Plug in solar

[ebee]

OK John, I will stand corrected, an unfused spur from a ring or radial is part of that ring circuit or radial circuit.
If it contains a fuse (such as an FCU or a SFCU then it becomes a circuit in its own right - that what I meant but you spotted my non-deliberate mistake.

 

[denso13]

We haven't seen approved installation instruction yet, but it seems they are defining a circuit as everything connected to a single breaker in a consumer unit, i.e., everything that a breaker turns off is one circuit.

 

[JohnW2]

We haven't seen approved installation instruction yet, but it seems they are defining a circuit as everything connected to a single breaker in a consumer unit, i.e., everything that a breaker turns off is one circuit.

That's the BS7671 definition of 'a circuit', but as I eluded to it gets a bit more complicated (sort-of ambiguous) when one had two or more overcurrent protective devices (OPDs, like breakers and fuses) in series (an FCU downstream of a breaker in a CU being a very common example).

In that situation, one of the OPDs (the one in the CU) will, indeed kill 'everything', thereby suggesting that everything downstream of that OPD is 'one circuit'. However, an OPD downstream of the first one (e.g.an FCU) only kills whatever is downstream of it, leaving the bits upstream (between OPDs) still energised (only 'killable' by the breaker in the CU), suggesting that the bits before and after the FCU must be different circuits, hence a total of two circuits.

That's why I wrote that when there are two OPDs, by the BS7671 definition one can at one and the same time have bits of wiring which constitute both 'one circuit' and 'two circuits'