Heat pump system

A heat pump system including a utilization side heat exchanger, a non-utilization side heat exchanger, a compressor for compressing and circulating a refrigerant fluid through said utilization side heat exchanger and said non-utilization side heat exchanger, a four-way valve for controlling a direction of refrigerant fluid flow through said utilization side heat exchanger and said non-utilization side heat exchanger, and an expansion valve provided between said utilization side heat exchanger and said non-utilization side heat exchanger for selectively controlling the circulation rate of said refrigerant fluid in accordance with an amount of valve opening of said expansion valve, wherein the improvement comprises:

• sensing means for detecting an inlet temperature of water undergoing heat exchange at said utilization side heat exchanger and an inlet temperature of air undergoing heat exchange at said non-utilization side heat exchanger;
• and
• controller means comprising a microprocessor and a read-only memory for controlling said amount of opening of said expansion valve in accordance with the sensed air and water temperatures, wherein said read-only memory stores data representing opening settings of said expansion valve corresponding to predetermined values of said inlet temperature of water at said utilization side heat exchanger and said inlet temperature of air at said non-utilization side heat exchanger for providing an optimum value of said expansion valve opening.