"Owain" wrote in message ...
Required if the supply to the house is PME or the outbuilding is more than a
certain distance away.

Hi,

This is an interesting matter which has puzzled me for a while.
According to an IEE source, when I enquired a while ago, the main
requirement for whether or not to use a local earth rod, is if the
earth fault loop impedance (Zs) becomes too high, at the outbuilding.
This is related to the distance, size of cable, and MCB used, and Ze
reading of the source.
If Zs is low enough then I was advised to use the main house earth.

I have not come across the PME factor?

Interestingly I am in negotiations to fit a new supply to a barn/
workshop from a house - which presently is on a TT supply, but will
soon be PME (It will be PME by the time the new feed is in use). The
barn is some 20m away, and will probably have a 6mm XLPE cable. I am
planning to have a local RCD in the barn. The supply cable (in the
house) won't be on an RCD.

I'd value some guidance on this.

Thanks, John