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SPDs in domestic DBs - no OCPD required.

alanblaby

Following a few debates here, and in other places about whether over-current protection is required for SPDs, BEAMA issued a statement in January saying, extra OCPDs are not always required for SPDs. Full details in the link below. 

As an aside, I do check the BEAMA site semi-regularly, but didnt spot this one until I had an email from Dehn yesterday.

Beama SPD guidance

Parents

  • So what is/was the intention?

    For SPD to contain their own suitable over-current protection (which deliberately omits the magnetic operation that MCBs have which can trip very quickly on very high currents - which is just what you don't want for SPDs) - if that can be accomplished with a blob of solder holding together a couple of spring contacts, so be it.


    What about BS 7671 Regulation 314.1 inconvenience?

    Well most of the time you won't need to isolate - the SPDs have a plug & socket arrangement. For other occasions it's a matter of balancing benefit against cost - we don't after all supply every socket and light fitting from its own dedicated overcurrent device. If you were fussed, a DP switch disconnector rather than a MCB might be a better choice.

       - Andy.

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  • So what is/was the intention?

    For SPD to contain their own suitable over-current protection (which deliberately omits the magnetic operation that MCBs have which can trip very quickly on very high currents - which is just what you don't want for SPDs) - if that can be accomplished with a blob of solder holding together a couple of spring contacts, so be it.


    What about BS 7671 Regulation 314.1 inconvenience?

    Well most of the time you won't need to isolate - the SPDs have a plug & socket arrangement. For other occasions it's a matter of balancing benefit against cost - we don't after all supply every socket and light fitting from its own dedicated overcurrent device. If you were fussed, a DP switch disconnector rather than a MCB might be a better choice.

       - Andy.

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