Which way do you do it?H

[Delboybully]

You cant calculate R1+R2 by taking Ze from Zs due to parallel paths. You should measure R1+R2 at every point on a radial or a ring circuit. This proves polarity and that each point has CPC continuity (you shouldnt be livening up an unsafe circuit). You should then measure Zs and put in the highest value on your certificate.

The testing on a CU change is the most important bit and can take some time depending on how many circuit and how many points

 

[Meggerman]

You cant calculate R1+R2 by taking Ze from Zs due to parallel paths. You should measure R1+R2 at every point on a radial or a ring circuit. This proves polarity and that each point has CPC continuity (you shouldnt be livening up an unsafe circuit). You should then measure Zs and put in the highest value on your certificate.

The testing on a CU change is the most important bit and can take some time depending on how many circuit and how many points

I think your confused with initial verification

 

[Delboybully]

You shouldnt make live an unsafe circuit. To prove it is safe you need to do R1+R2 and IR. But hey, thats how I see it. If I am wrong then I am willing to be corrected (it would save me some time on board changes)
You cant calculate R1+R2 by substracting Ze from Zs due to parallel paths. What about spurs?

 

[guest119]

Thats bad leaving boxes empty! Zs-ze shouldn't be relied upon due to parralel paths etc, but I guess it will give you a rough idea. Presumably then you don't go round each socket or light fitting then?

You need full testing after a cu change.
Including zs and polarity at every socket (which you will prove when doing r1, r2).
Also you must prove the switches at both sides of a twin socket at one of the visits.

Boydy

 

[D Skelton]

Technically there is no requirement to test after a CU change, those who do, and the extent to which they do it are complying with best practice guidelines only.

Zs-Ze isn't a recognised method although it can give a rough idea of what your R1+R2 values are, remember we aren't talking initial verification here. Bear in mind that during periodic inspection and testing even an R1+R2 is highly unlikely to be free of parallel paths either.

Me, I use test method 2 (no need to take off accessories as you can test at the screw [earth pin at sockets]) to every accessory and Zs at each point. A Buzz it 'n See to check polarity at sockets and a global IR will have been taken prior to old board coming off.

Mind you, last time I did a CU change was over a year ago! I'd be rusty now

 

[ipf]

Technically there is no requirement to test after a CU change, those who do, and the extent to which they do it are complying with best practice guidelines only.

Zs-Ze isn't a recognised method although it can give a rough idea of what your R1+R2 values are, remember we aren't talking initial verification here. Bear in mind that during periodic inspection and testing even an R1+R2 is highly unlikely to be free of parallel paths either.

Me, I use test method 2 (no need to take off accessories as you can test at the screw [earth pin at sockets]) to every accessory and Zs at each point. A Buzz it 'n See to check polarity at sockets and a global IR will have been taken prior to old board coming off.

Mind you, last time I did a CU change was over a year ago! I'd be rusty now

A very rough idea with the RCD involved, I'd say.

 

[NDG Elecs]

I generally r1r2 at every socket as how can you otherwise determine the OPD is correct. Take an instance last week, was getting decent r1r2/4 values at all sockets bar two. These were higher and then higher still. Spur off a spur, so changed OPD to 20A, and gave option for return to sort it out if they want.

I am not mad on the 'buzz it' socket testers but I do have one and do use it (mainly for determining what's on each breaker though).