US20090084119A1

US20090084119A1 - Sytem and method for detecting transducer failure in refrigerant systems

Info

Publication number: US20090084119A1
Application number: US11/989,656
Authority: US
Inventors: Alexander Lifson; Michael F. Taras
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2005-08-03
Filing date: 2005-08-03
Publication date: 2009-04-02
Also published as: EP1917506A1; WO2007018530A1; HK1125171A1; CA2617716A1; CN101283243B; CN101283243A

Abstract

There is provided a refrigerant system. First and second transducers are positioned within the refrigerant system to measure respective operational characteristics. There is a timer that determines that a shutdown has occurred for a specified period of time; and a comparator that compares an output of the first transducer to an output of the second transducer after that specified time and determines whether the outputs of the first and second transducers are within a tolerance band of each other. If the readings are not within tolerance band, then the transducer failure is detected and a warning/alarm requiring operator attention is issued.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to detecting transducer failures. More particularly, the present invention relates to detecting transducer failure in refrigerant systems.
2. Description of the Related Art
Refrigerant systems typically have multiple installed pressure and temperature transducers. These transducers are used to measure pressure and temperature characteristics in various locations within the refrigerant systems. The outputs of these transducers are then used to control operation of the refrigerant system, as well as to verify that the refrigerant system is operating within manufacturer's specifications. Furthermore, these transducer outputs are used to adjust operating parameters and to change modes of operation of the refrigerant system in response to varying environmental conditions.
However, due to such factors as improper handling practices, exposure to harsh environments, manufacturing defects, inappropriate installations techniques, wear and tear, and so forth, these transducers may be damaged, and therefore fail to function properly. This damage results in a transducer malfunction, or otherwise readings that noticeably deviate from factory specification. This, in turn, will cause system malfunctioning, since refrigerant system controllers relying on faulty transducer readings will have a faulty feedback.
Detecting a transducer failure, however, can be a time consuming and an effort intensive process. For example, in some test scenarios, each transducer is tested separately for a plurality of known operating conditions, and the output of each transducer is then compared against manufacturer's specifications to determine if the transducer is working properly.
Therefore, there is a need for a system and a method to verify proper operation and test transducers in a refrigerant system that addresses at least some of the concerns associated with conventional refrigerant transducer technology.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a refrigerant system. A first transducer and second transducer are provided for measuring a characteristic associated with a first component and a second component of the refrigerant system. A compressor is connected to the first and second components. A controller is connected to the first and second transducers. The controller has a timer that determines that a shutdown has occurred for a specified period of time; and a comparator that compares an output of the first transducer to an output of the second transducer and determines whether the outputs of the first and second transducers are within a desired tolerance band of each other.
In another embodiment, there is provided a method for detecting transducer failure. A compressor is shut down. Then, a specified time period is elapsed. A first output of a first transducer connected to a first component is measured. A second output of a second transducer connected to a second component is measured. The first output and said second output are compared to determine whether the first and second outputs are within a desired tolerance of one another. In yet another aspect, the first and second outputs are compared by utilizing conversion equations or correlations when different transducer types are used.
It is an object of the present application to detect transducer failure with less cost and time-consumption.
It is a further object of the present invention to timely detect transducer failure to prevent system malfunction and potential failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a controller according to the present invention for a refrigerant system that tests transducers for failure.

FIG. 2 is a method according to the present invention for testing transducers for failure in a refrigerant system.

DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a refrigerant system (“system”) generally represented by reference numeral 100 that has a first transducer 150 and a second transducer 160. System 100 also incorporates a first refrigerant system component (or component) 110, such as, for example, a condenser, a second refrigerant system component (or component) 120, such as, for example an evaporator, an expansion device 130, a compressor 140, a controller 165, and a data storage media 185.
An output of first transducer 150 is connected to a first input of controller 165. An output of second transducer 160 is connected to a second input of controller 165. An output of the first transducer 150, associated with the component 110, is connected to a controller 165. Similarly, an output of the second transducer 160, associated with the component 120, is also connected to the controller 165. A first transducer 150 is located on the high-pressure side of the compressor 140 and refrigerant system 100. A second transducer 160 is located on the low-pressure side of compressor 140 and refrigerant system 100. First transducer 150 and second transducer 160 are pressure transducers. Controller 165 may be connected to storage media 185. Controller 165 has a shutdown logic 170, a timer 175, and a comparator 180. In one further embodiment, controller 165 is also connected to a human-machine interface(s), such as a keyboard/mouse 187 for input, and a monitor screen 190 for output.
Generally, shutdown logic 170 shuts down compressor 140 that, while in operation, circulates refrigerant through refrigerant system 100. Then, timer 175 clocks a given amount of time, and then sends a start signal to comparator 180. Comparator 180 compares an output of first transducer 150 and an output of second transducer 160 to determine whether the obtained output readings are within a manufacture's specification of one another. In one embodiment, storage media 185 has computer instructions for accomplishing the above, specific values for the given amount of time that timer 175 is to wait, and the manufacturers specifications for first and second transducers 150 and 160 (i.e., what the various electrical output characteristics of the transducers should be at various pressures, and so on).
In system 100, first transducer 150 is located on the high-pressure side of compressor 140, and second transducer 160 is located on a low-pressure side of compressor 140. In one embodiment, both first transducer 150 and second transducer 160 are pressure transducers. In another embodiment, first refrigerant system component 110 is an evaporator, and second refrigerant system component 120 is a condenser. First and second transducers 150 and 160 can be associated with any other components of the refrigerant system 100 located on high and low-pressure sides.
If compressor 140 is operating, then first transducer 150 and second transducer 160 will measure disparate pressures or other characteristics under steady state or normal system 100 operation. During shutdown sequence of system 100, controller 165, through shutdown logic 170, shuts down compressor 140, so compressor 140 is no longer operating. Timer 175 then waits a specified period of time to elapse and then issues a signal to comparator 180. The waiting period is used to equalize, as much as practical, the pressures measured by first transducer 150 and second transducer 160. In one embodiment, the specified time period for waiting is one minute (60 seconds) but could be as long as a few minutes, such as 3 minutes (180 seconds). Comparator 180 then compares an output of first transducer 150 and second transducer 160 to one another to see if the outputs are identical, within the manufacturer's tolerance specification. If they are not identical within a manufacture's tolerance of one another, then at least one of first transducer 150 or second transducer 160 needs to be replaced. Therefore, a warning signal is sent to monitor 190 that informs an operator that an error condition has been detected in either first transducer 150 or second transducer 160 or otherwise alerts and alarms the operator that a fault condition has been detected.
Determining the difference between the outputs of two transducers, such as first transducer 150 and second transducer 160, and comparing this difference to a manufacture's tolerance specification by comparator 180, as opposed to testing first transducer 150 and second transducer 160 against their respective pre-defined transducer characteristics, will save troubleshooting time and effort as well as unit downtime. This determination can be performed in a number of situations, such as either in the field or in a factory during assembly.
Furthermore, more than two transducers can be used in system 100. For instance, the output of a third transducer (not illustrated) could also be compared against the output of first transducer 150 if the third transducer is located on the low-pressure side of compressor 140. Also, the output of the third transducer could also be compared against the output of second transducer 160 if the third transducer is located on the high-pressure side of compressor 140. Also, transducers positioned on the same side of the refrigerant system 100 but in different locations, for instance for redundancy, can be compared one against the other.
In a further embodiment, a plurality of transducers 150 may be connected to high-pressure side of system 100 (e.g. connected to component 110), and a plurality of transducers 160 may be connected to lower-pressure side of the system 100 (e.g. connected to component 120). With the plurality of transducers 150 and 160 one transducer can be, for instance, a pressure transducer 152, and a second transducer can be a temperature transducer 162. Alternatively, there can be two transducers of the same type (i.e., both transducers are pressure or temperature transducers).
In a further embodiment, a plurality of shutdowns occur over a relatively long period of time. In other words, shutdown logic 170 issues a plurality of shutdown commands over such a period of time. Then, after timer 175 and comparison logic 180 have both performed their respective functions, any trend in the measured deviation between first transducer 150 and second transducer 160 can be used as a diagnostics tool. Furthermore, the frequency of first and second transducer 150, 160 testing can vary as a function of the confidence in the reliability of transducers 150 and 160, their criticality to system functionality and particular application.
Although for purposes of the above discussion, first and second transducers 150 and 160 are described as pressure transducers, other types of transducers, such as temperature transducers, can also be used. However, it is noted that typically it takes a longer period of time for temperatures within system 100 to substantially equalize as compared to pressure transducers. Also, some precaution measures are to be taken if temperature transducers are utilized, since, under some circumstances, temperatures within system 100 could differ from one location to the other, which may cause first transducer 150 or second transducer 160 to provide false readings. In one embodiment, controller 165 or storage media 185 would have adjustments entered to account for such an offset.
In a still further embodiment, first transducer 150 is a pressure transducer and second transducer 160 is a temperature transducer. Once system 100 is stabilized and it is believed that temperatures or pressures are equalized, an output of first transducer 150 and second transducer 160 are compared to each other. However, the correlation between first transducer 150 and second transducer 160 (i.e., that so many measured units of temperature characteristic equals so many measured units of pressure characteristic) is typically programmed into controller 170 or storage media 185 ahead of time.
In a yet still further embodiment, comparator 180 operation can be initiated as part of system 100 startup logic, where first transducer 150 and second transducer 160 outputs are compared with each other just prior to starting compressor 140 and starting fans 162 and 164. In this case, the time for pressure and temperature parameters to equalize is therefore effectively extended to the maximum time interval between compressor 140 shutdown and startup.
It is understood that the schematics shown in FIG. 1 does not cover a vast majority of potential system 100 configurations, but is exemplary of one preferred embodiment. As shown, compressor 140 is connected to various elements in system 100, either directly or indirectly through other elements in system 100. In the context of this disclosure, evaporator and condenser are defined broadly to include all associated piping that connects the main body of the evaporator or condenser to the compressor or to the associated expansion devices. Thus, in one embodiment, transducers 150 and 160 can be placed at any location in the system including the piping associated with an evaporator, condenser or compressor, or other elements, such as expansion device 130.
FIG. 2 illustrates a method 200 for detecting a failure of first and second transducers 150 and 160. Generally, method 200 compares the output of first and second transducers 150 and 160 to each other to determine if the outputs are identical, within manufactures specification (i.e., that they are substantially identical), or otherwise the outputs bear some acceptable mathematical relationship to one another. If the comparison reveals that the relationship is violated, then it is determined that at least one of first and second transducers 150 and 160 needs to be replaced.
In step 210, the specified time that timer 175 waits after shutdown before issuing a signal to comparator 180 is determined or otherwise discovered by controller 165. Method 200 proceeds to step 220.
In step 220, the mathematical relationship between first transducer 150 and second transducer 160 is determined and loaded into comparator 180. This can be a 1:1 ratio in the case of substantially identical transducers, or some other relationship, such as when first transducer 150 is a pressure transducer, and second transducer 160 is a temperature transducer. Furthermore, manufacturer's specifications for tolerances for first and second transducers 150, 160 are also loaded into comparator 180. Method 200 proceeds to step 225.
In step 225, method 200 conveys manufacturer's tolerances for both first and second transducers 150, 160 to comparator 180. Method 200 proceeds to step 230.
In step 230, shutdown logic 170 shuts down compressor 140 and other components associated with refrigerant system 100. Method 200 then advances to step 240.
In step 240, timer 175 waits for the period of time specified in step 210. Method 200 proceeds to step 250.
In step 250, comparator 180 reads the outputs of first and second transducers 150 and 160. Method 200 proceeds to step 260.
In step 260, comparator 180 compares the outputs of first and second transducers 150 and 160 to see if the outputs of first and second transducers 150 and 160 are identical within the tolerances specified in step 225. If they are, then method 200 proceeds to step 265. If they are not, method 200 proceeds to step 260.
In step 265, neither the first or second transducers 150 and 160 are replaced, as an error condition has not been detected. Method 200 then stops.
In step 270, either first transducer 150, second transducer 160, or both, are not operating within manufacturing parameters. Therefore, the user is alerted via console 190.
In step 280, the user replaces either first transducer 150, second transducer 160, or both. Method 200 then stops.
It should be understood that various alternatives, combinations and modifications of the teachings described herein could be devised by those skilled in the art. The present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.

Claims

1. A refrigerant system, comprising:

a first component;

a second component, wherein said first and second components are both the same component;

a first transducer;

a second transducer, said first and second transducers being connected to said first and second component, respectively, for measuring a characteristic associated with said first and second component, a compressor connected to said first and second components;

a controller connected to said first and second transducers, wherein said controller further comprises: a shutdown logic that shuts down said compressor;

a timer that determines that a shut down has occurred for a specified period of time; and

a comparator that compares an output of said first transducer to an output of said second transducer and determines whether said outputs of said first and second transducers are within a tolerance band of each other.

2. The system of claim 1, wherein said first transducer is connected to a high-pressure side of said compressor, and said second transducer is connected to a low-pressure side of said compressor.

3. The system of claim 1, further comprising an output device that notifies a user if said outputs of said first and second transducers are not within said tolerance band of each other.

4. The system of claim 1, wherein said first transducer is a transducer selected from the group consisting of a pressure transducer and a temperature transducer.

5. The system of claim 1, further comprising a plurality of transducers that are connected to said first component.

6. The system of claim 1, wherein said comparator is programmed with said tolerance band.

7. The system of claim 1, wherein said comparator is programmed with a mathematical relationship for comparing said output of said first transducer to said output of said second transducer.

8. The system of claim 1, wherein said first component is selected from the group consisting of an evaporator and a condenser.

9. (canceled)

10. The system of claim 1, further comprising a media storage device connected to said controller.

11. A method for detecting transducer failure, comprising:

waiting for a specified time period to elapse after compressor shutdown;

measuring a first output of a first transducer connected to a first component;

measuring a second output of a second transducer connected to a second component;

comparing said first output and said second output; and

determining whether said first and second outputs are within a tolerance band of one another.

12. The method of claim 11, further comprising notifying an operator if said outputs of said first and second transducers are not within said tolerance band.

13. The method of claim 11, further comprising replacing at least one of said first and second transducers if said first and second outputs are not within said tolerance band.

14. The method of claim 11, further comprising defining said specified time period, wherein said specified time period is selected from the group consisting of more than 60 seconds, less than 180 seconds, and both more than 60 second but less than 180 seconds.

15. The method of claim 11, wherein said specified time period is defined as a time interval between said shutting down of said compressor and a restarting of said compressor.

16. The method of claim 11, further comprising loading said tolerance band to a comparator.

17. The method of claim 11, further comprising defining a mathematical relationship for said comparing of said output between said first transducer and said second transducer.

18. The method of claim 11, further comprising alerting a user if said first and second outputs are not within said tolerance band.

19. The method of claim 11, wherein said first and second transducer is a transducer selected from the group consisting of a pressure transducer and a temperature transducer.

20. (canceled)

21. The method of claim 11, wherein said tolerance band is equal to a manufacturer's tolerance specification.