Abstract: In a heating system, when a high limit opens a predetermined number of times in a single call for heat by the thermostat, the system provides for operating the circulator blower at the cool speed rather than at the heat speed.

Abstract: A thermostat includes a valve for controlling gas flow, an actuator for controlling operation of the valve, and a temperature sensing element. The temperature sensing element comprises two members, one of which is made of a material having a positive coefficient of thermal expansion and the other of which is made of a material having a negative coefficient of thermal expansion. Each member effects movement of the actuator in a first direction upon sensing a decrease in temperature to effect opening of the valve and in a second direction upon sensing an increase in temperature to effect closing of the valve.

Abstract: A system for enabling an electrical resistance igniter to attain ignition temperature within a few seconds and without exceeding a temperature which could damage the igniter. The system controls the level of power to the igniter based on the determined value of voltage available to energize the igniter and on the determined value of the igniter resistance.

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 starting device for single phase induction motors having a start capacitor is effective to disconnect the start capacitor at a desired motor speed in response to a specific phase relationship between the voltage across the main winding and the voltage across the start winding. The specific phase relationship is a condition wherein a phase angle defined by the phase relationship reverses from a decreasing value to an increasing value.

Abstract: A control system for a gas fired heating apparatus which apparatus includes a burner, two gas valves and a hot surface igniter, and which control system includes a single-pole, double-throw radiant heat sensing switch having normally-closed contacts which open and normally-open contacts which close in response to the igniter being at a temperature above gas ignition temperature. The normally-closed contacts are connected in series with the electrical winding of one of the gas valves to enable initial opening thereof; circuit means is provided to maintain the valve open when the normally-closed contacts are opened. The normally-open contacts are connected in series with the electrical winding of the other gas valve to enable opening thereof.

Abstract: A method of operating a relay includes shifting, by a predetermined time increment each time the relay coil is energized, the time in the sine wave of the applied AC power source at which the relay coil is energized. The method further provides for similarly shifting the time in the sine wave at which the relay coil is de-energized. When applied to a system having two relays, the method includes providing such shifting to both relays and further includes providing a predetermined time delay between the time one relay is de-energized and the other relay is energized.

Abstract: In a digital thermostat powered solely by batteries, when the battery voltage drops to a predetermined value, the thermostat effects a visual indication of the existence of a low voltage condition. If the batteries are not replaced within a predetermined time period thereafter, and the battery voltage remains adequate to operate the thermostat, the temperature setpoint is automatically altered by being lowered, if in the heating mode, or being raised, if in the cooling mode. The change in room temperature resulting from the change in temperature setpoint should prompt the user to replace the batteries. By proper manipulation of user operable means, the user can subsequently cancel the altered temperature setpoint and re-establish the desired temperature setpoint so as to provide for normal thermostat operation for a predetermined time period during which the batteries can be replaced.

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 gas valve includes two solenoid valves connected fluidically in series. A housing assembly contains a circuit board on which electrical components and a plurality of plug terminals and pin terminals are mounted. The plug terminals are adapted to be connected to the solenoid valves and the pin terminals are adapted to be connected to external circuitry. The housing assembly is adapted to be attached to the valve body either in a first position wherein the pin terminals extend in a first direction or in a second position wherein the pin terminals extend in a second direction. The housing assembly and the solenoid valves are adapted for enabling connection of the solenoid valves to the circuit board when the housing assembly is in either the first or second position. The solenoid valves are operated by direct current and are so mechanically constructed as to operate in a relatively quiet manner.

Abstract: A control system for a gas fired, direct ignition, induced draft furnace includes a radiant heat sensing switch responsive to a hot surface igniter and burner flame, a single-pole, double-throw pressure switch responsive to fluid flow effected by the inducer, and a plurality of relays responsive to the radiant heat sensing switch, the pressure switch, and various other connected switching means.

Abstract: A low voltage space thermostat adaptable for controlling a heating-only apparatus or a heating and cooling apparatus. The thermostat includes a DC power supply and a voltage step-up transformer having two primary windings and a secondary winding for supplying electrical power to the DC power supply when there is a demand for heating, cooling, or fan operation. The thermostat also includes circuit means for supplying electrical power to the DC power supply when there is no demand for heating, cooling, or fan operation. The thermostat further includes circuit means, responsive to the existence of electrical power at a particular one of its wiring terminals, for providing electrical isolation, from each other within the thermostat, of two transformers incorporated in a two-transformer heating and cooling apparatus.

Abstract: A self-resonating power supply for controlling operation of an electrostatic air cleaner wherein the ouput voltage to the cell is limited to a desired value by means of a regulated feedback circuit so as to prevent nuisance arcing in the cell and to minimize generation of ozone. The feedback circuit detects changes in the output voltage and responds to such changes by changing the biasing of a switching transistor so as to cause the output voltage to return to the desired value.

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 gas burner control system includes an electrical resistance igniter, gas valve means, and a microcomputer and related circuitry. The microcomputer and related circuitry control energizing of the igniter in such a manner so that the igniter, after successive ignition attempts, will eventually, in response to a learning routine, be heated to a desired ignition temperature. The microcomputer and related circuitry also control operation of a circulator blower in response to burner flame and provide for numerous checks on the integrity of system components.

Abstract: A solenoid operated fluid pressure regulating valve includes a valve responsive to outlet pressure to control the rate of fluid flow to a burner. The valve is biased to a first position to effect a low fire fluid flow rate and to a second position to effect a high fire fluid flow rate. The first and second positions are independently adjustable so as to enable independent field adjustment of the low and high fire fluid flow rates. Lower and upper limits to such field adjustments are established in the assembly of the valve.

Abstract: A gas burner control system includes an electrical resistance igniter, gas valve means, and a microcomputer and related circuitry. The microcomputer and related circuitry control energizing of the igniter in such a manner so that the igniter, after successive ignition attempts, will eventually, in response to a learning routine, be heated to a desired ignition temperature. The microcomputer and related circuitry also control operation of a circulator blower in response to burner flame and provide for numerous checks on the integrity of system components.

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.