In a conventional system, the temperature of the house and water each need to be controlled. This function is performed by thermostats, one, usually mounted on the wall in the living room or hall, and another attached to the hot water tank. If the air or water temperature falls below the level to which these are set, then the boiler will be triggered to provide more heat or hot water or both. A timer is used to allow this to happen only at certain times, usually mornings and evenings.
In combination system much the same happens, the main difference is that the water is heated "on demand" so there is no hot tank, the temperature of the water flow is controlled within the boiler. Of course there is a timer, again usually within the boiler, that controls when heat is available, water is always available as it is only heated as required.

Whichever type of system that you choose, we will fit high quality reliable controls from the Honeywell range.