On 13/11/2018 17:22, Pat Pending wrote:
Just put an electricity supply in to a shed at the bottom of the garden
- 4mm armoured cable to a separate CU in the shed. We have TT earthing,
so didn't use the cable earth and put in a 5/8" x 1m earth rod outside.
Measured the earth loop impedance, and I have 320 ohms - far too high
isn't it? Any suggestions?

Max 200 and ideally less than 100 ohms.

More earth rods and/or longer earth rods if you are able to drive them
into the soil.

This time of the year its wet and more imperative to aim for 100 ohms
for times when the ground is dry.