EP3821176B1

EP3821176B1 - Method and system for detecting a failure in hvac system

Info

Publication number: EP3821176B1
Application number: EP19745011.7A
Authority: EP
Inventors: Xinyu Wu; Sheng Li
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2018-07-09
Filing date: 2019-07-02
Publication date: 2024-05-08
Anticipated expiration: 2039-07-02
Also published as: US20210199325A1; CN110701727A; CN110701727B; WO2020014033A1; EP3821176A1

Description

The present invention relates to the field of detection and control, and more especially to a method and a system for detecting a fault of a HVAC system.
The HVAC (Heating, Ventilation and Air Conditioning) system has been widely applied, which brings great convenience and comfort to people's daily work and life. Since a HVAC system is generally provided with a large number of various components, some faults such as refrigerant leaks and damages to compressor capacitor are likely to occur, especially after long-term use. Although the prior art has provided a great many technical means to detect fault conditions in a HVAC system, these existing technical means still have flaws and deficiencies in the aspects such as complexity, correctness, convenience and user experience, which may be further improved and optimized.
CN 103090504 discloses a method of the type defined in the pre-amble of claim 1.
The present invention provides a method and a system for detecting a fault of a HVAC system, in order to address or at least relieve one or more of the above-described problems existing in prior arts and problems in other aspects.
Firstly, according to a first aspect of the present invention, the present invention provides a method for detecting a fault of a HVAC system, comprising the steps of:

obtaining room air temperatures and compressor equivalent runtime during the operation of the HVAC system;
calculating a rate of change per unit time of the room air temperatures within the compressor equivalent runtime; and
determining whether a fault occurs in the HVAC system based on a change in the rate of change per unit time of the room air temperatures;
characterised in that the method further comprises the steps of:
- setting value properties of the rate of change per unit time of the room air temperatures when the HVAC system operates in a cooling mode and a heating mode to be contrary, and distributing along a time axis the rate of change per unit time of the room air temperatures determined as abnormal values, the value properties indicating positive value or negative value;
- counting the number of the rate of change per unit time of the room air temperatures distributed on the time axis within a time window, or processing the values of the rate of change per unit time of the room air temperatures within the time window to obtain a processed value; and
- determining that a fault has occurred in the HVAC system if the number exceeds a predetermined value or the processed value exceeds a preset value.

In a method according to the present invention, optionally, the room air temperatures are obtained from a temperature controller for controlling the HVAC system.
In a method according to the present invention, optionally, operation data of each compression stage of the HVAC system is obtained from the HVAC system, and the compressor equivalent runtime is obtained by making a calculation based on a capacity ratio of each compression stage.
In a method according to the present invention, optionally, the method further comprises the step of:
outputting report information after the fault is determined to have occurred in the HVAC system.
In a method according to the present invention, optionally, the report information is transmitted to a cloud server via a wireless network, the wireless network comprising Wi-Fi, 4G, BT or ZigBee network.
In the method according to the present invention, optionally, the rate of change per unit time of the room air temperatures is determined as an abnormal value when the value property of the rate of change per unit time of the room air temperatures in the cooling mode or the heating mode is contrary to a set value property, or a difference value between the rate of change per unit time of the room air temperatures and zero is less than a preset value; and/or wherein the step of the processing of the values comprises calculating a sum of the values, calculating a arithmetic mean value of the values, or calculating a weighted mean value of the values.
Secondly, in a second aspect of the present invention, the present invention provides a system for detecting a fault of a HVAC system, comprising a processor configured to perform the steps of:

obtaining room air temperatures and compressor equivalent runtime during the operation of the HVAC system;
calculating a rate of change per unit time of the room air temperatures within the compressor equivalent runtime; and
determining whether a fault occurs in the HVAC system based on a change in the rate of change per unit time of the room air temperatures;
characterised in that the processor is further configured to perform the steps of:
- setting value properties of the rate of change per unit time of the room air temperatures when the HVAC system operates in a cooling mode and a heating mode to be contrary, and distributing along a time axis the rate of change per unit time of the room air temperatures determined as abnormal values, the value properties indicating positive value or negative value;
- counting the number of the rate of change per unit time of the room air temperatures distributed on the time axis within a time window, or processing the values of the rate of change per unit time of the room air temperatures within the time window to obtain a processed value; and
- determining that a fault has occurred in the HVAC system if the number exceeds a predetermined value or the processed value exceeds a preset value.

In the system according to the present invention, optionally, the room air temperatures are obtained by the processor from a temperature controller for controlling the HVAC system.
In the system according to the present invention, optionally, operation data of each compression stage of the HVAC system is obtained by the processor from the HVAC system, and the compressor equivalent runtime is obtained by the processor by making a calculation based on a capacity ratio of each compression stage.
In the system according to the present invention, optionally, the processor is further configured to:
output report information after the fault is determined to have occurred in the HVAC system.
In the system according to the present invention, optionally, the report information is transmitted to a cloud server via a wireless network, the wireless network comprising Wi-Fi, 4G, BT or ZigBee network.
In the system according to the present invention, optionally, the rate of change per unit time of the room air temperatures is determined as an abnormal value when the value property of the rate of change per unit time of the room air temperatures in the cooling mode or the heating mode is contrary to a set value property, or a difference value between the rate of change per unit time of the room air temperatures and zero is less than a preset value; and/or wherein the step of processing the values comprises calculating a sum of the values, calculating an arithmetic mean value of the values, or calculating a weighted mean value of the values.
From the following description in combination with figures, one will clearly understand the principles, characteristics, features and advantage of various technical solutions of the present invention. For instance, as will be understood, in comparison with prior arts, the method, system and storage for detecting a fault of a HVAC system according to the present invention have significant technical advantages and can be used for on-line fault detection of a HVAC system in order to effectively detect a series of faults such as faults of fast occurrence and faults involving slow degeneration of system performance, and output information such as alerts. This will help relevant staff to find and identify HVAC system terminals possibly having problems more easily, so as to carry out an examination and repair as early as possible, and thereby increase the security and user satisfaction of the HVAC system.
The technical solutions of the present invention will be further described in detail below in conjunction with the drawings and embodiments. However, it should be understood that the drawings are designed merely for illustrative purpose and are intended only to conceptually explain the configuration described herein. It is unnecessary to draw the drawings in proportion.

Fig. 1 is a schematic flow diagram illustrating an embodiment of a method for detecting a fault of a HVAC system.
Fig. 2 is a schematic diagram illustrating compression stage runtime in an example of a HVAC system with two compression stages.
Fig. 3 is a schematic diagram illustrating a corresponding relationship between room air temperature and runtime in an example of a HVAC system.
Fig. 4 is a schematic diagram illustrating using a time window example to take statistics of the distribution of a rate of change per unit time of the room air temperature.
Fig. 5 is a schematic diagram about determining that a fault has occurred in one HVAC system example based on a statistical result of the distribution of a rate of change per unit time of the room air temperature shown in Fig. 4.

Firstly, it should be noted that steps, compositions, features and advantages of a method and a system for detecting a fault of a HVAC system according to the present invention will be illustrated hereinafter by way of examples. However, all the descriptions should not impose any limitation to the present invention which is defined by the appending claims.
Fig. 1 exemplarily shows a basic flow of an embodiment of a method for detecting a fault of a HVAC system, which may be employed to on-line detect a fault of a HVAC system conveniently. In this embodiment, the method may comprise the steps of:
Firstly, in Step S11, obtaining room air temperatures during the operation of the HVAC system, and obtaining the equivalent runtime of the compressor during the operation of the HVAC system. The data will be used to calculate a rate of change per unit time of the room air temperature discussed hereinafter.
As for the room air temperatures, the temperature data may be obtained in various ways. For example, the temperature data may be acquired by one or more temperature measuring elements, devices, instruments or the like disposed in the HVAC system, and may also be obtained conveniently from a temperature controller configured to control the HVAC system. By way of an example only, Fig. 3 illustrates six room air temperature data A, B, C, D, E and F during the operation of HVAC system, which schematically shows room air temperature fluctuations during the operation of HVAC system.
As for the compressor equivalent runtime, since one HVAC system is generally provided with a plurality of compression stages, for example, provided with a plurality of compressors, or having one or more of the compressors provided with a plurality of compression stages. Thus, it is necessary to translate the runtime of all the compression stages in a HVAC system into a compressor equivalent runtime. Fig. 2 exemplarily shows a HVAC system provided with two compression stages, i.e. compression stage 1 and compression stage 2. As illustrated in Fig. 3, it schematically shows a compressor equivalent runtime line 3 of one HVAC system after translation
In the method, the above-described compressor equivalent runtime may be obtained in various ways, which will be exemplarily explained below.
For example, operation data of each of the compression stages can be obtained from a HVAC system, and then compressor equivalent runtime is obtained by making a calculation based on respective capacity ratios of these compressor stages. That is to say, by multiplying the runtime of each compression stage and its capacity ratio to obtain a product of each compression stage, and then adding such products of the compression stages, the compressor equivalent runtime can be obtained.
For another example, an equivalent translation table may be provided based on data from the producer or supplier of the HVAC system or the compressor(s) therein or from professional institutions, or data from a test of a HVAC system or the compressor(s) therein. Therefore, the corresponding compressor equivalent runtime can be obtained by directly by consulting the table.
Secondly, in Step S12, making a calculation based on the obtained room air temperatures and compressor equivalent runtime, to obtain a rate of change per unit time of the room air temperature within the compressor equivalent runtime, and distributing the obtained rate of change per unit time of the room air temperatures along a time axis. For example, a change rate per hour of room air temperature may be calculated by using one hour as a unit time. Certainly, without a deviation from the purport of the present invention, the method of the present invention also allows to select other proper time intervals (e.g., 15 minutes, 30 minutes, 1.5 hours, 2 hours, 5 hours, etc.) as the unit time to calculate the rate of change per unit time of the room air temperature.
Subsequently, in Step S13, after the rate of change per unit time of the room air temperature are calculated, determining whether a fault occurs in the HVAC system based on changes of the data. This is because the rate of change per unit time of the room air temperature roughly indicates the fluctuation of room air temperature in a set unit time. That is to say, the data may reflect the operation condition of the HVAC system.
For instance, if relatively many data obviously deviating an average level occur in the unit time s of room air temperature (e.g., the data exceed over 50% of other data values that conform to the average level), it means that there may be an abnormality or fault occurred in one or some of the component(s), unit(s) or module(s) in the current HVAC system, or that the HVAC system may have experienced slow degeneration of performance, and thereby the HVAC system fails to continuously operate stably, which is embodied as that abnormal fluctuations occur to the rate of change per unit time of the room air temperature. As such, it can be effectively detected and determined that a fault has happened to the HVAC system.
For another example, the obtained a rate of change per unit time of the room air temperature may be further differentiated based on an operation mode of the HVAC system, to facilitate a fault analysis of the HVAC system based on corresponding changes in the rate of change per unit time of the room air temperature. To be specific, as illustrated in Fig. 4, the obtained rate of change per unit time of the room air temperature are distributed along a time axis. For example, the unit time (such as one hour) employed in the calculation of a rate of change per unit time of the room air temperature is taken as the internal unit of the time axis. The value properties of the rate of change per unit time of the room air temperatures when the HVAC system operates in a cooling mode and a heating mode may be defined as follows: in the cooling mode, the rate of change per unit time of the room air temperature with a normal property of room air temperature is set as a negative value, which is below the zero axis indicated by the dotted line shown in Fig. 4, while the rate of change per unit time of the room air temperature with an abnormal property of room air temperature is set as a positive value, which is above the zero axis indicated by the dotted line shown in Fig. 4; in the heating mode, the rate of change per unit time of the room air temperature with a normal property of room air temperature is set as a positive value, which is above the zero axis indicated by the dotted line shown in Fig. 4, while the rate of change per unit time of the room air temperature with an abnormal property of room air temperature is set as a negative value, which is below the zero axis indicated by the dotted line shown in Fig. 4. To be specific, if the HVAC system operates in the cooling mode, a data dot 4 of a positive value will be determined as an abnormal value; if the HVAC system operates in the heating mode, a data dot 5 of a negative value will be determined as an abnormal value. The above-described abnormal values mean the values being deviated from a normal value. For example, the value property of the rate of change per unit time of the room air temperature in the cooling mode or a heating mode being absolutely contrary to a set value property (that is, the value property of a normal value should be a negative value in the cooling mode, while an abnormal value is indicated by a positive value in the cooling mode, whereas the value property of a normal value should be a positive value in the heating mode, while the abnormal value is indicated by a negative value in the heating mode). It should be understood that, although corresponding normal value properties and abnormal value properties are defined for different operation modes in the above embodiments, reversely defining the normal value property and abnormal value property is also feasible. For another example, if the difference value between a rate of change per unit time of the room air temperature and zero is smaller than a preset value (values close to zero such as -0.1, 0.1, -0.15 or 0.15), the rate of change per unit time of the room air temperature may be determined as an abnormal value.
Subsequently, a time window 6 (which may be a runtime window or a calendar time window, and which may be chosen and configured based on specific application requirements) is set, and the number of the rate of change per unit time of the room air temperature with positive values (the number is two in the embodiment of Fig. 4) or the number of the rate of change per unit time of the room air temperature with negative values (the number is eight in the embodiment of Fig. 4) within the time window 6 is counted.
If a sum of the number of positive values (or a sum of the number of negative values) exceeds a preset value T (which can be chosen and set according to specific application requirements), i.e., the circumstance illustrated by Fig. 5, in which if a dot P has already exceeded the preset value T, it can be determined that a fault has been occurred in the HVAC system, wherein the fault is likely to be a fault of fast occurrence in the HVAC system (e.g., an operation abnormality occurs to a compressor capacitor), or a fault caused by slow performance degeneration of the HVAC system (e.g., a refrigerant leak, or pipe blocking of a heat exchanger) or others alike.
Moreover, it should be noted that, the method allows using various other approaches to determine a HVAC system default based on the above-described rate of change per unit time of the room air temperature. For example, the values of the rate of change per unit time of the room air temperature (i.e., the values of abnormal dots) appearing within the time window 6 may be processed to obtain a processed value, and then it is determined whether a fault occurs in the HVAC system based on whether the obtained processed value exceeds a set value (which can be chosen and set according to specific application requirements). That is, if the processed value exceeds the set value, it can be determined that a fault has occurred in the HVAC system. Fig 5 illustrates such a determination circumstance as well.
For example, various calculation ways may be employed for processing the values of abnormal dots, and they may include, but not be limited to: calculating a sum of the values of these abnormal dots, calculating an arithmetic mean value of the values of these abnormal dots, and calculating a weighted mean value of the values of these abnormal dots. It should be understood that, the method of the present invention completely allows using more other possible calculating ways to process values of abnormal dots. Such a value processing result can reflect serious circumstances of these abnormal dots deviating from a normal value or a normal range. Further, the result may be compared with a set value to determine the possibility of fault occurrence in a HVAC system.
In optional cases, when it is determined via detection that a fault has occurred in a HVAC system, some corresponding measures may be employed. For example, report information may be output, which may include, but not be limited to, alerting in the forms such as text, images, sound and/or light so as to urge relevant staff be aware of the fault of the HVAC system and thus can go for fixing the fault as early as possible. For another example, the above-described information may be uploaded to a cloud server via a wireless network (such as Wi-Fi, 4G, BT or ZigBee network). In this manner, staff may conveniently and quickly identify, from a cloud server, the HVAC system terminal that has outputted the report information and possibly has a problem. Thus, the HVAC system terminal possibly having a problem can be inspected and repaired as soon as possible, and at this time, the owner of the HVAC system might know nothing about that a problem has occurred to the HVAC system (such as refrigerant leaks and damages to compressor capacitor) and that adverse influences might be caused by it momentarily. Therefore, this will extremely increase user satisfaction and can increase security and reliability of the HVAC system.
As an aspect that is apparently better than prior arts, the present invention further provides a system for detecting a fault of a HVAC system. Such a system is provided with a processor, which is configured to perform the steps of:

firstly, obtaining room air temperatures during the operation of the HVAC system (e.g., from a controller for controlling the HVAC system), and obtaining compressor equivalent runtime during the operation of the HVAC system (e.g., by the means exemplarily discussed above).
secondly, calculating a rate of change per unit time of the room air temperature within the compressor equivalent runtime (e.g., by the means exemplarily discussed above); and
subsequently, determining whether a fault occurs in the HVAC system based on a change in the rate of change per unit time of the room air temperatures (e.g., by the means exemplarily discussed above).

Moreover, in some optional cases, the above-described processor may also be configured to perform the steps of:

setting value properties of the rate of change per unit time of the room air temperatures when the HVAC system operates in a cooling mode and a heating mode to be negative values (or positive ones) and positive values (or negative ones), respectively, and distributing along a time axis the rate of change per unit time of the room air temperatures when they are determined as abnormal values;
counting the number of the rate of change per unit time of the room air temperatures distributed on the time axis within a time window (which may be a runtime window or a calendar time window, and which may be chosen and configured according to requirements of specific applications); and
determining that a fault has occurred in the HVAC system if the counted number exceeds a preset value.

Moreover, in some optional cases, the above-described processor may be further configured to: output report information after the fault is determined to have occurred in the HVAC system. As mentioned above, the report information may be uploaded to a cloud server via a wireless network (such as Wi-Fi, 4G, BT or ZigBee network) such that relevant staff can be informed in time and then inspection, repair and the like can be carried out.
It should understood that, elaborations have been made in preceding text about description of the method of the present invention, which are directed to the technical contents such as the compressor equivalent runtime, the rate of change per unit time of the room air temperature, the time window, the differentiation of a rate of change per unit time of the room air temperature based on the cooling mode and the heating mode, the determination of abnormal values and processing of abnormal values, and thus, one may directly refer to specific description in corresponding portions of preceding text, and no redundant identical or similar technical contents about the system according to the present invention will be stated here.
The method and a system for detecting a fault of a HVAC system according to the present invention are explained above by way of examples, which are merely intended for the purpose of explaining the principle and implementing means of the present invention, rather than limiting it. One skilled in the art may further make a variety of modifications and improvements without departing from the scope of the present invention, which is defined by the claims

Claims

A method for detecting a fault of a HVAC system, comprising the steps of:
obtaining room air temperatures and compressor equivalent runtime during the operation of the HVAC system;

calculating a rate of change per unit time of the room air temperatures within the compressor equivalent runtime; and

determining whether a fault occurs in the HVAC system based on a change in the rate of change per unit time of the room air temperatures

characterized by the steps of:
setting value properties of the rate of change per unit time of the room air temperatures when the HVAC system operates in a cooling mode and a heating mode to be contrary, and distributing along a time axis the rate of change per unit time of the room air temperatures determined as abnormal values, the value properties indicating positive value or negative value;

counting the number of the rate of change per unit time of the room air temperatures distributed on the time axis within a time window, or processing the values of the rate of change per unit time of the room air temperatures within the time window to obtain a processed value; and

determining that a fault has occurred in the HVAC system if the number exceeds a predetermined value or the processed value exceeds a preset value.
The method according to claim 1, wherein the room air temperatures are obtained from a temperature controller for controlling the HVAC system.
The method according to claim 1, wherein operation data of each compression stage of the HVAC system is obtained from the HVAC system, and the compressor equivalent runtime is obtained by making a calculation based on a capacity ratio of each compression stage.
The method according to any preceding claim, further comprising the step of:
outputting report information after the fault is determined to have occurred in the HVAC system.
The method according to claim 4, wherein the report information is transmitted to a cloud server via a wireless network, the wireless network comprising Wi-Fi, 4G, BT or ZigBee network.
The method according to any preceding claim, wherein the rate of change per unit time of the room air temperatures is determined as an abnormal value when the value property of the rate of change per unit time of the room air temperatures in the cooling mode or the heating mode is contrary to a set value property, or a difference value between the rate of change per unit time of the room air temperatures and zero is less than a preset value; and/or wherein the step of processing the values comprises calculating a sum of the values, calculating a arithmetic mean value of the values, or calculating a weighted mean value of the values.
A system for detecting a fault of a HVAC system, comprising a processor configured to perform the steps of:
obtaining room air temperatures and compressor equivalent runtime during the operation of the HVAC system;

calculating a rate of change per unit time of the room air temperatures within the compressor equivalent runtime; and

determining whether a fault occurs in the HVAC system based on a change in the rate of change per unit time of the room air temperatures;

characterized in that the processor is further configured to perform the steps of:
setting value properties of the rate of change per unit time of the room air temperatures when the HVAC system operates in a cooling mode and a heating mode to be contrary, and distributing along a time axis the rate of change per unit time of the room air temperatures determined as abnormal values, the value properties indicating positive value or negative value;

counting the number of the rate of change per unit time of the room air temperatures distributed on the time axis within a time window, or processing values of the rate of change per unit time of the room air temperatures within the time window to obtain a processed value; and

determining that a fault has occurred in the HVAC system if the number exceeds a predetermined value or the processed value exceeds a preset value.
The system according to claim 7, wherein the room air temperatures are obtained by the processor from a temperature controller for controlling the HVAC system.
The system according to claim 7, wherein operation data of each compression stage is obtained by the processor from the HVAC system, and the compressor equivalent runtime is obtained by the processor by making a calculation based on a capacity ratio of each compression stage.
The system according to any of claims 7 to 9, wherein the processor is further configured to:
output report information after the fault is determined to have occurred in the HVAC system.
The system according to claim 10, wherein the report information is transmitted to a cloud server via a wireless network, the wireless network comprising Wi-Fi, 4G, BT or ZigBee network.
The system according to any of claims 7 to 11, wherein the rate of change per unit time of the room air temperatures is determined as an abnormal value when the value property of the rate of change per unit time of the room air temperatures in the cooling mode or the heating mode is contrary to a set value property, or a difference value between the rate of change per unit time of the room air temperatures and zero is less than a preset value; and/or wherein the step of processing the values comprises calculating a sum of the values, calculating an arithmetic mean value of the values, or calculating a weighted mean value of the values.