Main earthing by gas pipe.

[pevvers]

I wasn't talking about an earth fault, by the way.

I was talking about the normal operating current taking this path as oposed to travelling down the neutral(of higher impedance)

Huh? Why would any current other than slight leakage be flowing in the earth in normal operating circumstances?

Both conductors are going to be completely separate upstream until you hit the supply in a TN-C-S system, so surely unless you have a neutral-earth short circuit then there would be no path for the current to get on the earth?

 

[WayneL]

Huh? Why would any current other than slight leakage be flowing in the earth in normal operating circumstances?

Both conductors are going to be completely separate upstream until you hit the supply in a TN-C-S system, so surely unless you have a neutral-earth short circuit then there would be no path for the current to get on the earth?

But if you bond the gas pipe (with the 0.19 ohm Ze) to the MET, the MET is connected to the neutral at the service head.

So when the normal operating current of the installation flows down the neutral to the service head, it has a choice of path back to the transformer......down the neutral (Ze 0.35) or down the Earthing conductor/Bonding conductor/gas pipe (Ze 0.19).

Where do you think most of it will go?

This is why losing the supply neutral on a PME (PEN) system is so worrying.

And this is why I said 0.19 was awfully low for a gas pipe.
You will always get some current flowing down the parallel paths, but it shouldn't be anywhere near that amount.

 

[pevvers]

But if you bond the gas pipe (with the 0.19 ohm Ze) to the MET, the MET is connected to the neutral at the service head.

So when the normal operating current of the installation flows down the neutral to the service head, it has a choice of path back to the transformer......down the neutral (Ze 0.35) or down the Earthing conductor/Bonding conductor/gas pipe (Ze 0.19).

Where do you think most of it will go?

This is why losing the supply neutral on a PME (PEN) system is so worrying.

And this is why I said 0.19 was awfully low for a gas pipe.
You will always get some current flowing down the parallel paths, but it shouldn't be anywhere near that amount.

Hmm, I like you, you make me think!!

I doubt very much that the earth is actually 0.19 ohms, as it is just a large earth electrode, so methinks the test has been wrong or this is due to parallel paths somehow...

I agree with losing the neutral on a PME supply, but that's why it's an ME and not just an E.

 

[pushrod]

Hmm, I like you, you make me think!!

I doubt very much that the earth is actually 0.19 ohms, as it is just a large earth electrode, so methinks the test has been wrong or this is due to parallel paths somehow...

.

I think Des probs hit the nail on the head with post #15

 

[jimes]

disused pipes can be used but id try for pme

 

[miLarKey]

My thoughts exactly.....If you have to ask whether it is acceptable to use a gas pipe as a main earth you do not have sufficient knowledge to be carrying out a PIR.

*******Removed******* I knew it wasn't acceptable for BS7671:2008 but the wiring was over 60 years.

 

[Engineer54]

So you haven't been around for nearly 3 years, and come back having a rant at a respected member, for making what was a valid observation!!

See you in another 3 years then!! lol!!

 

[Geordie Spark]

*******Removed******* I knew it wasn't acceptable for BS7671:2008 but the wiring was over 60 years.

Did you manage to sort the problem ok??

 

[miLarKey]

So you haven't been around for nearly 3 years, and come back having a rant at a respected member, for making what was a valid observation!!

See you in another 3 years then!! lol!!

I have been around I have just had better things to do then spend time on here. I am in a band now that is doing very well and I only found your quote as I was carrying out a google search for something else. I am so glad I do not have work in the electrical/building trade any more. You my be a respected member on here but you a definitely not respected by me.

*********Removed********

Btw to all you other members re the gas pipe, it was a very old 3" in diameter one that was in a 1930's purpose built flat in London. This is why I think the readings were low due to the size of it and parallel paths. Thank you to all of you that responded to me in a helpful manner.

 

[miLarKey]

Did you manage to sort the problem ok??

I gave them a price to install and earth spike. But same old story: "We don't have the money".

Thanks for asking.

 

[Marvo]

Foul language and abusive posts aren't tolerated.

 

[telectrix]

Foul language and abusive posts aren't tolerated.

i,m surprised a 30 day ban has not been made. marvo, you must be in a good mood. :chillpill:

 

[Marvo]

I was doing several other things at the same time so I'm a bit slow this afternoon

 

[Engineer54]

I am so glad I do not have work in the electrical/building trade any more. You my be a respected member on here but you a definitely not respected by me.

Just as well you're out of the industry, if you actually left the installation as was, without a primary means of main earthing!!

In a Band now eh, so now probably on a constant high, on wacky baccy or stronger, .....another flash in the pan musician that think what they have to say, is somehow more important than any others opinion!! lol!!

 

[Mpe123]

What code would you guys have given this on the eicr?
It was a question on my recent 2391 exam.

 

[loz2754]

C2 according to Electrical Safety First best practice guide 4.

 

[Mpe123]

C2 according to Electrical Safety First best practice guide 4.

That's what I put. Thanks ?