Plastic switch in external meter box

What is the essential difference between a switchfuse and a 1-way consumer unit?

A few.


One is called a consumer unit as it is done to a standard where it is intended for use by ordinary persons, but it's also the application; is that the only consumers equipment?


DBOs [ consumer units] to BSEN 61439-3 are limited to 63 amp per way; note your example is 45 amp, also it is pre 61439-3, but I get the gist. KMFs and switch fuses can have HRC up to 80 amp /100 amp respectively. The KMF/switchfuse devices usually serve a full blown consumer unit to BSEN 61439-3, in that instance it is clear the consumer unit is the thing intended for use by an ordinary person.


Those are the essential differences, but there are other things beyond BS7671 and the clumsy wording of 421.1.201,

like the Building regs and particular requirements for dwellings.

421.1.201  is only “what shall comply with 61439-3”. Firstly it is "consumer units". In my opinion the "similar switchgear" was to cover the potential use of TPN DBs for a 3 phase domestic or converted to single phase for lots of ways; it becomes a DBO when used in a domestic, most are now 61439-3 anyhow, but when the reg was published, some TPN distribution boards were not manufactured as DBOs. The Consumer Unit is specifically intended for use by ordinary persons, a DBO. Also the similar bit is for self assembled consumer units where you purchase an enclosure separately and the devices separately. I will go with a consumer unit like enclosure with a main switch with one or more ways/MCB’s that you can re-arrange yourself to not escape being 61439-3. But we have to be careful what we attribute “similar switchgear” to. It could lead to a bit of a conflict with notification requirements for building regs.

Replacing a 800KMF with a new one is not notifiable works because it is not a consumer unit.

What is the essential difference between a switchfuse and a 1-way consumer unit?

A few.


One is called a consumer unit as it is done to a standard where it is intended for use by ordinary persons, but it's also the application; is that the only consumers equipment?


DBOs [ consumer units] to BSEN 61439-3 are limited to 63 amp per way; note your example is 45 amp, also it is pre 61439-3, but I get the gist. KMFs and switch fuses can have HRC up to 80 amp /100 amp respectively. The KMF/switchfuse devices usually serve a full blown consumer unit to BSEN 61439-3, in that instance it is clear the consumer unit is the thing intended for use by an ordinary person.


Those are the essential differences, but there are other things beyond BS7671 and the clumsy wording of 421.1.201,

like the Building regs and particular requirements for dwellings.

421.1.201  is only “what shall comply with 61439-3”. Firstly it is "consumer units". In my opinion the "similar switchgear" was to cover the potential use of TPN DBs for a 3 phase domestic or converted to single phase for lots of ways; it becomes a DBO when used in a domestic, most are now 61439-3 anyhow, but when the reg was published, some TPN distribution boards were not manufactured as DBOs. The Consumer Unit is specifically intended for use by ordinary persons, a DBO. Also the similar bit is for self assembled consumer units where you purchase an enclosure separately and the devices separately. I will go with a consumer unit like enclosure with a main switch with one or more ways/MCB’s that you can re-arrange yourself to not escape being 61439-3. But we have to be careful what we attribute “similar switchgear” to. It could lead to a bit of a conflict with notification requirements for building regs.

Replacing a 800KMF with a new one is not notifiable works because it is not a consumer unit.