Why Use an Earth Rod when a Disc will do?

If you dig a hole and bury a electrode tape, disc, etc then backfill with expensive concrete, but it doesn't give a good test result you have spent over £300 of the customers money without achieving the required outcome. 

With a rod you just screw another extension on and drive it all down  deeper.

Years ago two electricians installed a forty five feet long rod on the old power station site at Stourport on Severn, which is the bottom of Hartlebury Common a sandy heath using no more than a lump hammer. 

Sparkingchip said:

With a rod you just screw another extension on and drive it all down  deeper.

Into things you can't see ... and provided the wrong kind of rock isn't in the way.

Great if it's a greenfield site, or out in rural areas, but in urban areas, I think I'd be recommending far more caution these days.

I don’t disagree that knocking in rods comes with risks, but you still need to dig a hole three feet deep for the disc to get it down below frost point and that’s not risk free in an urban environment, if you dig a hole a couple of feet square and three feet deep that actually getting on for half a ton of soil that needs to be dug out and reinstated, without taking up and relaying any paving.

The discs are designed to fit onto the base of a telegraph pole in a hole that will normally be drilled into the ground with a very large auger mounted on a purpose built pole wagon, that hardly comes without an element of risk.

Sparkingchip said:

I don’t disagree that knocking in rods comes with risks, but you still need to dig a hole three feet deep for the disc to get it down below frost point and that’s not risk free in an urban environment, if you dig a hole a couple of feet square and three feet deep that actually getting on for half a ton of soil that needs to be dug out and reinstated, without taking up and relaying any paving.

Agreed ... but the issue is you can hand-dig the hole with an insulated spade. I think the fact this is a safer option is corroborated by the companies that do 1000s of these jobs.

Sparkingchip said:

The discs are designed to fit onto the base of a telegraph pole in a hole that will normally be drilled into the ground with a very large auger mounted on a purpose built pole wagon, that hardly comes without an element of risk.

Agreed ... but the discs are also easier to fit in existing situations where "banging in a rod" is fraught with H&S risks in the UK. Again, speak to the companies that install 100s or 1000s of these.

you could hand dig with  a plastic spade, and then drop in a  normal electrode and be richer ;-)

mapj1 said:

you could hand dig with  a plastic spade, and then drop in a  normal electrode and be richer ;-)

Well ... all joking aside, no!

To achieve same earth electrode resistance would likely require say 3 rods in triangle formation, perhaps 2-3 m deep, and therefore a triangular hole at least 2 m each side, and at least 2 m deep ?

Which is why I think a 600 mm square mat buried 600 mm deep is probably going to be the cheapest option overall, and most-often achievable?

Agree if we are burying a mat. But the condudisk seems to be quite high Z for what it is.  My point was not a joke though, if you are going to bother with the trouble of digging a hole to bury something, there are better things to put in that hole both in terms of cost and electrode resistance.The biggest advantage of that disc is lost if you do not already have a disk shaped hole anyway as part of other works.

Mike.

It would be good to know what items/combination of items folk have used in the past . Along with reasons and conclusions of Ra gained. I have done every few and always a rod (well actually two rods a min of two rod lengths apart , test each one on its own then connect both and re-test). 

Sparkingchip said:

if you dig a hole a couple of feet square and three feet deep that actually getting on for half a ton of soil

I reckon that's about 1/3 cubic metre, or about the same as a row of spuds (1 ft x 1 ft x 12 ft).

I know all about the soil conditions here on the sunny (or not so sunny) south coast on account of digging out bindweed. A foot of good topsoil, a foot of clay, and then flints, which is where hand digging stops.

I haven't needed to whack in a rod, but I suspect that one would find a way through the flints.