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!
