A thermostat is provided for controlling a heating apparatus having two individually actuatable heating elements in order to more accurately control the heat output of the apparatus. The thermostat is designed such that at environment of temperatures below a set temperature t.sub.1, less than the desired temperature t, both heating elements are actuated. As the environmental temperature increases beyond the set temperature t.sub.1, the thermostat deactuates the main heating element and the secondary heating element alone is controlled to regulate variations in environmental temperature around the desired temperature level t. Both thermostatic functions are combined in a single device. Means are provided for adjusting the desired temperature level t and the set temperature t.sub.1 simultaneously for maintaining the difference .DELTA. t therebetween at a constant magnitude. Further, means are also provided for adjusting the difference .DELTA. t between the set temperature t, and the desired temperature level t.sub.1. The result is energy conservation and a more stable environmental temperature.
A dual stage thermostat for an electrical space heating system in which there are two microswitches connected in parallel and operated by a common bimetallic strip. The first switch when closed connects a heating element to a power supply through a diode which reduces by half the power applied to the element. The second switch when closed connects the heating element directly to the power supply. The temperature at which the second switch opens is set about 1.5.degree. F. lower than that at which the first switch opens. Thus, as the room temperature approaches the desired temperature, the heater element is switched from full to half power, producing less temperature overshoot and saving energy. The thermostat may be used with any standard two wire heater.
