Earthing a spur to a surface box.


Postby DAVYESS » Mon Sep 14, 2009 2:43 pm

I hope to run a spur to a plastic ,wall mounted, twin switch, single pole socket in my conservatory. The donor socket has two twin and earths in it with the earth connection connected again to a lug in the corner of the metal box. As I have a plastic box for the receiving socket is it ok to connect an earth wire from the earth connection on the socket to a screw drilled through the back of the box into the wall?
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Postby chriscba » Mon Sep 14, 2009 6:26 pm

The plastic doesnt need earthing, only if the box is metal it needs a earth. Just connect your t&e from your socket to your spur, make sure you connect the earth in the socket connections.
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Postby sparx » Mon Sep 14, 2009 7:21 pm

Hi, Excuse the pun but there is no EARTHLY reason to connect an earth wire to ANY back box if wiring is in twin/earth! the Earth wires called CPC's should go direct to the earth terminal on the socket!
The unnecessary and in my view undesirable practice of crowding an unrequired wire in a cramped box is a piece of folklaw perpetrated by numpties at the NICEIC on their members.
This originates from a mis reading of reg.543.2.7 which says :
where using the earthed metal work of a wiring system such as conduit,trunking, steelwire armouring as the CPC then a wire shall be connected to bring the earth FROM the box TO the accessory, not vice-versa.
So in answer to your question connect CPC from donor socket to new sockets earth terminal, you can't earth a plastic box!

regards SPARX
Last edited by sparx on Fri Sep 18, 2009 10:11 pm, edited 1 time in total.
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Postby DAVYESS » Tue Sep 15, 2009 6:36 pm

Thank you for your helpful information. I liked the pun!

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Postby DAVYESS » Tue Sep 15, 2009 6:42 pm

[quote="chriscba"]The plastic doesnt need earthing, only if the box is metal it needs a earth. Just connect your t&e from your socket to your spur, make sure you connect the earth in the socket connections.[/quote]

Thanks for your help it clears up my query.
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