Abstract: A retrofit air conditioning system for use with an existing induction air conditioning system is disclosed, wherein the existing system includes a central fan unit supplying air to a plurality of distribution units in corresponding rooms. The retrofit air conditioning system includes a retrofit air conditioning unit sized for receipt in an existing distribution unit. The retrofit air conditioning unit includes a fan downstream of an adjustable damper for inducing conditioned air from the central fan unit and for inducing recirculated air from the room. A microcontroller receives a temperature signal from a thermostat and produces a damper signal to adjust the damper in accordance with the sensed temperature. Also disclosed is a retrofit central fan unit for use with the retrofit induction unit, wherein the retrofit central fan unit supplies varying amounts of conditioned air to the distribution units to maintain a constant supply pressure.