Fault on Ring Main


Postby charliewm » Mon Aug 09, 2010 9:48 pm

Fault has developed on a ring circuit. There is end to end continuity on each conductor and the insulation tests on L/N, L/CPC/N/CPC although low (5.70) is not 0.00. The problem is that half the sockets work and half do not. My feeling is that the neutral return has broken down but yet there is continuity. Any ideas would be appreciated.
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Postby sparx » Tue Aug 10, 2010 8:33 am

hi,
a couple of thoughts....
assuming good equal end to ends, it may be that you have a bridged ring, or if all u/s sockets are in same area it may in fact be a looped spur with a loose connection which end to ends won't show.
I assume these u/s ones aren't in a conservatory or such like which could have been fed from ring via a hidden FCU with a blown fuse! have had both of these before.
The correct way to find this kind of fault is to do a fig 8 connection at consumer unit so start of L goes to end of N & vice-versa, then when L-N resistance checked at each socket should be all the same, any higher reading ones will not be on the ring, the reading will climb the further along a spur you go.
Presume from your post that you have sufficient 'competance' to do this safely.

regards
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