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 controller and method for operating an HVAC system including an air conditioning unit, such as a gas furnace, having three stages of heat output and responsive to signals from a single stage or two stage thermostat. The W1, W2, and W3 inputs to the controller may be configured for receipt of a single stage control signal simultaneously or paired as W1, W2 or W2, W3. The system controller is configured to determine which input connection arrangement is in existence and operates the system in mock one stage or mock two stage modes depending on the signals received from a single or two stage thermostat, respectively.

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: A multistage furnace for heating residential or commercial spaces is operated by a single stage thermostat and a return air temperature sensor providing sensed temperature information to a controller. The furnace is started at a first, low firing rate and after a predetermined time is increased to a second firing rate if the rate of change of temperature of air returning to the furnace from the space is less than a predetermined amount. The method of operation is carried further to increase the firing rate to second and third rates based on predetermined rates of temperature change of return air from the enclosed space as sensed by the return air sensor.