calculated R1 + R2

[Martindhughes]

When changing a consumer unit - instead of performing R1 + R2 test is it ok to carry out ZS at every point in the circuit and then calculate zs ?

 

[Sintra]

No you never calculate R1 + R2 except for design purposes.

 

[johnboy6083]

I completely agree. To reinforce the point: what of your Zs was low due to parallel paths, that hide a dodgy connection on the circuit?
Its a similar thing, when you leave bonding connected for a Ze. The bonding can & often does hide a high impedance on the incoming service!

 

[Farmelectrics]

^^^^^^^^^^ agree with above but in past ive seen companys that do calculate r1 r2 readings when doing periodic inspecting in supermarkets that had there testers doing live test only on lighting circuts recording zs and with using ze they would calculate r1 r2 the supermarkets wouldnt let the sparks turn of the lighting its not right but its happening out there

 

[Sintra]

In that scenario I still wouldn't calculate. On an EICR it is best to state it as a limitation and mark as not tested rather than guessing.

 

[Farmelectrics]

sintra thats what i used to do a while back when doing them id put live tests only on lighting circuts but the companys niceic guy would calculate them saying the more readings on the test sheet it looks better honest and he was there niceic approved guy

 

[Martindhughes]

Thank you one and all - I now see the error of my thinking ie the only way of testing the cpc particular to the circuit being tested is to have it disconnected from the board and away from other potential paths.