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Using BS3871 MCB to protect ne submain

Alan B

Is it ok to connect a new submain to an existing spare 3 phase BS3871 MCB in a light industrial installation. The alternative is to change the entire main DB.

Submain will be clipped direct to wall and steel roof beam. It will feed a new 3 phase DB, probably equipped with two 3 phase 16A MCB's.

My understanding is that BS 60898 replaced BS3871 and the standards are similar, I am sure there are some differences, but do they make a significant impact on safety? In my mind providing they disconnect in the required time everything should be acceptable? Main risks will be after the sub board using modern devices.

Thanks

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    The device actually providing (intended to provide?) ADS needs to provide isolation (whether on purpose or by accident).

    But presumably not necessarily provide isolation by the same means as disconnection for ADS. A rewireable fuse for instance isn't guaranteed to provide a 3mm (or whatever) gap when it blows - so isolation must be provided by pulling the carrier. So a push-button Wylex-standard MCB for instance, could similarly provide isolation by being pulled - so perhaps doesn't have to provide full isolation via its contacts? (OK not much use for conventional MCBs that are hard wired-in, but as a point of order).

        - Andy.

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  • 0

    The device actually providing (intended to provide?) ADS needs to provide isolation (whether on purpose or by accident).

    But presumably not necessarily provide isolation by the same means as disconnection for ADS. A rewireable fuse for instance isn't guaranteed to provide a 3mm (or whatever) gap when it blows - so isolation must be provided by pulling the carrier. So a push-button Wylex-standard MCB for instance, could similarly provide isolation by being pulled - so perhaps doesn't have to provide full isolation via its contacts? (OK not much use for conventional MCBs that are hard wired-in, but as a point of order).

        - Andy.

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