Abstract: Controlling a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace using a low pressure limit switch configured to actuate at a first pressure, an intermediate pressure limit switch configured to actuate at a second pressure, and a high pressure limit switch configured to actuate at a third pressure, the second pressure being between the first and third pressure, selectively operating the modulating gas furnace in one of a cycling mode, a modulating mode in a lower range, and a modulating mode in an upper range, the modulating mode in the lower range being associated with an output capacity range between the output capacity ranges of the cycling mode and the modulating mode in the upper range, and selectively operating the furnace in response to at least one of the low pressure limit switch, the intermediate pressure limit switch, and the high pressure limit switch.

Abstract: In a multistage combustion furnace having a motor driven inducer blower and a pressure sensing device or set of switches for sensing pressure in the combustion gas flowpath through the furnace, a high firing rate blower speed and low firing rate blower speed are set based on the blower speed setting required for a medium firing rate. Each particular furnace, having its own pressures and combustion gas resistance to flow characteristics, may be provided with a database of inducer blower motor speeds required to achieve predetermined pressures in the combustion gas flowpath for a variety of combustion gas venting systems generating such resistance.

Abstract: A method controls a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace, learning an intermediate value associated with an intermediate capacity between a minimum output capacity of the gas furnace and a maximum output capacity of the gas furnace, learning one of a high value associated with the maximum output capacity and a low value associated with a minimum output capacity, establishing an estimated operating curve using either the intermediate value and the low value or using the intermediate value and the high value, and operating the gas furnace in accordance with the estimated operating curve.

Abstract: Controlling a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace using a low pressure limit switch configured to actuate at a first pressure, an intermediate pressure limit switch configured to actuate at a second pressure, and a high pressure limit switch configured to actuate at a third pressure, the second pressure being between the first and third pressure, selectively operating the modulating gas furnace in one of a cycling mode, a modulating mode in a lower range, and a modulating mode in an upper range, the modulating mode in the lower range being associated with an output capacity range between the output capacity ranges of the cycling mode and the modulating mode in the upper range, and selectively operating the furnace in response to at least one of the low pressure limit switch, the intermediate pressure limit switch, and the high pressure limit switch.

Abstract: Controlling a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace using a low pressure limit switch configured to actuate at a first pressure, an intermediate pressure limit switch configured to actuate at a second pressure, and a high pressure limit switch configured to actuate at a third pressure, the second pressure being between the first and third pressure, selectively operating the modulating gas furnace in one of a cycling mode, a modulating mode in a lower range, and a modulating mode in an upper range, the modulating mode in the lower range being associated with an output capacity range between the output capacity ranges of the cycling mode and the modulating mode in the upper range, and selectively operating the furnace in response to at least one of the low pressure limit switch, the intermediate pressure limit switch, and the high pressure limit switch.

Abstract: A method controls a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace, learning an intermediate value associated with an intermediate capacity between a minimum output capacity of the gas furnace and a maximum output capacity of the gas furnace, learning one of a high value associated with the maximum output capacity and a low value associated with a minimum output capacity, establishing an estimated operating curve using either the intermediate value and the low value or using the intermediate value and the high value, and operating the gas furnace in accordance with the estimated operating curve.

Abstract: A method controls a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace, learning an intermediate value associated with an intermediate capacity between a minimum output capacity of the gas furnace and a maximum output capacity of the gas furnace, learning one of a high value associated with the maximum output capacity and a low value associated with a minimum output capacity, establishing an estimated operating curve using either the intermediate value and the low value or using the intermediate value and the high value, and operating the gas furnace in accordance with the estimated operating curve.

Abstract: HVAC apparatus is configured to include a control system with a controller which may be connected directly to a personality module for transferring information stored in the controller related to historic operating conditions of the apparatus to the module, or information may be transferred to the controller from the module to configure the controller for operation of the apparatus at selected operating conditions of temperature, pressure and blower motor speed, for example. The personality module includes a memory circuit and a connector for releasably connecting the module to the control system of the apparatus for transferring information between the module and the controller.

Abstract: Heating, ventilating and air conditioning (HVAC) equipment units are provided with controllers which may be interconnected to a third or common controller, such as a communicating thermostat, and provide information in a process to determine if two or more of such air conditioning units may be operated as twinned units. Information is transmitted over a data bus between the controllers for the respective air conditioning units and the common controller to determine if the air conditioning units are the same type, of a same family and of essentially the same capacity before permitting twinned operation. If one of the air conditioning units is not twinnable, an alarm signal is generated to prevent operation of the air conditioning units in a multiple-unit configuration.

Abstract: A user interface for a control system for an air conditioning apparatus includes a visual display and keys for scrolling menu items and entering commands to the control system. The interface is mounted in the apparatus cabinet and on a rotatable bracket to orient the interface for ease of reading the display and actuating the respective keys.

Abstract: Controlling a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace using a low pressure limit switch configured to actuate at a first pressure, an intermediate pressure limit switch configured to actuate at a second pressure, and a high pressure limit switch configured to actuate at a third pressure, the second pressure being between the first and third pressure, selectively operating the modulating gas furnace in one of a cycling mode, a modulating mode in a lower range, and a modulating mode in an upper range, the modulating mode in the lower range being associated with an output capacity range between the output capacity ranges of the cycling mode and the modulating mode in the upper range, and selectively operating the furnace in response to at least one of the low pressure limit switch, the intermediate pressure limit switch, and the high pressure limit switch.

Abstract: A method controls a modulating gas furnace by monitoring a differential pressure associated with the modulating gas furnace, learning an intermediate value associated with an intermediate capacity between a minimum output capacity of the gas furnace and a maximum output capacity of the gas furnace, learning one of a high value associated with the maximum output capacity and a low value associated with a minimum output capacity, establishing an estimated operating curve using either the intermediate value and the low value or using the intermediate value and the high value, and operating the gas furnace in accordance with the estimated operating curve.

Abstract: An air conditioning (HVAC) system for a residential dwelling or other building with enclosed spaces includes multiple thermostats hard wire interconnected or communicating via radio frequency transceivers. The thermostats each include control circuits for adjusting the setpoint temperature at any one thermostat and displaying the set temperature at all thermostats, setting the time at any one thermostat and displaying the time at all thermostats, controlling the thermostat temperature setting from a selected one of the thermostats and providing a setpoint for control of the air conditioning system based on an average temperature sensed by all of the thermostats. A method for correctly setting a thermostat time display to one of Daylight Saving Time or Standard Time and displaying an icon identifying one or the other is disclosed.

Abstract: An air conditioning apparatus including a heater or furnace includes a controller for receiving control signals from a thermostat and from a user interface for initiating a contingency mode of operation when a signal from the thermostat is not available. The user interface includes a visual display and multiple keys for entering the contingency mode which includes selecting a capacity of heat output of the apparatus and a duty cycle. The user interface may be disposed in the apparatus cabinet and connected directly to a microprocessor based controller for the apparatus. The contingency mode is automatically aborted if a fault signal is received by the controller, a signal is received from a thermostat or power to the apparatus is interrupted.

Abstract: An HVAC system includes a variable speed electric motor driven fan for circulating air to an enclosed space through an indoor unit for providing heating or cooling effect to air circulated through the indoor unit. A controller with user or system installer actuatable switches includes a programmable microcontroller providing a pulse width modulated (PWM) signal to a motor control unit to select a predetermined air flowrate less than full air flowrate during system startup and shutdown. User input parameters include selected percentages of full air flowrate to satisfy requirements for reduced noise level, lower humidity and for improved sensible heating of air being circulated, the latter being effective particularly for heat pump applications. Selection of pre-run, short run and shutdown cycles may be provided.

Abstract: An air conditioning (HVAC) system for a residential dwelling or other building with enclosed spaces includes multiple thermostats hard wire interconnected or communicating via radio frequency transceivers. The thermostats each include control circuits for adjusting the setpoint temperature at any one thermostat and displaying the set temperature at all thermostats, setting the time at any one thermostat and displaying the time at all thermostats, controlling the thermostat temperature setting from a selected one of the thermostats and providing a setpoint for control of the air conditioning system based on an average temperature sensed by all of the thermostats. A method for correctly setting a thermostat time display to one of Daylight Saving Time or Standard Time and displaying an icon identifying one or the other is disclosed.

Abstract: An air conditioning (HVAC) system for a residential dwelling or other building with enclosed spaces includes multiple thermostats hard wire interconnected or communicating via radio frequency transceivers. The thermostats each include control circuits for adjusting the setpoint temperature at any one thermostat and displaying the set temperature at all thermostats, setting the time at any one thermostat and displaying the time at all thermostats, controlling the thermostat temperature setting from a selected one of the thermostats and providing a setpoint for control of the air conditioning system based on an average temperature sensed by all of the thermostats. A method for correctly setting a thermostat time display to one of Daylight Saving Time or Standard Time and displaying an icon identifying one or the other is disclosed.

Abstract: A user interface for a control system for an air conditioning apparatus includes a visual display and keys for scrolling menu items and entering commands to the control system. The interface is mounted in the apparatus cabinet and on a rotatable bracket to orient the interface for ease of reading the display and actuating the respective keys.

Abstract: An air conditioning apparatus including a heater or furnace includes a controller for receiving control signals from a thermostat and from a user interface for initiating a contingency mode of operation when a signal from the thermostat is not available. The user interface includes a visual display and multiple keys for entering the contingency mode which includes selecting a capacity of heat output of the apparatus and a duty cycle. The user interface may be disposed in the apparatus cabinet and connected directly to a microprocessor based controller for the apparatus. The contingency mode is automatically aborted if a fault signal is received by the controller, a signal is received from a thermostat or power to the apparatus is interrupted.

Abstract: In a multistage combustion furnace having a motor driven inducer blower and a pressure sensing device or set of switches for sensing pressure in the combustion gas flowpath through the furnace, a high firing rate blower speed and low firing rate blower speed are set based on the blower speed setting required for a medium firing rate. Each particular furnace, having its own pressures and combustion gas resistance to flow characteristics, may be provided with a database of inducer blower motor speeds required to achieve predetermined pressures in the combustion gas flowpath for a variety of combustion gas venting systems generating such resistance.