Measuring Zs

securespark · Posted: Thu Nov 05, 2009 10:32 pm Post Subject: Measuring Zs

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?

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Spark123 · Posted: Thu Nov 05, 2009 10:34 pm Post Subject:

Yep, he should be adding R1+R2 to Ze

securespark · Posted: Thu Nov 05, 2009 10:36 pm Post Subject:

Always get them muxed ip....

So you think the QS is being harsh?

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As George Michael once said, "..if you're gonna do it, do it right, right?"

Taylortwocities · Posted: Thu Nov 05, 2009 10:39 pm Post Subject:

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.

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GaryMo · Posted: Thu Nov 05, 2009 10:40 pm Post Subject:

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 · Posted: Thu Nov 05, 2009 10:41 pm Post Subject:

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

securespark · Posted: Thu Nov 05, 2009 10:49 pm Post Subject:

Thanks for confirming my suspicions, guys.

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

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As George Michael once said, "..if you're gonna do it, do it right, right?"