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Discuss Best ZE on TT in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

On a rewire with another member of the forum a few months back and he beat my record mate but he cheated. He took the measurement on the existing rod(s) (on my recommendation I hasten to add) and we decided to leave that in place.
 
But surely, ....No-one can achieve TN values, or a sub 1 ohm Ra values from a Roded TT system!!! Well that's what some here would have you believe anyway!! Others just don't even bother and put all they're faith in a RCD!! lol!!
 
But surely, ....No-one can achieve TN values, or a sub 1 ohm Ra values from a Roded TT system!!! Well that's what some here would have you believe anyway!! Others just don't even bother and put all they're faith in a RCD!! lol!!


Course they do, they forget to disconnect any parallel paths.:o_O:

On the 13 ohms I mentioned, with bonding connected to gas and water supplies, when i took the measurement again, the Ra had dropped to 0.3 or there abouts
 
Course they do, they forget to disconnect any parallel paths.:o_O:

On the 13 ohms I mentioned, with bonding connected to gas and water supplies, when i took the measurement again, the Ra had dropped to 0.3 or there abouts


That would be Zs!! And i doubt very much that any bonding would pull your Zs down to 0.30 ohms. ....Not unless someone down the street has a PME connection, as both the water and gas main pipes generally have an underground protective anti corrosion covering...
 
No seriously E54, i'm being genuine.

Zs at origin then i suppose.

I don't disbelieve you, far from it. But there will be a reason for that dramatic fall in your Zs values, and the most likely one being PME connections along the street. Be they official or unofficial PME connections. ..lol!!
 
Yes, you're right E54. Its only 3 small cottages that are TT, for some reason everything else has been converted at some point.

Water is still supplied in lead which pretty sure won't have any corrosion protection applied.
 
Yes, you're right E54. Its only 3 small cottages that are TT, for some reason everything else has been converted at some point.

Water is still supplied in lead which pretty sure won't have any corrosion protection applied.


You say that, but my parents house had a lead water supply, when we came to add an extension and dug out for the foundations, that lead pipe had a DENSO type tape (Grease impregnated tape, ..horrible stuff) wrap!!
 
Oh yes, know the stuff well. Takes days to clean your hand up after using it!

Its just from other experiences really with working in close proximity to this place. Other houses have alterations done and only ever seen the lead naked in the ground.

Know what you mean though
 

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