TT Supply, Testing Questions..

[Spudnik]

Im sorry but,
I prefer to inform what the requirements are rather than any personal options which may convey stricter results than are needed and may confuse.....

Totally agree there Des.

Didnt mean to preach!

However, generally its not hard to get a result below 100, without even trying!

 

[Stedger]

This has been a fantastic read, and very informative.
Thanks alot guys!

 

[TPES]

That 21 ohms is the suppliers maximum or stated, for the star point of the supply transformer and their own earth electrode
The maximum for the operation of a 30m/amp rcd is 1667 ohms however,

Any reading of your earth (which includes the suppliers 21ohms)should be under 200ohms

Anything above this figure could be considered as unstable,because for instance it may rise in drier whether when soil conditions are different

The 100ohms mentioned is an NIC figure erring on the side of extra safety and is guidance for their members only,the IEE regulations are the figures to follow for everyone else

Excellent des, Thanks for a good answer. Just what i wanted to know

It is difficult to see from your pics but the lower cu has a link from its earth terminal to the one above. My guess from what you say is that the yellow/green from the lower goes to an earth rod as well as another one from the the upper cu to a different earth rod. In this case surely they are effectively the same assembly, possibly a second rod being put in to improve the first. That being the case the only concern as I see it is that one rod is a rods length away from the other.

This is exactly what has happened here.. Just as you've said.

So as you say this second rod would have been put in to improve the Ze/electrode reading?

Do i just take the lowest reading from either rod and record this on both of the sepearte test results for each CU?