Tn-C-S Or Tn-S

[Sidewinder]

Those figures don't add up.

A loop impedance of 0.35 gives a PSSC of just 657 Amps

Were those figures by measurement? or just somebody's guess?

PD,

These are typical DNO figures which are the worst case scenario, so we can design our kit and be sure that they will not go outside these values basically, so the EFLI could be so low that you get 16kA, or it could be up to 0.35 Ohms.

This depends on the exact install I believe, so they quote a general figure;

 

[revor]

That is correct they have quoted what the worst case scenario is. The same figures are illustrated in the rather excellent DVD by Megger /NICEIC on initial inspection and test for domestic properties. The guy I spoke to at SP did say that the impedance would be less than 0.35 they would not leave it any higher. We will see what the actual value is when it gets measured. He also did say that all installations they now do are PME