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: A microcomputer-based spark ignition gas burner control system includes program logic to ensure compatibility of spark ignition and a microcomputer. The program logic provides for periodically re-defining the I/O (input/output) ports so as to negate the adverse effect of any electrical noise generated in the system. The program logic also provides, during ignition, a cyclically re-occurring finite time period during which sparking occurs followed by a finite time period during which flame detect circuit means is enabled. The system further includes a fault-tolerant spark generating circuit to ensure that sparking is inhibited during times that the combustion chamber is being purged of any combustible mixture.

Abstract: A gas valve for providing two levels of flow capacity to a burner is adapted to enable easy conversion of the valve from use with one type of gas to use with another type. To this end, a low-flow passageway, which establishes the low-flow capacity, is sized to provide the desired low-flow capacity when the valve is used with one type of gas. An opening, axially aligned with the passageway, receives a screw means which simply prevents the escape of gas to the exterior of the valve. When the valve is to be converted to use with another type of gas having a higher BTU content, the pressure regulator and burner orifice screw are changed, and the screw means in the axially aligned opening is replaced with a metering screw means which, in addition to preventing the escape of gas, has a portion which extends into the low-flow passageway so as to reduce the effective opening area of the low-flow passageway.

Abstract: A gas burner control system for controlling operation of a furnace having a blower fluidically connected to the combustion chamber of the furnace utilizes a mass flow sensor for preventing or discontinuing burner operation in the event of a blower failure or a predetermined degree of blockage in the fluid flow path controlled by the blower. The mass flow sensor includes circuit means which enables use of unmatched sensors, enables establishing of a desired value of temperature difference between sensors, enables establishing a temperature difference that is not constant so as to compensate for different ambient air densities, and enables compensating for voltage variations at different ambient air temperatures.

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 an igniter, two serially-arranged gas valves for controlling the flow of gas to the burner, and a microcomputer and related circuitry for controlling energizing of the igniter and valves. The microcomputer and its related circuitry provide for numerous options in system functions and for numerous checks on the integrity of the system components.

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: Upon a call for heat, gas flows to a pilot burner, a spark generating circuit is energized to ignite the pilot burner, and an oscillator is energized. When flame appears, the output signal of the oscillator is effective, through flame responsive means including capacitor means and solid-state switch means, to enable energizing of the primary winding of a coupling transformer at the frequency of the oscillator signal. When so energized, sufficient power transfer occurs between the primary and secondary windings of the coupling transformer to enable energizing of a relay winding, which energizing terminates energizing of the spark generating circuit and allows gas to flow to the main burner.

Abstract: A gas valve device includes a pressure regulator and two solenoid operated valves connected fluidically in series. The valve body therein is selectively cored and machined so as to provide a gas valve device which is compact in physical size, inexpensive to produce, and versatile in that it provides a choice of several gas outlet directions.

Abstract: An oil burner primary control in an interrupted ignition burner control system includes a regulating circuit for regulating the voltage across a flame-responsive photo-conductive cell. The regulating circuit ensures that, in the event the cell becomes defective so as to exhibit abnormal resistance characteristics, the system will not permit fuel to flow unless a burner flame exists or unless the igniter and a safety circuit are energized.

Abstract: An electronic air flow responsive switch is connected in circuit with a humidistat switch for controlling operation of a humidifier in a forced air heating system. The air flow responsive switch includes a self-heating PTC (positive temperature coefficient) thermistor which enables operation of the humidifier only when the humidistat switch is closed and there exists sufficient air flow for cooling the thermistor. The air flow responsive switch and humidistat switch are mounted in a single enclosure and include plug and cord arrangements for simplifying installation of the device.

Abstract: A generally concave-shaped gas burner head is provided with circumferentially spaced means on the periphery of top and bottom portions for enabling water accumulated therein due to condensation of water vapor to flow out of the burner head without interfering with the burner flame at outlet ports on the periphery of the burner head. In one embodiment, the burner head is provided with a plurality of openings in a peripheral portion of the top portion which cooperate with a plurality of grooves in a downwardly sloping peripheral portion of the bottom portion. In another embodiment, a plurality of tabs in a peripheral portion of the top portion cooperate with a plurality of arcuate openings in a generally flat peripheral portion of the bottom portion.

Abstract: A control system for fluid fuel burners, particularly for blue-flame oil burners, utilizes flame conduction to control energizing of the light emitting portion of an optical coupler. Circuit means including the light responsive portion of the optical coupler is effective, in the presence of a predetermined level of illumination from the light emitting portion which occurs in the absence of a burner flame, to enable flow of a combustible fuel-air mixture and energizing of ignition means, and, in the subsequent absence of the predetermined level of illumination when burner flame exists, to terminate energizing of the ignition means and to enable continued flow of the combustible mixture. The control system further includes means for reducing the rate and level of illumination of the light emitting portion so that it requires a predetermined time period for the light emitting portion to be energized to the predetermined level of illumination.

Abstract: A filter assembly in an air cleaner includes a lower wire-form adapted to receive two opposite ends of a pliable filter material. Spaced wires on the lower wire-form enable manual forming of pleats in the filter material and define the tops of such pleats. A complementary upper wire-form is engageable with the lower wire-form and attached filter to define the bottoms of such pleats.

Abstract: A snap-on cover for a bobbin-wound electrical coil assembly includes a plurality of displaceable tabs aligned with slots provided for lead exits in the end flanges of the bobbin. Those tabs aligned with slots containing leads are displaced whereas those tabs aligned with unused slots are not displaced and effectively cover such unused slots.

Abstract: Actuators for a program timer are removably attached to the timer dial in a snap-on manner to enable simple and easy removal or installing of the actuators to effect changing the schedule of operation of the timer.

Abstract: A pilot burner assembly comprises a pilot burner, a flame responsive means, and an electrode, all attached in close relationship to a common mounting bracket. The electrode is frictionally attached co-axially with an insulating sleeve and the sleeve is frictionally attached to the mounting bracket so that the spark gap between the tip of the electrode and a portion of the pilot burner is adjustable without having to bend the electrode.

Abstract: A space thermostat for controlling temperature at different levels during different time periods includes a programmable microprocessor which has been pre-programmed to provide a plurality of chronologically annunciated displays. Each display contains a time and temperature within a specific time range. A multi-segment keyboard is provided to enable the homeowner to set the correct clock time and day of the week, to recall each display, and to change, if necessary, the time and temperature of each display so as to establish a desired seven-day time-temperature schedule.

Abstract: A gas burner control system includes a main burner, two electrically controlled valves connected fluidically in series with the burner, an electrical resistance igniter, a temperature responsive switch, and a diode steering circuit for controlling energizing of the valve windings and the igniter. The connected polarities of the diodes in the steering circuit are such that the winding of the first valve is energized by the alternating current power source when the source is of one polarity and the winding of the second valve is energized by the source when the source is of the opposite polarity.