Apparatus and method for defrosting a heat exchanger in a refrigeration circuit

A method of operating a refrigeration circuit having a compressor, an indoor heat exchanger, a first outdoor heat exchanger, a second outdoor heat exchanger, restrictor means, expansion means and appropriate interconnecting piping including valve means which comprises the steps of:

• placing the valve means in the appropriate position in the cooling mode of operation to direct refrigerant from the compressor serially through the two outdoor heat exchangers, the expansion means and the indoor heat exchanger back to the compressor;
• placing the valve means in the appropriate position in the heating mode of operation to direct the refrigerant from the compressor serially through the indoor heat exchanger, the expansion means, the two outdoor heat exchangers and back to the compressor;
• and
• placing the valve means in a defrost mode of operation to direct refrigerant from the compressor serially to one of the outdoor heat exchangers, the restrictor means, the other outdoor heat exchanger and back to the compressor.

An outdoor heat exchange unit for use in a refrigeration circuit, the refrigeration circuit including a compressor and an indoor heat exchanger, which comprises:

• a first outdoor heat exchanger;
• a second outdoor heat exchanger;
• fan means for circulating air in heat exchange relationship with the heat exchangers;
• a conduit means including a plurality of valve means being located to allow refrigerant flow between the compressor and said first and second outdoor heat exchangers;
• a refrigerant line connecting the first outdoor heat exchanger to the second outdoor heat exchanger, said line being sufficiently sized to prevent a significant pressure drop as refrigerant flows between the two heat exchangers;
• a refrigerant line valve mounted in the refrigerant line, said valve having an open position allowing refrigerant flow without restriction and a closed position preventing refrigerant flow;
• a bypass line connecting the first heat exchanger to the second heat exchanger in parallel with the refrigerant line and refrigerant line valve;
• and
• restriction means mounted in the bypass line to effect a pressure drop in refrigerant flowing between the first and second outdoor heat exchangers through the bypass line.