Safe Isolation

[Nicktric]

I'm going for registration and getting ready for the assessment, sorry to run this probably blatantly obvious procedure past you but when I'm asked to dead test a circuit, after isolating, removal of the CU cover and do the 3 point, if the property is empty do I need to lock off and add an electrician at work sign? I don't normally in an empty house, but don't want to fall at the first and not sure what they will expect. Thanks for the advice

 

[IQ Electrical]

Cheers my only concern is getting flustered when he asks me a max Zs for a circuit for example and getting page numbers for tables mixed up although I am planning to learn all the main figures like Ze Zs RCD for common circuits.
If he asks me what an acceptable r2 result is, is 1.67 x phase or neutral loop of that circuit acceptable?This is only for r2 isn't it? And if he asks what I would expect an r1 r2 to be for a given circuit should I be referring to resistance/meter tables in the OSG?
On that note if a wander lead option is available isn't it ideal to get an r2 as it is a quicker check and more accurate if you have already checked phase and neutral continuity than guessing length of cable run and applying to tables? Am I missing something here like a formula to equate r1 +r2 to r1 and rn I know if I have Zs and Ze I can find the Max R1 + R2 but that won't show me the figures I should expect r1&r2 relative to my r1 and rn. You see, pre assessment jitters already!

I suspect the assessor will want to see at least one of the usual tests-R1+R2, IR, Zs and RCD possibly with a ring continuity chucked in for good measure.

When you've got the results, he'll want to see that you know what to do with them, that they match your Electrical Installation Certificate (within reason) and if they comply with BS 7671:2008.

Don't get involved with wander lead R2 measuring, stick to R1+R2, especially if it's an empty property with unrestricted access.

Don't mention deriving R1+R2 from Zs and Ze as you mentioned above, this does not 'back calculate' due to parallel paths and the assessor will expect you to know that.

When you measure r1 and r2 on the ring final, the sum of those values divided by 4 should give you an expected approximate R1+R2 for the circuit (not withstanding any spurs).

As a QS with the ECA and the NICEIC domestic installer scheme, I've done around 20 of these assessments and stopped worrying after the first one!

 

[telectrix]

on a ring final, R1+R2 = (r1+r2)/4 is what you would expect.