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EV TN system

lyledunn
722.312.2.1 in IS10101:2020 has only one stipulation and ignores all the TN-C-S issues highlighted in BS7671 2018 A1 regarding PME even though the vast majority of installations in Ireland are PME.

It says; "In TN system, the final circuit supplying a connecting point shall be a TN-S system". A rather unusual way of putting things. It sounds almost like a bit of bad translation. More to the point, I always thought that unless you had an intervening transformer TN-S referred to the whole system from source to final connected equipment.
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    I always thought that unless you had an intervening transformer TN-S referred to the whole system from source to final connected equipment.

    Logically it does - but that hasn't stopped standard writers who perhaps should have known better coming up with phrases such as "The usual form of a TN-C-S system is as shown, where the supply system is TN-C and the arrangement in the installation is TN-S" (thankfully removed from the latest version of BS 7671 but has been there previously, and I've seen very similar wording on other standards too, so presume it was copied from somewhere common).


    Perhaps Ireland has a less unreliable PME system than the UK?


       - Andy.
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    I always thought that unless you had an intervening transformer TN-S referred to the whole system from source to final connected equipment.

    Logically it does - but that hasn't stopped standard writers who perhaps should have known better coming up with phrases such as "The usual form of a TN-C-S system is as shown, where the supply system is TN-C and the arrangement in the installation is TN-S" (thankfully removed from the latest version of BS 7671 but has been there previously, and I've seen very similar wording on other standards too, so presume it was copied from somewhere common).


    Perhaps Ireland has a less unreliable PME system than the UK?


       - Andy.
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