Programmer switches the boiler on/off via the 2 or 3 port valves in accordance with pre-set times.  As a programmer has 2 channels it is used to select different on/off times for hot water and central heating.  Often integrated into boiler control panel.

Timeswitches switches the boiler on/off in accordance with pre-set times.  it is not possible to programme hot water and central heating individually. Often timeswitches are integrated into the boiler control panel.

Room Thermostat monitors air temperature and switches the boiler on/off relative to set temperature.  Usually located in the hallway or the lounge.

Programmable Room Thermostat allows the programming of different room temperatures at different times of the day thus combining the functions of the timeswitch and the room thermostat and, as a result, giving better control and therefore better comfort conditions.  Programmable room thermostats would usually be located in the hallway or lounge.

Wireless Room Thermostats are available for situations where it is impractical to run a wire between the boiler and the controls.

Thermostatic Radiator Valves monitor air temperature in the room and closes off the flow of hot water to the radiator when the set temperature is achieved.  As the room starts to cool down the valve will re-open allowing heat to flow to the radiator again. 

Manual Radiator Valves are used to turn off/on the flow of water through the radiator.

Cylinder Thermostat is a control which is strapped onto the hot water cylinder and monitors the temperature of the domestic water.   It will switch on/off the boiler via the hot water motorised valve.  To reduce build up of limescale in the cylinder the thermostat should not be set above 60 degrees Celsius.

Outside Temperature Sensors can be wired into the system to allow more accurate control in differing weather conditions.

Frost Thermostat is used to protect the boiler against freezing.  Usually installed when the boiler is located in an unheated space e.g. garage, outhouse etc.  Many modern boilers have a built in frost thermostat.

Zone Valves 2 port or 3 port motorised valves are used to split the system into zones.  Commonly used to separate central heating and hot water and to separate, for example, upstairs and downstairs heating circuits.  These are operated via the thermostats and programmer to open or close hot water flow through the pipe and to switch on/off the boiler as appropriate.