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Metering enclosures - is plastic OK?

jbrameld

We have a bit of our business that installs additional submetering into non-domestic premises.  This typically involves fitting CTs to sub-main/distribution circuit cables and connecting those to a meter in a DIN rail enclosure that we provide.  There will be an associated supply for the meters, usually as a dedicated final circuit from a local distribution board with the circuit protection fitted in that board.

We use plastic DIN rail enclosures generally, as we do not regard these as 'switchgear'.

We had a challenge on one project (in a hospital) where the client (after installation) declared these to be switchgear and non-compliant with the regulations as they were not metal.  All arguments relating to definitions to BS7671 fell on deaf ears, and the hospital-specific guidance which he cited made no mention of such a requirement.  Pointing this out was similarly futile.  

Eventually we replaced them for metal enclosures - and charged the customer for the replacement.

It got me wondering though - is there anything from a regulatory perspective that would mandate use of steel enclosures for (just) metering?  Would that change if there was an MCB/RCBO in the same box providing protection for the meter (s)(and nothing else)?

Thanks,

Jason.

  • 0 in reply to gkenyon

    It is difficult without a clear definition of an assembly though - e.g. if I take a socket from one manufacturer, a back box from another, a grommet from the third, screws from a fourth, possibly even a telescopic stud bracket from a fifth and put them all together on site - is that an assembly? If so I'm in a lot of trouble, if not where is the line drawn?

       - Andy.

  • 0 in reply to AJJewsbury

    I think that we are agreed that you can select whichever devices you want from a manufacturer's catalogue in one of their distribution boards, but if you put somebody else's device in there, you become the manufacturer.

    So, developing Andy's train of thought, the same might apply to a DB. Once you cut a hole in the back or side and insert a grommet or gland, have you created a new assembly? No.

    AJJewsbury said:
    If so I'm in a lot of trouble, if not where is the line drawn?

    It seems to me that the line is rather fuzzy.

    gkenyon said:

    Can you put 'assemblies' together and 'self-declare'? ... yes, that's entirely possible, as it's not a product that's placed on the open-market, but keeping a technical file of the design and build is important to demonstrate either:

    (a) how you think you've met the requirements of standards; or

    (b) how you otherwise claim you have met the 'essential requirements' of the Electrical Equipment (Safety) Regulations.

    It is certainly wise to do so, but imagine if a domestic sparks had to do that every time that he (or she) constructed an installation. Different entirely in e.g. a hospital.

    If you have not placed the assembly on the market, the Electrical Equipment (Safety) Regulations 2016 do not apply:

    Electrical equipment to which these Regulations apply

    3.—(1) Subject to paragraph (2), these Regulations apply to electrical equipment—

    (a) placed on the market on or after the commencement date; and ... [voltage range]

  • 0 in reply to AJJewsbury

    Yes - exaclty.

    And where does our electrician fitting a doorbell transformer in a DIN-rail enclosure sit with all this?

    Are they expected to maintain a technical file every time they do this, and assess the EMC performance of that 'assembly', and what the internal temperature conditions might be?

  • 0 in reply to jbrameld

    In principle, that is the idea, and exactly the same is true for folk assembling burglar alarms cameras and security systems with sensors in various places, full heating systems out of valves and pumps and controllers from various makers and so forth. For the doorbell the technical file could be as simple as a postcard size document block diagram of the system and provided a copy as part of the user instructions, but in practice is often absent.

    Mike

  • 0 in reply to mapj1

    Yes - I suspect proper compliance at this level is rather rare.

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