TNCS Outbuilding earthing arrangement

[davesparks]

There is no Regulation requiring out buildings to be TT.
The main reason for considering making an out building TT is simply cost.
Is it cheaper to run a 10mm bonding conductor from the house MET to the out building, or to install an earth rod at the out building?

For an installation with 10mm bonding then I doubt there is much cost difference.
However if the installation needs 50mm bonding and an outbuilding is to have a 32A submain the TT option may be considerably cheaper

 

[Deleted member 26818]

Yes, and it may be that the difference in cost is negligible when compared to the greater safety afforded by PME over TT.

 

[Monkeyblaine]

Sorry for making you spell it out. But thank you very much for clearing my thinking.

 

[Had8Lives]

Its a Di Log 9083p I think. It is meant to be non tripping but always does.

Are you putting the neutral and earth probes on the earth connection together? I was taught at college to do it, but not all testers need it and the DC bias that is meant to 'hold' the RCD on, will trip it.