Abstract: An auxiliary heating/cooling system controller is connected in series between the household thermostat and the furnace burner valve and compressor. The controller includes a timing control which is responsive to a preset time interval valve and the plenum temperature to cycle the furnace burner on and off in order to moderate the temperature of the furnace heat exchanger, thus improving furnace efficiency. Upon installation the controller is programmed with a digital valve corresponding to the delay between a call for heat from the household thermostat and the initiation of the furnace fan. This value is then used to set a timer in the controller which synchronizes the initiation of the duty cycle control of the burner to the start of the fan at the beginning of a heating cycle, and to control the cycle time of the burner. A plenum thermostat monitors the temperature of the air produced by the furnace and if the air exceeds a predetermined limit the OFF time of the burner is increased.

Abstract: An underground duct is connected to other ductwork and controls associated with a building for automatically selectively passing outdoor air through the underground duct to the normally outdoor coils of a heat pump, recirculating air through the underground duct to the heat pump outdoor coils and back through the underground duct, and passing outdoor air directly to the heat pump outdoor coils and also passing outdoor air through the underground duct to recondition it, in order to achieve optimum heat pump efficiency for selectively heating and cooling the building. Alternatively, air from the underground duct or from outdoors is selectively passed directly into the building for optimum cooling thereof while a dehumidifier is used to remove latent heat from the air; and other heat sources may be used with direct recirculation of air through the building and addition of a portion of tempered air from the underground duct for slightly pressurizing the building interior with heated air.