421.1.201

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?

I don't ... but I might guess at a third possibility - the manufacturers are pushing metal CUs.


(Far be it from me to suggest that they might have a vested interest in suggesting that the only way to have a fire-safe CU is to have a metal one - and thus problems with plastic ones were inherent, unavoidable and so nothing in particular to do with them - rather than letting people wonder why the plastic ones kept bursting into flames when the product standard required them to pass a glow-wire test).


   - Andy.

I can't answer the direct question, but I note that a recent review of domestic electrical fire origins in Sweden puts CUs high in the list, leaving me wondering how long before someone thinks of doing something about it. For places with combustible surroundings the principle of fire-safe CUs strikes me as very sensible, and I've several times pointed to the UK's change.  

Some things haven't got better over time, like the move from diazed fuses in brass/steel/porcelain housings, over to plastic MCBs in light plastic boxes without backs, mounted on plasterboard or worse. Perhaps the "TT countries" would be more bothered than others about making a change. Or the countries where CUs are as tall as a person (well - several rows of din-rails).

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.