Earthing systems

Papa_Bear

Hi all,

Im just wondering what earthing system is used in a suburban housing estate that's approx 60 yrs old. Im guessing it's a TN-C-S system. What confuses me is that there appears to be only two main service cables entering the house through the front wall from roof level (below sofit).
There is a henely block on the fuse board but I can't tell if a main PE conductor is connected to it. As far as I see there is only earths to each radial circuit. If it were to be a TT system (unlikely), would the main PE be attatched to the henley block?

Thanks.

Par1

Papa_Bear wrote: »

Hi all,

Im just wondering what earthing system is used in a suburban housing estate that's approx 60 yrs old. Im guessing it's a TN-C-S system. What confuses me is that there appears to be only two main service cables entering the house through the front wall from roof level (below sofit).
There is a henely block on the fuse board but I can't tell if a main PE conductor is connected to it. As far as I see there is only earths to each radial circuit. If it were to be a TT system (unlikely), would the main PE be attatched to the henley block?

Thanks.

Sometimes its done in the meter under the sealed cover and can be as small as 2.5mm. Do a loop impedance test and you will find your answer weather its neutralised or not.

mikeyjames9

I have never seen domestic TN-S here

only TN-C-S and direct earthing

as par1 said you may see a smaller main earth connected to meter, a fault loop impedance test would confirm it within reason(there's a possibility of other N-E links elsewhere)

Par1

mikeyjames9 wrote: »

I have never seen domestic TN-S here

only TN-C-S and direct earthing

as par1 said you may see a smaller main earth connected to meter, a fault loop impedance test would confirm it within reason(there's a possibility of other N-E links elsewhere)

Very true, i should of mentioned to do test on incoming mains. People years ago were notorious for looping neutrals onto earths to create themselves an earth at a metal light (because the man in the shop told them thats how he does it).....iv heard that excuse more than once

Par1

TNS is not chosen as a prefered method because of the demand/cost of equipotential bonding and also the low power factor/high inductance of long runs of cable can be an issue especially for testing criteria.