Discuss Tingle from earth rod. in the Electrical Forum area at ElectriciansForums.net

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HappyHippyDad

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I have just been out for a pre works visit to fit an electric shower.

I cant access the CU as it has a cupboard built in the way.

It's a TT and when I touched the earth rod whilst clearing the mud out of the way (I wanted to actually see the connection) I got a shock. It was more of a tingle, but still a shock.

The water has main bonding, the gas doesn't (at least I cant see the main bond).

I put an earth leakage clamp meter around the main earth and got 0.01mA, so basically nothing.

The main switch is a 100mA RCD.

The earth rod was covered in wet mud.

I haven't done any other tests.

Why would I get a tingle? If I get the job, I'll be IR testing so I can see if there are any N-E faults. Is that the only reason why there may be potential on the earth rod?

Also, why did my clamp meter not read anything? I'm not sure if my clamp meter reads DC though.
 
Hi - if you’re getting tingles then it means there must be a potential difference between the 2 things you are touching. Maybe 25 to 50V just to pick a number.

So my thoughts are - RCD not working - rod Ra way too high - as you can’t access the CU then it’s possible a whole lot of nasty is in there - and - perhaps the rod is the return path for current that’s not from that RCD / CU.
 
Hi - if you’re getting tingles then it means there must be a potential difference between the 2 things you are touching. Maybe 25 to 50V just to pick a number.

So my thoughts are - RCD not working - rod Ra way too high - as you can’t access the CU then it’s possible a whole lot of nasty is in there - and - perhaps the rod is the return path for current that’s not from that RCD / CU.
So the 2 things I would have been touching are the earth rod and the ground surrounding it. I cant remember if I had my other hand touching the ground or not, or if it was just my boots. I'm pretty sure my other hand would have been touching the surrounding wet muddy ground. I can't believe I would have felt a tingle if it had just been my rubber soled boots touching the ground, pretty scary if it was.

It's a 100mA RCD, so if it is not tripping then it means < 100mA of fault current, or Ra perhaps >500ohms. Or, as you say, perhaps it's another RCD/CU. There are 2 other CU's but I am 95% sure they are fed from the main CU, plus I did not see a henley block splitting the meter tails. Of course they may just be taken from before the RCD in the main board!

Embarrassingly I do get a bit confused between AC and DC. Is the fault current leaking to earth AC or DC or could it be either? I'm trying to understand why I didn't see any fault current with the clamp meter. The first clamp meter I used was not an earth leakage clamp meter and it stated AC. The second clamp meter I used was an earth leakage clamp meter and I am unsure if it measures just AC or DC as well.
 
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I'm trying to understand why I didn't see any fault current with the clamp meter

You weren't measuring the current under the same conditions at the time of the "Tingle" incident and I suggest you don't try to.
You've measured the background current going to, or maybe even coming from the rod without your body in circuit to elsewhere.
The 0.01ma current is what's flowing without you touching the Earth Rod.

As Wilko, there a Potential difference between the point on the rod where you touched it and whatever you touched.

There's lots of possibles to investigate,
The rod may have been hammered into the Dno supply cable or into a steel gas service and diverted current is coming into the property from elsewhere.
It's possibly more likely a crap connection on the top of the rod, or the rod's disintegrated in the ground.
 
You weren't measuring the current under the same conditions at the time of the "Tingle" incident and I suggest you don't try to.
You've measured the background current going to, or maybe even coming from the rod without your body in circuit to elsewhere.
The 0.01ma current is what's flowing without you touching the Earth Rod.

As Wilko, there a Potential difference between the point on the rod where you touched it and whatever you touched.

There's lots of possibles to investigate,
The rod may have been hammered into the Dno supply cable or into a steel gas service and diverted current is coming into the property from elsewhere.
It's possibly more likely a crap connection on the top of the rod, or the rod's disintegrated in the ground.
Thanks Snowhead,
Can you explain a little more why a poor connection on the top of the rod could lead to a tingle?
If it was a poor connection would it still require some kind of fault to be causing the tingle, or are you saying the poor connection itself can somehow cause a shock?
 
Yes there's fault current from somewhere, maybe from the installation maybe being imported.
Instead of the fault current going to earth via the Rod path, which may have a higher resistance that it should, it chose to go through you and your lower resistance earth path.
 
Is the fault current leaking to earth AC or DC or could it be either?
If the fault is coming from an AC system, like in a house, then the fault current will be AC.

I think there’s a serious issue with this installation, and it’s going to be tricky to solve. The customer will need to be aware of additional costs early.

would love to see photo of CU as it is now with whatever’s in front of it.
 
If the fault is coming from an AC system, like in a house, then the fault current will be AC.

I think there’s a serious issue with this installation, and it’s going to be tricky to solve. The customer will need to be aware of additional costs early.

would love to see photo of CU as it is now with whatever’s in front of it.
Here you go.. best shot of it that I took. Why do you think it will be tricky? Is it not likely to be a N-E fault, so standard fault finding?
Tingle from earth rod. Tingle CU - EletriciansForums.net
 
Can you explain a little more why a poor connection on the top of the rod could lead to a tingle?
A poor connection could possibly lead to a tingle if there are a lot of IT devices with intentional leakage built in. But then that same tingle should appear on earthed surfaces inside the home as well. If you can't access CU, I would simply test between a socket neutral and earth.

Later you could begin your faultfinding proper by disconnecting the rod earth at the CU and testing the loose end to Neutral. This will confirm whether the fault is being exported or imported.
 
I'd start the other end, start with no-trip Zs at a socket near the board, RCD test from same socket.
This could all be one static discharge couldn't it?
 
interesting thread @happyhippydad good luck with this one, how old is the rod install?
Gosh, impossible to say. It's green and yellow earthing, so if that was put in the same time as the rod then 1978 onwards!
A poor connection could possibly lead to a tingle if there are a lot of IT devices with intentional leakage built in. But then that same tingle should appear on earthed surfaces inside the home as well. If you can't access CU, I would simply test between a socket neutral and earth.

Later you could begin your faultfinding proper by disconnecting the rod earth at the CU and testing the loose end to Neutral. This will confirm whether the fault is being exported or imported.
Could you expand a little please LMS? What different results would I expect to get if imported or exported (N-E)?

Also, I'm a bit muddled with the terminology. I assume they mean either coming from within the premises (i.e after the cutout fuse) or before the cutout fuse. If so, which is which?
 
Could you expand a little please LMS? What different results would I expect to get if imported or exported (N-E)?

Also, I'm a bit muddled with the terminology. I assume they mean either coming from within the premises (i.e after the cutout fuse) or before the cutout fuse. If so, which is which?
By importing, current flows into home earthing system via either shared metallic services, or the rod in contact with something other than earth.

By exporting, current flows out of homes earthing system as a result of either a fault (L to E, N to E) or "natural leakage"

As, its TT, in order to confirm which of the two is the issue, I would suggest disconnecting the rod earth at the MET. Test between the loose end and main Neutral. You should get a few volts at most depending on the load on the neutral.

Then test between the MET and main Neutral.
 
I have just been out for a pre works visit to fit an electric shower.



It's a TT and when I touched the earth rod whilst clearing the mud out of the way (I wanted to actually see the connection) I got a shock. It was more of a tingle, but still a shock.
P. S.

I, m very interested in this one. By definition TT installations are more vulnerable to "intentional leakage" than TNC-S.
 
By importing, current flows into home earthing system via either shared metallic services, or the rod in contact with something other than earth.

By exporting, current flows out of homes earthing system as a result of either a fault (L to E, N to E) or "natural leakage"

As, its TT, in order to confirm which of the two is the issue, I would suggest disconnecting the rod earth at the MET. Test between the loose end and main Neutral. You should get a few volts at most depending on the load on the neutral.

Then test between the MET and main Neutral.
Still not sure what results indicate imported or exported.

If imported, it could be (as you said) via shared services or rod in contact with something other than earth. If it's coming in from shared services then it will show up as voltage between MET (rod disconnected) and neutral (as the Main bonding will be connected). If it is coming in from the rod then it will show as voltage between loose end and neutral. Both of these tests indicate importing?
 
Still not sure what results indicate imported or exported.
If a voltage of a few volts max shows up between main N and loose end of rod earth than all is in order. You can confirm by again touching rod and "tingle" will be gone. This confirms rod is "not importing".
Your "stray voltage" should now be measurable between MET and main N.
I would next turn off all power (double pole) to all circuits and do the same test again. If stray voltage disappears than the issue is eminating from within the electrical infrastructure (either a fault or natural leakage).
If "stray voltage" is still present when you retested than the issue is eminating from outside and you will need to start investigating bonding from shared services one by one
 
If a voltage of a few volts max shows up between main N and loose end of rod earth than all is in order. You can confirm by again touching rod and "tingle" will be gone. This confirms rod is "not importing".
Your "stray voltage" should now be measurable between MET and main N.
I would next turn off all power (double pole) to all circuits and do the same test again. If stray voltage disappears than the issue is eminating from within the electrical infrastructure (either a fault or natural leakage).
If "stray voltage" is still present when you retested than the issue is eminating from outside and you will need to start investigating bonding from shared services one by one
Thanks for taking the time to go through that LMS ?
 

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