After an unrelated problem with my hot water, I spotted that the immersion heaters in my pressurised hot water cylinder have no voltage going to them. I'm guessing that explains why the hot water temperature has been a bit variable for the past few weeks. The heaters are each connected to their own FCU.
Our heating system was installed 3 years ago and since then I've had the consumer unit replaced, so I am wondering whether the guy who did this missed these out.
Can anyone offer some hints to start diagnosing the problem beyond my speculation?