Method of controlling a carbon dioxide heat pump water heating system

• US 20050268625A1
• Filed: 06/07/2004
• Published: 12/08/2005
• Est. Priority Date: 06/07/2004
• Status: Active Grant

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Chen, Yu, Park, Young Kyu, Zhang, Lili, Concha, Julio, Eisenhower, Bryan, Sienel, Tobias, Nieter, Jeffrey, Pondicq-Cassou, Nicolas
• Granted Patent: US 7,010,925 B2
• Time in Patent Office: Days
• US Class Current: 62/129
• CPC Class Codes: F25B 2309/061 with cycle highest pressure above the supercritical pressure
• CPC Class Codes: F25B 2339/047 Water-cooled condensers
• CPC Class Codes: F25B 2700/1931 Discharge pressures
• CPC Class Codes: F25B 2700/1933 Suction pressures
• CPC Class Codes: F25B 2700/21151 at the suction side of the compressor
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25B 9/008 the refrigerant being carbon dioxide

Abstract

A method of detecting and diagnosing operating conditions for a heat pump water heating system includes the steps of monitoring system operating conditions and comparing actual operating conditions to predicted operating conditions. The predicted operating conditions are based on expected pressures and temperatures given current system inputs. A difference between the actual and expected values for refrigerant pressures and temperature outside a desired range provides indication of a fault in the system. The system controller initiates a prompt to alert of the need for maintenance and direct to potential causes.

Claims

1. A method of detecting heat pump operating conditions comprising the steps of:

a) compressing a refrigerant with a compressor device;

b) cooling the refrigerant by exchanging heat with a fluid medium;

c) expanding said refrigerant to a low pressure in an expansion device;

d) evaporating said refrigerant within a heat exchanger;

e) monitoring a operating condition;

f) comparing said monitored operating condition with a predicted operating condition; and

g) determining a fault condition in response to a magnitude of difference between the monitored operating condition and the predicted operating condition.

2. The method of claim 1, wherein said refrigerant is carbon dioxide.

3. The method of claim 1, wherein said heat pump exchanges heat with a water heater.

4. The method of claim 1, wherein a first pressure is monitored between said compressor and said heat exchanger.

5. The method of claim 4, wherein said step g) comprises determining a fault condition in response to actuation of said expansion device actuation not followed by a corresponding change in the first pressure.

6. The method of claim 1, wherein a second pressure is monitored between the evaporator and the compressor, and a temperature of said refrigerant is monitored between said compressor and said evaporator.

7. The method of claim 6, wherein a loss of refrigerant is determined responsive to a predicted temperature based on said second pressure being outside an actual monitored temperature.

8. The method of claim 6, wherein said evaporator includes a fan for blowing air across said evaporator, and a fault with said fan determined in response to an actual temperature being different than an expected temperature.

9. The method of claim 1, including a second temperature sensor disposed within the water circuit for measuring water temperature entering said evaporator.

10. The method of claim 9, wherein a fault is detected with said water pump in response to said temperature being less than a predicted temperature.

11. The method of claim 9, including a sensor monitoring pump speed, and a calcification of said heat exchanger determined in response to predetermined difference between predicted water temperature based on pump flow and actual water temperature.

12. The method of claim 1, wherein a loss of refrigerant is determined responsive to a superheat condition detected, wherein said superheat condition is a difference between a predicted temperature corresponding to a pressure, and an actual temperature.