Cascade heat pump for heating water and for cooling or heating a comfort zone

A heat pump system for selectively heating water by extracting heat from relatively cold outdoor ambient air while operating in cascade fashion, and heating or cooling air supplied to a comfort zone, comprising

• a. a first refrigerant fluid loop including
• i. a first compressor selectively operative to compress a first refrigerant fluid, including a first suction port and a first dischage port;
• ii. a refrigerant-to-water heat exchanger connected in fluid communication with the first discharge port, wherein water is heated and the compressed first refrigerant fluid is condensed as a result of heat transfer therebetween when the system is operated in a first or a second mode;
• iii. first expansion means connected to the refrigerant-to-water heat exchanger, for expanding and reducing the pressure of the condensed first refrigerant fluid;
• iv. a tri-fluid heat exchanger connected in fluid communication with the first expansion means, including non-communicating first and second circuits, and air passages, in heat transfer relationship with each other;
• said expanding first refrigerant fluid being vaporized while flowing through the first circuit, by heat transfer with air flowing through the air passages, thereby cooling the air when the system is operating in the first mode, and by heat transfer with a second refrigerant fluid when the system is operating in the second mode;
• said first circuit also being in fluid communication with the first suction port, whereby vaporized first refrigerant fluid is returned to the first compressor;
• b. a second refrigerant fluid loop including
• i. a second compressor selectively operative to compress the second refrigerant fluid, and including a second suction port, and a second discharge port connected in fluid communication with the second circuit in the tri-fluid heat exchanger, said second compressor being selectively energized in the second mode, placing the first and the second refrigerant fluid loops in cascade relationship with each other, whereby heat transfer between the first and second refrigerant fluids in the tri-fluid heat exchanger vaporizes the first refrigerant fluid and condenses the second refrigerant fluid, and being selectively energized in a third mode wherein heat transfer between the compressed second refrigerant fluid and air in the tri-fluid heat exchanger heats the air and condenses the second refrigerant fluid;
• ii. second expansion means connected in fluid communication to the tri-fluid heat exchanger second circuit, for expanding and reducing the pressure of the second refrigerant fluid condensed therein;
• iii. an outdoor heat exchanger connected in fluid communication with the second expansion means and operative to provide heat transfer between the expanding second refrigerant fluid and outdoor ambient air when the system is operating in the second and third modes, whereby heat is extracted from the outdoor ambient air to vaporize the second refrigerant fluid, said outdoor heat exchanger also being connected in fluid communication with the second compressor for return of the vaporized second refrigerant fluid to the second suction port.

A method for selectively heating water with heat from relatively cold outdoor ambient air using a heat pump system operable in cascade fashion, and heating or cooling air supplied to a comfort zone, comprising the steps of

• a. in a first mode:
• i. compressing a vaporized first refrigerant fluid;
• ii. condensing the compressed first refrigerant fluid by providing heat transfer with water, thereby heating the water;
• iii. expanding and reducing the pressure of the condensed first refrigerant fluid;
• iv. vaporizing the expanded first refrigerant fluid by heat transfer with air supplied to cool a comfort zone;
• b. in a second mode including above steps (i) through (iii), the further steps of:
• iv. compressing a vaporized second refrigerant fluid;
• v. condensing the compressed second refrigerant fluid by heat transfer with the first refrigerant fluid, thereby vaporizing the first refrigerant fluid;
• vi. expanding and reducing the pressure of the condensed second refrigerant fluid;
• vii. vaporizing the expanded second refrigerant fluid by heat transfer with outdoor ambient air;
• and
• c. in a third mode, including the above steps in (b), (iv), (vi), and (vii), and in order after step (b) (iv), the further step of condensing the compressed second refrigerant fluid by heat transfer with air supplied to heat the comfort zone.