readings for tt system

[meady]

Hi people

I carried out a cu change today, on a sunday off all days . It was on a tt system by the way. I upgraded the main earth to 16mm with new stake and upgraded bonding. The ze reading I got was 28.5 ohms. All other test were good, r1+r2, ir tests were fine but im not to sure about the zs readings I got. On the sockets I was getting around 4.5. Not done much testing on tt system so I just wanted to run the zs reading by you guys.

Thanks

 

[kme]

Sounds OK - If your Ze (Ra on TT) i.e. earth loop down the Earthing conductor ONLY was 28.5, it is less than the stable limit of 100 ohm given by regs.

When you reconnect the EC to the MET, you provide parallel paths via the bonding conductors. So when you test your S/O, you get 4.5 ohms, which is perfectly acceptable. Many times on TT, you`ll be lucky to get 100 ohm.

HTH

KME

 

[meady]

Sounds OK - If your Ze (Ra on TT) i.e. earth loop down the Earthing conductor ONLY was 28.5, it is less than the stable limit of 100 ohm given by regs.When you reconnect the EC to the MET, you provide parallel paths via the bonding conductors. So when you test your S/O, you get 4.5 ohms, which is perfectly acceptable. Many times on TT, you`ll be lucky to get 100 ohm.

HTH

KME

Thats a weight of my mind, yeah my Ze, Ra was disconnected from the MET and was well happy with that reading but was just concearnrd about the Zs. Thinking about it now it makes sense taking into account of parallel paths.

 

[kme]

Glad to help.

 

[batty]

As lomg as everthing goes through an RCD of some sorts those readings will be fine.

Batty

 

[cheggers]

why did you use a 16mm earth

 

[Apache]

why did you use a 16mm earth

Some of the electricity companies insist.

 

[PC Electrics]

And,

if next door has TN-s or TN-C-S and there is electrical continuity on either the gas or water pipes, then you can get low Zs readings below 1ohm even on a TT with an Ra of 20+ohm thanks to parallel paths.

 

[meady]

why did you use a 16mm earth

I used 16mm because it's quite a long run + it's future proof. Sods law the regs will change soon so it gives me peace of mind that the connection is upto standard.

 

[Badger]

Sounds OK - If your Ze (Ra on TT) i.e. earth loop down the Earthing conductor ONLY was 28.5, it is less than the stable limit of 100 ohm given by regs.When you reconnect the EC to the MET, you provide parallel paths via the bonding conductors. So when you test your S/O, you get 4.5 ohms, which is perfectly acceptable. Many times on TT, you`ll be lucky to get 100 ohm.

HTH

KME

yeah but i find p!$$!ng on it helps :^O :^O:^O:^O:^O:coat