Thermal control for liquid heating appliance

A thermal control for a liquid heating appliance includes a tristable subassembly 20 that can be added to the thermal control 1 to provide selection of boil and sub-boil modes. The subassembly relies on the bias of a trip lever spring 3 in the thermal control to achieve a stable off position, without requiring any additional spring in the subassembly. The subassembly includes a mode selection lever 21 that is moveable by a user actuator, such that the subassembly can be manually moved from the boil or sub-boil modes to an off position. The user actuator 30 may have a pivot point P3 displaced beyond the pivot point 25 of the mode selection lever 21, to reduce the travel of the end of the user actuator. A lift-off switchoff mechanism may be provided by means of a bifurcated spring (Figs 10,11).