Ah. The OP seems to have now indicated that the fuse holder below it (which I thought was a DNO one) is actually part of the installation, so that (if I'm now understanding correctly) the switch/isolator above is 'just a switch/isolator' (not a switch-fuse).I take it its "K Main Fuse", but whats the K stand for, first time i have ever heard of it, does not look big enough to have a fuse in, was it rewirable
Kind Regards, John