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Bonding matters

Discussion in 'Electrics UK' started by timbim, 13 Aug 2014.

  1. timbim

    timbim

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    I've done some plumbing work recently, without considering the implications this may have on bonding. I've read a few things and only really become more confused. There are two main areas of concern that I have.

    1. A resin sink has been replaced with stainless steel. The (metal) tap is now connected to the (copper) plumbing with flexible hoses where before it was soldered directly. The sink has a macerator installed on the half bowl. The wastes are all plastic.
    2. A pipe running to an outside tap has been interrupted by a plastic fitting between the bonding point and the (metal) outside tap. The pipe is not buried in the ground at any point, the tap is on a brick wall in a paved area.

    My understanding is that I don't need to bond anything (indeed, the sink isn't fitted with any provision to bond), but someone has previously bonded just about everything in sight so I'm not too sure.

    Thanks
     
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  3. securespark

    securespark

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    Is this a college/ theoretical question?

    Is it a domestic or commercial environment?

    What does BS7671:2008 say about bonding in kitchens?
     
  4. EFLImpudence

    EFLImpudence

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    Supplementary bonding is not rquired in a kitchen.
    I presume the macerator (right word?) is earthed.

    It will be better like that.

    You are correct - as long as the Main Bonding of the services at the entry point of the premises is applied.
     
  5. timbim

    timbim

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    Thought as much
    It is earthed, and it would appear that I don't call it what everyone else calls them.

    Plastic water supply, but there is buried copper supplying another outside tap. Remaining plumbing (all copper) remains bonded.

    Thanks.
     
  6. ericmark

    ericmark

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    Back to basics why bond.
    The advantage of bonding is any fault will likely cause automatic disconnection before any one is injured by the fault. And it stops faults from being transmitted from one room to another. Typical is a standard lamp falling on a radiator so the filament touches the radiator is visible in the room where it has happened so people in the room are aware of the danger but if that fault is transmitted by the pipes to another room then people are unaware of the danger. Either bonding so the lamp supply auto disconnects or isolating with plastic pipe will both ensure the fault is not transmitted into another room.

    The disadvantage of bonding is it means there is a return path. Bird on the power cable is OK as it is not connected to any return path so with no bonding anyone touching a live part is less likely to get a lethal shock.

    So using RCD protection it is considered no bonding likely is the lesser of the two evils but without RCD protection to bond is considered as the lesser.

    So as to if bonding is required or not depends on what version of the regulations the installation has been wired to. Wired to BS7671:2008 then bonding is not required but wired to 13th edition where lights do not have earths then yes bonding is required.

    As to 14, 15, and 16th it is hard to give a definitive answer as I of hand can't remember what was required but to date there is with the exception of special earth free installations nothing to stop one bonding so simple thing if not sure then bond.
     
  7. JohnW2

    JohnW2

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    Sorry, eric, and with respect, but that is NOT bonding, or the reason for bonding - you're talking about earthing

    Bonding exists for only one reason - to minimise the pd between two parts, and it's nothing to do with facilitating the operation of protective devices (which si what earthing is for).

    Kind Regards, John
     
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  9. EFLImpudence

    EFLImpudence

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    No. That's Earthing. Bonding is nothing to do with ADS,

    No. That's Earthing.
    We do not have to cater for such occurrences.

    No. Transferring such occurrences is not a consideration.

    No. There will already be a path to Earth via the Earthing.
    If there is not (not Earthed) then the part should not be bonded.

    Not likely in a house.

    No. Earthing where required will disconnect the supply.
    Lamps falling on metal parts (spoon) is not a consideration.

    No.

    No. Bonding equalises the potential between two parts that may be touched simultaneously.

    No. Main Bonding of extraneous-conductive-parts is mandatory.

    Don't understand.

    No. Bonding must be brought up to current regulations.

    No. If unsure, get someone who is.
     
  10. ericmark

    ericmark

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    Although in theroy bonding is not earthing since some metal item in any room is likely to be earthed in real terms it is the same.

    However if one is sure bonding is not earthed then yes you have a valid point but I would expect something is always earthed.
     
  11. EFLImpudence

    EFLImpudence

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    No theory. Parts only requires bonding because they are earthed.

    If the bonding is not earthed then it is not needed and could be removed.
     
  12. ericmark

    ericmark

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    That is what I said bonding and earthing are the same thing as if not earthed bonding not required.
     
  13. ericmark

    ericmark

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    OK not quite true I bond items to ensure no RF interference and as we get into UHF then more like plumbing than wiring with wave guides but as far as a standard house bonding and earthing are the same.
     
  14. JohnW2

    JohnW2

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    If an item is already earthed, then that will facilitate ADS - so you do not, as you suggested, need additional bonding to ensure that you have ADS.

    The most important type of bonding, Main Protective Bonding (or Main Equipotential Bonding), has got absolutely nothing to do with the operation of protective devices.

    Kind Regards, John
     
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