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SPD sub main distribution installation.

wessex
Looking for a little clarity on using type 2 SPD protection in a sub main distribution board and the need to export a 16mm2 earthing conductor from the main earthing terminal. the idea fits regulations 534.4.8 and 534.4.10, but for me the idea does not spring from the regs. Looking at GN1, pages 61 to 65 and at table 3.13 doesn't  seem to give me much clarity. I'm missing something obvious. It leads me to think that a relatively small supply to an adjacent garage or garden workshop may require SPD protection at the destination and consideration given to running 16mm2 CPC.

Any clarity gratefully received or just point out the obvious.
  • 0
    I might be missing something too, but in my head you only need 16mm² connections for type 1 SPDs at the origin of the installation - on  the end of a submain using the installation's earthing facility I can't see either applying.


    If the submain fed a detached building that had its own separate earthing system (e.g. TT island) then you might want to repeat the origin SPDs there and if the installation needed type 1 ones then you might consider type 1 ones in the outbuilding too and so might want 16mm²- but then the connection would be to a local electrode rather than the c.p.c. in the submain - so still no need for a 16mm² PE conductor in the submain.


       - Andy.
  • 0
    Many thanks for getting back.

    Would it make any difference if there where no SPD protection at the origin distribution board to my supposed 16mm2 requirement and if so could it be negated by installation of SPD protection at the origin ?

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