mains supply to flats

[foghorn]

had a customer enquirey to change card meters in some flats each flat is fed with 10mm twin and earth and each flat has its own earth stake on fuse fusebox side of flat,each flat has a 30ma rcd inbetween incoming supply cable and fusebox. however there is no earth stake for the incoming supplies to each flat only earth stakes for the circuits from each fusebox, my question is and my thinking is install a earth rod for all supply cables to the flats at the front end of the installation have a 30 ma time delayed rcd for each 10mm cable as it is twin and earth buried into a wall
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any advice appeciated

 

[johnboy6083]

is this a TT system? if yes then yes, the submains from the ryfield ect must be protected by an RCD, as Zs wont allow compliant disconnection times. As you have said the best way of acheiving discrimination is with the use of S type devices. I would also have a decent rod at or near th intake position. whats your Ra for interest?

 

[foghorn]

it gets better no ryefield board only one single phase100 amp then henley blocks into x4 main switches and fuse then twin and earth to flats no rod at main incoming only from each consumer unit in the flats so as i see it the supply cables have no earth only the out going circuits from the consumer units in each flat so i cant see how i can legally replace card meters if no main earth for incoming supplies my thinking is needs ryefield board henley blocks into time delayed rdc for each supply to flats and new rod for incoming supply with 16mm main earth for each time delayed rcd then 100mm supplies to flats so now we have main earth for mains supply and 30 matime delayed for protection for supply cable.am i correct in what im thinking
thanls sorry to babble on

 

[johnboy6083]

if the earth rods are the property of the buildinmg owner/freeholder, then you could link them all tgether, and use that to provide a MET at the intake position, although i would like to see one there nyway. Is there any sign of overloading of the main tails, or is it adequate for its use?

 

[foghorn]

no signs of over loading at the tails but i think he definately needs to have time delayed rcd for each flat as its twin and earth buried in a wall gong from main switches to flats and i also think he needs to have seperate earth stale fo meter tails at the incoming seperate from thr flats i believe he will be wanting to upgrade to 3 phase as he wants the flats to have their own metering and energy networks wont do this with out the upgrade not had anything to do with ryefield boards either,