TT off water main or tncs with no earth (Victorian house city centre)

[James Kinrosd]

Hi guys came across this today, Ze of 37 ohms, surprised me as thought it was a tncs- Victorian house, Db from 1989, no docs- could it be a TT off the water main? 10mm bonding to gas and another 10mm out of sight. The met on the rhs of tncs
block not connected to neutral- can anyone help me with some ideas? Cheers.

 

[Midwest]

Hard to tell from your pic, set up would suggest TT. Have you followed the route of the EC and see where it terminates, the head looks like PME, have you asked the DNO?

Just re-read your post, you say the earth is not connected to the neutral link?

 

[BOYD BARKLEY]

Hard to tell from your pic, set up would suggest TT. Have you followed the route of the EC and see where it terminates, the head looks like PME, have you asked the DNO?

Just re-read your post, you say the earth is not connected to the neutral link?

Try to get a PME terminal from the DNO or you could drive a new spike in directly below in the sub floor and convert to tt system,
then sell them a new board.

 

[westward10]

I know what I would do

 

[James Kinrosd]

EV disappears below floor to back of house possibly to water main. Rang DNO, they were not helpful- have to wait for an appointment. Earth not connected to neutral- inside the block, seals already broken. Checked neighbour's, his is the same but neutral connected to earth inside the block - looks like his is tncs and he had a 0.54 Zsat the kitchen ring..

 

[The Ghost]

ggg

 

[ruston]

EV disappears below floor to back of house possibly to water main. Rang DNO, they were not helpful- have to wait for an appointment. Earth not connected to neutral- inside the block, seals already broken. Checked neighbour's, his is the same but neutral connected to earth inside the block - looks like his is tncs and he had a 0.54 Zsat the kitchen ring..

Any sticker on the neighbours?

 

[James Kinrosd]

No it's even older....

 

[James Kinrosd]

Just wanted to know really if there was a practice 40-50 years back of using water mains as TT.....?

 

[ruston]

@James Kinrosd. A water pipe can be used with the owners permission .

 

[Taylortwocities]

A water pipe can be used with the owners permission .

Until it gets replaced with a plastic one, then you are stuffed.

 

[ruston]

Until it gets replaced with a plastic one, then you are stuffed.

There is a proviso about it's security , but I cannot remember it off the top of my head now lol.

 

[Rpa07]

ggg

If this were multiple choice @Vortigern, you would have failed having only got 1 out of 3 correct. The other answers were c and a by the way!

 

[BOYD BARKLEY]

Until it gets replaced with a plastic one, then you are stuffed.

It was common practise many moons ago to use the pipe as means of earthing . You still can with the owners permission which would be a pain to get and unreliable as pointed out,with constant upgrading etc.to plastic

 

[ruston]

It was common practise many moons ago to use the pipe as means of earthing . You still can with the owners permission which would be a pain to get and unreliable as pointed out,with constant upgrading etc.to plastic

It was common up here as there are a lot of TT systems .
A lot were in the colliery housing areas , the replacement plastic pipes left the old cast pipes intact , usually under the gardens , so fairly safe until the houses are demolished .
The last one I worked on many years ago the RA was 6 Ohms.

 

[BOYD BARKLEY]

If that's the the case and yo've got 37 ohms yo've cracked it any thing under 100 is fine.

 

[James Kinrosd]

Many thanks for your replies guys! Even if left as is, or with an additional earth spike, am thinking the board would have to be updated to protect the circuits on the right hand side that only have a 100ma RCD to bring them under a 30ma RCD.....

 

[James Kinrosd]

Many thanks for your replies guys! Even if left as is, or with an additional earth spike, am thinking the board would have to be updated to protect the circuits on the right hand side that only have a 100ma RCD to bring them under a 30ma RCD.....

 

[ipf]

It was common up here as there are a lot of TT systems .
A lot were in the colliery housing areas , the replacement plastic pipes left the old cast pipes intact , usually under the gardens , so fairly safe until the houses are demolished .
The last one I worked on many years ago the RA was 6 Ohms.

Innovative more than informative, rus. I like that.
Common sense really, though, as you say.

 

[ruston]

Yes ' The death of common sense ' lol.
The ground was so wet around these houses anyway even with rods the readings were quite good. They are still standing and in use to this day.
Not by Miners though . ( cap intended)

 

[mhar]

What is the earthing block to the rh side of the cutout?
The cutout is just one of the solid n e ones which doesn't require a link. That cannot be taken as an indication that PME is available

 

[suffolkspark]

have you taken a reading to see if you can just stick that conveniently located earth wire in that neutral block or are we just overcomplicating things here?

 

[James Kinrosd]

The earth block runs into the terminal and there is space for a link, the neighbour's block is identical and has a link- here's the a pic of the next door one...

 

[James Kinrosd]

Yes I read through the neutral got a nice 0.27 Ohms...

 

[NDG Elecs]

I had a dodgy homemade tns the other week with a Ze in the kilo ohms. DNO came out, officially declared it was never a tns (probably was in reality, should check a few neighbours maybe) and that I should TT it. Very decent initial Ra of 11 ohms from one rod, with a Zs that dropped to 1.35 ohms ish on a B32 with the water bond. I am very tempted to bang another rod in to see if I can bring the Zs's down further, albeit with a lot of thanks to the water supply pipe!

 

[Octopus]

I was under the impression that you can only use a water pipe of it's your own private supply ..

 

[BOYD BARKLEY]

I was under the impression that you can only use a water pipe of it's your own private supply ..

542.2.6 Dose state that.

I was under the impression that you can only use a water pipe of it's your own private supply ..

I was under the impression that you can only use a water pipe of it's your own private supply ..

 

[ruston]

It goes on to say that other metallic water supply pipework should not be used as an earth electrode unless precautions against it's removal and it has been considered for such use.

 

[BOYD BARKLEY]

It goes on to say that other metallic water supply pipework should not be used as an earth electrode unless precautions against it's removal and it has been considered for such use.

Yes, it dose.

 

[Taylortwocities]

You should keep an eye on the 18th. It has a few things to say about this

Chapter 54
CLICK

 

[BOYD BARKLEY]

You should keep an eye on the 18th. It has a few things to say about this

Chapter 54
CLICK

Thankyou. Here we go again, many questions will follow the path of
ambiguity. They love it don't they !

 

[mjb]

Looks like a TNS from a lead covered cable.
Originally supply cables did not provide an earth point the lead just providing protection for the cable, so many services are actually TNS with no earth terminal.

 

[Nigel]

Did you ky disconnect all parrellel paths before doing the Ze test?

 

[stevels4]

The earth block runs into the terminal and there is space for a link, the neighbour's block is identical and has a link- here's the a pic of the next door one...View attachment 41076

That is TNS.

 

[davesparks]

The earth block runs into the terminal and there is space for a link, the neighbour's block is identical and has a link- here's the a pic of the next door one...View attachment 41076

That is a TNS cutout fed by a split concentric cable, you can just see the bare earth conductors connected to the earth terminal internally.

However this begs the question of why you are breaking the seals and taking cutouts apart?

 

[davesparks]

If that's the the case and yo've got 37 ohms yo've cracked it any thing under 100 is fine.

Where did you get that bit of nonsense from? Direct from the -------- generator at NICEIC headquarters?

 

[BOYD BARKLEY]

Where did you get that bit of nonsense from? Direct from the ******** generator at NICEIC headquarters?

For embedded metal work or earth rod ********

Where did you get that bit of nonsense from? Direct from the ******** generator at NICEIC headquarters?

 

[davesparks]

For embedded metal work or earth rod ********

Eh? I asked where you got that value from, not what you were referring to.

 

[BOYD BARKLEY]

Eh? I asked where you got that value from, not what you were referring to.

200 Ohms is the value recommended not to be exceeded in regs, as you well kn0w . Yes NICEIC do recommend under 100. For an earth electrode. So far as the nonsense is concerned(I'll be objective here not obstructive)If you look at B.S.7430 IT RECOMMENDS 100 ohms max and 2 meters of rod as the top meter of soil can be unreliable. Eh?

 

[Sylvia Namusisi]

@James Kinrosd. A water pipe can be used with the owners permission .

Not with the current regs,it will not comply.You would have to drive a new earth electrode down.

 

[Sylvia Namusisi]

No

I was under the impression that you can only use a water pipe of it's your own private supply ..

No Sir,not allowed private or public.

 

[sparksburnout]

No
No Sir,not allowed private or public.

Oooerr Mrs.

 

[DPG]

No
No Sir,not allowed private or public.

Thought under certain conditions it was allowed .

 

[Octopus]

No
No Sir,not allowed private or public.

Reg number?

 

[sparksburnout]

Reg number?

 

[Octopus]

No
No Sir,not allowed private or public.

Maybe you need to read 542.2.6 BYB again .................

 

[Sylvia Namusisi]

Maybe you need to read 542.2.6 BYB again .................

Yes true ,that is the reg no.thank you.

 

[DPG]

Yes true ,that is the reg no.thank you.

And does it say that it is completely prohibited to ever use a water pipe??

 

[Octopus]

And does it say that it is completely prohibited to ever use a water pipe??

No it doesn't ...

 

[Sylvia Namusisi]

And does it say that it is completely prohibited to ever use a water pipe??

Yes, last sentence of 542.2.6 -Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use.