Zs with TT system

[markymark2406]

Trying to clear something. Up here as there are so many conflicting answers.

I'm getting over 200 ohms earth loop at sockets in a property on a TT earth arrangement, what is the maximum permissible ?

 

[Spark123]

200 ohms is the max for reliability in guidance docs.
The max in the regs 1666 ohms for a 30mA RCD protected socket circuit (50v/0.03A=1666 ohms).
So although the theoretical maximum is above 200 ohms, this should not be exceeded as it is considered unreliable.

 

[Taylortwocities]

200Ω is the guidance max for the earth electrode itself. With no bonds to other services in place.

If you get 200Ω+ at a socket, you need to check on your bonding and investigate improving the Ze of the earth electrode.

PS I hope that is a 30mA RCD, and it is running to spec.

 

[markymark2406]

Ok so to get a proper correct figure disconnect the bonding to the water and gas (as pictured)?
I think I may get the service provider to see if they can PME the earth but obviously the Ze needs to be below 0.35 for them to do this, if so is the main rcd ok to remain?

 

[Taylortwocities]

@markymark2406 FFS. You are obviously doing this job and getting paid for it.
You do not have a clue.

With a Zs that high, lets say you remove the RCD. Where do you think the earth fault path will be if there is an earth/live fault?


I hope you have got insurance, you are going to need it.

 

[markymark2406]

I'm only asking and learning off the answers people give, I'm not touching anything !

 

[securespark]

Numerical spark - it's only 1 ohm, but I thought the regs said 1667, which I think is wrong, as it puts the touch voltage above 50V.

I used to be guided by the 100 Ohm maximum that ECA used to set (don't know if it's still the same).

If you have a reading above 100, investigate it to find out why.

OP - in the earth block at the intake, you have one to the CU and two others - do these go to the service pipes?

You may have a poor earth off the pipework and no earth electrode!

 

[ban-all-sheds]

I'm only asking and learning off the answers people give, I'm not touching anything !

Ok so i have NVQ part3, i have the 17th edition, shortly to be undertaking testing and inspecting course and exam.

What have you been doing since then? Did you do the T&I course? Did you pass the exam? Or given that you can't even do simple cable sizing calculations or basic maths, was it all too much for you?

//www.diynot.com/diy/threads/swa-size.174636/

Same Q 8 months later, same "qualified electrician" who can't do cable sizing: //www.diynot.com/diy/threads/cable-culculations-for-shed.205483/

And another: //www.diynot.com/diy/threads/outside-heaters.235103/​

But back to asking and learning:

Im going to be embarking on a 2391 inspection and testing course next years, just wondered what the best and easily understood book would be to read?

Guidance Notes 3 and Brian Scaddens Inspection, Testing and Certification was all I needed to pass my C&G 2391.

Marky - why ask questions here if you are going to do SFA with the answers you get?