Plug in solar

[ebee]

I will not muddy the waters by suggesting that a bog standard house is one circuit (from the cut out) - remove that fuse and you have lost that one circuit.

Ignoring the fact that you might add wind, rain or sun (or a squirrel running in a cage wheel) as an alternative or an extra supply.

 

[JohnW2]

I will not muddy the waters by suggesting that a bog standard house is one circuit (from the cut out) - remove that fuse and you have lost that one circuit.

Quite so. I wouldn't call that "muddying the waters" since it's really just explaining, by example (I've used different examples), why the BS 7671 definition of "a circuit" is not really fit for purpose

Kind Regards, Johnel running in a cage wheel) as an alternative or an extra supply

 

[denso13]

Given two OPDs [say an MCB in the CU followed by an FCU (with fuse) somewhere along the length of the 'physical' circuit run (i.e.'all the wiring') ], the upstream device (MCB in CU) will, indeed (per BS7671) define the entirety of that 'physical circuit' (including any branches or unfused 'spurs'). However, the other OPD (fuse in FCU) will define everything downstream of the OPD as being the entirety of one circuit, thereby leaving eveything upstream of the FCU as being a separate, second, 'circuit'!!
So, depending upon how one looks at it, such a situation can satisfy the BS7671 definition of one circuit OR of two circuits

I do get all that but I still think, for a DIY install, then it would be everything that the CU MCB turns off.

 

[denso13]

will not muddy the waters by suggesting that a bog standard house is one circuit (from the cut out) - remove that fuse and you have lost that one circuit.

Or remove the substation fuse and a whole area goes down. Does that mean one circuit covers multiple houses?