Consumer Unit Change

[Andy78]

I know what you are saying Andy, and yeah OK it's a tiny bit naughty. But cheating L-L up by 0.02 ohms and the CPC down by the same is hardly likely to be picked up on. You will know how values can dance around a bit when testing low impedances.
This install sounds safe to me. It's not like doing a drive by EICR is it.

Totally agree in this specific instance, maybe not in another though.

I know my Elecsa assessor would have picked up on different values as an opportunity for a bonus question such as "Why do you think the values are not as expected ?" or "What could be causing the change in values between measurements ?" But then, most aren't as thorough/bothered as him.

 

[NDG Elecs]

I just had a look at that BRE report and it does use yellow and red plugs to fix some of the supports up. And scan reading it some of these failed. I was responding to Westward originally in relation to the post saying that the plugs would likely hold firm. It was my belief also that they would hold firm, but maybe they won't. So perhaps concrete screws are the way forward.

 

[Pete999]

Make sure you TT it. Wooden shed, so got to be a wooden earth spike. No, hold on a minute - that wooden work. OK, I'll get me coat. Daz

Why wooden it work

 

[Midwest]

I just had a look at that BRE report and it does use yellow and red plugs to fix some of the supports up. And scan reading it some of these failed. I was responding to Westward originally in relation to the post saying that the plugs would likely hold firm. It was my belief also that they would hold firm, but maybe they won't. So perhaps concrete screws are the way forward.

But that report relates to the installation of electrical cables supports & fixings, and the IET references the report as fire performance of cable supports. Regulation 421.1.201, which specifically makes recommendations about the non combustibility of consumer units and similar switchgear, does not make any specific recommendations on how to fix them to the wall.

Perhaps the 18th edition may have a new note, or 421.1.202 which will tell us to use non combustible fixings. But until then, I don't think we should make that strategic decision IMO.

Thanks for finding & posting the report though.

 

[westward10]

Why wooden it work

It wood if it was wet.

 

[Nickj]

Hi Guys,

Attached are my forms. Would appreciate it if you could check to see if I've ticked the correct boxes and my results look ok.

One other cause for concern is item 7.7 on the schedule of inspections.

The earthing conductor present before the board change was 6mm and so it needed to be upgraded to at least 10mm (tails are 16mm). I upgraded to 16mm.

I did not realise at the time that the tails and earthing conductor were 3 core.

It was not possible for me to bring the new earthing conductor along the same path as the 3 core cable without a lot of chasing.

I opted to bring the new earthing conductor into the house by a different route aided with trunking and fire clips where needed.

All circuits and tails were chased when installed (some 40 years ago) and entered the old fuse board through the back. I have brought all those cables through the back of the new consumer unit however I could not (without chasing and running the risk of damaging the already installed cabling) bring the new earthing conductor in through the rear.

I have read varying opinions on this with some saying it is ok for the earthing conductor to enter through a separate hole of the consumer unit (with some saying niceic advise that it doesnt apply to meter tails and earthign conductor so long as meter tails L & N enter same hole) and some saying it's not ok and should be noted as a deviation from the regs.

What would you guys do for assessment purposes? Would you enter it as a deviation? Would an assessor accept a deviation like this?

Sincere thanks to you all for the help so far

 

[NDG Elecs]

Hi Nick,

I would not list the main earth coming into the CU by itself as a deviation. I have never heard anyone ever say that it would be. Nor do I understand why it would be. Meter tails should be brought through together on metal enclosures due to possible eddy currents. That is what item 7.7 refers to.

Had a quick look through your cert. Couple of bits I noticed; on schedule of test results polarity is to be ticked. Think you have mistakenly put a megohm figure in mate. Also, as it's all RCBO protected I would expect different values for x1 & x5 tests. Seems to be a lot of 28.8 across the various RCBOs. Also you have not put anything in the "description of installation" box on the first page...I would put new consumer unit and upgrade to main earth and bonding in that box. I would also mention that you carried out remedial works to the RFC CPC due to the end to end value you got.

What are the IR readings? Does that say >2 ?? My test meters highest reading is >299Mohms @500V, which is the value I write down.
And why were some Zs' calculated?

Other than the niggly bits I mention it looks OK with a quick scan.

 

[Nickj]

Hi ndg,

Thanks for scanning over the forms. I too was surprised at all the 28.8s across 3 of the rcbos but they were all tested individually. For lights and heating they were tested at board and for cooker and sockets they were tested at the sockets.

I did indeed miss polarity box, I hope I wouldn't have when I wrote it out as a final copy!

Yes all irs are >2

I picked up on this forum about the main earth needing to come in with the meter tails. regulation 521.5.1. Some say that it doesn't apply to tails, with some saying niceic don't consider the tails with this regulation. quite confused by it all as it's new to me.

 

[NDG Elecs]

OK, fair play re the x1 x5, but test the cooker and sockets at the board to.

Does your meter not go higher than >2Mohms... They normally do.

Maybe I am wrong re the main earth. I thought it was just live conductors only that had to be together or the board slotted. If I am wrong, thankfully I have used the tail glands on all my metal CUs!

 

[NDG Elecs]

Item 7.2 tick! A 60947-3 is a linked switch.