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The Downing Street problem

AJJewsbury
No, nothing to do with politics - just earthing and bonding - just recent events have perhaps given us an interesting example.


As I'm sure everyone has noticed of late, No.10 Downing Street has a nice electric lamp for its front door - supported by an arch from the iron railings. Similarly, immediately next door to the left (contrary to usual UK practice, designated No.11) also has lights fixed from the railings - two in this case, at least one of which appears to share the same railing system as No.10.


If pictures help: No.10 and No.11


For the sake of this discussion let's assume No.10 and No.11 have separate DNO supplies and the light fittings are all Class I.


If you had to do the design for feeding the lights outside either or both premises (and had no ill-intent to the occupants) what sort of earthing and bonding arrangements would you specify? (and would regulation 714.411.3.1.2 figure in your thinking?)


  - Andy.


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  • Former Community Member
    0 Former Community Member

    AJJewsbury:





    For the sake of this discussion let's assume No.10 and No.11 have separate DNO supplies and the light fittings are all Class I.


    If you had to do the design for feeding the lights outside either or both premises (and had no ill-intent to the occupants) what sort of earthing and bonding arrangements would you specify? (and would regulation 714.411.3.1.2 figure in your thinking?)


      


     




    Hi Andy, what does that reg say, I haven't any books with me, and are both properties PME?


    If both are Pme, the only thing I can think of would be adding a class 1 light to railings already earthed via next doors class 1 light would mean that both cpcs could be affected if there should be a supply neutral failure in either property, presuming all other services are modern plastic and there are no other main bonded shared metallic parts? 

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  • Former Community Member
    0 Former Community Member

    AJJewsbury:





    For the sake of this discussion let's assume No.10 and No.11 have separate DNO supplies and the light fittings are all Class I.


    If you had to do the design for feeding the lights outside either or both premises (and had no ill-intent to the occupants) what sort of earthing and bonding arrangements would you specify? (and would regulation 714.411.3.1.2 figure in your thinking?)


      


     




    Hi Andy, what does that reg say, I haven't any books with me, and are both properties PME?


    If both are Pme, the only thing I can think of would be adding a class 1 light to railings already earthed via next doors class 1 light would mean that both cpcs could be affected if there should be a supply neutral failure in either property, presuming all other services are modern plastic and there are no other main bonded shared metallic parts? 

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