Abstract: A multi-section evaporator is employed in a heat pump system which includes a compressor, a condenser and an evaporator. A control valve is connected between each adjacent set of evaporator sections and the control valve is operable in response to temperature and/or pressure conditions sensed by a sensor. In response to a sensed condition, one or more sections of the evaporator are brought into operation concurrently with the previously operating section(s). Thus, the effective size of the evaporator is variable depending on the sensed condition.