On my boiler - yours may be different - I have three primary controls plus of course control valves on the radiators.
One control on the boiler itself adjusts the temperature of the heated water coming from the boiler - mine is set to the mid way position.
Another control governs the central heating air temperature - A room thermostat that governs the boiler firing and the overall flow of water through the radiators.
A third control is strapped to the outside of the Hot Water Storage tank in the Airing Cupboard - you will not have this if your boiler is a Combi (combination). The control on the tank is a hot water stat - This thermostat governs the boiler firing and sets the temperature of the water from the hot taps. I think mine is set to about 60º C. It needs to be hot enough to kill bugs in the water but not too hot to cause scalding.
Peccavi, January 2011
