Replacing an earthing rod

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neb

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#315037 9-Jun-2024 08:54

Asking for a friend who lives in a place built by dodgy cowboy builders, there's two earthing rods which consist of one rod cut in half and in any case only one is connected. They want to replace it with something proper, all the ones I've seen are hot-dip galvo but some sites they've looked at say you should use copper. Does anyone have any thoughts on this? The ground is clay, but I don't know much more about it than that. I'd imagine installing a soft copper rod into clay wouldn't go well, and also don't know the relative merits of copper vs. zinc in clay.

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#3246410 9-Jun-2024 09:10

Both are steel rods, plated with zinc/copper. Either is acceptable. Solid copper is technically acceptable but as you suspect won't drive well. A fence post driver works reasonably well to pound them in; a demolition hammer with a cup-type bit is excellent. Doing it with a sledge is just a pain.

No particular comments on copper vs galv and which will last better in clay. I haven't heard of clay being particularly high corrosion but it's not really something I've seen discussed. Galv is probably cheaper.

There are alternate options that may work for you in some cases. These include:

If you have an open trench, you can bury a length copper or galv steel (including pipe, cable, or steel strip), 0.5m deep and 7.5m long.
If you are pouring new concrete foundations, you can use the conductive rebar. No specific values are given for either the length of rebar to be earthed or the size of the foundation, but there are apparently 'gotchas' with this method.

Eva888

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#3246419 9-Jun-2024 09:34

We just had this done by our electrician. He came armed with a long galvanised looking pipe and he hammered it into the ground. I was surprised at how it went in so easily as our ground is clay and rocky compacted fill at that site.

Ge0rge

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#3246424 9-Jun-2024 10:23

Probably worth noting that replacing or moving the earth rod is considered high risk work by the EWRB.

SomeoneSomewhere

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#3246425 9-Jun-2024 10:28

Ooh, now you're getting into argument territory. It's the regs that define high-risk work, and they're pretty clear that "maintenance or replacement of a fitting in an existing installation" is low risk work, and the list of high risk work (including mains work) only applies if it is not low risk work.

But yes, getting an inspector out is recommended anyway.

timmmay

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#3246449 9-Jun-2024 12:35

I was surprised how long the earthing rod was when we had an electrician replace ours a few years ago. It hammered into the ground fine though. I wonder if there's any risk doing this if you have a faulty appliance in your house.

Goosey

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#3246454 9-Jun-2024 12:59

timmmay:

I was surprised how long the earthing rod was when we had an electrician replace ours a few years ago. It hammered into the ground fine though. I wonder if there's any risk doing this if you have a faulty appliance in your house.

wouldn’t it be standard practice to switch off the mains to carry out this work…maybe even switch off the “pole fuse”?

Daynger

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#3246514 9-Jun-2024 15:19

timmmay:

I was surprised how long the earthing rod was when we had an electrician replace ours a few years ago. It hammered into the ground fine though. I wonder if there's any risk doing this if you have a faulty appliance in your house.

The real danger is if you have a bad neutral, or your neighbour does.

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SomeoneSomewhere

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#3246542 9-Jun-2024 16:41

Or transposed mains, though you hopefully notice that first.

neb

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#3246756 10-Jun-2024 06:22

Good point, hadn't thought of that, I'll make sure to check that first. Assuming there's no potential difference between the existing earth connection and the new one then it's just a case of cutting the power, hooking up the additional rod, and reapplying power? Although given @SomeoneSomewhere's comment it may make more sense to get a sparkie to do it with a proper post driver than trying to do it with a sledge.

SomeoneSomewhere

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#3246760 10-Jun-2024 07:01

It is definitely prescribed work to replace the electrode, not DIY. If you want to drive it yourself, though, I doubt you'll find any objections.

You might want a services locate; on modern builds the earth stake tends to be near where the other services enter underground (, water, power, gas, fibre) and I've seen I think two cases of sparkies driving through a water pipe.

neb

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#3246761 10-Jun-2024 07:06

It's not actually a replacement but just adding a second one alongside the existing one which seems dodgy. Not sure if that affects things.

johno1234

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#3246767 10-Jun-2024 07:58

Be a hell of a job in some Auckland volcanic locations. E.g. in Mt Eden some streets are basically rock.

Aren’t most houses grounded twice: once by the ground wire back to the pole and once be the earth rod?

Our earth wire at Whangamatā broke off in a storm and it was quite dangerous. The lines company came over promptly and replaced it but commented that the earth rods in the area are in dry sand and make poor earth sinks leaving the house ungrounded.

neb

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#3246770 10-Jun-2024 08:05

This is in soggy clay AFAIK. I haven't seen the precise location yet but I suspect lack of wetness won't be an issue, more the surplus of it.

Daynger

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#3246879 10-Jun-2024 11:00

neb:

It's not actually a replacement but just adding a second one alongside the existing one which seems dodgy. Not sure if that affects things.

When you move the wire on to the new peg, that is still replacement of the peg.

MadEngineer

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#3246884 10-Jun-2024 11:14

I’d strongly advise against doing this unless you’re a sparky

I was going to make some helpful suggestions but simply there are lots that can go wrong here

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