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SPD Installation...

Hi All,

A few of questions regarding stand alone SPD installation to domestic properties...

1, Should a stand along SPD be fitted in a metal clad enclosure as I see many plastic options similar to the isolator type units fitted by DNO.

2, Do they need to be protected by MCB?

3 Can I install directly to spare connection in Henley block?

  • 1)  No, plastic is fine as it is not a consumer unit or similar switchgear. You may want to fit it into a metal enclosure, but it isnt required by BS7671 in domestic premises.

    2) Some do, some don't. I fitted an Hager CU recently with integrated SPD next to the main switch. No CB protecting it. However, 2 external ones I have fitted do require to be protected by an OCPD.

    3) Possibly, check the SPD manufacturers instructions.

  • Note that adding it as a "spur" at a Henley block is quite likely to exceed the recommended max length unless it butted right up against the block. Much better to have the SPD and enclosure inline with the tails, like an isolator.