Consumer Unit Change

[Nickj]

Hi All,

I am tomorrow going to be changing a consumer unit ahead of my Elecsa assessment next week.

Just wanted to check that I'm not missing anything with regards to amendment 3.

I'm going to be using a BG consumer unit supplied with RCBOs.

It has a cut out at back for cable entry and so I am going to pass all cables through that using a grommet strip around the metal edges. Do I need to seal the entry hole? I believe not however I have heard arguments that it needs to be sealed. Passing all cables through the rear entry may require de-rating cables due to grouping however the cables enter the current board (3036's) through the rear. Can i therefore assume ratings are fine?

I am going to attach the consumer unit to the wall using dewalt wall dogs which require no anchor in wall meaning I don't have to worry about plastic wall plugs falling out in the event of a fire.


If the cables are too short (I sincerely hope they won't be) I'll use an adaptable box above the board to mount a din rail to extend wiring. Does this adaptable box need to be non-combustible too? (associated switch gear covers this possibly?)

Thanks in advance

Nick

 

[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?