A mechanical central heating timer is an electromechanical scheduling device that gates the boiler's heating circuit by mapping wall-clock time onto a continuously rotating 24-hour dial, so that a physical index mark passing a set of user-configurable tappets opens or closes the demand contact. The device operates as a three-state control selector — permanently off, permanently on, and timer-governed — where only the timer state defers control to the programmed dial pattern; correct operation depends on the dial's rotational phase being synchronised to actual local time, since the dial has no absolute time reference of its own and only measures elapsed rotation. This belongs to plumbing and domestic heating controls within building services engineering, and is the mechanical predecessor of the electronic programmer in the general class of time-based heating control.
A mechanical central heating timer is an electromechanical scheduling device that gates the boiler's heating circuit by mapping wall-clock time onto a continuously rotating 24-hour dial, so that a ph…