Consumer Unit Change

[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.

 

[Midwest]

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.

Don't stress yourself. You'll see from that thread, the difference in interpretation of the regs. Some say the regs are in black & white. Well that's one thread, shows that's not the case.

GN1 refers to 'Live cables ..........if entering ........through different holes', defining 'Live' cables bought on the debate. It also says 'All the conductors of a circuit should generally follow the same route'. (GN1 last paragraph page 97).

You'll see from #105 from that thread, the OP rang NIC technical Advice on regulation 521.5.1 - http://www.electriciansforums.co.uk/threads/advice-on-regulation-521-5-1.103579/page-8. and was advised;
'The context of the appropriate protective conductor in regulation 521.5.1 doesnt include a main earthing conductor as its not part of an a.c circuit in bs7671 as it is classed as a separate entity'. That was a year ago, so can't seem advice changing dramatically, unless technical argue as much as us!

 

[Nickj]

If I could rewind a couple of weeks id opt to do a full rewire. So much easier to control every element that way. I have a rewire job lined up for the new year (assuming I can pass Tuesday!).

Murdoch if questioned by an assessor how would you answer 521.5.1 with regard to the main earth entering separately?

The regs aren't very explicit it seems nor is gn1 (based in the earlier quote I gave from midwest).

 

[Pat H]

Wiska M40 IP68 IP Rated Brass Gland for Terminating Tails into Consumer Unit | eBay - http://www.ebay.co.uk/itm/Wiska-M40-IP68-IP-Rated-Brass-Gland-for-Terminating-Tails-into-Consumer-Unit-/182008076235?hash=item2a6086d7cb:g:cr8AAOSw7aBVCxvT
Is a gland that can optionally take a 16mm earth as well.

 

[Midwest]

PS; get that EIC written up again in your best's handwriting in black ink. You might be re-doing the form electronically after you assessment, but the inspector will be pouring all over your forms.

Have you got all the other documents required for your assessment?

 

[Nickj]

That form was purely a working copy and is in pencil. Todays task is to write it up neatly (2 copies). I'd like to print it however not been able to find a non pdf version that I can type onto.

All other paperwork will be found (pretty sure I know where it all is) or printed (insurance in email form at present) today and put into a folder for him to browse through.

Should I call elecsa tomorrow or do you all think (I take on board it's an opinion) that it will be fine as it is?

How would you answer if questioned about the regulation specifically?

Could this result in a fail or deferral?

 

[Pat H]

The argument for the earth being with the live conductors is that in a fault condition current will flow in the earth and if separate eddy currents will flow. However in a fault condition the small time the current flows won't be enough to generate enough heat to be of concern.

 

[Risteard]

Given that the minimum insulation resistance is for the installation I would prefer to measure all circuits in parallel. Also BS7671 DOES require the Earthing conductor to be collectively surrounded with the live conductors where entering a ferromagnetic enclosure.

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" .

 

[Nickj]

A global ir with rcbos would be difficult to achieve since the test would pick up the rcbos?

I was always taught to test each circuit separately.

It seems I'm going to have to call elecsa regarding the main earth and it seems highly likely that tomorrow I'm going to have to tear the install apart to route the main earth through the rear entry with the tails.

Not what I wanted to hear, I'm stressed enough as I is without having to tear apart the work I did

 

[Pat H]

You could leave it as it is. Discuss with the assessor and based on his input decide if re-routing the earth is required.
You don't want to do all that work for him (or her) to say it wasn't an issue.

 

[Risteard]

It may be impracticable with RCBOs but then you need to consider the effects of resistances in parallel through calculation to verify compliance.

A global ir with rcbos would be difficult to achieve since the test would pick up the rcbos?

I was always taught to test each circuit separately.

It seems I'm going to have to call elecsa regarding the main earth and it seems highly likely that tomorrow I'm going to have to tear the install apart to route the main earth through the rear entry with the tails.

Not what I wanted to hear, I'm stressed enough as I is without having to tear apart the work I did

 

[Octopus]

It seems I'm going to have to call elecsa regarding the main earth and it seems highly likely that tomorrow I'm going to have to tear the install apart to route the main earth through the rear entry with the tails.

Suggest you read 521.5.1 (BYB) again... first sentence ends "are contained within the same enclosure".... then the 2nd sentence says "where such conductors enter a ferrous enclosure, they shall be arranged such that the conductors are only collectively surrounded by ferromagnetic material"

Which is a loads of gobbledygook!

The muppets who write and update BS 7671 should have reviewed such regs when the AMD3 CU's were introduced.....

IMHO I don't think you should pull anything apart..... before your assessment, if and I say if you get pulled up on this, have your decision making criteria rehearsed. If the assessor disagrees get him to spell it out why he thinks the L, N and E should be together when entering a metal CU. You do get time to correct any issues....

I've said this on many times, BS 7671 should be submitted to the Plain English Society, and be reviewed BEFORE the next amendment as the whole document is littered with such issues.... that's what happens when many people write single documents - for the best example look no further than the Bible.

 

[westward10]

Don't even bring it up, unless the assessor questions it.

 

[Nickj]

Thank you. If I left it as it is and the assessor didn't like it even after a discussion then would that result in a re-assessment or would I be given the time to alter it and submit photographic evidence that it has been altered after which I'd be accepted?

Not entirely sure what to expect. I know it can be an outright fail or there are instances that photographic evidence of corrected non conformance can allow you to be accepted.

 

[Midwest]

If I could rewind a couple of weeks id opt to do a full rewire. So much easier to control every element that way. I have a rewire job lined up for the new year (assuming I can pass Tuesday!).

Murdoch if questioned by an assessor how would you answer 521.5.1 with regard to the main earth entering separately?

You could tell a little white lie, and say you rang Tech support, and was given the answer as in #105 of 'that thread'. When I ring tech support, they never ask for you or company name or EPP number. I could be Mrs Miggans from the pie shop, for all they know (no jokes.... please ).

I agree with Murdoch, 521.5.1, in this context, is not clear. MFI use to write better assembly instructions than BS7671 submissions. You could ring tomorrow, if you have time to change it, if tech support rules in favour of the red corner. But don't if its going to take some time. The day would be better spent, making sure you have everything in places, and just get all the basics set up in your head, for the questions you'll get asked.

Think you need to put that to one side for now. Worst case scenario, is your have to have the inspector back for tea & biscuits.

Good luck, and go and have a beer. Resolves most things in my personal experience.

 

[Midwest]

Thank you. If I left it as it is and the assessor didn't like it even after a discussion then would that result in a re-assessment or would I be given the time to alter it and submit photographic evidence that it has been altered after which I'd be accepted?

Not entirely sure what to expect. I know it can be an outright fail or there are instances that photographic evidence of corrected non conformance can allow you to be accepted.

It's difficult to tell from here sat looking at screen, but it appears your approach is quite professional, which I expect would be reflected in your work. Which is the main thing they are after. Doubt if there is anyone on this forum that does everything explicitly as BS7671 says (if you can understand everything it says!).

 

[westward10]

I know it is a bit late but did you try to see if you could pull another earthing conductor through using the old one to pull it through.

 

[Nickj]

That was my original plan of action westward however the old 6mm earthing conductor was packaged with the tails in the form of 2 core and earth.

I then tried to follow the same route as the tails thinking it would be easiest however my rods couldn't get through so I took a different route and used trunking along with fire clips where needed.

Knowing what I know now I could have chased out the final approach and entered through the rear with the rest of cables.

If I redid it that's exactly what I'd do. whether it is worth redoing tomorrow with assessment on Tuesday is quite the dilemma. I could end up with a less neat install due to the constrains than I have now.

I'd like to avoid a reassessment at all costs due to it meaning another 6 week wait for appointment etc.

Damned if I do damned if I don't

 

[Richard Burns]

From the point of view of the assessor, if he asks about this, you have cogent and reasoned statements indicating that you had considered the issues and decided that the situation was safe and compliant with BS7671 as far as you understand it.
If you can state this with the assessor at the time and therefore show that you are competent then this should be acceptable.
If the assessor still decides that rectification is necessary then, because you are already demonstrating competence, a simple photographic resolution should be sufficient.

 

[Pat H]

I agree in the unlikely event the assessor feels the earth needs re-routing and you agree to that change a simple photo by email should be enough. They maynot even need that.

 

[Nickj]

That's a relief. I'll leave it as is and argue my case if it comes up.

Now to find all my paperwork...