Hi anthonybragg
I won't recap the whole scenario, basically it's a charity refurb of an old building. I am just a cable-jockey. I install the cables for what the electrician tells me, and he comes along and connects it to the DB and tests it. The DB is all RCBOs, and I don't touch it. I put the cables insitu, he then installs the RCBOs and tests.
I think I am quite competent to split the ring already installed into two radials, fit the timer, buy the required components and install them, but I don't go near the inside of the DB, because while I would like to think I could do the installation there, I don't have the knowledge to test, which is the important bit...
The RFC was installed fine, and tested fine too, but the rogue installation of the immersion heater in my absence led to my query on here. A change in spec means a change in thinking/design. I have a fair grasp of simple circuits, and I have a solid grasp of proving dead, but the real electrician is the man I listen to, and the man who will sign it off, so I will simply install what I am told is ok, and leave it to the real guy to connect and test. So far I have put in 8 circuits in this building, all of which have tested fine.
Get an electrician in? Yes! I am happy with that! I recognised a problem with that plugged in immerser, and I am very grateful for all the input I have received. Thank you all for your kind advice which makes my life easier, points me in the right direction, and hopefully means that when the true spark arrives he will find everything in order.