That is not my interpretation and nor do I think that it is many people's interpretation.
Everyone who says otherwise is not looking at what the regulations actually
SAY.
Anybody who publishes "interpretations" or "guidance" which shows a single cpc ring when the csa is not 10mm² or 4mm² as per 543.7.1.203(i) or (ii) is publishing something which contradicts what the regulations actually
SAY.
Look at what 543.7.1.203(i), (ii) & (iii) talk about.
(i) A
single protective conductor having...
(ii) A
single copper protective conductor having...
(iii)
Two individual protective conductors,
each complying with the requirements of Section 543...
With the latter, it is important to consider 543.2.9:
Except where the circuit protective conductor is formed by a metal covering or enclosure containing all of the conductors of the the ring, the circuit protective conductor of every ring final circuit shall be run in the form of a ring having both ends connected to the earthing terminal at the origin of the circuit.
So what the regulations say when you read 543.7.1.203(iii) and 543.2.9 in conjunction is
Two individual protective conductors,
each run in the form of a ring and
each having both ends connected to the earthing terminal at the origin of the circuit.
Taking a ring cpc and putting the ends into separate terminals does not create
two individual rings.
As for 543.7.1.203(iii), in the case of a (single) ring, each and every point in the circuit is connected to the MET via two separate CPCs (the two arms of the ring).
But two arms of the ring are not
each a ring themselves.
Forget circuits, cpcs, rings etc etc for a minute, and just think of the general situation where you have
two individual {things}, each of which having {some sort of property}.
As you have two individual {things} you must be able to take one {thing} away and be left with the one remaining {thing}. Since each separate {thing} had (some kind of property} your one remaining {thing} has {some kind of property}.
If you
cannot take one away as described then you
cannot have had two in the first place.
Indeed, how are you suggesting that one could connect a socket to the MET by two parallel CPCs (which you accept is compliant) without creating "A (single) ring" (which you claim is not compliant)??
If I may be allowed, for the purposes of illustration, to use non-standard colours, like this:
As you can see, I can remove either of the two individual rings and be left with one remaining ring
Have you ever seen a circuit with two CPC rings (i.e. 4 connections from each socket to MET)??
No, but then I'm not likely to have seen
any circuits except the ones in my house.
I am as sure as I can be that my interpretation of the regs is correct, and that most people other than you believe and do likewise.
You are not alone in refusing, for some reason I cannot fathom, to simply read and think about regulations actually
SAY, or what the implications are if your theories on topology are correct.
If you believe that a different arrangement complies with 543.7.1.203(iii) and 543.2.9 in conjunction, then please post a drawing which shows what you consider to be two individual cpcs each run in the form of a ring and each having both ends connected to the earthing terminal at the origin of the circuit. Please use a different colour for each individual cpc in the form of a ring, and then post a drawing which shows one of those two individual cpcs entirely removed to leave one remaining cpc run in the form of a ring having both ends connected to the earthing terminal at the origin of the circuit.
