Well it's smaller than the steel knockout and makes it nice and easy to feed the cables into the back of the CU, so what's the point in making the cutout smaller and more fiddly ?
This seems to be a common thing with drivers of large status symbol cars,generally arrogant sh1tes, pretty much every day I get one coming at me really wide, and I'm in a Peugeot Expert van so not a small vehicle.
They also have an overwhelming urge to try dangerous and totally unnecessary...
That MK socket was probably damaged by extreme heat from the live pin on the plug - quite possibly the fuse wasn't tight enough, but it's pretty inevitable if you put a constant 3kW on it for any length of time.
I tend to go for the opposite approach and tell them to f*ck off within a few seconds. Didn't go down too well when a vicar rang recently and I got the wrong end of the stick.... 😁
I think the OP means that the boiler switching pair comes from two sources , the stat/s for the original system and the heatmiser u/f controller, but both from the same circuit, this is perfectly ok if I'm right.......
Even if the Zs is sufficiently low not to require additional protection it wouldn't do any harm to install a 100ma S type RCD at the switch fuse end, just in case of failure of the downstream RCD/s.
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