Variable speed fan motor control for forced air heating/cooling system

摘要

A forced air heating and/or cooling system utilizing a permanent split capacitor (PSC) or shaded pole AC induction motor and including an actuator for energizing a source of heating and/or cooling effect may be controlled by a controller circuit which is operable to continuously vary the speed of the fan motor during a start-up phase and a shut-down phase of the heating and/or cooling cycle. The controller circuit includes terminals for connection to the source of electrical energy for the heating and/or cooling system and for connection to the system controls without altering the control function or circuitry thereof. The controller circuit includes elements for operating the fan motor to continuously vary its speed on start-up over a first predetermined time period and to continuously vary its speed down to a predetermined minimum on shutdown of the heating or cooling equipment over a second predetermined time period to minimize temperature stratification of air in the space being cooled or heated and to maximize capture of residual heat/cooling effect of the system. Another embodiment of the controller circuit includes temperature sensors which are operable to control start-up and shutdown of the fan motor over continuously variable speed operating cycles in response to sensed temperature of the air being circulated by the fan.