Refrigeration – Automatic control – Preventing – removing or handling atmospheric condensate
Reexamination Certificate
2007-06-12
2007-06-12
Tyler, Cheryl (Department: 3744)
Refrigeration
Automatic control
Preventing, removing or handling atmospheric condensate
C062S154000, C062S155000, C062S156000
Reexamination Certificate
active
10776374
ABSTRACT:
A heat pump, and in particular a heat pump for heating a hot water supply is provided with an improved defrost mode. The defrost mode is actuated to remove frost from an outdoor evaporator that may accumulate during cold weather operation. An algorithm for operation of the defrost mode is developed experimentally by seeking to maximize the heat transfer provided by the refrigerant. A heating system condition is experimentally related to the heat transfer capacity. One then maximizes the average heat transfer capacity to determine the optimum initiation point for the defrost mode. Further, protections are included into the defrost mode. When the heat pump is utilized to heat hot water, methods are provided to prevent the water that remains in the heat exchanger from becoming unduly heated. In one method, the water pump may be periodically operated to move the water. In a second method, a control ensures the discharge pressure of the refrigerant leaving the compressor is reduced, and that the water pump is not stopped until that reduced temperature falls below a predetermined maximum. The temperature reduction is achieved through a dual control loop wherein a temperature that is too high results in a new desired discharge pressure. The control achieves the new desired pressure by controlling the expansion device. In another protection feature, as a control determines that the defrost mode is nearing its end, an evaporator fan is run to remove melted water from the evaporator coils, and also to ensure the refrigerant leaving the evaporator does not reach unduly high pressure or temperatures.
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International Search Report, Mar. 1, 2006.
Chen Yu
Concha Julio
Park Young Kyu
Sienel Tobias H.
Bankhead Gene
Carlson & Gaskey & Olds
Carrier Corporation
Tyler Cheryl
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