Earthing Rods. where best to place?

RichardY · Jul 1, 2012

HI - can I just check something please? Where is the best place to put an earthing rod ? Would it be directly outside the front or back door, or can it be placed anywhere outside. Is there any maximum or minimum distance required ?
Thanks.

Engineer54 · Jul 3, 2012

trev said:
My apologies E54, a poorly worded post from me. The beer was flowing after a particularly tough couple of days.
Note to self-more think, less jump in half cut

And i always thought you were a Tea Totaler!! lol!!

ackbarthestar · Jul 3, 2012

I here a lot about 'Twigs' recently.
I went into my local electrical trade counter and asked for a twig to provide an earthing point and they sent me to another Branch.

'Twigs' are perfectly acceptable as long as you know the quality of the ground. How many of you are able to carry out a 4-lead ground resistivity test? The old method of proprietary earth testing seems to have been forgotten, particularly in FE colleges.

Many of the top of the range 17th ed. MFTs have this function.

Engineer54 · Jul 3, 2012

Those twigs are about as useful as a test electrode, that you would use with a 4 or 3 lead propriety earth tester... Maybe on the off chance, as a very temporary earth electrode, say on a small portable/mobile Gen-set!!

Apart from that i wouldn't waste my time or money on them. If your installing a permanent earth rod position, ...Do it right first time with a couple of coupled 5/8'' rods. At the very least you would have more than a decent chance of attaining your rod positions stability...

ackbarthestar · Jul 3, 2012

I'm not going to agree with you since that wasn't my point.
Its a bit like saying Oh there's no cpc with that lighting circuit, Oh just stick a RCD on it or I can't figure out why the impedance is so high on this circuit, Oh just RCD it.......
I really don't think that building ones electrical knowledge should be made up from off-the-shelf answers is the way to proceed as a professional electrician.

If a twig is not sufficient then why is it not, what are the alternatives, what about the costs, will the customer bear the additional cost, how can I provide a convincing argument to convince the client that more work is needed to provide a safe reliable earthing point.

Twigs do work you know.....

Engineer54 · Jul 3, 2012

If a twig is not sufficient then why is it not, what are the alternatives, what about the costs, will the customer bear the additional cost, how can I provide a convincing argument to convince the client that more work is needed to provide a safe reliable earthing point.

Twigs do work you know.....

They are not extendible for one thing, so unlikely to be anywhere near stable between seasons. So certainly not a safe and reliable earthing point. I wouldn't use a single 1m 5/8'' or 3/4'' rod either, for the same reason. As for giving a convincing argument, i'm sure you could a more than convincing argument to any potential customer...

So no they don't work very well at all, not if your after providing a decent TT system to your customer. Surely 2 X 5/8'' coupled rods with a flush earth pit is not going to break anyones bank account. And whatever Ra value you initially attain with those coupled rods (and it'll certainly be far better than with any twig), will only improve over time....

ackbarthestar · Jul 3, 2012

You are still only expressing a generalized opinion.
In rocky climates you will certainly need more than a twig, even more than two or three coupled 5/8" rods coupled together, if you can get them in, that is.

Where depth cannot be achieved economically then spreading the electrode area and soil additives may be the only answer. We have been here before.

'Twigs' are sold by all electrical trade counters, and supplied by manufacturers not because they don't work but they offer a likely simplified compromise where the likelihood of RCDs will be used in conjunction.

Therefore, probably you're right, thinking about it - if in doubt stick an RCD on it. It simplifies everything and you don't have to fully understand what the hells happening.....

Engineer54 · Jul 3, 2012

ackbarthestar said:
You are still only expressing a generalized opinion.
In rocky climates you will certainly need more than a twig, even more than two or three coupled 5/8" rods coupled together, if you can get them in, that is.

Where depth cannot be achieved economically then spreading the electrode area and soil additives may be the only answer. We have been here before.

'Twigs' are sold by all electrical trade counters, and supplied by manufacturers not because they don't work but they offer a likely simplified compromise where the likelihood of RCDs will be used in conjunction.

Therefore, probably you're right, thinking about it - if in doubt stick an RCD on it. It simplifies everything and you don't have to fully understand what the hells happening.....

I don't believe i'm expressing a generalized opinion at all, and I'm talking about general conditions, certainly not rocky climates, that would need a whole different outlook altogether on providing a decent TT system. Your now in the realms of drilling bore holes and providing electrode enhancement materials. Which is, about as far away as you can get from using short twigs!!

Rather than using a number of short rods, in say where the soil cover over rock is around a metre, then you would stand a far better chance of achieving anywhere near a decent Ra value complimented by stability, is using copper tape in excavated trench(s) There are several variations to this, one being laying 3 or 4 coupled rods etc!! Again using conductive enhancement materials surrounding the tape electrode. I still wouldn't use short rods driven in the conventional way in such conditions, as this type of ground is going to be very susceptible to freezing and/or drying out during season changes, over most of the length/depth of the rod. eg, stability goes out the window. Now it's starting to become quite expensive to provide a domestic houshold with a decent TT system... lol!!

Virtually ALL TT systems in the UK will require an RCD anyway, ...how many of them will be provided with an additional protection up-front 100Ma S type RCD is another matter.
Manufacturers cater for a market, as do the wholesalers and the like, not because anything they produce or sell works. A case in point, is these children's socket outlet blanks!! When i came into this industry, the nominal size of a standard rod was extendible 3/4'' or 5/8'' X 10 feet or thereabouts. A far cry from today's 1 m rods, be they extensible or not!!