US4660386A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Diagnostic system for detecting faulty sensors in liquid chiller air conditioning system
Assignee: York International Corp
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Filing: 1985-09-18
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Granted: 1987-04-28
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Expires: 2005-09-18
Abstract
Abstract When sensors are employed to monitor the evaporator refrigerant pressure and the leaving chilled liquid temperature in an air conditioning system of the type having a liquid chiller, the sensor outputs will normally have a prescribed relationship with respect to each other as long as the sensors are functioning properly and regardless of the operating condition of the air conditioning system. By effectively comparing the output of one sensor relative to that of the other sensor, a faulty condition of either sensor may be detected. This is achieved by calculating the equivalent evaporator temperature, from the evaporator refrigerant pressure, and subtracting the equivalent temperature from the leaving chilled liquid temperature to obtain a difference temperature which is then compared to a predetermined known temperature range representing normal functioning of the two sensors. When one of the sensors is defective the difference temperature will fall outside of the range. If that occurs, a warning message that a faulty sensor has been detected is displayed to operating personnel and the air conditioning system's compressor is shut down as a safety precaution.
Inventors
- 👤 John C. Hansen
- 👤 Harold B. Ginder
- 👤 Lloyd A. Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 00:04
CPC Classifications
F; F25; F25B; F25B49/00; F25B49/005
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
180 words
In an air conditioning system having a liquid chiller wherein refrigerant flows through an evaporator to chill liquid circulating through a heat exchange coil in the evaporator, a pressure sensor sensing the pressure of the refrigerant in the evaporator while a temperature sensor senses the temperature of the chilled liquid leaving the evaporator, a diagnostic system for detecting when either one of the sensors is faulty, comprising: means for developing, from the output of the pressure sensor, a refrigerant pressure signal representing the evaporator refrigerant pressure; means for developing, from the output of the temperature sensor, a liquid temperature signal representing the leaving chilled liquid temperature; computing means for determining, from the difference between the evaporator refrigerant temperature which is represented by said refrigerant pressure signal, and the leaving chilled liquid temperature which is represented by said liquid temperature signal, if the output of one or the sensors is in error, thereby indicating that the sensor is faulty; and warning means, controlled by said computing means, for providing a warning message to operating personnel when a faulty sensor is detected.
Claim 2
Dependent Claim
180 words
In an air conditioning system having a liquid chiller wherein refrigerant flows through an evaporator to chill liquid circulating through a heat exchange coil in the evaporator, a pressure sensor sensing the pressure of the refrigerant in the evaporator while a temperature sensor senses the temperature of the chilled liquid leaving the evaporator, a diagnostic system for detecting when either one of the sensors is faulty, comprising: means for developing, from the output of the pressure sensor, a refrigerant pressure signal representing the evaporator refrigerant pressure; means for developing, from the output of the temperature sensor, a liquid temperature signal representing the leaving chilled liquid temperature; computing means for determining, from the difference between the evaporator refrigerant temperature which is represented by said refrigerant pressure signal, and the leaving chilled liquid temperature which is represented by said liquid temperature signal, if the output of one or the sensors is in error, thereby indicating that the sensor is faulty; and warning means, controlled by said computing means, for providing a warning message to operating personnel when a faulty sensor is detected.
Claim 3
Dependent Claim
34 words
A diagnostic system according to claim 1 wherein said computing means determines if a predetermined known relationship exists between the sensor outputs, a faulty sensor being indicated when the known relationship is not found.
Claim 4
Dependent Claim
21 words
A diagnostic system according to claim 1 wherein said warning means provides a visual display when a faulty sensor is discovered.
Claim 5
Dependent Claim
33 words
A diagnostic system according to claim 1 and including means, controlled by said computing means, for shutting the air conditioning system's compressor down as a safety precaution whenever a faulty sensor is found.
Claim 6
Dependent Claim
14 words
A diagnostic system according to claim 1 wherein said computing means includes a microcomputer.
Claim 7
Dependent Claim
42 words
A diagnostic system according to claim 1 wherein operation of said computing means is delayed for a preset time period following power up of the air conditioning system to allow the evaporator refrigerant pressure and the leaving chilled liquid temperature to stabilize.
Claim 8
Dependent Claim
55 words
A diagnostic system according to claim 1 wherein said computing means calculates, from said refrigerant pressure signal, the equivalent evaporator refrigerant temperature based on the pressure-temperature relationship of the refrigerant, and wherein the equivalent evaporator refrigerant temperature and the leaving chilled liquid temperature are effectively compared in determining whether one of the sensors is defective.
Claim 9
Dependent Claim
77 words
A diagnostic system according to claim 7 wherein the equivalent evaporator refrigerant temperature is subtracted from the leaving chilled liquid temperature to obtain a difference temperature which is then compared to a predetermined known temperature range representing normal functioning of the sensors, the difference temperature falling outside of the range when one of the sensors is faulty, and wherein said warning means is actuated in response to determining that the difference temperature lies outside of the range.
Claim 10
Dependent Claim
41 words
A diagnostic system according to claim 8 wherein the equivalent evaporator refrigerant temperature and the leaving chilled liquid temperature are represented by binary numbers and a binary subtraction of those numbers produces a resultant binary number which represents the difference temperature.
Claim 11
Dependent Claim
46 words
A diagnostic system according to claim 8 wherein the predetermined known temperature range extends from about -2.5° F. to about 25° F., the difference temperature falling within that range under any operating condition of the air conditioning system as long as the sensors are functioning properly.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-04-27 | 1990-10-27 | 1991-04-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-27 | 1994-10-27 | 1995-04-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-27 | 1998-10-27 | 1999-04-28 | $7700.00 | Window Closed / Lapsed |