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How a simple job can go wrong quickly....

Former Community Member
Former Community Member
Not my work before I relate:


Existing 3-ph circuit breaker DB in a shop has a 30 mA 4 pole RCD belatedly fitted in a separate enclosure to provide blanket RCD protection. OK, not ideal.

Electrician asked to install extra 13 A socket-outlet in window during shop hours so padlocks off the circuit's circuit-breaker and proceeds, He lets the circuit neutral and cpc touch when fitting the socket-outlet and out trips the RCD as expected. Resets and shop keeper then announces that the card reader, till, air-con and some lights not working.


All that equipment now duff (technical term!).


For an interesting weekend quiz, what happened?


Without hindsight and the work being done during opening hours, what would you have done differently?


Regards


BOD






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  • 0
    I think that this is a design issue. Fitting a 3ph RCD to other than 3 phase loads is asking for trouble and shouldn't be done, as I have come across similar problems. My own solution would be to have a separate single phase DB for single phase loads, with its own RCD as required. Chris is right that perhaps RCBOs should be the correct choice, without a 3 phase RCD also, but there could also be some 3 phase sockets! This area probably needs looking at in BS7671, as it seems that more problems may be made by this supposed "safety" situation of RCD protection. It could be that some hefty single phase surge suppressors might have saved things but I am doubtful.
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  • 0
    I think that this is a design issue. Fitting a 3ph RCD to other than 3 phase loads is asking for trouble and shouldn't be done, as I have come across similar problems. My own solution would be to have a separate single phase DB for single phase loads, with its own RCD as required. Chris is right that perhaps RCBOs should be the correct choice, without a 3 phase RCD also, but there could also be some 3 phase sockets! This area probably needs looking at in BS7671, as it seems that more problems may be made by this supposed "safety" situation of RCD protection. It could be that some hefty single phase surge suppressors might have saved things but I am doubtful.
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