Your argument is quite compelling because it's made me think about it again and I was starting to question my own view, but having just re-read the definitions and 314.4 I'm sticking to my guns and this is why.
These are in fact two circuits and I will explain this later, and assuming this, these are not now electrically separate as they have been connected together.
Fundamentally, yes they are two circuits... or more precisely, they were two circuits as they were originally designed, installed and connected to two different protective devices at the origin.
To address your question about the origin, since there is no definition of origin for a circuit, it seems sensible to base it on that of 'origin of the installation' i.e. the point of supply of electrical energy, which in this case is the protective device the circuit is connected to.
The definition of 'final circuit' is there to differentiate it from a distribution circuit and in this context is largely a red herring I believe.
The mere act of changing the origin of one of these circuits to that of the other means they become one circuit. It isn't the cabling that defines a circuit, it's the origin. The cable is not a point of supply of electrical energy for the circuit, the protective device it is connected to is.
Taking your argument that the cables are the origin to the extreme, you're saying you can't have a spur off a ring final circuit that originates at the device that protects the ring conductors because they aren't the same cables, which I think you'll agree is a nonsense.
You seem to be conflicted.
Not conflicted, just sensible.
Yes I have ‘lumped’ two circuits together as ‘temporary stop gap solution’.
I did it as a temporary stop gap solution knowing that, in my view and yours presumably as you have inferred, it’s ok as a temporary fix. But if its ok as a temporary fix, by definition it isn't meant as a permanent solution.
When you combine two circuits in this manner, there is a risk that the protective device will be overloaded as a result and thus subject to nuisance tripping under normal use because the installation was previously divided to minimise the chances of that happening.
Hence I would consider it a temporary solution to get the customer back on-line ASAP whilst a more permanent solution is implemented.
However, in the case of two lighting circuits, it's unlikely (based on the OPs description) the OCPD at the origin is going to be subjected to an overload when they are combined, so this is an acceptable thing to do.
Therefore the man from Stroma is correct. It doesn’t comply with the intention of the regulation. It is electrically safe taking into consideration the anticipated loads on those circuits but is does not comply. My temporary fix was not left like it.
Very different situations as outlined above, so I disagree. Mr. Stroma was incorrect.
Theres nothing wrong with having a lighting circuit on a 16a breaker as long as the cable is sufficient.
I think I said that
I'm not sure what you mean by the ring on a 20a breaker though.
Basically a ring final circuit on a 20A circuit breaker, most likely as a result of installation methods (cable in insulation for example). I've seen it a couple of times. Wired in 2.5/1.5mm but due to installation methods, a 32A breaker runs the risk of overloading the cable (thermal effects) so a 20A breaker has been deemed suitable.
My question is would you wire two ring circuits into one 32a breaker allowing of course for the loads anticipated on those circuits and leave it like it permanently and sign a completion certificate saying that it fully complies with BS7671.
Would I do it? No. But based on 433.1.204, providing the cabling complies, it's questionable whether it would contravene any regulations.
