Earth and Supply Two Questions - Electricians Forum | Electrical Forum | An electrical forum for electricians in the UK

Pat Tester · 03-07-2008

On a barn conversion for a client fitted 3 way garage c/u with rcbo's to supply 16 & 30 amp sockets for site supply. This is in a GRP box supplied by 3 phase supply from EDF. They required an earth rod to be put in to connect up to meter. Client now wants supply routed into basement. Questions: Will EDF be happy to extend the swa from
transformer about 200 yards away into basement and put meter down there ? Would it be better to continue with external meter box and for me to run supply into basement and fit fused 3 phase isolator down there ?

Would you run 25mm tails in Conduit or use swa into basement about 15 m max

Another question: EDF have stated that 'PME will be provided 0.35 ohm so TN-C-S can be used if appropriate.' In 'area's of special risk' it is unlikely you can meet bonding requirements, so a TT system should be employed, and not to utilise the PME terminal. All circuits excluding Fire alarm will be on RCBO's.
In what instance would I need to use an earth rod and not the PME ?
As stated transformer is only 200 yards from supply.

Thanks in advance.

03-07-2008

Quote:

Originally Posted by Pat Tester

On a barn conversion for a client fitted 3 way garage c/u with rcbo's to supply 16 & 30 amp sockets for site supply. This is in a GRP box supplied by 3 phase supply from EDF. They required an earth rod to be put in to connect up to meter. Client now wants supply routed into basement. Questions: Will EDF be happy to extend the swa from
transformer about 200 yards away into basement and put meter down there ? Would it be better to continue with external meter box and for me to run supply into basement and fit fused 3 phase isolator down there ?

Would you run 25mm tails in Conduit or use swa into basement about 15 m max

Another question: EDF have stated that 'PME will be provided 0.35 ohm so TN-C-S can be used if appropriate.' In 'area's of special risk' it is unlikely you can meet bonding requirements, so a TT system should be employed, and not to utilise the PME terminal. All circuits excluding Fire alarm will be on RCBO's.
In what instance would I need to use an earth rod and not the PME ?
As stated transformer is only 200 yards from supply.

Thanks in advance.

well, anywhere where it not fixed for a start

Look at the exclusions from using PME in BS7671:2008, all quoting the ESQCR's:

caravans
construction sites (except fixed building such as canteens)
marinas
mobile/transportable units

etc etc