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.

 

[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
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