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Earthing and Bonding

Former Community Member
Former Community Member
Hi All


Working on a scheme whereby we have a private transformer serving the site - TN-S arrangement. This comes into the building, we then split to feed a switchboard in one part of the building which is existing, the second split heads to a new build part which has the second switchboard. This new build contains swimming pool. The supply to the new switchboard is via a busbar 3L+N+PER. Question relating to earth bars - we currently have the main earthing bar at the intake point which is at the existing switchboard location - we then had cable feeding out to the new earth bar at the new switchboard location. Contractor is proposing that they remove this interlinking earth cable between bars, and take a bond directly from the new switchboard earth bar to the new earth bar in the room. Does this sound feasible - to me doesnt sound right, but I can't find anything specific to say not.


Many thanks
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    KC83:

    Essentially saying that the aluminium conductor within the interlinking busbar becomes the earthing and bonding conductor. So what i'm reading so far is that if the aluminium CSA is sufficient size to equal the main earthing conductor it should be okay to use this as both the protective earth and the bonding conductor?


    Generally, but not necessarily. I think that one has to be precise about the nomenclature. If "main earthing conductor" is the earthing conductor of the entire installation, I cannot think of any circumstances when any bonding would be larger than it. So earthing conductor selected i.a.w. Table 54.7 and main protective bonding conductor selected i.a.w. Table 54.8.


    If "main earthing conductor" means the link between the two parts of the building, it could be smaller than the bonding - see Andy's garden shed example above.


    For a combined conductor, just select the bigger of the two.


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  • 0
    KC83:

    Essentially saying that the aluminium conductor within the interlinking busbar becomes the earthing and bonding conductor. So what i'm reading so far is that if the aluminium CSA is sufficient size to equal the main earthing conductor it should be okay to use this as both the protective earth and the bonding conductor?


    Generally, but not necessarily. I think that one has to be precise about the nomenclature. If "main earthing conductor" is the earthing conductor of the entire installation, I cannot think of any circumstances when any bonding would be larger than it. So earthing conductor selected i.a.w. Table 54.7 and main protective bonding conductor selected i.a.w. Table 54.8.


    If "main earthing conductor" means the link between the two parts of the building, it could be smaller than the bonding - see Andy's garden shed example above.


    For a combined conductor, just select the bigger of the two.


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