How to Find Leak to Ground?

[Banana7]

When a voltage sensor is touched to a ground wire, it signals a little bit of AC voltage. I turned off all the individual breakers, try isolating the bleeding circuit, and still the ground wire shows a little bit of voltage. Finally, I turned off the main breaker and now the ground wire shows no voltage.  How do I find what is leaking to the ground circuit?

[Muhendis]

Some machines like computers, microwave ovens and washing machines have filters which seem designed to leak a little bit.

This is normal.

Having leakage with all individual breakers off may be indicative of a swapped live neutral wire 

 

[Crossy]

7 hours ago, Banana7 said:

it signals a little bit of AC voltage

 

How much is your "little bit"?

 

In a TNC-S (MEN) system such as we have in Thailand it's quite possible for there to be a small portion of the overall neutral current flowing through individual ground rods.

 

Unless the voltage in question is significant there is no issue.

 

It is possible that you are seeing a symptom of a poor joint in the neutral somewhere upstream from your location, but in order to know we need to know the magnitude of your "little bit" and what you are using as the reference point.

[bluejets]

A megger is used on all disconnected circuits to determine their "leakage" or down to earth value.

Interpreting these values is another issue.

Your "voltage sensor" is not worth didly squat as a measurement or indication of any problem.

 

Edited April 2 by bluejets

[Banana7]

On 4/3/2024 at 6:47 AM, bluejets said:

A megger is used on all disconnected circuits to determine their "leakage" or down to earth value.

Interpreting these values is another issue.

Your "voltage sensor" is not worth didly squat as a measurement or indication of any problem.

 

I don't want to argue with you, but I disagree with your comment. My voltage sensor has proven to very valuable and effective tool when doing any electrical work.

[Banana7]

On 4/2/2024 at 7:21 AM, Crossy said:

 

How much is your "little bit"?

 

In a TNC-S (MEN) system such as we have in Thailand it's quite possible for there to be a small portion of the overall neutral current flowing through individual ground rods.

 

Unless the voltage in question is significant there is no issue.

 

It is possible that you are seeing a symptom of a poor joint in the neutral somewhere upstream from your location, but in order to know we need to know the magnitude of your "little bit" and what you are using as the reference point.

It is 4.5 volts in the ground line.

 

How do I find the source of this voltage? I turn off all the individual breakers, but it doesn't disappear until the main breaker is off.

Edited April 4 by Banana7

[Crossy]

10 minutes ago, Banana7 said:

It is 4.5 volts in the ground line.

 

What are you using as the reference point for the 4.5V? (where is the other lead of your voltmeter?)

 

It's 99.99% chance there's no problem at all, but could you post a photo of your distribution board with the lid off (care please). We need to see what supply connection you have in order to be sure if there's an issue or not.

[Crossy]

17 minutes ago, Banana7 said:

I don't want to argue with you, but I disagree with your comment. My voltage sensor has proven to very valuable and effective tool when doing any electrical work.

 

But not for measuring a leakage CURRENT.

[Banana7]

2 minutes ago, Crossy said:

 

What are you using as the reference point for the 4.5V? (where is the other lead of your voltmeter?)

 

It's 99.99% chance there's no problem at all, but could you post a photo of your distribution board with the lid off (care please). We need to see what supply connection you have in order to be sure if there's an issue or not.

One lead is on the ground circuit, second is on a brass value on the water line. Voltage goes to zero, if the ground circuit is connected to the brass valve. If the ground circuit is not connected to the brass valve, with all breakers on or off, I can feel a slight tingling when touching metallic shower hose. This is in an old condo, and the building has no inherent ground wiring.

 

 

[Crossy]

So where is your electrical ground (that's not your water pipe) coming from? If it's actually floating (not really connected to anything) then you could be seeing capacitive coupling from a live wire or possibly the mains inlet filter of your desktop PC (or pretty well any modern appliance).

 

4.5V isn't going big enough to feel.

 

Please post a photo of the distribution board with the lid off.

 

Are you in a rental or do you own the condo?

 

 

Note that while not ideal you could use the water pipe as a functional ground (IF it is NOT part of the fire suppression system) but you would need an RCD/RCBO for safety as the actual properties of that pipe are unknown.

[Banana7]

Why do you think it is capacitive coupling when all the breakers are off? I do feel a slight tingle on the shower hose. That big wire connected to the ground bar runs to the power distribution room for the entire floor, and is connected to exposed building rebar. I own the condo. I appreciate your help!

Edited April 4 by Banana7

[Crossy]

OK RCBO - check

 

That there's a wire running to the building steel at least means there's been an attempt to get a decent ground in there (how good does that connection look?).

 

System would be TT, no apparent link N-E at the board.

 

That your RCBO isn't tripping suggests that there isn't a dangerous leak, does that tingle go away if you link the existing ground to the water-pipe?

 

 

[Banana7]

1 minute ago, Crossy said:

OK RCBO - check

 

That there's a wire running to the building steel at least means there's been an attempt to get a decent ground in there (how good does that connection look?).

 

System would be TT, no apparent link N-E at the board.

 

That your RCBO isn't tripping suggests that there isn't a dangerous leak, does that tingle go away if you link the existing ground to the water-pipe?

 

 

In the distribution room, rebar is old (30-35 yrs.) completely rusty. I don't have access to the distribution room right now, its locked. What is TT?

Tingle disappears when the ground wire is connected to the brass water valve, which controls the water coming into the condo.

Could the leak be increasing my electricity consumption/bill?

 

[Crossy]

OK. "Leak" won't affect your energy consumption.

 

TT is just a type of earthing system https://en.wikipedia.org/wiki/Earthing_system most of Thailand is now TNC-S with MEN but don't go trying to convert.

 

You could try to get the building handy-person to clean up the connection to the building steel which ought to solve your problem. Otherwise just connect your earth to the water pipe and be happy.

 

Very important - DO NOT connect to the pipe if it's part of the fire-suppression system (Yes, I know I'm repeating myself here).

[Banana7]

Anybody have any ideas on how to find where the voltage is going to the ground wire, even when all the breakers are turned off?

[Crossy]

1 hour ago, Banana7 said:

Anybody have any ideas on how to find where the voltage is going to the ground wire, even when all the breakers are turned off?

 

Get yourself a proper insulation tester and learn how to use it and you'll be good to go.

 

But one doesn't usually use a voltmeter for measuring earth leakage anyway.

 

I've already given you some solutions, if you choose to ignore them that's your problem.

 

[Banana7]

10 minutes ago, Crossy said:

 

Get yourself a proper insulation tester and learn how to use it and you'll be good to go.

 

But one doesn't usually use a voltmeter for measuring earth leakage anyway.

 

I've already given you some solutions, if you choose to ignore them that's your problem.

 

I went through this thread again, and I don't see any recommendations from you other than to clean the rebar connection and in this last post, about getting a insulation tester. The original question has never been answered, "how to find the voltage leak source to the ground wire".

 

The voltage is getting into the ground wire and yes, verified by the using a volt meter and a voltage sensor and if the water valve grounding is disconnected, there is tingling feeling when touching the shower hose. This is not answering the question, what is the source!

 

I am eager to try most any practical solution. What do you think about pulling the neutrals out of the breaker box, and if one neutral stops the voltage into the ground, then examine/replace that circuit or suspect components attached to the circuit?

 

 

[Crossy]

OK it's like this.

 

You are measuring a small (maybe feeling a bigger) voltage between two "grounds". This may be caused by a high resistance connection in the ground coupled with naturally "leaky" appliances (anything with a mains inlet filter), they don't necessarily need to be in your condo if other units share that ground to the re-bar, or even capacitive coupling from other live wires if that connection is really, really bad.

 

You need to eliminate/minimise this voltage.

 

You do this by making sure that your electrical ground is as good as practical (clean up that rusty connection).

 

If this isn't practical/possible then you can use your "better" ground (the water pipe) in addition to the iffy main ground.

 

From an earlier post: -

 

Without visiting your place with a box full of test-gear it's not possible to define exactly what you are seeing, but the suggestions should clear most of the common issues.

 

Try the simple fixes first. When they don't come back and we can delve deeper.

 

 

[bluejets]

On 4/4/2024 at 6:36 PM, Banana7 said:

I don't want to argue with you

....best don't as you say.