Refrigeration – With indicator or tester – Diverse function indicators or testers
Reexamination Certificate
1999-01-19
2001-05-22
Tanner, Harry B. (Department: 3744)
Refrigeration
With indicator or tester
Diverse function indicators or testers
C062S131000
Reexamination Certificate
active
06233952
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to refrigeration systems in general, and, in particular, to a pretrip routine for testing a refrigeration system prior to operating a refrigeration system in a cooling or heating/defrost mode of operation.
BACKGROUND OF THE PRIOR ART
A pretrip routine for testing a refrigeration system described in U.S. Pat. No. 5,172,561 operates by controlling system components first according to a cooling mode scheme, and then according to a heating/defrost mode scheme. During each of the simulated cooling and heat/defrost modes, a control unit monitors an air-aide temperature differential of a refrigeration system evaporator. If the evaporator air side temperature differential is within a range of temperature differentials indicative of the refrigeration system operating properly in each of the simulated cooling and heating/defrost modes, then the refrigeration system is determined to be operational.
The approach described in U.S. Pat. No. 5,172,561 suffers from two major limitations. The first limitation is that the approach is susceptible to false failures. Under certain operating conditions, the evaporator temperature differential will be outside of a range of temperature differential indicative of proper operation in spite of the system being fully operational. Evaporator temperature is likely to be outside of a range indicative of proper operation particularly under extremely humid work space conditions.
The second major limitation of the approach described in U.S. Pat. No. 5,172,561 is that the approach cannot isolate problems within particular refrigeration system components. When a refrigeration system failure is indicated, the system provides only a general alarm that problem exists somewhere in the system, and cannot identify which particular components in the system have failed. Fixing problems pursuant to a general alarm may require inspection of each of several system components.
There is a need for a refrigeration system pretrip routine which is not susceptible to false failures and which can isolate particular problems within a refrigeration system.
SUMMARY OF THE INVENTION
According to its major aspects and broadly stated, the present invention is a pretrip routine for testing a refrigeration system comprising a series of tests for testing aspects of mechanical operation of various individual components of the refrigeration system. The pretrip routine of the invention validates operation of a refrigeration system as a whole by testing the mechanical operation of individual system components, and, in testing the operation of those various system components, readily isolates particular problems within particular components of a refrigeration system.
In a preferred embodiment, a control unit executes the method of the invention by first testing mechanical operation of a refrigeration system compressor, then tests for leaks in high-to-low-side valves of a refrigeration system, before testing for leaks in a discharge test valve. A control unit may also test the opening/closing operation of various refrigeration system valves before, intermediate or subsequent to executing the above tests. In a compressor operation test, a control unit may check loading/unloading operation of a compressor by changing the loading state of a compressor and monitoring for changes in a discharge pressure differential indicator. In a leak test, a control unit may shut a compressor engine off and monitor for changes in a discharge pressure differential indicator. A control unit may test the opening/closing operation of a refrigeration system valve by changing the state of a valve and monitors for changes in a differential pressure indicator subsequent to the state change.
These and other details, advantages and benefits of the present invention will become apparent from the detailed description of the preferred embodiment hereinbelow.
REFERENCES:
patent: 4211089 (1980-07-01), Mueller et al.
patent: 4852361 (1989-08-01), Oike
patent: 5140825 (1992-08-01), Hanson et al.
patent: 5172561 (1992-12-01), Hanson et al.
patent: 5363667 (1994-11-01), Janke et al.
patent: 5579648 (1996-12-01), Hanson et al.
Dobmeier Thomas J.
Kopp Peter H.
Malone Garret J.
Porter Kevin J.
Rabbia Mark B.
Carrier Corporation
Tanner Harry B.
Wall Marjama & Bilinski
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