to their local met - I thought they did.

     




     

    Good engineering practice would say yes, as it reintroduces a local zone of protection for each demise - BS 7671 isn't so prescriptive  - so if you can bond the intakes, then you probably wouldn't each flat, for minimum compliance


    Break down the components of extraneous-conductive-part - does it introduce a potential not already present and can it be touched


    OMS
  • 0

    geov:

    Well peeps, the view from Gas Safe engineers is that they are not permitted under their Regs to instal a plastic insert to “break” the continuity of the copper gas pipe?.


     



    Don't they have "insulating sections" at the meter to do just that?


    Depending on where the meter is, this may achieve the desired result.
     

  • 0
    Certainly the gas meters in the houses round here give a  metallic connecition from inlet to outlet.

    The offical advice (quoting form) here

    ENA Engineering Recommendation G12 published by the Energy Networks Association



    ENA Engineering Recommendation G12 Issue 4 Amendment 1 December 2015 Requirements for the Application of Protective Multiple Earthing to Low Voltage Networks contains clause 5.2.1 which states: 



    Provision of earth terminal requires that where a metallic gas service is provided to a consumer’s premises with a PME earth terminal, an insulated insert should be fitted in the gas service.



    HistoricalnotefromENA:



    Prior to these standards (in particular IGEM GL/5), IJs were occasionally installed downstream of the ECV. This was to comply with PME requirements, and so these IJs are still required. 



    IGEM/G/5 Edition 2 document published by the Institution of Gas Engineers and Managers



    IGEM/G/5 Edition 2 document (clause 11.2) contains requirements for insulating fittings. Clause 11.2.1 states:



    … insulating fittings shall be installed in all metal pipe, whether gas carrying or containing a PE liner, capable of providing electrical continuity between earth and the above ground pipework.



    Clause 11.2.2 states:



    Insulation fittings shall be installed in accessible location as close to the pipes entry into the building or, in the case of external pipework, as close as possible to the pipes exit to the ground and upstream of any ECV. The uninsulated section of the exposed pipe shall be as short as possible.

     




    Now by saying it has to be before the ECV, and therefore before the gas meter, it is not in the remit of Gas Safe, but Transco - who on the transmission and distribution side of things are allowed to use plastic pipes and fittings.


    Plastic pipe and fittings after the meter would be considered  a big 'no',, and is probably what the Gas Safe chaps are thnking of when they say they can't do it.


    Sometimes referred to as a monolithic insulating joint or 'MIJ' by some maker's literature.


  • 0

    mapj1:

    Certainly the gas meters in the houses round here give a  metallic connecition from inlet to outlet.

    The offical advice (quoting form) here




    Provision of earth terminal requires that where a metallic gas service is provided to a consumer’s premises with a PME earth terminal, an insulated insert should be fitted in the gas service.




    In the OP, we are told that some of the flats' installations have PME stickers, so it probably doesn't apply in this case; but the above quote doesn't help where a TN-S supply has been "PME'd" subsequent to the installation of a metal gas pipe all the way to the meter. 

  • 0



    It’s a listed building so nothing can be run externally,..




    Buried?

  • 0
    We are talking PME bonding here, so at the main intake position the services , water, gas etc will need to be sized to the incomer. For say a 3x200amp which is likely on this project the bonds will be 25mmsq. (Earthing conductor 35mmsq). Each flat will need to be bonded with 10mmsq and 16mmsq Earth lead. You cannot have a mix of earth types in blocks of flats where PME is utilised. This is a statutory requirement, not to be confused with "wiring regulations" where a separate earth return or RCDs are used, Furthermore, non bonding on services where insulated inserts are fitted is not permitted. "Wiring regulations" installations such as BNO blocks are non statutory.


    Regards, UKPN.
  • 0

    UKPN:

     Furthermore, non bonding on services where insulated inserts are fitted is not permitted. 



    I will translate that.

    "Bonding on services where insulated inserts are fitted is mandatory."



    Where would you connect the bonding conductor?
     

  • 0

    I would make the main visible bonding conductor a "feature".



    Or if it's the sort of place with ornate skirting boards/architraves, the old school approach was to buckle clip cables somewhere within the moulded areas and paint over - they then bend in and become quite unnoticeable.

     

    We are talking PME bonding here, so at the main intake position the services , water, gas etc will need to be sized to the incomer. For say a 3x200amp which is likely on this project the bonds will be 25mmsq. (Earthing conductor 35mmsq).



    But what if there isn't a single main intake position? - the OP seems to imply that each flat has its own independent supply straight from outside (I've certainly seen multiple commercial units within a single building of a similar vintage done that way).


    This is a statutory requirement, not to be confused with "wiring regulations" where a separate earth return or RCDs are used, Furthermore, non bonding on services where insulated inserts are fitted is not permitted. "Wiring regulations" installations such as BNO blocks are non statutory.



    Which statutory documents says this? I can't find anything like that kind of detail in the The Electricity Safety, Quality and Continuity Regulations 2002 and I don't know of any other current legislation in this area so it would be useful to know what I've missed.


      - Andy.

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