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Best location for a SPD

AncientMariner
Our existing supply arrangement is underground TN-S into the DNO's external access meterbox where the Cut-Out, Meter and DNO supplied 2-pole Isolator are located. From the Isolator 25mm tails through the wall to a Proteus metal cased 100 Amp Switch Fuse (Approx 19 x 31 x 6 cm) located where the original meter and CU were located. From the Switch Fuse, a 25mm sub-main of about 10 metres to Hager CU (plastic) in the attached garage.

The above all from when the house was rewired circa 2002.

We seem to have more than our fair share of lamp failures, GU10 Halogens and the GU10 LEDs that I replaced them with - Crompton and B&Q. Also 6-foot LED fluorescent replacements. Add to those, Broadband Routers and VoIP adapters. We are about 150 metres from the sub-station (which supplied underground).

As I see it, the only two locations for a SPD would be either at the Switch Fuse or at the Consumer Unit. I'm assuming that at the Switch Fuse would be preferable. Also, no other earth connection than the existing DNO supplied one from the TN-S supply?


Thanks.  Clive
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    +1 for at the CU - as wally says better to have the SPDs not too far from what's to be protected, plus better placed there to provide protection from surges due switching etc. on one circuit affecting other circuits.


    If main bonding is taken from the intake/switch-fuse rather than the CU however, there is an argument for having SPDs there - as the L-c.p.c. protection by more local SPDs could be undermined somewhat by class 1 items being in contact with extraneous-conductive-parts. I'm sure the manufacturers would recommend SPDs at every stage of distribution.

     

       - Andy.
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  • 0
    +1 for at the CU - as wally says better to have the SPDs not too far from what's to be protected, plus better placed there to provide protection from surges due switching etc. on one circuit affecting other circuits.


    If main bonding is taken from the intake/switch-fuse rather than the CU however, there is an argument for having SPDs there - as the L-c.p.c. protection by more local SPDs could be undermined somewhat by class 1 items being in contact with extraneous-conductive-parts. I'm sure the manufacturers would recommend SPDs at every stage of distribution.

     

       - Andy.
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