Out Building Has No Earth

[Pippyboy1916]

Ze in main building 0.09 ohms

 

[malcolmsanford]

Then you have either lost the exported earth, or it as never been exported and is relying on parallel paths. So the next step is to check the continuity of your sub main.

 

[Pippyboy1916]

the earth is lost to the out building, im asking about the earth rod to the out building and putting a rcd on the main switch? a statement was made about the rcd taken over the disconnion times, wel that mean u can have a nail where the mcb's are and i really know thats no kosher!

earth rod yes or no?

 

[malcolmsanford]

Yes you can put an earth rod in and make the out buildings TT.

If you wish you can fit a RCD as a main switch. You will though have to decide now what size RCD as a main switch, are you going to fit a 100mA RCd as that main switch then 30mA for socket circuits and any other circuits that are needing a 30mA. What about fitting a main isolator and RCBO's if the installation is not to big.

Back to original OP, if your circuits are protected by a 30mA RCD then your Zs values will be 1667, so don't get hung up about high values for the MCB, as they are providing overload protection only.

Another plus to a local TT system is that if there are any metal services or metal work frame to the out building then you can bond using the local CU earth bar, rather than running a bonding conductor back to the original MET.

 

[Pippyboy1916]

cheers, so if the board has an rcd on it, up can have Zs of upto 1667 ohms? in the main building it has an rcd before the isolator. just not happy the out building has reallly no earth. the question is that this inspection can be passed as satisfactory?

 

[SimpleSimon]

No because you have an outbuilding with no earth what-so-ever. I would put that down as a cat 1.