I have a rather elderly heating installation (Y-Plan) which has worked pretty much as expected since I moved into this house a few years ago.
However, I'm now finding that the bathroom radiator (plumbed with the DHW) is staying hot, presumably drawing heat from the tank, when neither heating nor hot water are supposed to be on. It's making for a warm bathroom but cold showers.
At first I thought the circulation pump might be staying on for some reason, but I can't hear it running or feel it vibrating when it's supposed to be off.
It may just be a coincidence, but I fitted a shower pump (well, actually a whole house pump) a couple of days before I first noticed the towel rail staying hot: I don't see how this would have affected the system though.
Any ideas as to what to look at would be appreciated because I really don't have a clue!