Length of earth rod

message from Pandora on 12 May 2004

I'm proposing to run a 230V electricity supply to my garage (30m from
house) using underground SWA cable.

I need a ground rod to supply the garage with a safe earth. The
salesman at Furse told me that the standard domestic rod is 3/8"
diameter x 1.2m length.

A few electrical wholesalers I've phoned, however, stock 3/8" x 4ft as
"standard". Is 4ft likely to be OK? The garage is above quite a high
water table.

Can I drive the rod straight into the soil outside the garage and
protect the top with a cover?

I'll measure the rod resistance on a dry day soon after installation.

Grunff replied to Pandora on 12 May 2004

4 foot = 1.2192m - so what's the problem?

Pandora replied to Grunff on 13 May 2004

Doh!!! How stupid do I feel?

Hope my family and friends never come across this thread.

troubleinstore replied to Pandora on 13 May 2004

Nah, don't worry about it. Even the so called professionals make
mistakes and boy, have I seen some.

Nick Brooks replied to Pandora on 12 May 2004

4 feet = 1.2192 meter

Should be OK

possibly not if your soil is really hard/stony in which case you'll have
to dig

Christian McArdle replied to Pandora on 12 May 2004

4ft IS 1.2m.

There is no mandated length. You must test the rod with specialised test
equipment (NOT a multimeter!) to determine the impedence and ensure that it
is low enough (and likely to remain so). The length (or number) required
will depend very much on your soil type and expected seasonal conditions.

Christian.

Archived message: Length of earth rod (UK DIY Home Repairs)