Consumer Unit Change

[westward10]

Are they definitely 1.5 cpcs and not 1.0.

 

[Midwest]

Wonder if OP reconnected old socket (faulty leg). Perhaps temporarily remove socket and replace with strip connectors or similar. Good point re the cpc sizes Westward though.

 

[Midwest]

Could even be imperial sized cable, bit before my time, cough, so don't know how they compare L/N to cpc?

 

[westward10]

Could even be imperial sized cable, bit before my time, cough, so don't know how they compare L/N to cpc?

I think the cpc on imperial size cables weren't much different to the line size.

 

[Pete999]

Could even be imperial sized cable, bit before my time, cough, so don't know how they compare L/N to cpc?

7/029 Live =3/036 cpc I think will look for a comparison chart when the vino has worn off.

 

[tony mc]

He said the cables were solid as he was asking for extending advice and imperial are stranded and better cables IMO!
Could be older 2.5 T/E with 1mm CPC!

 

[sparksburnout]

7/029 Live =3/036 cpc I think will look for a comparison chart when the vino has worn off.

Pierre or you on the **ss every evening?

 

[Pete999]

Pierre or you on the **ss every evening?

Thursday off

 

[Pete999]

Pierre or you on the **ss every evening?

Not on the ----, just like the odd glass, nothing serious, it's just people's take on my posts, aint really been on the razz for many a year or two, had my fill of that during my world tour, red wine is my tipple, now I'm retired, but er in doors has got me on a shed building course for OAPs, of course I will be asking advice on how to run a supply to the sheds I build. LOL

 

[DPG]

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

 

[sparksburnout]

Not on the ****, just like the odd glass, nothing serious, it's just people's take on my posts, aint really been on the razz for many a year or two, had my fill of that during my world tour, red wine is my tipple, now I'm retired, but er in doors has got me on a shed building course for OAPs, of course I will be asking advice on how to run a supply to the sheds I build. LOL

Now i'd like to expand on this. I too like the odd tipple, of an evening, well most evenings to be honest. Beer mostly but also appreciate a decent red. Seems to be a bit of an undercurrent of frowning upon this sort of thing, can't even turn on my favourite planet rock radio station now without somebody harping on about cutting down: "Do you really need that glass of wine while cooking the dinner". I enjoy a little livener around the 5 O'clock mark myself, bit like yourself by the sounds of it. Do you think it is becoming frowned upon?

 

[westward10]

Who cares, white Pino or Gavi for me.

 

[Wilko]

Speaking to Mr Quack recently, he was extolling the virtues of moderation. Then he stopped and said - you know the medical definition of an alcoholic? That's the patient who drinks more than the Doc. Looks like I'm ok then .

 

[Midwest]

Pierre or you on the **ss every evening?

Not wishing to defend anybody here, but that's none of your business. People make like hearted remarks on this forum, to scoff themselves. You shouldn't be judgemental.

 

[Nickj]

I'm fairly certain it's 1.5mm cpc. I can check tomorrow but pretty sure.

Its going to be quite a timely thing to solve where the roughly 0.2Ohm increase is coming from.

Would you guys invest the time to find the cause or would you say 1 ohm is close enough to calculated value and with all other results being good change board?

In your opinion, based on previous assessments, is this something that could fail an assessment?

 

[westward10]

Depends how on the ball the assessor is, clear the problem and it is one less worry. It wouldn't be something you would outright fail on

 

[NDG Elecs]

I'm fairly certain it's 1.5mm cpc. I can check tomorrow but pretty sure.

Its going to be quite a timely thing to solve where the roughly 0.2Ohm increase is coming from.

Would you guys invest the time to find the cause or would you say 1 ohm is close enough to calculated value and with all other results being good change board?

In your opinion, based on previous assessments, is this something that could fail an assessment?

What is 0.20 ohms between friends on a conductor that is usually only called upon when something goes wrong. Zs's are good and you have additional RCD protection. Personally I would not worry too much. And yes I would be tempted to record the L and N end to end's as being a little higher and the CPC as a little lower! The assessors are generally pen pushers that like to look at paperwork and not the nitty gritty side of things I have found. That's not having a go at them, it's just the way they are. So, if the paperwork looks about right they are generally happy, and as long as the install is safe. Which I think this one is by the sound of it.

Don't shout at me though if he ain't happy!!
Well done for finding it though mate. I am a little surprised that no one on here asked whether there was a possible long forgotten socket, as it is something a lot of members will have come across, especially on EICRs.

 

[NDG Elecs]

Good luck Nick with your assessment, and you've have been given some good advice by members, especially fault finding!

As regards the fixings for the CU, I take NDG's point, but I do not think that relates to the fixing of CU's more to that of cable supports in escape routes. reg 421.1.201 was all to do with (so I'm told), remove a source of fuel (plastic CU) from the source of a fire. So sealing holes (intumescent), fixings etc don't relate.

As regards using a plastic enclosure above a CU to extend cables, I was advised by Elecsa Tech support a while back (wrongly IMO) that such an enclosure would not comply with the reg, and could not be used in such circumstance. Now that we've had some time, to allow for the dust to settle as it were, I have asked Elecsa for some clarification on the subject. Thought you should perhaps know this before your assessment, just in case. Having said that, when I had my recent assessment, the Elecsa Inspector raised his eyebrows when I told him of the advise given.

Personally, I would use MF joint boxes, in ceiling void above CU, if the cables weren't long enough to terminate in new CU or Ideal in-line splice connectors inside the CU. I would only do that for one or two circuits. Anymore, and I would consider part rewire.

Hi Mid,

My link was a bit off as you say. I have not looked at the full download for a little while but I thought it did a test of standard red/brown wall plugs to hold some of the cable supports up whereby they failed after the fire test. Might be wrong though!

I would think that a CU would hold quite steady in a fire largely due to the various copper conductors stopping it from dropping significantly. But fair play to the OP using a belts and braces approach to keeping it on the wall.

 

[Andy78]

What is 0.20 ohms between friends on a conductor that is usually only called upon when something goes wrong. Zs's are good and you have additional RCD protection. Personally I would not worry too much. And yes I would be tempted to record the L and N end to end's as being a little higher and the CPC as a little lower! The assessors are generally pen pushers that like to look at paperwork and not the nitty gritty side of things I have found. That's not having a go at them, it's just the way they are. So, if the paperwork looks about right they are generally happy, and as long as the install is safe. Which I think this one is by the sound of it.

Don't shout at me though if he ain't happy!!
Well done for finding it though mate. I am a little surprised that no one on here asked whether there was a possible long forgotten socket, as it is something a lot of members will have come across, especially on EICRs.

I'd be tempted to record the values as they are seeing as repeating tests and comparing them to recorded values is a usual part of the assessment procedure. I'd rather be explaining an identified anomaly, the action already taken, and the reasons behind not being overly concerned about it, than why values don't match those of the schedule of test results.

 

[NDG Elecs]

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.

 

[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.

 

[Wilko]

Hi Nick, A few thoughts in addition to NDGs good points.
Meter tails item 7.7 - reg 521.5.1 says (in last part) 'does not preclude the use of an additional protective conductor ... to enter enclosure individually'. To me, the expected method is for line, neutral and protective conductor to enter together. IMHO what you have is functionally safe due to current levels, but may well be questioned. So have a close read of 521.5.1 and be ready to discuss.
Also, I think you might be questioned about IR > 2meg results. It is expected that this be the actual result you measured. A result near 2meg would be widely viewed as needing further investigation. Just saying.
A couple of others to confirm :
Max demand is 35A ?
Metal partitions are ticked in 8.14 ?
Adequacy of working space is blank in 9.4 ?
Hope that helps

 

[Pat H]

IR is normally recorded as the reading your test kit shows not that its above the required resistance.

 

[Midwest]

Lets not have the RCBO/RCD must be tested at the CU debate again.

As regards your 'main earth', have a butchers at this thread if you got a spare half hour;

Advice on regulation 521.5.1 - http://www.electriciansforums.co.uk/threads/advice-on-regulation-521-5-1.103579/

Can honestly say, I'm still confused and I read the thread at the time. Think the OP had it right at #105, as in your case, you using this job as your assessment. So ring your scheme and ask, and whatever they advise, do (IMO)

 

[westward10]

I hope you are going to submit nice neat paperwork and that is your trial run. I believe if your paperwork is untidy this gives an immediate poor impression.

 

[Pat H]

As a slight deviation has anyone re-generated these forms to be easier to use?
The actual layout isn't great and many entry locations are just too small to enter details in a legible way.

 

[Midwest]

I hope you are going to submit nice neat paperwork and that is your trial run. I believe if your paperwork is untidy this gives an immediate poor impression.

Think that's his 'working copy', well I hope so. I use to do that, until I lost a page of test results. Now use a desk diary, harder to lose

 

[Midwest]

As a slight deviation has anyone re-generated these forms to be easier to use?
The actual layout isn't great and many entry locations are just too small to enter details in a legible way.

Are you in a scheme?

 

[Nickj]

Thanks for all the input. I recorded ir as >2 as that's what the electrician I used to work for did. I note your points and will re-record the actual measurements tomorrow (they were all greatly in excess of 2 - none were under 600).

I'll call elecsa first thing tomorrow morning and ask their view. If they want it coming through the back then I'll need to scramble in order to get it done tomorrow as assessment is Tuesday!

Those results are indeed just a working copy. I'll use an electronic system after assessment but that system isn't in place yet.

Nightmare scenario!

 

[Nickj]

To pick up on maximum demand question.

I've put 35A. I came up wih that figure by adding all the breakers together and taking 40% of their total as maximum demand.

I see maximum demand done in so many different ways and I see different opinions on it.

Some say add all breakers and put that result regardless of whether it's greater than main fuse (an approach I'm not keen on?)

Some will use osg and put that figure.

Some use the 40% rule.

I have 32a ring (no diversity can be applied)

32a cooker circuit (I think I worked it out at 27a using diversity)

16a heating (no diversity allowed if immersion - unsure if there is one, then unsure how to calc if there isn't one)

6a lights - 8 lights in house, allow 100w per light so 800w, 3.5a.

Adding all that is greater than 60a.

What would you guys put?

 

[Octopus]

Thanks for all the input. I recorded ir as >2 as that's what the electrician I used to work for did. I note your points and will re-record the actual measurements tomorrow (they were all greatly in excess of 2 - none were under 600).

I'll call elecsa first thing tomorrow morning and ask their view. If they want it coming through the back then I'll need to scramble in order to get it done tomorrow as assessment is Tuesday!

Those results are indeed just a working copy. I'll use an electronic system after assessment but that system isn't in place yet.

Nightmare scenario!

IMHO thats a terrible way to do it and train you!

I can only assume that he did a global IR to achieve such numbers but in reality its a very unhelpful way of doing it when doing a CU change and introducing RCD's.

I always test IR before using a global measure (as a check) but then as the new CU takes "shape" I connect ALL the CPC's to the CU and test all the circuits individually L-N, L-E and N-E - that way you will see the "real" situation in the install.

It would seem that many people do the global IR as L&N to earth, which is simply lazy - the only way to check the installation IR properly you need to isolate as many of the appliances as possible......

As an example I did a global IR recently and got really terrible L&N to E readings - so went round unplugging as much as possible and then found it was 1 circuit in particular - further searching revealed a RCD FCU in the back of a cupboard - so this was swapped for a std unit and the readings improved dramatically

 

[Nickj]

I also checked each individeally murdoch (as did the electrician I worked for) I just put the >2 as that's what I believed should be entered.

I take notice of what's been said here and will remeasure and record them tomorrow.

Depending on what elecsa say I may need to remove the board to bring the main earth through the rear so taking ir again wont be much more effort.

I do hope they are happy for main earth to come through separately as to get all that work done the day before assessment is cutting way too close!

 

[Pat H]

The reason we state the measurement we get is that you may well get a result that's well above 2 mohm but lower than your kits max reading. That value is important as later measurements may show a degradation in IR.
So we record the actual meter result and that's implicit its greater than the minimum reg requires.

 

[Nickj]

Midwest, I have read that thread and I note what you said in one post

"Thought I would invest in the latest copy of Guidance note 1, Selection & Erection. Curious, I looked up 'Ferromagnetic enclosures, cable entering; (521.5.1) All the conductors of a circuit should generally follow the same route. Live cables of the same circuit may cause overheating if they enter a ferromagnetic enclosure through different openings (page 97, 7.4)"

I don't own gn1, I'm slowly buying and reading them all however gn1 is not one I've bought yet.

Reading that further confuses me. all conductors "should" not "must" therefore surely not required? I understand that l and n could cause issues but I don't see a problem with main earth coming through a separate hole.

I do hope elecsa can give me a definitive answer tomorrow at 8am. I'm worried about finishing on time of I have to reroute it all now.

Stress levels through the roof right now.

 

[Pat H]

Unless under fault conditions no current flows in the CPC so eddy currents related to that are immaterial. So as long as the L & N are together then fine.

 

[westward10]

Wouldn't lose sleep over earthing conductor through a separate entry, Pat is quite correct. Put your IR as >500 as >2 indicates a problem.

 

[NDG Elecs]

Don't stress too much Nick! The assessors are usually fine n easygoing. I would bring the point up with him about the main earth and have some other tech questions at the ready to; they like that kind of stuff!

Get a couple of packets of taste the difference cookies and you will be fine....

 

[Nickj]

Pat, I agree and I saw no reason not to run the earth through a separate hole until I read on this forum about 521.5.1.

Paragraph one is met as they are all in same enclosure.

It's paragraph 2 that causes issues,

"Where such conductors enter a ferrous enclosure, they shall be arranged such that the conductors are only collectively surrounded by ferromagnetic material"

Paragraph 3 is irrelevant I think in my case as the tails aren't SWA.

 

[Nickj]

In your experiences, would something like this cause a fail or deferral? I really can't afford for another assessment both financially and more importantly time wise.

 

[Octopus]

I also checked each individually murdoch (as did the electrician I worked for) I just put the >2 as that's what I believed should be entered.

I take notice of what's been said here and will remeasure and record them tomorrow.

Depending on what elecsa say I may need to remove the board to bring the main earth through the rear so taking ir again wont be much more effort.

I do hope they are happy for main earth to come through separately as to get all that work done the day before assessment is cutting way too close!

Recording the individual circuit readings is the best way to go ..... because if you called back later for, say tripping, you can compare readings to see if any have changed.....

There is NO requirement to bring the main earth through the same aperture as the tails..... so don't waste your time making the call. There are special glands that allow you to bring the tails and earth together but that's a "nice to have" .

 

[Pat H]

Yes but that relates to conductors conducting currents and the issues with eddy currents. The CPC isn't normally conducting so irrelevant.
I'd raise it with the assessor and say you've considered the regs and the reasons (you can even add you've taken advice) and you are happy with your solution.

I'm not in a scheme yet. hoping for my niceic assessment in the next month or so but in no rush.