Abstract: A pressure switch assembly is used with a furnace controller having a first input and a second input. A first pressure switch is configured to actuate at a first combustion pressure level and is connected to the first input. A second pressure switch is configured to actuate at a second combustion pressure level, and a third pressure switch is configured to actuate at a third combustion pressure level. Pressure signals provided on the second input from at least one of the second pressure switch and the third pressure switch are used by the furnace controller to derive actuation states of the second and third pressure switches.

Abstract: A network projector interface system is provided. In one embodiment, the system includes client software stored on a recordable medium and at least partially executable on a client computer on a network, where the client software provides a client interface configured to aid a user in directing a presentation file to a selected network projector. The system also includes presentation manager software stored on a recordable medium executable on the network, where the presentation manager software produces a presentation manager configured to manage storage and access to the presentation file, and a network projector coupled to a projector computer, where the projector computer is coupled to the network and communicates with the presentation manager to display the presentation file on the selected network projector.

Abstract: A network projector interface system is provided. In one embodiment, the system includes client software stored on a recordable medium and at least partially executable on a client computer on a network, where the client software provides a client interface configured to aid a user in directing a presentation file to a selected network projector. The system also includes presentation manager software stored on a recordable medium executable on the network, where the presentation manager software produces a presentation manager configured to manage storage and access to the presentation file, and a network projector coupled to a projector computer, where the projector computer is coupled to the network and communicates with the presentation manager to display the presentation file on the selected network projector.

Abstract: An inducer wheel or impeller in which the hub may be formed by machining, rather than by molding, and which possesses a generally cylindrical cavity having a flattened section without a tapered inner diameter. Consequently, the hub may be mounted on a rotatable shaft having a corresponding flattened portion of a rotatable shaft with relatively small tolerance between the periphery of the shaft and the interior cavity wall of the hub uniformly along the shaft length. A plastic rotor may be molded onto the hub such that the plastic abuttingly contacts the flattened region of the rotatable shaft and surrounds and covers a relatively large peripheral area of the hub. A method of making such an inducer wheel is disclosed, and the inducer wheel made by such a method is also disclosed.

Abstract: When a single-stage thermostat is appropriately connected to a two-stage cooling system, a microprocessor control activates low and high stages of cooling based on preset parameters. The cooling load requirement is determined and compared to the maximum load requirement that can be satisfied in low-stage cooling mode and the minimum load requirement which can be satisfied in high-stage cooling mode. The desired low-stage cooling time limit is then determined for the next cycle. After the first cycle, the desired low-stage cooling time limit may be equal to zero in which case the next cycle is spent in high-stage cooling mode, or, if greater than zero, the next cycle runs in low-stage cooling mode up to the desired low-stage cooling time limit, with an additional high-stage cooling mode run if the thermostat is not satisfied within the desired time.

Abstract: A method for adjusting the continuous speed of the blower of a heating and/or cooling system of the type including a thermostat having a mode selector switch which has at least one heating position, a cooling position, and an off position, a fan switch having an on position or state and an auto position or state, and a programmable control device responsive to the thermostat for generating speed select signals for use in setting the speed of the blower motor. The programmable control device is programmed or reprogrammed so that, when the mode selector switch is in its off position or when there is no call for heating or cooling at the thermostat, time dependent movements of the fan switch away from and back to its on position are recognized as requests for changes in the continuous speed of the blower motor.

Abstract: A combustion air regulating apparatus which is adapted for use with two stage induced draft furnaces and which allows such furnaces to be used with low cost AC inducer motors of the type having one or a small number of nominally fixed operating speeds. A flow restrictor assembly is disposed in fluidic series with the air intake and the exhaust vent to controllably restrict the flow of air through the burner box when the inducer motor operates at its low speed. A pressure sensing assembly is connected to sense a pressure approximately equal to that across the heat exchanger, and to control the flow resistance of the flow restrictor assembly to maintain a sufficient level of excess air when the furnace operates in its low stage. A solenoid valve responsive to the establishment of high stage furnace operation causes the flow restrictor assembly to establish and maintain its minimum flow resistance during operation in that stage.

Abstract: A furnace control apparatus is described wherein a flow of gas into a burner assembly is directly dependent on an indicia of burner combustion air airflow, such as heat exchanger pressure drop. According to one embodiment of the invention, a first communication fluid line is interposed between a gas valve regulator and a heat exchanger at a first point, and a second communication fluid line is interposed between a gas valve regulator a heat exchanger at a second point. The main valve of the gas valve is responsive to the pressure differential between the first and second points so that a flow of gas into a furnace burner assembly is commensurate with a present flow level of combustion air.

Abstract: The present invention is a method and apparatus for controlling the flow of combustion air and/or combustion products through a furnace which may experience changing flow restrictions. The method provides constant flow through an induced-draft furnace by determining torque values applied to an inducer motor of the furnace from a lookup table, which is established by operating a test furnace under changing flow restrictions, typically by measuring furnace flue gas carbon monoxide concentration. A lookup table according to the invention may include motor operating performance plots for controlling inducer speed under operating conditions, and threshold plots, which may be employed for determining activation of furnace events such as ignition, gas valve energizing, and shutdown. In an adaptive method of the invention, an adaptive lookup table is provided by averaging torque values from each of several lookup tables.

Abstract: An adjustable shock absorber having a movable sealing piston located within the shock absorber for sealing fluid and a suspension adjuster connected to the shock absorber for moving fluid between the adjuster and the shock absorber so as to change the overall length of the shock absorber without changing the stroke length.

Abstract: An adjustable suspension system which has a shock absorber affixed to the suspension system, a movable sealing piston located within a shock absorber for sealing fluid and a suspension adjuster connected to the shock absorber for moving fluid between the adjuster and the shock absorber. A conduit connects the suspension adjuster and the shock absorber. The conduit also includes a hose connecting the suspension adjuster with the shock absorber. A shock housing is adjacent to and outside the shock body. The shock housing surrounds the periphery of the shock body. The shock housing and the shock body define a passageway for fluid. The shock body has a portion that defines at least one port hole between the shock cap and the sealing piston. The shock absorber includes a fluid chamber defined by a shock cap, a shock body, and the sealing piston.

Abstract: A method is disclosed for testing a heating and cooling system having a plurality of variable speed motors. Each motor has means for generating an output signal indicative of the motor's speed. The test method includes setting the first motor to a first speed setting and reading the output signal indicative of the motor speed. The first motor is then set to a second speed setting and the motor speed output signal is read again. This procedure is repeated for the remaining motors in the system. Then, each motor speed output reading is compared with a pre-determined acceptable range of speeds for that motor. If the reading value is outside of the desired of the desired range, an appropriate error signal is produced.

Abstract: In a heating system with a plurality of heat sources, wherein at least a first heat source is normally activated at a first, higher ambient temperature and at least one additional heat source is normally activated at a second, lower ambient temperature, a method for maintaining a desired comfort level in a comfort zone when the first heat source is deactivated comprising the steps of: recognizing that the first heat source is deactivated; and initiating at least one of the additional heat sources when the first, higher ambient temperature is reached.

Abstract: A method for providing a low fire mode and a high fire mode of a heating cycle in a current cycle of a furnace as a function of the previous heating cycle wherein the current heating cycle is a function exclusively of time run in low fire mode and time run in high fire mode of the previous heating cycle, comprising the steps of: (1) determining the existence of a heating load to be satisfied; (2) running burners in low fire mode for a first time interval that does not exceed a predetermined limit, L.sub.des ; (3) running the burners in high fire mode for a second time interval until the heating load is satisfied; (4) calculating a BtU load requirement, as a function of the first time interval and the second time interval; and (5) determining the desired low fire mode time limit, L.sub.des, for the next cycle from the calculated BtU load requirement.

Abstract: In a heating system containing twinned furnaces capable of independently operating at multiple levels, a method for providing multiple heating modes to satisfy a required heating load during a given cycle, there being some total number of heating modes, wherein each heating mode may be activated for a time interval whose length is a function of furnace activity during the most recent previous cycle.

Abstract: In a fixed-firing rate induced draft furnace, having a heat exchanger and an integrated control inducer motor, an improved method of controlling excess air comprising the steps of: providing at least one pressure switch that is responsive to a preselected pressure drop level in the heat exchanger, the pressure drop level being selected so as to be commensurate with a theoretically desired excess air level under firing operating conditions; accelerating the integrated control inducer motor until the pressure switch closes and thereupon recording a first motor speed and a first current level; calculating a first torque value based on the first motor speed and the first current level; and regulating torque applied to the integrated control inducer motor in accordance with the first torque value.

Abstract: A two-stage furnace is operable at a high fire full rate mode and at a low fire partial rate mode when there is a call for high heat or low heat, respectively. In order for the furnace to be less prone to vent gas condensate formation when operating at low fire, and to permit the heat exchanger and vent pipe to reach equilibrium as soon as possible on both low fire and high fire, a shorter blower-on delay is provided for high fire and longer blower-on delay is provided on low fire.

Abstract: In a gas furnace designed for operation with natural gas, the use of propane as a fuel is facilitated by increasing the inducer speed by a factor which is obtained by comparing the higher inducer speed necessary to bring down the heat exchanger temperature to an acceptable level, with the original lower inducer speed that had caused the temperature to exceed the allowed limit. Provision is made for electronically applying the multiplying factor by simply operating a gas selector switch.

Abstract: A furnace which normally operates from a residential AC power source is adapted to operate on auxiliary DC power by changing the normal control function to substantially prevent the furnace from operating in the high heat mode during periods of auxiliary power use. Relays can be used to automatically connect the emergency power and to effect the change of the control function.

Abstract: A two-stage gas furnace control system automatically shifts into a high fire only mode if, in two consecutive low fire heating cycles a limit switch is tripped to indicate that a gas valve is stuck in a high fire condition. In this way, continued operation is allowed to proceed in a safe manner. Provision is also made to lock out the system from further operation if, while in the high fire only mode, the limit switch is tripped in a predetermined consecutive number of cycles or if, while in a preemptive low fire only mode, the limit switch is tripped.