Interested to read this stuff about the thermostat. My radiators at the top of the house (2 storey regular detachedhouse) have recently become very hot, indeed too hot to touch. I know this has nothing to do with the thermostat in the hall which governs whether heating is on/off, so guess it must have to do with the one on the cylinder itself (hercal 3). There is no temperature, however, just settings from 1-8 and the engineer who fitted the cylinder abt 5 yrs ago left it on 5. I have turned it down to 4, now 3 with no discernable difference in temp. How do the numbers correlate to 55 or 60 degrees mentioned above? and should I turn it down lower?