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Does the din rail housing for a double pole DC MCB for battery storage count as "consumer units and similar switchgear"?

Akbar Ramzan

Regulation 421.1.201 says that within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall be manufactured or enclosed in a non-combustible material.
Many installers are using plastic enclosures however to house a double pole MCB which acts as a means of isolation as well as overload and short circuit protection. This seems wrong, especially when dealing with a DC source with high energy withstand requirements. They are using this in escape routes within the house. It doesn't help that many batteries come with an MCB hidden under a plastic cover but I don't think that is within the scope of BS7671. Also many wholesalers are selling plastic enclosures alongside the MCB and many example installation pictures of inverters have a plastic enclosure for the MCB.

Does the MCB enclosure for a battery count as "consumer units and similar switchgear"?

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  • 0

    Without doubt, it is not a consumer unit.

    I doubt that it is any more similar than the typical "REC2" isolator which one finds nowadays betwixt the meter and CU.

  • 0 in reply to Chris Pearson


    The difference between this MCB and just a plain isolator is that it contains current sensing which will produce substantially more heat and it needs to be able to operate under several kA fault conditions and quench high energy arcs etc.
    Would a plastic (,albeit "flame retardant PC",) enclosure as pictured be deemed suitable?

    And if so what difference would this be to say an RCBO in its own consumer unit to supply a shower?

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  • 0 in reply to Chris Pearson


    The difference between this MCB and just a plain isolator is that it contains current sensing which will produce substantially more heat and it needs to be able to operate under several kA fault conditions and quench high energy arcs etc.
    Would a plastic (,albeit "flame retardant PC",) enclosure as pictured be deemed suitable?

    And if so what difference would this be to say an RCBO in its own consumer unit to supply a shower?

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