Testing Results

[SSE]

I'm by no means an expert at testing hence the reason I'm asking this question so was just wondering in general is r1+r2 bigger or smaller than Zs. From the testing I've done I've noticed they seem to be pretty similar but sometimes r1+r2 is bigger than Zs and sometimes smaller!

 

[Guest123]

It would very much depend on the earthing system of the installation as this affects the Ze which inturn affects Zs.

 

[SSE]

It would very much depend on the earthing system of the installation as this affects the Ze which inturn affects Zs.

All systems that have tested recently have been tncs.

 

[lukeallen88]

r1+r2 should in theory be smaller because zs is (r1+r2)+ze.

 

[Izzy's Dad]

All systems that have tested recently have been tncs.

So, Ze should be max of 0.35 ohms and Zs = Ze + (r1+r2)

 

[leokiss]

Parallel earth paths throw results out sometimes as do the connections of the test leads to the circuits.

 

[SSE]

Cool, cheers for replies. Another quick question, obviosly each house would be different and only looking for guidance but how long roughly should it take to do a PIR on a property that has 6 circuits on the domestic board and 8 circuits on the heating board if you were to do it by yourself? Including screwing everything off and on and filling in the forms?

 

[leokiss]

It would depend how deep you wanna dig which is down to your discretion,i think the rule of thumb is a minimum of 15% of installation.

 

[SSE]

Just checking some of the results on previous test sheets and Ze +(r1 +r2)=Zs is just about right although not bang on, is this quite normal or is it normally bang on?

 

[Sintra]

In a perfect world they would be dead on but due to parallel paths, connections of leads, slight inaccuracy of test equipment etc. the tested results will vary slightly from the calculated ones.

 

[SSE]

In a perfect world they would be dead on but due to parallel paths, connections of leads, slight inaccuracy of test equipment etc. the tested results will vary slightly from the calculated ones.

Cheers.

Also after seeing the formula in one of the first replies I remember being taught at college that formula and I know one person that uses the formula instead of taking direct measurement, is this common?