First NIC inspection (electrical domestic installer)

[securespark]

There was me thinking it was somefink to do wiv electro-motive force....

 

[automationman]

Thank you all for your advice. I eventually found the earth rod under the main entrance floorboards. Had two 10mm CPCs connected to it.
One CPC went direct to the main earth of the CU (the CPC that I could see when I changed the CU) and then another CPC which went all over the place but eventually found it bonded to a radiator return in the kitchen. Removed the radiator connection and got an RA of 59ohms (much more realistic!!!!) Out of interest did an ELI test on the 10mm to the radiator pipe and got an ELI of 0.9 Not too suprising since it has full continuity to most of the plumbing in the house since everything is bonded. For the sake of future clarity I removed the CPC from the radiator to the rod and just bonded up the radiator with other pipes in the vacinity. Now its possible to take the RA of the rod at the CU. Performing a ZE at the CU with rod not connected yields a Ze of 0.96. The rod makes little difference to the Ze but of course I am aware that it is the only reliable and "legal" earth since the other could dissapear at any time when the water board put plastic in the roads. I did replace the 10mm rod CPC with 16mm. The max load for the property did not require 16mm (via the calculation) but it seemed like the right thing to do since the CPC was solid green (not green/yellow) and a lower resistance path to earth always sounds good to me...

One last question for you: do I need to show the NIC inspector any design drawings? I have drawings for the rewire but not for the CU replacement.

Thanks again, saved my bacon!!

 

[securespark]

You can get away with as low as 2.5 for the earthing conductor on TT systems, but there's nothing wrong with 16mm².

 

[1john]

He wont want to see any drawings

 

[automationman]

Its a pass!! thanks for all your advice.

Would you believe that an RCD (Wylex) failed during the RCD test during the first inspection!!! I had a spare one, put it in and all ok again. What are the odds of that happening??? I had just finished showing him an r1+r2 on that circuit (0.12ohms on a 4mm radial) re-connected, did the rcd test and the RCD just stayed in! Re-checked the wiring and re-checked the r1+r2 but all was ok. Changed the RCD and the new one was fine. I have just tested the failed RCD here at home and it still fails.. I'm just happy that he recognized that it was not my fault.

I have to say that despite being very nervous about it beforehand, I really enjoyed the two inspections and got some good tips from the inspector who was very experienced. I did put a label on the light switch (the one where you need to isolate two MCBs) and he was quite impressed with that.

Did well on the inspection and testing. two slight errors on the certs which he put me straight on but other than that he was happy to sign me off.

Thanks again for all the advice, very much appreciated. Now to go outside and smash that RCD with an earth rod... for the sake of diagnosing the problem further of course..

 

[JohnnyG]

Congrats.
That flaky RCD might've stood you in good stead as it's all very well testing a known sound installation but in the real world things do go wrong and being able to rectify them correctly is something assessors probably don't actually see candidates doing often

 

[SparkyNinja]

Congrats on passing. You'll now be able to advise others when their first NIC inspection nerves kick in.

 

[automationman]

Yes thats a good point regarding rectifications of problems. In the long run I think it did do me some good as far as being assessed. Of course at the time when the test failed I was sure I could see the coast of Autralia through the hole that opened up in the ground

I was pleasantly surprised by the inspection/assessment. I have seen a lot of negative comments about the NIC domestic installer scheme but the inspector was very thorough and asked me to demonstrate all important tests and interpret results. Went over my two certs in detail and asked me to reproduce (as far as was reasonable) Ze at both sites and r+1+r2s on a couple of circuits. Asked lots of questions about building regs, RCD test trip times, TT earthing systems, equipotential bonding regs. He did it all in an encouraging way which kept me relaxed. I feel that it is a reasonable and comprehensive test of competence on single phase, max 100amp domestic systems and that coupled with the yearly follow up assessments makes me feel that its not a bad scheme. Do all domestic installers stick to the regs between assessments, possibly not and some will be better/more competent than others but in general I think it works.

I would like to see them put additional emphasis on electrical priciples both in the quals needed and in the NIC assessment but other than that 8 out of 10... in my opinion. I don't know anything about the other schemes, whether more/less strict etc...