Max Zs on certification

[Dan007]

Please can people clarify what value they insert in the Max Zs field on certification.

I've always input 100%. Currently in disagreement with another person as they are specifying 80%.

Done my 2391 in 2008 and I was taught and told it's always 100% and it's down to the QS to interpret the results and ensure they fall with 80% allowing for correction factors.

Third argument is that in GN3 and OSG they specifically state 80% - however I always understood these to be quick reference pocket guides while on site.

In the mentioned publications and BBB the model forms show 100% in the compelte fields for examples. Secondly the small print at the bottom makes reference to the Publication and values in Chapter 41 aka BBB and 100% values.

Your thoughts please people

 

[westward10]

Hello Dan welcome, I have edited your post as you said you could not do it in #2, deleted.

 

[SparkyChick]

Personally I put down the adjusted value, because that for me is the real (if you like) value to which the circuit must conform.

 

[Strima]

I always put in as required by BS7671, no arguments then or confusion.

 

[johnduffell]

The purpose of a well designed form is to make sure you only have to think about one thing at a time.
Therefore when filling it in you should do the full calculation, and when measuring the zs all you do is measure and fill in. Then to determine compliance you just compare the two without any other thought.
If part of the calculation is mixed with the comparison things would get very hairy.

 

[Wilko]

My 20p worth - I put in the values list for max Zs in the tables of Chapter 41. There's a little footnote at the bottom of Generic Schedule of Test Results in BBB p483 that sort of says to do this (in typical IET fashion). I pop the 80% value in the remarks column for JD's excellent reasons.

 

[Risteard]

You should not insert an adjusted value but the actual maximum value as per BS7671.

 

[Dan007]

Typically most seem to think the same as myself. Always insert the maximum as the certificate requests.

Again the foot note does indeed require values from Chapter 41.

 

[Dan007]

Anyone have anything from BS7671 minus the footnotes in the example forms?

 

[Nigel]

You should put in 100% value as that is what the true max Zs is and what the OCPD has been tested to.