current at main earth confusion

[sivoodoo]

Hi all,

Using a clamp meter I am reading 1.2A on the main earthing conductor,
also at the main protective bonding conductor to water pipe,

BUT not the gas pipe,

Why is there a current present and why is it not present at the protective bonding to gas?

The supply is domestic single phase PME.

Be aware I am a student so go easy if im missing the obvious (it was a heavy night last night!)
Cheers
Si.

 

[Spudnik]

To me its sounds like a possible fault in the installation somewhere as there should be no current present on the MET.

First point is to switch off the entire installation and test again.

If it disappears, then energise each circuit and test one by one and see if it reappears.

An IR test is also a good idea.

 

[sivoodoo]

Thanks for the quick response,
I will check your advice and report back,
Cheers

I switched off everything at the main switch and im still getting a reading,

it fluctuates between 0.7A and 1.4A when everything is off at the main switch on the db.

????

 

[Guest123]

Hi.

What about disconnecting your main earthing conductor from the consumer unit (main switch off obviously) and trying clamp meter only on this conductor??

You will be able to see if it's installation side or DNO side then and go from there. Obvously being pme earth and neutral are combined at service head so even with main switch off you still have neutral at consumer unit.

 

[sivoodoo]

I will try as you suggest lenny, cheers.

 

[ian.settle1]

Thanks for the quick response,
I will check your advice and report back,
Cheers

I switched off everything at the main switch and im still getting a reading,

it fluctuates between 0.7A and 1.4A when everything is off at the main switch on the db.

????

A surrounding building may have a fault and the lowest resistance path to earth is via water main to the property you are working on then to the incoming earth.

 

[sivoodoo]

interesting, thanks ian, obviously im going to investigate further to make sure.

What does one do about such a situation if that was the case?

cheers

 

[mrloy99]

A surrounding building may have a fault and the lowest resistance path to earth is via water main to the property you are working on then to the incoming earth.

Have you tried with a voltmeter?

 

[sivoodoo]

no, what would be the best procedure?

 

[mrloy99]

no, what would be the best procedure?

I'm assuming there must be a voltage present for the current to flow.
You say you have TN-cs ,PME,but is there any possibility that you haveTN-S.? Is your tong tester anologue or digital? If anologue your tester could be showing false readings due to the way that the meter is held.With main switch off are you reading anything on main tails?
If you use a voltmeter ,with main sw off.test from neutral to your separated earth cables. Sounds a mite odd.

 

[maddfridge]

Hi all,

Using a clamp meter I am reading 1.2A on the main earthing conductor,
also at the main protective bonding conductor to water pipe,

BUT not the gas pipe,

Why is there a current present and why is it not present at the protective bonding to gas?

The supply is domestic single phase PME.

Be aware I am a student so go easy if im missing the obvious (it was a heavy night last night!)
Cheers
Si.

hi there

could be my old friend parallel earth path and inductance but f would do what the other guys suggest first and see from there.

if it is still there disconnect the supplementry bonding from the water pipe and test again not forgeting to reconnect the supp bonding of course

cheers

 

[sivoodoo]

ok guys thanks for the responses,
here are my results:

With everyting conected as normal and energised:
Main bonding to water is reading = fluctuating between 0.7A and 1.9A
Main bonding to gas reading = 0A
Main bonding from cut out to DB = fluctuating between 0.7A and 1.9A

Disconect main water bonding from DB:
Main bonding to water is reading = 0A
Main bonding to gas is reading = 0A
Main bonding from cut out to DB is reading = 0A

Disconect main water bonding from water pipe:
Main bonding to water is reading = 0A
Main bonding to gas is reading = 0A
Main bonding from cut out to DB is reading = 0A

Disconect main bonding from cut out to DB
Main bonding to water is reading = 0A
Main bonding to gas is reading = 0A
Main bonding from cut out to DB is reading = 0A

Disconect main gas bonding from DB
Main bonding to water is reading = fluctuating between 0.7A and 1.9A
Main bonding to gas reading = 0A
Main bonding from cut out to DB = fluctuating between 0.7A and 1.9A

Voltage reaing from Main water bonding to Neutral is 0.1V

A bit of a puzzle for me any advice please,
Thanks
Simon.

 

[mrloy99]

ok guys thanks for the responses,
here are my results:

With everyting conected as normal and energised:
Main bonding to water is reading = fluctuating between 0.7A and 1.9A
Main bonding to gas reading = 0A
Main bonding from cut out to DB = fluctuating between 0.7A and 1.9A

Disconect main water bonding from DB:
Main bonding to water is reading = 0A
Main bonding to gas is reading = 0A
Main bonding from cut out to DB is reading = 0A

Disconect main water bonding from water pipe:
Main bonding to water is reading = 0A
Main bonding to gas is reading = 0A
Main bonding from cut out to DB is reading = 0A

Disconect main bonding from cut out to DB
Main bonding to water is reading = 0A
Main bonding to gas is reading = 0A
Main bonding from cut out to DB is reading = 0A

Disconect main gas bonding from DB
Main bonding to water is reading = fluctuating between 0.7A and 1.9A
Main bonding to gas reading = 0A
Main bonding from cut out to DB = fluctuating between 0.7A and 1.9A

Voltage reaing from Main water bonding to Neutral is 0.1V

A bit of a puzzle for me any advice please,
Thanks
Simon.

Hi it would appear that the prefered path of current to earth is via your water pipe.The neutral will be connected to earth at many points between your house and the supply transformer .I suppose this is what protective MULTIPLE earthing is all about.

 

[sivoodoo]

Yes thanks, but why is there a current on the earth? Im still investigating..

 

[mrloy99]

Yes thanks, but why is there a current on the earth? Im still investigating..

I think if you think of it in terms of the return path,your neutral,flows to earth,and your waterpipe is the best earth ,closest to you.(your N&E being combined in the service head)This is maybe the path of least resistance. As for the gas,you have maybe got a plastic pipe feeding your house from the street.