Zs testing

[pushrod]

Just wondering if everyone actually does a Zs test when filling in a schedule of results. In the OSG it says that you can measure it or calculate it by addition. I appreciate the different value stuff, just thinking it is a lot easier and quicker to be adding 2 figures together than taking things apart and getting your test meter out again.

Cheers.

 

[johnboy6083]

i think calculation is the way to go, as it gives you the worst case scenario. IE, the ZS reading might come in ok, but only because of some supplemantary bonding somewhere giving a better path to earth. In a few years, when the bathroom is changed, and the bonding is removed because it is no longer needed, then you have affected the protection of you original circuit that you measured ZS on.
Also it reduces the need to work live, as EAWR regs state: you should only work live where it is not reasonably practical not to do so.

I predict a good debate on this one!

 

[Ponty Massive]

I haven't got a D LOC on my tester, too much work taking out the RCD so calculation for me!!

 

[Deleted member 9648]

I measure when practical...but calculate for RCBo's as they always trip and calculate most of the time on lighting circuits,as most light fittings are not exactly Zs tester friendly....and even if you do manage to connect the probes the ******* 6a type B mcb pops out so you end up calculating anyway.

 

[Spudnik]

From what i understand, it is acceptable to calculate Zs on a PIR, but not on a new or altered installation.

 

[Guest123]

Always measure.

 

[Sparky Ninja]

Always measure.

+1

 

[mrmatt]

Someone always told me skip whatever test you want but if I find out you skipped the ZS test I'll sack you!

so always measure

 

[Sintra]

I always measure one reason being if you have a faulty mcb or main switch in the installation with high resistance accross the device then the only test that will pick up this problem is a measured Zs.

 

[kung]

measure sockets & calculate radials

 

[Graeme Harrold]

Always test, as its the final belt and braces check on a circuit. Takes seconds anyway.......

 

[WayneL]

From what i understand, it is acceptable to calculate Zs on a PIR, but not on a new or altered installation.

And how would you do that?


I vote for 'measure it' - especially if your only reason for not measuring it, is that you are too lazy to get out of your van and get your meter out

 

[johnboy6083]

Ive got to admit, i didn't think about the loop test being the only one that tests the MCB (for resistance anyway). Thats a good point. I suppose that when youve done a lot of testing that you get to know what results to expect on a R1+R2, so that my earlier point about a Zs being misleading is null and void.

Happy to be educated!