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?

Its higher than ideal certainly, although will still pass enough fault
current to trip a 30mA RCD in most circumstances.

To get a lower Ze, you will need either/or longer earth rod / additional
earth roods spaced away from the first one. Most rods can be coupled to
additional ones to increase the length.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/