Earth arrangements confusion

alan132 · Aug 12, 2017

Working on a old property in a slightly remote area installing a new circuit.

When I looked at the earthing it looked like a tns but I investigated and found a old 2.5mm running towards the rod.

My problem is I am getting a ze reading of 0.25 ohms.

Ino we had a really heavy down poor the day before but to be that low?

I am wait for the dno to confirm the earthing but they ain't rushing.

Any thoughts
I know a good reading for tt is 200 ohms or lower. This is the first one I have worked on

Wilko · Aug 12, 2017

I think you are right to be concerned as there will always be risks banging in a rod. As we spend a bit of time looking at the existing bonding, I have a go at estimating where I think the services would run from that, look of water connection at property boundary etc. I speak to owner and get their take on where services may be. If I've any doubt remaining, I dig a bit by hand which is the only thing that saved me in the attached pic. The cost of ground penetrating radar hire is £300 or so per day, and probably be about the same if you get a specialist company to do a report on a domestic plot. Folks won't pay for that to have a new circuit in their house, but it's the only way to be sure about what's below.

[ElectriciansForums.net] Earth arrangements confusion

Phil Thompson · Aug 12, 2017

Double post

Phil Thompson · Aug 12, 2017

I try and opt to locate spike to the rear of a property to avoid any services (here they're always brought from the road/street to the front of a property) and assess drainage and guttering on a property so as to avoid any drainage pipes.

If frontal location was only option and I wasn't 99% certain I was safe to put a spike down I'd likely have to get further assessment done as whilst a cable finder will locate telephone, virgin and mains etc, water and gas pipes are ran in pvc pipe. So would not show up on any scanner that I've seen.
Although in general the services are brought the most direct route from street to gas metering equipment/internal stop cock. But not always. Although it's very rare to find them travelling an indirect route here.
Fortunately it's very rare for me to find TT properties here with no spike already installed, so it's not actually something I have to do very often. That was first this year and only did 2 last year and 1 of those was a new build property in the countryside where all services were visible.

But common sense and a basic knowledge of how services are routed to properties helps decide.

Midwest · Aug 12, 2017

Thanks for the replies chaps, that was a close en Wiko. My son's having an extension done. When they were digging the footings, they found some unexpected drainage pipes. Thames Water came out and camera'd them, and found another waste pipe. Both were 3' feet down, and if I'd look for a place to put a rod, I'd hit both!

If this 18th proposal goes ahead, it might prove expensive.

Phil Thompson · Aug 12, 2017

Definitely, Those cable finders are £500 and upwards, but doesn't help with gas and water pipe location.

davesparks · Aug 12, 2017

Midwest said:
Thanks for the replies chaps, that was a close en Wiko. My son's having an extension done. When they were digging the footings, they found some unexpected drainage pipes. Thames Water came out and camera'd them, and found another waste pipe. Both were 3' feet down, and if I'd look for a place to put a rod, I'd hit both!

If this 18th proposal goes ahead, it might prove expensive.

With all little bit of planning it should be possible to arrange to use the reinforcing in the concrete as the earth electrode on new builds and extensions.

Midwest · Aug 12, 2017

davesparks said:
With all little bit of planning it should be possible to arrange to use the reinforcing in the concrete as the earth electrode on new builds and extensions.

I understand that's the provision. However, if the requirement for earth rod is applied to 132.16, and I'm putting an extra socket in an old terraced house in the town centre, it's going to be difficult and not cheap.

Toneyz · Aug 12, 2017

If I stand corrected I thought the draft said on the lines of preferably. I think that they will accept that when you go around to Mrs Muggins house to fit an extra socket it would not be practical to go and run earth cable outside to a earth electrode.

Midwest · Aug 12, 2017

anthonybragg said:
If I stand corrected I thought the draft said on the lines of preferably. I think that they will accept that when you go around to Mrs Muggins house to fit an extra socket it would not be practical to go and run earth cable outside to a earth electrode.

Reg 542.1.201 .........Additionally, there shall be an earth electrode, supplementing any earthing facility provided by the distributor, in accordance with 542.2.3 (which describes earth foundations).

Still not quite clear on this draft reg, perhaps I (and others have read it incorrectly?)

Wilko · Aug 12, 2017

Oh dear - "shall" has no wiggle room in it ... let's us hope there's a clause somewhere that can keep up from this one's grasp.

alan132 · Aug 13, 2017

Back to my post.
Should of mention the service head is 2 separate connection blocks

And there is no earth coming off the neutral.

2 cables come in from the roof stright to the service connections

Deleted member 9648 · Aug 13, 2017

I'm confused having just read this thread....first it was a possible TNS with a strap on the sheath....now it's two singles coming in overhead?
Am I missing something?

alan132 · Aug 13, 2017

Yh I couldnt confirm it then later I explain it was a tube that the cables come through

westward10 · Aug 13, 2017

Any chance of a picture.

alan132 · Aug 13, 2017

Will have to get one when I go back.

Earth arrangements confusion

alan132

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Wilko

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Phil Thompson

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Phil Thompson

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Midwest

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Phil Thompson

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davesparks

Midwest

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Toneyz

Midwest

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Wilko

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alan132

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Deleted member 9648

alan132

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westward10

alan132

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