It's a Back Boiler
The central heating is fine.
Immersion heater rarely used.
The hot water is set to come on twice a day for an hour each time.
If water is put on for more hot water and left on (oops) it does not boil
up, make scary noises or make the feed tank warm/hot.
The cylinder thermostat is a Drayton HTS3
is in contact
with the tank 3/4 of the way down and it set to 60°
So there's the info and here's the problem:
The hot water temp is scalding (but not boiling) hot :-| It doesn't matter
what temp the thermostat it is set at.
I've googled for an answer, but there are too many answers to do with
central heating. So what might be the problem oh helpful ones?