zs tabulated values

[r.b]

As a rule of thumb do you always times the tabulated values in the regs by 0.8 and tally this up with your measured value of zs.If your measured value is lower than this calculation is this deemed as a failure above this value a pass?

 

[philbas]

Other way around, below is a pass, above is a fail.

You want your Zs to be as low as possible.

 

[bhamoggy]

Do you mean if its under the regs book requirement but over the amount once multiplied by .8 ?

For example zs 1.44 in the regs and 1.15 once divided by .8 rule of thumb. And maybe measured zs is 1.3

That grey zone area is , and I stand to be corrected here, but when your zs is only multiplied by .8 if the cable temperatures are likely to increase.

Like I say, I may be wrong.

 

[sparkytim]

If the test measured value does not meet the ADJUSTED value, i.e. 1.15 in your example then it is NOT ACCEPTABLE as the ACTUAL value under Fault condition will be nearer to 1.44 due to the effect of temperature increase.

As RCDs now provide protection on most circuits (Max value for 30 m A 1666.66 ohms) then Zs not often a problem.