Abstract: A programmable digital thermostat is adapted to be powered by the conventional AC power source to which the thermostat is normally connected when installed in a dwelling. The thermostat has no provision for mounting a battery therein. Means are provided for enabling a temporary connection of a battery to the thermostat to provide power for programming the thermostat so as to enable the user to program the thermostat before installing it.

Abstract: A gas valve comprises the combination of a control valve having a valve body made of polymeric material and a thermally responsive shutoff valve having a metal valve body. The shutoff valve is connected upstream of the control valve and is adapted to be connected to a gas source. The shutoff valve is effective for terminating flow of gas to the control valve in response to exposure to an abnormal temperature value.

Abstract: A digital thermostat includes a microcontroller and a single rotary encoder switch having an adjusting shaft and a knob connected to the shaft. The shaft of the switch is rotatable by the knob to a plurality of discrete angular positions, each of which enables the switch to provide a unique signal to the microcontroller. Each unique signal is interpreted by the microcontroller so as to establish a desired set point temperature. Each discrete angular switch position also effects a visual display, through an opening in the thermostat cover, of the desired set point temperature.

Abstract: A heating and cooling apparatus wherein either or both the heating apparatus and cooling apparatus are two-stage is controlled by a thermostat through four connecting wires. A signal on one of the wires enables the functions of controlling operation of the circulator fan and controlling second-stage operation of whichever apparatus is two-stage.

Abstract: A low-voltage space thermostat for controlling operation of a heating and cooling system is provided with integral circuit means for detecting the existence of an unacceptably high voltage potential between two wiring terminals therein. Such a high voltage potential exists when the power source in the system comprises two transformers connected out of phase with each other.

Abstract: A programmable electronic thermostat is provided for controlling operation of a multistage heating apparatus comprising a heat pump and auxiliary heat. A salient feature is a program which provides for economical recovery from a setback temperature. The program includes logic which determines, at the beginning of the recovery time, whether any or all of the auxiliary stages will be temporarily locked out and thus prevented from being energized. This determination is based on a characteristic which is dependent upon the heating demand that is presently being placed on the heating apparatus. The program also includes logic which determines, near the end of the recovery time, whether any or all of the locked stages are to be unlocked. This determination is based on the magnitude of the difference between the temperature existing at the time of determination and the temperature desired at the end of the recovery time.

Abstract: An electro-optical display in a programmable electronic thermostat includes a plurality of selectively energized display elements which cooperate with a 24-hour time indicia to provide a continuous visual display of the time periods during which a specific programmed space temperature is to be maintained.

Abstract: A control module in a hot surface ignition system includes a microcomputer programmed to provide a pre-selected igniter warm-up time period for enabling the igniter to heat up to gas ignition temperature during normal system operation, and is further programmed to provide, for test purposes only, an accelerated igniter warm-up time period which is shorter than the pre-selected igniter warm-up time period but sufficiently long for enabling the igniter to heat up to a temperature sufficiently high to ignite gas. The program for providing the accelerated igniter warm-up time period is automatically executed in response to a unique signal effected by the control module in conjunction with a detachably connected test device.

Abstract: A direct ignition gas burner control system includes a microcomputer for controlling energizing of an electrical resistance igniter, for subsequently effecting flow of gas to the burner when the igniter is at gas ignition temperature, and for effecting continued flow of gas in response to current flow through the burner flame.

Abstract: A direct ignition gas burner control system includes a microcomputer for controlling energizing of an electrical resistance igniter, for subsequently effecting flow of gas to the burner when the igniter is at gas ignition temperature, and for effecting continued flow of gas in response to current flow through the burner flame.