Are you suggesting that what was left (an MCB connected to metre or so of downstream cable) would not constitute 'a circuit'?
Since it does not supply electrical equipment, it is not a circuit, in the same way the lighting circuit is not a circuit unless at least one light is switched on.
So every time you switch a light on, to make a circuit, but not a new circuit, the circuit has been made before.
BS 7671 states "supplied from the same origin and protected against over current by the same protective device(s)." this means adding FCU will form a new circuit, however if supplied from a ring final then can't have any new circuit supplied from a final circuit. It is the final circuit so there can't be any more.
We are not looking at electrics here, we are looking at the English language.
So if a bit of electrical equipment has not been supplied from a protective device before then it is a new circuit. Unless supplied from a final circuit, so there is a little leeway here as we need to define a final circuit.
So for the example given where an immersion heater is removed and replaced with sockets, I think we must accept it was a final circuit, as will most circuits starting at the consumer unit, where it is not so cut and dried is where it feeds a second consumer unit, however if a MCB/RCBO/Fuse has ever fed a piece of electrical equipment (not another distribution unit) then in English had to show not new.
However as I said before, it would need a court to decide, so the main thing is if using an installation certificate or a minor works certificate, I would say if using a minor works it is not a new circuit, that does not mean it is a new circuit if using a installation certificate, but if a minor works has been used, it shows the person doing the work considered at the time it was not a new circuit.
Clearly any electrical work must be to the required standard and to show it is to required standard or at least the person doing the work thought it was, it needs a completed minor works certificate. If some one fails to complete the paperwork, it points to them trying to distance themselves from the work done, and would make it hard to show they considered what they have done was compliant, clearly even with a minor works certificate the work could still be a death trap, but it would point to the worker being unaware of it being a death trap, rather than a simple laissez-faire attitude.
Most laws are written with the idea they will be added to with case law, the Welsh Part P leaves very little leeway, I question if the Blagdon pond wiring system really gets around the law that a garden is a special location, however since they have not been taken to court to my knowledge, it seems we in Wales can get away with using it, and I think it is a get away with it, rather then following the sprite of the law.
To install a consumer unit with a 13 amp or other size socket supplied from every overload device which can then latter be replaced with another device would not be in the sprite of the law, but I would think it would be a brave inspector to try and take it to court as illegal, he is more likely to use electricity as work act or other law and look at dangers rather than the silly method used to try and get around the law.
