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More unprotected wiring inside CU on TT. (..SPD cables)

justinneedham
Since Amd 3 and much arguing, the industry and IET seem to have become more settled about use of no up-front RCD on all TT when using all-RCBO installation in metal boards. (GN3 takes a slightly more dim view of doing this on split load boards due to the unprotected feeds to the RCCB’s).

Since we are now duly fitting SPD device directly after the main switch, even on an all RCBO set-up, we have now added additional non-RCD'ed vulnerable wiring - The cable loop from MCB to SPD, or depending  if MCB is not necessary for the SPD, maybe from main switch direct to SPD. Since few manufacturers yet seem to offer factory made cables or a specified methodology to do this, (Some do- Hager being one, most don't), connectivity is likely as not to get made up on-site, maybe not as reliable as they could otherwise be, and certainly outside the control of the board manufacturer.

So does this raise the bar WRT the practice on TT of neglecting to fit up-front S type on all RCBO board? There are certainly now more flappy bits to fall out than there were. -  Do we still rely on our good workmanship and tight connections or does it suggest up-front 100mA S type in place of main switch needs to be a recommendation again?

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    Zoomup:

    With TT installations I install a 100mA S type R.C.D. in an insulated enclosure before any metal enclosed consumer units.  This design provides me with a better protection to future serious legal action than any other method. REC2s are contained in insulated enclosures and are situated before the consumer unit, so why not my S type R.C.D as well?


    Z.




    Indeed, it seems to be assumed that metal enclosures are necessary. But BS7671 merely says non combustible (or similar, not got the book to hand). I'd be MORE than happy to install an up front RCD in a self extinguishing plastic enclosure.  (Work in a fairly large town so not too much TT around)

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  • 0

    Zoomup:

    With TT installations I install a 100mA S type R.C.D. in an insulated enclosure before any metal enclosed consumer units.  This design provides me with a better protection to future serious legal action than any other method. REC2s are contained in insulated enclosures and are situated before the consumer unit, so why not my S type R.C.D as well?


    Z.




    Indeed, it seems to be assumed that metal enclosures are necessary. But BS7671 merely says non combustible (or similar, not got the book to hand). I'd be MORE than happy to install an up front RCD in a self extinguishing plastic enclosure.  (Work in a fairly large town so not too much TT around)

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