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421.1.201

lyledunn
I note that this U.K. only regulation is now included in the new Irish standard IS10101:2020 as sub-clause 421.2. I am not sure if this is the U.K. committee persuading the Irish committee of the merits of non-combustible consumer units or if the U.K. committee has persuaded CENELEC such that the regulation will be included in future amendments to HD60364-4-42. Anyone know?

By the way, unlike the U.K. regulation the Irish equivalent does not seem to allow for the alternative of placing a plastic unit in an enclosure constructed of non-combustible material.
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    The elephant in the room is the TT supply, in that you have the possible failure mode (fire or no fire) where a pre-RCD live comes in contact with the metal enclosure and therefore makes all the earthed metal in the  whole  building live, and may not trip anything - well if it is just the company fuse and the fault loop impedance of a typical earth rod, then the electricity bill may rise, and folk will report tingles, but there is no chance of any ADS.

    I'm not sure how much Ireland or Sweden makes use of TT  earthing, but unless you allow for an RCD in plastic enclosure as a pre-consumer unit device then that remains an un-mitigated risk. Round here TT is found on farms and on quite a lot of pre-war houses in smaller villages. In the smaller (being  a pole-pig transformer for a cluster of a few buildings) cases the electrode at the HV/LV transformer  end the may well be the dominant impedance in the loop, and no amount of extra electrodes at  the house actually helps - indeed  a very good earth, that is better than the one at the origin can make it more unsatisfactory for other users of the same transformer, by moving the neutral -earth offset voltage.
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    The elephant in the room is the TT supply, in that you have the possible failure mode (fire or no fire) where a pre-RCD live comes in contact with the metal enclosure and therefore makes all the earthed metal in the  whole  building live, and may not trip anything - well if it is just the company fuse and the fault loop impedance of a typical earth rod, then the electricity bill may rise, and folk will report tingles, but there is no chance of any ADS.

    I'm not sure how much Ireland or Sweden makes use of TT  earthing, but unless you allow for an RCD in plastic enclosure as a pre-consumer unit device then that remains an un-mitigated risk. Round here TT is found on farms and on quite a lot of pre-war houses in smaller villages. In the smaller (being  a pole-pig transformer for a cluster of a few buildings) cases the electrode at the HV/LV transformer  end the may well be the dominant impedance in the loop, and no amount of extra electrodes at  the house actually helps - indeed  a very good earth, that is better than the one at the origin can make it more unsatisfactory for other users of the same transformer, by moving the neutral -earth offset voltage.
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