max Zs

[wolfboy]

Hi can you put me straight on this.
When testing a new installation your measured Zs must be less than 80% of regs figure, allowing for temperature difference at testing and normal operating.
So when doing a periodic, as this installation is already at normal operating temperature, your measured Zs must be less than 100% of regs figure?
sorry if im being blonde here

 

[saveloy]

Forgive me if I misunderstand your post, but I think you are getting confused between ambient temperature, and conductor operating temperature under fault conditions.

Under fault conditions conductor temp will rise considerably thus increasing the resistance of the conductor.
When testing Zs your meter will not replicate the rise in temperature and thus the increased resistance/Zs. That is why we only go to 80% of max Zs values in the BRB.

It makes no difference whether the installation is new or old. Max measured Zs must always be 80% or less than max values in the BRB.

Hope this helps