Heat pump including auxiliary outdoor heat exchanger acting as defroster and sub-cooler

A heat pump including a refrigerant compressor, an indoor heat exchanger, a main outdoor heat exchanger, each of said heat exchangers having a plurality of finned parallel tubes, and a refrigerant flow circuit including a reversal valve for routing a refrigerant from said compressor to said indoor heat exchanger during heating operation and routing the refrigerant from said compressor to said main outdoor heat exchanger during cooling operation, comprising:

• an auxiliary outdoor heat exchanger having a plurality of finned parallel tubes mounted below said main outdoor heat exchanger and connected in series between said indoor and main outdoor heat exchangers so as to have a higher temperature than said main outdoor heat exchanger to melt any ice which might have formed underneath the main outdoor heat exchanger during the heating operation and to sub-cool the refrigerant during the cooling operation;
• first capillary tubes each being respectively connected at one end to a respective one of said finned tubes of said main outdoor heat exchanger;
• a one-way valve and a liquid receiver respectively connected in series between the other end of said first capillary tubes and said finned tubes of the auxiliary outdoor heat exchanger, said one-way valve permitting the passage of refrigerant from said main heat exchanger to said liquid receiver during the cooling operation and preventing the passage of refrigerant from said liquid receiver during the heating operation;
• a second capillary tube connected to provide a bypass passage for the refrigerant from said liquid receiver during the heating operation to said main outdoor heat exchanger;
• and
• third capillary tubes each being respectively connected at one end to a respective one of the finned tubes of said indoor heat exchanger and connected at the other end to said auxiliary outdoor heat exchanger.