A consumer unit is a type tested distribution unit OK that bits simple. However there is often a reference to 16th Edition, and 17th Edition and the question is does the type testing change between the editions? So if I fit a 16th Edition consumer unit today is it in fact a consumer unit or a distribution unit. As far as I am aware the consumer unit is only required for domestic installations. I am aware if you don't follow manufactures instructions then it's no longer a consumer unit for example if you fit MCB's made by another manufacturer. So it has to comply with BS EN 60439-3 but there are so many no one but the manufacturers are likely to buy copies and we as the user just hope. Some things are not as expected for example British General state you can use any Nexus devices not just BG. Technical details state "They support compliance with the latest 17th Edition Wiring Regulations" not current so that are saying on the website in spite of being plastic they will comply with amendment 3. Personally I think they have failed to update. Their website only specifies a screwdriver other specify a torque screwdriver and without reading BS EN 60439-3 I have no idea how closely you need to follow instructions for the whole unit to continue to be classed as a consumer unit. I have called the old wilex fuse boxes consumer units but I would not think BS EN 60439-3 existed when they were made so they would not be consumer units. So what is the demarcation line between a consumer unit and a distribution unit? Some bits are easy if designed for over 300 volt, 250A incomer or 125A output then not a consumer unit. I expect any fuse box made before 1989 is not a consumer unit as that's date of first document. So my house built 1979/80 does not have a consumer unit but would that means it fails an EICR it is RCD protected.
Domestic properties generally have consumer units. Throughout the decades the references have altered, fuse board, distribution board, consumer unit. They are all effectively the same thing with different labels. In reality there is no reference to 16th edition or 17th edition or any other edition for that matter. These reference labels are given by the electrical press and have no real relevance. As progressive updates of the Regulations happen then there are changes to components and installation requirements. This does not mean, and never has, that older equipment is unsafe or needs to be updated. That again is a myth propagated by the rumour factory every time the Regs change. Type tested units are for the manufacturers benefit. All the components within are manufactured to the same BS EN but the subtle differences ensure steady demand for the parts is maintained else price would override the choice and it gives the manufacturer basis for warranty compliance. Mcbs are BS EN 60898, rewireable semi-enclosed fuses BS3036, RCBOs BS EN 61009. The problem arises that the shape of the device made by different manufacturers is not the same. Although the performance is the same and the BS EN type is the same they don't tend to sit correctly on the busbar and may not fit at all. This is more the issue than the performance so it is not good to mix different makes in the same board. Cost and availability is the driving factor behind it.
Myself I don't think there is any differentiation between a consumer unit (cu) and a distribution board (db) A consumer unit is just domestic terminology for a db. It seems to be accepted that within domestic electrical deployment parameters that the db is called a cu. However in an industrial environ it would be called a db - you would never call a tp db a cu for instance..it just not on tbqh.
As MGW says: " A consumer unit is a type tested distribution unit" BS7671 defines 'Consumer Unit' and 'Distribution Board' in Chapter 2 (Definitions). It defines a CU as being a particular type of DB, but with main differences in that: (i) a CU must contain double-pole switching for isolation of associated circuits, and (ii) a CU comprises type-tested components.
Whilst a consumer unit is a type of distribution board, it is not correct to state that all distribution boards are consumer units as they are not. So the terms are not synonymous.
BS EN 61439-3 is the current standard A consumer unit is designed to be used by "ordinary" persons. A DB is designed to be used by skilled/instructed persons Part 3 on goes up to 250A rating
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