Measuring Zs

[securespark]

A colleague has phoned me today with a tech. query.

He has been pulled up by his QS for calculating Zs by adding r1+r2 to the Ze.

Is this fair?

 

[Spark123]

Yep, he should be adding R1+R2 to Ze

 

[securespark]

Always get them muxed ip....

So you think the QS is being harsh?

 

[Taylortwocities]

NOT FAIR

612.9 says (when determining EFLI) the relavent impedances shall be measured or determined by an alternative method.
GN3 states Zs can be determined by adding Ze to R1+R2 and Zs will be that figure or less - due to paralleled earth paths.

Personally I don't entirely trust the EFLI figures measured by 'No RCD Trip' testers. I'd go for Ze + R1 + R2 any time.

 

[GaryMo]

Yes, the QS is being harsh.

Why should your colleague subject himself to live testing when there's no need to? Calculation is more than adequate.

 

[Spark123]

IMO it is better by direct measurement where you can, low current testers often measure high.

 

[securespark]

Thanks for confirming my suspicions, guys.

He'll be a happy chappy tomorrow when I ring him!