Refrigeration – Processes – Circulating external gas
Reexamination Certificate
2001-07-06
2002-03-12
Tapolcai, William E. (Department: 3744)
Refrigeration
Processes
Circulating external gas
C062S127000, C062S129000, C062S158000, C062S213000
Reexamination Certificate
active
06354093
ABSTRACT:
TECHNICAL FIELD
This invention pertains generally to refrigeration and freezer units, and more specifically to a control system for such units and related methods for controlling defrost, monitoring the status of a system condenser coil, and monitoring for refrigerant leaks.
BACKGROUND OF THE INVENTION
Cooling systems are utilized in many different types of refrigeration units and freezer units. For example, commercial refrigeration and freezer units used by those in the food industry such as restaurants generally include some variation of the standard cooling system which has existed for many years. Similarly, numerous control schemes for such cooling systems are known, including control schemes for defrost operations of the cooling systems in order to eliminate frost build up on the evaporator coils of such systems. However, improvements in such defrost control schemes are continually sought.
One problem associated with such cooling systems is that air is generally passed through a condenser to remove heat from the refrigerant. The intake air to the condenser passes through the condenser coil. As particulates build up on the condenser, air flow through the coil decreases and system efficiency may be reduced. Accordingly, it would be desirable to provide the ability to detect a clogged condenser in order to clean the condenser when needed.
Another problem associated with such cooling systems is the occurrence of refrigerant leaks in the system. Accordingly, it would be desirable to provide the ability to detect such refrigerant leaks.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a method of defrosting a refrigeration unit or a freezer unit involves the steps of (a) monitoring a compressor running time, (b) monitoring an evaporator coil temperature, (c) monitoring a first time period since a last cooled compartment door open alarm of the unit, (d) monitoring a second time period since a last defrost operation, (e) monitoring a third time period during which the cooled compartment door is closed, and (f) controlling initiation of a defrost operation as a function of the monitored compressor running time, the monitored evaporator coil temperature, the monitored first time period, the monitored second time period, and the monitored third time period. Various sets of conditions may be established for triggering initiation of the defrost operation.
In another aspect of the invention a method of monitoring a refrigeration system for refrigerant leaks involves (a) monitoring a running time of a compressor, (b) monitoring a temperature of a discharge line of the compressor, (c) controlling activation of a line leak alarm based at least in part upon: (i) the running time of the compressor exceeding a threshold running time; and (ii) comparison of the discharge line temperature to a threshold discharge line temperature.
Yet a further aspect of the invention provides a method of monitoring the condenser of a cooling system. The method involves (a) monitoring a running time of a compressor, (b) monitoring a temperature of a discharge line of the compressor, (c) controlling activation of a clogged condenser alarm based at least in part upon: (i) the running time of the compressor exceeding a threshold running time; and (ii) comparison of the discharge line temperature to a threshold discharge line temperature.
An electronic controller may be utilized to implement the foregoing methods in conjunction with various sensors associated with the system components.
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Davis Ronald
Lewis Laura
Slade Alvin
Ali Mohammad M.
Tapolcai William E.
Thompson Hine LLP
Traulsen & Company, Inc.
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