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As far as I know there is no genuine guidance on downward doors, obviously if you are maintaining a fire barrier then it may be the best approach to ensure that the lid will not be able to remain open. From a practical point of view it is dumb and stupid, oh something has tripped I cannot see through the metal lid so I had better open it, oh I am now holding on to an earthed piece of metal while I put my fingers into a consumer unit that is shaded from the light above so I cannot see if anything is wrong.

On fire retention, this is the idiotic guidance from guidance note four that now explains the intent of the regulation, as opposed to the letter of the regulation, of course anyone who does not have guidance note four will obviously be able to infer this from the lack of any mention of it in the regulation!

This is what GN4 has to say:
3.8.1 Consumer units and similar assemblies in domestic premises
Regulation 421.1.201, which was added to BS 7671:2008 by Amendment No. 3 (2015), requires consumer units and similar switchgear assemblies installed in domestic (household) premises to comply with BS EN 61439-3 and to either:

(a) have their enclosure manufactured from non-combustible material or
(b) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.

An example of a non-combustible material, according to Note 1 to Regulation 421.1.201, is ferrous metal, such as steel.

The implementation date for Regulation 421.1.201 is 1 January 2016 (six months after Amendment No. 3 comes into effect); see Note 2 to the regulation. However, this does not preclude compliance with the regulation prior to that date.

Where option (b) above is used, it is important that the cabinet or enclosure is suitably selected and erected to meet the requirements of Regulation 132.12. These relate to adequacy of space for initial installation and later replacement individual items equipment, and accessibility of the equipment for operation, inspection, testing, fault detection, maintenance and repair.

The intent of Regulation 421.1.201 is, as far as is reasonably practicable, to contain any fire within the non-combustible enclosure or cabinet and to minimise the emission of flames to the surroundings or into conduits trunking or ducting. Consequently. both of the following are necessary, irrespective of which of options (a) or (b) is adopted.
The non-combustible enclosure or cabinet must provide a complete envelope (e.g. base, cover, door and any components such as hinges, screws and catches) as necessary to maintain fire containment. All blanks, circuit-breakers and other devices must be contained within the non-combustible enclosure or cabinet. The installer must seal all openings into the non-combustible enclosure or cabinet for cables, conduits, trunking or ducting that remain after the installation of cables. Good workmanship and proper materials must be used and account must be taken of the manufacturer's relevant instructions, if any.

The phase 'similar switchgear assemblies' in Regulation 421.1.201 means assemblies used for the same fundamental application as a consumer unit. An example could be a three-phase distribution board intended to be operated by ordinary persons.

Regulation 421.1.201 is intended to apply consumer units and similar switchgear assemblies to BS EN 61439-3 inside all domestic (household) premises, including their integral / attached garages and outbuildings and those in close proximity.


EDIT: Sorry about the tone of the post, I am just really annoyed with this approach, as you may be able to tell!
 
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Interesting isn't it. We will be expected to fit a AMD3 metal type KMF in the white box. Yet can guarantee the DNO can still fit thier 60947-3 in small insulated DIN enclosure in very same white box as they don't work to BS7671.
 
Some meter operators will refuse to work in a meter cupboard which contains exposed earth metal due to the greatly increased risk when working live.
 
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Any ways had to go supposedly fit new CU & main isolator as good practice yesterday & upon removing old Bakelite & wood 3036 board found 5 x extra circuits and a 2 way lighting circuit linked by the twist together & tape up method behind the ply section really nasty stuff and to top it off no main earth from TN-S MET & no bonding at all to incoming water ! What code would you all put on this ? DNO just laughed & said good luck on a Friday mate & fitted new meter & tails I provided to 100A switch fuse & then left !. Customer away til tonight so nothing more done as no access to property as key was supposed to be left & not.
 
What code would you all put on this ?

You can't put any code on an Electrical Installation Certificate. The certificate declares that the work carried out is compliant with BS 7671:2008 (2015).

As such the only course of action would be to correct it.
 
Doing a job the other day where a main fuse disintegrated in the bosses hand - called SSE out to sort and asked them to fit double pole isolator while they were there as we would be adding an additional cu and didn't want to faff with getting the new fuse re-sealed later in the day. - SSE said talk to metering outfit, nothing to do with them as DNO - he did however give us an isolator switch off his van to fit ourselves though!!

both hanger and Wylex both do a switch in a housing specifically for this application - my interpretation of the rules is that this would be allowable inside an external meter box even though it is plastic, just not inside a property.

personaly I fitted a control gear switch fuse in a metal housing (tails borderline on 3m and a bit) - huge compared to the old plastic MF but was only about 35+vat - build quality not great though.

Hager and Wylex both sell the din rail fuse holder and relevant bits to make an amnd3 compliant solution but it ain't cheap!
 

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