Abstract: A method and apparatus for controlling operation of a heating system (particularly a central heating system) including a boiler directly heating and passing water to a pipe network proide for sensing the temperature of the pipe network at a position therein remote from the boiler and controlling operation of the boiler in accordance with that sensed temperature. The apparatus includes switch means (operational amplifiers or comparators)--responsive to a voltage output by a device including a transducer sensing the temperature of the pipe network and--operable to allow the boiler to fire until the sensed temperature reaches a first level and then prevent the boiler firing until the sensed temperature falls below a second level less than the first. The two temperature levels may be varied, and the second level may be varied in dependence upon an ambient temperature remote from an area being heated.