Earth Rod. Milton Keynes.

Chris Pearson:

Why was the board changed? He showed us the innards of the old one and told us that they were still in good condition.


He didn't explain the Zs of 1.4 Ω at the hall socket. Could it have been via bonding to gas or water (or both) and thence to a supplier's earth elsewhere in the street?


We couldn't see the service head so let's assume that the N-E link was open. I wonder whether anybody enquired whether a supplier's earth might have been available. If it had been, it would have avoided that unsightly conduit running up the front wall.


All a bit odd!

I know the area Chris, and P.M.E. earthing would normally be available.


Years ago when the houses only had a TT supply I expect that the V.O.E.L.C.B. earth rods would have been installed much too close to underground metal service gas and water pipes, so were not out of the effective resistance areas of such. This would have compromised the safety operation of the V.O.E.L.C.B.s. 


Even though parallel earth paths existed to the earth rod it was not always the case that danger was present. Crabtree suggested that this may have been a good thing as a, It reduced nuisance tripping of the V.O.E.L.C.B.

b, It may actually allow the operation of protective devices like fuses or circuit breakers.


and the V.O.E.L.C.B. would still protect earthed installation metalwork against Voltage up to 50 Volts maximum if the rod was out of the resistance area of parallel earths.


I expect that water and gas pipe bonding produced his low loop impedance rather than the building fabric.


Edit. Add. In this area the main fuse is in a separate insulated carrier  sealed with wire, and the neutral block is also in a separate sealed block, Henley block  style. So not both in one cutout head..


Z.

Chris Pearson:

Why was the board changed? He showed us the innards of the old one and told us that they were still in good condition.


He didn't explain the Zs of 1.4 Ω at the hall socket. Could it have been via bonding to gas or water (or both) and thence to a supplier's earth elsewhere in the street?


We couldn't see the service head so let's assume that the N-E link was open. I wonder whether anybody enquired whether a supplier's earth might have been available. If it had been, it would have avoided that unsightly conduit running up the front wall.


All a bit odd!

I know the area Chris, and P.M.E. earthing would normally be available.


Years ago when the houses only had a TT supply I expect that the V.O.E.L.C.B. earth rods would have been installed much too close to underground metal service gas and water pipes, so were not out of the effective resistance areas of such. This would have compromised the safety operation of the V.O.E.L.C.B.s. 


Even though parallel earth paths existed to the earth rod it was not always the case that danger was present. Crabtree suggested that this may have been a good thing as a, It reduced nuisance tripping of the V.O.E.L.C.B.

b, It may actually allow the operation of protective devices like fuses or circuit breakers.


and the V.O.E.L.C.B. would still protect earthed installation metalwork against Voltage up to 50 Volts maximum if the rod was out of the resistance area of parallel earths.


I expect that water and gas pipe bonding produced his low loop impedance rather than the building fabric.


Edit. Add. In this area the main fuse is in a separate insulated carrier  sealed with wire, and the neutral block is also in a separate sealed block, Henley block  style. So not both in one cutout head..


Z.