Just recently had an inspection and took the assessor to a re-wire we did a couple of months ago, as soon as I opened the cupboard to the mains I remembered I used a piece of 10mm as the main earth as I did not have a piece of 16mm long enough with me, needed about 1.5M. Now yes I know the regs say half the tails size bla bla bla. however the cut out fuse was an 80A 88 and it was only a small house anyway so totally acceptable to use 16mm tails with 10mm earth in the first place. The assessor however was quite concerned that it was only 10mm and made my mate go out and buy a piece of 16mm and change it whilst he was present. As I have stated I am fully aware it was a technical regs breach but could someone please care to explain how it could in any way be deemed in the least bit dangerous in any way shape or form. Look at it this way, I install 16mm main tails/10mm earth and everything is hunky dory, the main earth is able to carry the full load current no matter what the scenario. I then up the main tails to 25mm, how is the main earth suddenly unable to cope despite everything else staying the same. I am of the believing that me and me alone will decide whether something I do is dangerous, I don't need anyone else telling me what to do, if something in the regs tells me it's safe to do but I don't believe it is there is no way on earth that I'm going to do it no matter what anyone else says, we should be left to our own devices to get on with our lives without state interference every 2 minutes.
Must say I have never fitted 25mm tails in a dom situation because they were never indicated, however have always used a 16mm main earth even if the 88 was a 60/80 amper..why? I haven't got a clue tbqh.
A TNS you can use an adiabatic equationto find the earth size, so prolly 10mm might have been ok. PME is based on the incomer size so it would prolly have to be 16mm. I don't really get why your accessor didn't explain this to you.
IF it's PME then potentially you could end up with volt drop if the neutral link is broken which could be felt as a voltage if you touch the earth with true earth at the same time.
If it's PME and the supplier's neutral is lost then you end up with the earthing conductor becoming the neutral for the whole installation...
It is a fallacy that there is a requirement in the Regulations for the main earth to be half the CSA of the neutral. The Regulations allow the main earth to be so selected, if the designer is unable to, or can't be bothered to calculate the minimum CSA using the adiabatic equation. In the circumstances described in the OP, I would request a detailed explanation in writing as to why the Assessor has deemed in this instance, that compliance with the requirements of the Regulations is unacceptable.
A TNS you can use an adiabatic equation to find the earth size, so prolly 10mm might have been ok. PME is based on the incomer size so it would prolly have to be 16mm. I don't really get why your accessor didn't explain this to you. It was more me trying to explain it to him. It was a TNS supply and I know from experience that a 10mm earth well covers it, I didn't want to be smart and start working it out in front of him though. He wasn't interested whether it was safe or not though, he was just banging on about being half the tails size. I also understand if the supply is PME then the earth may be carrying a fault current for much longer so should be more substantial. Having said that though if the neutral was broken the most likely return path for the current would be down the bonding connections which are only 10mm anyway. On the job I showed him the Ze was 0.33 giving a technical size of the earth of 6.2 with my working out.
Going by his opine if you came across that in a condition report you would have to fail it. Could be an expensive mistake if the customer upgrades and then finds they didn't have to.
The assessor however was quite concerned that it was only 10mm and made my mate go out and buy a piece of 16mm and change it whilst he was present.. . Sorry, but I find that unbelievable, if my assessor told me that I would remind him where his monthly salary comes from! If he noted to that it was a mistake and could you replace as and when then sure As for a demand for an immediate change. . Pfft! Turn it in.
They can force you to correct anything immediately dangerous while they carry out the inspection, but cannot force you to do anything non urgent. Anything they request you put right gets done and you are requested to send in photographic evidence that you have done it. The OSG did used to show a 16mm main earth for 16/25 tails, but the regulations do not state this is a requirement. You can select the earthing conductor size from table 54.7 (formally 54g), or by calculation, using the adiabatic equation. Using the table is obviously easier to ensure compliance, but is to a requirement.
The assessor however was quite concerned that it was only 10mm and made my mate go out and buy a piece of 16mm and change it whilst he was present.. . Sorry, but I find that unbelievable, if my assessor told me that I would remind him where his monthly salary comes from! If he noted to that it was a mistake and could you replace as and when then sure As for a demand for an immediate change. . Pfft! Turn it in. His words were, its a non compliance, I would prefer if you changed it whilst I was here. I think it was so he could give us a clean sheet with no corrections to report back with at a later date as LEC says. It did happen...honestly....sorry you had to go for a lie down.
I don't think we should be too hard on this assessor, after all he could have just marked it down as a non compliance and not given you the opportunity to correct it whilst he waited. I'm not saying he was right or that the OP was in the wrong but I will say that when I know I might be using a particular job for assessment I make doubly sure to cross all the t's and dot all the i's!
I had a TP DB installed inside a key lockable Himel type enclosure, to prevent access. When being inspected by the NIC, he noticed no next inspection label on the DB. A little bit of a disagreement, as it was a submain, not the origin, but hey, if he wanted to mark it down, that's fine, it's not a killer. Trouble was, when closing the OUTER lockable door, we suddenly saw the label stuck there, not on the inner door. So no non-compliance at all. Trouble was, he mad already written it on the paperwork and could not back out of it. Grrr.
Unsafe undersized earthing conductor, hardly raises alarm bells for fire/shock and burns does it? That assesor must be running out of reasons to substantiate his jobs-worth to ask for an upgrade in CSA of that cable (all of a few metres on a SP+N supply) on site immediately I for one being old school and my area engineer knows me al too well would never sniff at this sort of comment Sorry mate I still think it was out of order. Si
How has anyone come to the conclusion that it is a non-compliance? According to the OP, 10mm is larger than required by the adiabatic equation.
Just like to add a video that explains about the adiabatic equation amongst other things. Its from JWs channel who really does do some excellent videos on electrical things.