Ring Main route?


Postby bb700 » Fri Feb 18, 2011 6:12 pm

This query is for a friend.
He has moved to a bigger house which was recently profesionally re-wired
( bills & certificates etc. to prove).
He has found that one Ring main feeds the front halve of the house (two bedrooms , study & lounge) & the second Ring main feeds the other halve (back bedroom , living room & day room ). The kitchen has dedicated radial.
I must admit the house is an unusual shape & size.
Depending on the lay-out is this practice often used .
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Postby ericmark » Sat Feb 19, 2011 6:44 pm

Yes. The problem with the upstairs downstairs split is the lower floor can need too much cable to keep the earth loop impedance within the allowed limits with a large house because of the 1/3 rule in drilling beams. Splitting side to side needs less cable so one can get the earth loop impedance. Or where RCD's are used the volt drop within the limits set.

However some still frown on the idea. The problem is identifying what socket is fed from what MCB. In theory an electrician should isolate and a MCB will only isolate with a TN system so one should to be on safe side always turn off main isolator. But many don't follow the rules and isolate with the MCB's and don't prove dead as they should. So the less common split could catch out some one cutting corners. However think electricians should not cut corners and if they get caught out then really it's their own fault for not checking.
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