Copper 'earth' rod deep in the ground?

[davidst01]

I'm having a so-called 'experienced' electric guy come soon to fix a few lights. 

 

Last yr on the ground floor of our newly renovated building we had a different electrician put in a new large elec box with proper grounding (so he says). He showed me where they put the copper rod with concrete over the top now. He was the same guy who did the wiring on a shower where I was subsequently feeling minor electric shocks when touching the metal tap. This issue has since been resolved. But now I want to dig up the concrete and check if the copper rod thing is done correctly. If not all it represents is 'fake safety'. 

 

Thus, my question is...

1. what are we looking for once the concrete is dug up. How deep should it be? Should it be covered in soil?

2. What am I looking for to see if it is actually fake safety?

 

thanks

[Tayaout]

https://s.lazada.co.th/s.ZVmAA

[NCC1701A]

17 minutes ago, davidst01 said:

1. what are we looking for once the concrete is dug up. How deep should it be? Should it be covered in soil?

yes it should be driven into the earth (soil). two meters is typical but some are 3 meters. It should not be encased in concrete, it can be covered at the top with concrete.  

[sometimewoodworker]

29 minutes ago, davidst01 said:

1. what are we looking for once the concrete is dug up. How deep should it be? Should it be covered in soil?

The important point is that the soil must be constantly damp, if the earth is dry as a bone then it's in the wrong location.

[Crossy]

Rather than dig everything up (you really can't tell much just by looking), find a sparks with a proper earth resistance tester and test what you have, it could be just fine.

 

Otherwise just bash in a second rod >2.4m long and wire it together with the existing rod (I would wire it to the board itself as if there was no existing rod). In reality this is likely the cheapest and easiest solution.

 

[davidst01]

1 hour ago, Crossy said:

Rather than dig everything up (you really can't tell much just by looking), find a sparks with a proper earth resistance tester and test what you have, it could be just fine.

 

Otherwise just bash in a second rod >2.4m long and wire it together with the existing rod (I would wire it to the board itself as if there was no existing rod). In reality this is likely the cheapest and easiest solution.

 

Are you referring to one of these:

https://www.lazada.co.th/products/uni-t-ut501a-1000v-insulation-earth-ground-resistance-multimeter-voltmeter-tester-i331300834-s636756198.html?spm=a2o4m.searchlist.list.13.3340d1c0c8H0Xj&search=1

 

He pulled out a small device and when touching a wire it showed the voltage. Can that be used on the copper rod?

[Crossy]

1 hour ago, davidst01 said:

Are you referring to one of these:

https://www.lazada.co.th/products/uni-t-ut501a-1000v-insulation-earth-ground-resistance-multimeter-voltmeter-tester-i331300834-s636756198.html?spm=a2o4m.searchlist.list.13.3340d1c0c8H0Xj&search=1

 

He pulled out a small device and when touching a wire it showed the voltage. Can that be used on the copper rod?

 

No that Lazada unit is an insulation tester. The small device is some sort of voltage tester, not really suitable for checking an earth.

 

You or your man need one of these (and the knowledge of how to use it) https://www.lazada.co.th/products/vc4105a-digital-earth-ground-resistance-tester-meter-lcd-0012000-ac200v-i317488457-s596860968.html

 

Just banging in another rod would be a lot cheaper.

[tjo o tjim]

As Crossy says... bang another rod in the ground.  Ideally drill a hole, confirm the ground is moist, and then bang the rod in.  Don’t put it in the same general vicinity as the original, and it will only improve things.  

[faraday]

21 hours ago, Crossy said:

Rather than dig everything up (you really can't tell much just by looking), find a sparks with a proper earth resistance tester and test what you have, it could be just fine.

 

Otherwise just bash in a second rod >2.4m long and wire it together with the existing rod (I would wire it to the board itself as if there was no existing rod). In reality this is likely the cheapest and easiest solution.

 

Not that I doubt you Crossy, but why does the rod need to be more than 2.4metres?

 

 

[bankruatsteve]

15 minutes ago, faraday said:

Not that I doubt you Crossy, but why does the rod need to be more than 2.4metres?

 

The oracles of dirt say so and the gurus of electric code obey.

[Crossy]

25 minutes ago, faraday said:

Not that I doubt you Crossy, but why does the rod need to be more than 2.4metres?

 

PEA / MEA regulations.

 

It likely doesn't need to be that deep to give an acceptable ground resistance but the code here is prescriptive like the NEC "do it like this and it's to code" rather than proscriptive like BS7671 "this is what you need to achieve, as the designer you decide how to achieve it".

[davidst01]

On 7/24/2019 at 4:37 PM, Crossy said:

 

No that Lazada unit is an insulation tester. The small device is some sort of voltage tester, not really suitable for checking an earth.

 

You or your man need one of these (and the knowledge of how to use it) https://www.lazada.co.th/products/vc4105a-digital-earth-ground-resistance-tester-meter-lcd-0012000-ac200v-i317488457-s596860968.html

 

Just banging in another rod would be a lot cheaper.

hi, My update is that our electrician came around today to check things. I told him I wanted to check the copper rod and he used the drill to remove the top surface of the concrete. He didnt have a proper digital device as per your link above. But he did have a lightbulb with 2 wires attached. He stuck one end in the electric extension cord that was plugged into the drill. He touched the other wire from the bulb to the top of the copper rod thing. The light on the bulb flickered a little and then we heard the power cut out inside with a few beeping noises. He said that this test confirms the earth rod / grounding is working. Is this a valid test. Is he correct?

 

thanks so much

[Crossy]

9 hours ago, davidst01 said:

Is this a valid test.

 

Sort of. It could be a valid test of the rod, but it doesn't verify that the rod is actually connected to the board, a screwdriver stuck in the lawn would have done the same.

 

He should have disconnected the rod from the rest of the system at the board. Bet he didn't (he could have tested the rod from the other end of the cable then).

 

What device tripped and beeped?

 

I must admit I'm a bit confused as to exactly what you have in your building by way of actual distribution boards, breakers etc. It would be really useful if you could post photos of all of your electrical installation so we can work out what's going on.

 

 

 

[MartinL]

I'm having an electrician in to rewire a small single storey house soon. He did the new installation on our house some time ago so I know he's OK but ... 

 

I've asked him to fit a new earth rod and would just like some reassurance on the installation.

 

There's an always-wet, but not flooded, water soakaway that would seem to be an ideal location for the rod - any reasons why it might not be suitable? 

 

Also, does the electrical standard specify a minimum conductor size between rod and board or a maximum distance between them? 

[bankruatsteve]

A "new rod"? If you already have one, is there reason to put a new one? Anyway... Earth is earth - a bit wet is perhaps "better". Some will say 10mm2 is needed for the ground connection but 2.5mm2 is OK. 

[Crossy]

I would wire a new rod with at least 6mm² simply for protection against mechanical damage.

 

UK regs would want 16mm² (yes 16) on a TNC-S system (like Thailand is).

[Led Lolly Yellow Lolly]

On 7/24/2019 at 12:34 PM, NCC1701A said:

yes it should be driven into the earth (soil). two meters is typical but some are 3 meters. It should not be encased in concrete, it can be covered at the top with concrete.  

Not wishing to be a pedant but IMO a ground rod should never be covered in concrete. It makes inspection impossible.

[Led Lolly Yellow Lolly]

Just to add to the above, it is acceptable to completely bury an earth connection in certain circumstances and if certain rules are followed.

 

Number one, the ground conductor must be exothermically welded to the ground rod itself. This eliminates corrosion completely, but it's difficult and dangerous to do it properly. Any local PEA supplier will have the exothermic weld kits, they're inexpensive and commonly know locally as 'one shots'.

 

Secondly, you must install a ground disconnect box. Inside it will have one of these: https://www.an-wallis.co.uk/products/earthing/disconnecting-link

This facilitates an easy method of disconnecting for tests to be carried out.