L
LankyWill
That is not a method of testing, it is a method of calculating an estimated value.
It is not a viable method of attaining a value for the continuity of the CPC, for initial verification it is a requirement that the R1+R2 or R2 be measured prior to making a circuit live,
not sure thats fact dave, im sure it states, measure or calculate. If the earth path was compromised the zs reading would show this so its no different to R1+R2 and saves loads of time.