Potential difference between supplier's earth and water/gas earth...

[Crosswire]

Anyone ever noticed a difference between these? Just curious.........

 

[Marvo]

With bonding or without bonding?

 

[telectrix]

might see it with 1 of these new-fangled digital contraptions. not with a AVO 8.

 

[Crosswire]

Without bonding..................

 

[Marvo]

I think I've only once tested across unbonded services many years ago whilst trying to establish the root cause of a corrosion problem that resulted in a massive amount of copper pipework being condemned and replaced. I can't remember the exact readings we got but we were looking more for a DC potential than an AC voltage.

 

[44ALLAN]

Anyone ever noticed a difference between these? Just curious.........

Have you ?

Have you put a clamp meter on your main bonds etc..............copper pipework?
You'll be amazed

 

[Crosswire]

Have you ?

Have you put a clamp meter on your main bonds etc..............copper pipework?
You'll be amazed

To be honest, I haven't.

But I am intrigued by your post, and I will do so on the next available opportunity.

Have you measured current on bonds or pipework? Maybe with a nominal voltage to 'earth'?

 

[Farmelectrics]

44alan explain more

 

[JD6400]

I have no idea where I first heard this , but I have always understood that the reason for having to TT agricultural installations with livestock present , was to prevent " Dirty DNO earths " from importing in stray voltage !? In the days of the sixteenth , I think it was all agricultural installations ? But after having a look for my old copy of the sixteenth I appear to have lost it so can not check that last bit !

 

[44ALLAN]

44alan explain more

Well actually the OP was asking about pd which as you know is potential difference/voltage which we obviously negate where necessary by bonding..............not earthing.

If you have a clamp meter........which you should have as their handy bits of kit.
Go around your place of work and clamp your 'earths' and 'bonds' and see if you get any readings.
10mA is safe they say...............I can get 360mA on my main gas bond !!
Question is ..........is it leaking out or coming in

 

[Knobhead]

Before bonding is applied I’d be amazed if you didn’t get a PD between services.

It would help if you put a bit more meat on the bones. What readings did you get? What is the earthing arrangement?

 

[guest119]

I have no idea where I first heard this , but I have always understood that the reason for having to TT agricultural installations with livestock present , was to prevent " Dirty DNO earths " from importing in stray voltage !? In the days of the sixteenth , I think it was all agricultural installations ? But after having a look for my old copy of the sixteenth I appear to have lost it so can not check that last bit !

Which is the essence of a parallel thread at the moment re petrol stations.

Boydy

 

[JD6400]

I will have a look at it , Thanks

 

[skydog23]

Electrolytic reaction by two dissimilar metals will produce a voltage. I.e. a battery.
I owned land rovers for many years and you could nearly hear them generating lol.
I can't see why copper or steel pipes could be any different in a dissimilar medium, and produce a voltage. How much I have no idea ?

 

[JD6400]

Electrolytic reaction by two dissimilar metals will produce a voltage. I.e. a battery.
I owned land rovers for many years and you could nearly hear them generating lol.
I can't see why copper or steel pipes could be any different in a dissimilar medium, and produce a voltage. How much I have no idea ?

As I understand it , this was made significantly worse due to the early models having a positive earth ?

 

[Knobhead]

The Ford Popular 100E suffered the same problem. A mate has one, I converted it to –ve earth a few years back.

Back to the OP, what readings did you get?