WO2017072327A2

WO2017072327A2 - Electronic filter condition monitoring system and method

Info

Publication number: WO2017072327A2
Application number: PCT/EP2016/076142
Authority: WO
Inventors: Michael Bonello; Scott Carter
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-10-28
Filing date: 2016-10-28
Publication date: 2017-05-04
Anticipated expiration: 2018-04-28
Also published as: WO2017072327A3

Abstract

A system for monitoring the condition of an air filter in a heating, ventilation, and air conditioning (HVAC) system. The system measures an instantaneous current traveling through a blower of the HVAC system. The system receives data including the measured instantaneous current from the current sensing device. The system then compares the measured instantaneous current with a baseline current that was previously measured traveling through the blower. Based upon the comparison, the system generates a filter condition indicator related to the cleanliness of the air filter.

Description

ELECTRONIC FILTER CONDITION MONITORING SYSTEM

AND METHOD

BACKGROUND

The monitoring and maintenance of air filters in heating, ventilation, and air

conditioning (HVAC) units and systems has traditionally been performed manually by an individual who is assigned the task of physically inspecting and cleaning the air filter. This inspection and cleaning tends to take place periodically or according to a maintenance schedule, which may range from a cycle of eight weeks to six months. Furthermore, it is common that the timing of such inspections and cleanings is subjectively set by an engineering manager, or similar individual, based on his/her experience.

Such conventional systems and methods tend to suffer from a number of drawbacks. For instance, they can be very labor intensive. In addition, such systems and methods are prone to human error and can be inconsistent from one individual to another. In addition, there is no reliable way of confirming that the air filters have been inspected and properly cleaned, or whether cleaned at all, unless another person is independently assigned to randomly check the condition of the filters. This type of follow-up inspection is rarely implemented due to increased costs and lack of personnel.

In addition, because the inspection is manual and performed solely according to a maintenance schedule, there is no real indicator of when an air filter may have been blocked or is dirtied. For instance, if an air-filter is partially or fully blocked shortly after an inspection due to a dust storm or dust generated during construction in the vicinity of the air-conditioned space, there is no warning or real-time system to inform the engineering manager of such a blockage. This can detrimentally increase the air conditioning energy costs, and wear and tear on the mechanical parts of the air-conditioning unit due to longer operating times.

There is thus a need for a monitoring system that can more quickly and efficiently determine the operational status of an air filter found in HVAC systems, and provide real-time monitoring and alarms to a user or intended recipient when the air filter requires cleaning or replacement.

The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.

BRIEF SUMMARY

Embodiments disclosed herein include a system for monitoring the condition of an air filter in an HVAC system. The system measures a first current traveling through a blower of the HVAC system. The system receives data including the measured first current from the current sensing device. The system then compares the measured first current with a baseline current that was previously measured traveling through the blower. Based upon the comparison, the system generates a filter condition indicator related to the cleanliness of the air filter.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

Additional features and advantages will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the teachings herein. Features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. Features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and other advantages and features can be obtained, a more particular description of the subject matter briefly described above will be rendered by reference to specific embodiments which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments and are not therefore to be considered to be limiting in scope, embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Figure 1 depicts a schematic view of an embodiment of an HVAC system.

Figure 2 depicts a schematic view an embodiment of an electronic filter-condition monitoring (EFCM) system.

Figure 3 depicts a flow chart of steps in an embodiment of a method for monitoring the condition of an air filter.

DETAILED DESCRIPTION

The following discussion now refers to a number of methods and method acts that may be performed. Although the method acts may be discussed in a certain order or illustrated in a flow chart as occurring in a particular order, no particular ordering is required unless specifically stated, or required because an act is dependent on another act being completed prior to the act being performed.

A better understanding of different embodiments of the disclosure may be had from the following description read with the accompanying drawings in which like reference characters refer to like elements. While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments are in the drawings and are described below. It should be understood, however, there is no intention to limit the disclosure to the specific embodiments disclosed, but on the contrary, the intention covers all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure.

Also, it will be understood that unless a term is expressly defined in this application to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning. Any element in a claim that does not explicitly state "means for" performing a specified function, or "step for" performing a specific function is not to be interpreted as a "means" or "step" clause as specified in 35 U.S.C. § 112, paragraph 6.

The present disclosure is directed to embodiments of monitoring or electronic filter- condition monitoring (EFCM) systems and methods for detection of the condition of the air filter found in HVAC systems. The condition or cleanliness of the air filter generally refers to the amount of dirt, dust, or any other obstructing materials accumulated on or in the air filter. These obstructing materials can progressively block the air filter and curtail the flow of air in the space fed by the HVAC system. Space generally refers to a volume where air is conditioned mechanically, such as at, for example, a hotel room or office. The reduction of air flow can result in a longer time for the space to reach the desired temperature, thus increasing the air conditioning energy costs, and the wear and tear on the mechanical parts of the HVAC system due to longer operating times.

Figure 1 depicts a schematic view of an embodiment of an HVAC system 100. Disclosed embodiments of the EFCM system 150 include software, hardware, and/or firmware arranged to provide real-time indication of the condition of an air filter 120 in an HVAC system 100 using measurements of the current through and voltage across a blower 110 (i.e., fan) of the HVAC system 100. The blower may be functional to move air either into or out of a space. In at least one embodiment, the EFCM system 150 includes a current sensing device 130 and a voltage sensing device 140 to measure current through and voltage across the blower 110. The EFCM system 150 uses the measured current and voltage to generate data or information related to the cleanliness of the air filter.

Figure 2 depicts a schematic view of an embodiment of an EFCM system 150. In at least one embodiment, the EFCM system 150 receives analog sensor data which is processed through an analog-to-digital converter 250 (i.e., ADC 250). Additionally, the EFCM system 150 includes one or more processors (i.e., processor(s) 210) arranged to execute computer executable instructions. The processor(s) 210 operate the voltage sensing device 140 and/or the current sensing device 130. The EFCM system 150 also includes an integrated microcontroller 260 with ancillary analog, passive components. Furthermore, the EFCM system 150 includes a specific signal processor 240, such as a mixed-signal integrated circuit. In at least one embodiment, the processor(s) 210 are in communication with a memory store 200. The memory store 200 stores data including values of electric current and voltages as received by the sensing units.

A communications module 270 communicates over a wired or wireless network. In an embodiment, a plurality of EFCM systems 150 are networked or grouped together to provide filter-condition monitoring across a plurality of HVAC systems 100 located in one or more different locations. The communications module 270 sends filter condition information to a requesting device, such as, but not limited to, a computer or other device arranged to communicate with a single EFCM system 150 or a plurality of EFCM systems 150. The EFCM system 150 is also configurable to exchange information on a peer-to-peer basis. In at least one embodiment, the EFCM system 150 sends data related to the status of the monitored air filter only when queried. This is known as a master- slave system.

The networking of a plurality of EFCM systems 150 beneficially provides value to a user through ease of access to a plurality of systems over either a local or wide area network. The networking of a plurality of EFCM systems 150 also advantageously allows for the remote upgrade of the functions and instructions in the processor or processing module within each EFCM system.

In at least one embodiment, the EFCM system 150 is a standalone module that includes one or more of a plurality of indicators such as, but not limited to, audible (e.g., a piezo-buzzer), visual (e.g. colored LEDs), a numeric display showing the percentage of cleanliness, or other means of communicating the condition of the air filter to the user. It will be appreciated that embodiments of the EFCM system are easy to setup, easy to use and provide timely information on the condition of a monitored filter.

The I/O interface 230 is arranged to communicate with and receive signals from sensors 280, including the current sensing device 130. In at least one embodiment, the current sensing device 130 includes a current sensor, such as an ammeter. The current sensing device 130 is configured to measure current drawn by the blower 110 (e.g., fan) of an HVAC system. The current sensing device 130 may comprise a Hall-effect device but can be any suitable sensing device. In at least one embodiment, the current sensing device 130 is associated with a current sensing device 130 configured to receive both direct and alternating current flowing into the blower 110. Additionally, the I O interface 230 is arranged to communicate with and receive signals from a voltage sensing device 140. The voltage sensing device 140 is configured to measure voltage across the blower 110. The voltage sensing device 140 can be any suitable sensing device such as, but not limited to, a Hall-effect device. The current and voltage sensing devices can be different devices or integrated with one another.

As depicted in Figure 1, the current sensing device 130 and the voltage sensing devices 140 are positioned on the electrical main supply of a blower 110. It should be appreciated that the blower 110 is provided and referenced to illustrate the monitored part of the HVAC system for ease of reference. In other embodiments, the EFM system 100 is adaptable to monitor other components of an air conditioner unit or system.

In at least one embodiment, the voltage sensing device 140 includes a current sensing device (e.g., a Hall-effect device) and a temperature stable resistor (low temperature coefficient of resistance) through which current flows. The resistor of the voltage sensing device 140 is placed across the blower 110 causing it to be submitted to the same voltage as the blower 110. When a variation in voltage occurs, the variation translates into an equivalent change in current, which, in turn, is measured by the current sensing device. It should be appreciated that the combination of a resistor and a Hall-effect device is exemplary only and other configurations capable of measuring voltage across the blower are possible.

In at least one embodiment, the signal processor 240 receives and processes signals from the I/O interface 230. The signal processor 240 is any suitable device, such as a combination of passive and semiconductor devices, including resistors, capacitors, voltage clamp diodes and transient over-voltage components. In at least one embodiment, the signal processor 240 includes two identical signal processing channels to process the signals from the current sensing device and the voltage sensing device.

In at least one embodiment, the processor(s) 210 is a unitary unit that includes one or more of the microcontroller 260, ADC 250, signal processor 240, I/O interface 230, and/or communication module 270. However, for the sake of clarity and example the various components are discussed separately.

In at least one embodiment, the signal processor 240 communicates processed signals to the processor(s) 210. The processor(s) 210 are arranged to analyze signals or data including the measured current through and voltage across the blower 210. Based upon the analyzed signals and data, the processor(s) 210 generate information related to the condition of the air filter.

The disclosed EFCM system 150 includes an analogue to digital converter ("ADC") 250 and a micro-controller module 250. The ADC 250 can be separate from or integrated with the micro -controller module 250. In at least one embodiment, the processed signals from the signal processor 240 are fed into the ADC 142, which converts the processed signals into digital signals.

The micro-controller module 250 receives the digital signals from the ADC 142. The micro -controller module 250 uses the digital signals to generate filter condition information. For instance, changes in current and/or voltage detected by the sensing devices 130, 140 are processed by the EFCM system 150 to provide a measure of the cleanliness of the filter. The EFCM system 150 is coupled to a communications module 270 that communicates at least a portion of the filter condition information to an intended recipient via a wired or wireless connection.

The filter condition information can include one or more warnings that the air filter needs cleaning. The filter condition information also can include indicators that the HVAC system is in excellent condition, good condition, average condition, poor condition, or the like. The filter condition information can include an indication of what percentage of the air filter is blocked or obstructed to air flow. In at least one embodiment, the filter condition information is presented graphically, pictorially, or as a percentage of cleanliness to the intended recipient. The filter condition information can also be made available on a web-based filter condition software, which is either hosted on a local computer or in the cloud. This beneficially provides an engineering manager a real-time warning or indication of a potentially serious problem, reducing the likelihood of decreased energy cost and wear and tear on the mechanical parts of the HVAC system.

In at least one embodiment, a user initially calibrates the EFCM system 100. Prior to calibrating the system, the air filter 120 preferably is cleaned or replaced with a new, clean air filter 120 by an operator setting up the EFCM system 100. As part of the calibration, the EFCM system 150 stores within the memory store 200 a baseline electrical current flowing through and/or a baseline voltage across the blower 110 at each of the three typical speeds of the blower 210, which are typically labelled by the manufacturer of the air-conditioning unit as Low, Medium, and High.

It is probable that the current flowing through the blower 110 at any one speed is not constant but fluctuates due to mechanical imperfections in the rotary parts (such as, albeit not only, due to balancing or wear and tear) and imperfect magnetic coupling within the blower magnetic circuit. As such, in at least one embodiment, the EFCM system 150 stores a baseline high value and a baseline low value for the current and/or voltage at each respective speed, a baseline average value for the current and/or voltage at each respective speed, just the baseline high value for the current and/or voltage at each respective speed, just the baseline low value for the current and/or voltage at each respective speed, or some other baseline value(s) derived from the measured current and/or voltage. In at least one embodiment, the same process is then repeated with a dirty air filter, or a material which curtails air flow to the blower. The EFCM system 150 stores the baseline value(s) of the electrical current and/or voltage at each one of the three speeds of the blower 210. As such, the EFCM system 150 determines baseline clean values and baseline dirty values for each respective speed accounting for both a clean and a dirty air filter 120.

In at least one embodiment, the EFCM system 150 then calculates the difference in current at each speed when using a clean filter versus a dirty filter. Once the system calibration is done, the EFCM system 150 continually or periodically checks the current state of the air filter 120. For example, the current sensing unit gathers the instantaneous current flowing through the blower 110. As used herein, instantaneous current and voltage readings and values comprise the most recently gathered measurements from the sensors 280. The EFCM system 150 then compares the measured instantaneous current to the baseline current values at each respective speed. Based upon the comparison, the EFCM system 150 identifies a current operating speed of the blower 110. For example, if the blower 110 is off, the current flowing through it is zero. In contrast, the EFCM system 150 identifies that the speed is set too low by subtracting the instantaneous current flowing through the blower 110 from the baseline current flowing through the blower 110 at low speed with a clean filter during system calibration time. If the difference is less than zero, then the speed is at the low setting. The process is repeated with each respective baseline current value measured during calibration time until the speed is determined. As such, the EFCM system 150 is capable of accounting for a drop in current flowing through the blower with increased blockage of airflow through the filter. The EFCM system 150 can also be adapted for situations where the current increases with increasing blockage of air-flow.

Once the EFCM system 150 identifies the current operating speed of the blower 110, the EFCM system 150 compares the instantaneous current to the baseline dirty and/or clean values that were previously measured. For example, in at least one embodiment, the EFCM system 150 calculates a baseline difference between the baseline clean value and the baseline dirty value at the identified speed. The EFCM system 150 then compares the baseline difference to the difference between the baseline clean value and the instantaneous current at the same given speed. If the difference between the baseline clean value and the instantaneous current is greater than the baseline difference, then the EFCM system 150 generates an indicator that the air filter 120 needs to be changed or cleaned.

In at least one embodiment, the voltage across the blower 110 may also fluctuate with time. The voltage fluctuations may generate errors in the measured blower current. In order to compensate for this fluctuation, the EFCM system 150 calculates a ratio between the baseline voltage and the instantaneous voltage. The EFCM system 150 then adjusts the instantaneous current by the calculated ratio. When determining the state of the air filter 120, the EFCM system 150 uses the adjusted instantaneous current in place of the unadjusted instantaneous current. This adjustment allows the instantaneous current to properly account for fluctuations in the voltage.

Using the above discussed calculations, the EFCM system 150 determines the level of cleanliness of the air filter. In at least one embodiment, the EFCM system 150 determines two states of the air filter 120, clean and dirty. In other embodiments, the EFCM system 150 includes determining a plurality of states of cleanliness for the air filter. For example, the EFCM system 150 may determine three states: clean, fair, and dirty. Each state may be defined based upon a ratio of the baseline difference. For example, the baseline difference divided by two may be defined as the fair state. When determining the current state of the air filter 120, if the difference between the baseline clean value and the instantaneous current is within a threshold of the baseline difference divided by two, then the EFCM system 150 generates an indicator that the air filter 120 is in fair condition. Using similar methods, it is understandable how further states can be created.

In at least one embodiment, the EFCM system 150 determines the cleanliness of the filter by comparing the instantaneous current flowing through the blower 110 to the baseline current measured during calibration with a dirty air filter. If the instantaneous current is equal to or smaller than the calibration current, the filter is deemed dirty. Optionally, if a plurality of levels of cleanliness are required, the exemplary method can be adapted for a plurality of values by introducing a plurality of intermediate variables to denote each level of cleanliness desired by the user.

Additionally, in at least one embodiment, the EFCM system 150 periodically updates, or adjusts, the baseline values. Over time as normal wear and tear affect the HVAC system 100, the current and voltage values may naturally and permanently change. As such, in at least one embodiment, every time an air filter 120 is changed the EFCM system 150 recalibrates and generates updated baseline current and voltage values. In an additional or alternative embodiment, periodically the EFCM system 150 generates an indicator requesting that a calibration be performed.

In at least one embodiment, the EFCM system 150 adjusts the baseline current value by measuring an instantaneous current value (i.e., a calibration current) traveling through a blower 110 immediately after the air filter 120 has been changed. Additionally or alternatively, the EFCM system 150 measures the calibration current value when a dirty air filter is installed. The EFCM system 150 then updates the baseline current value to reflect the calibration current value. In at least one embodiment, the exemplary monitoring software includes a user interface that depicts the status of the filter condition as semaphores comprising three exemplary colors, such as red, amber and green. Green may be the exemplary color to denote clean filter; amber may be the exemplary color denoting fair, or partly dirty, filter, whereas red could be the exemplary color for dirty filter, which would need immediate attention.

Accordingly, embodiments of the above EFCM system 150 can provide significant benefits over conventional monitoring and maintenance systems. For instance, the EFCM system 150 embodiments provide an engineering manager or other individual a substantially real-time indication of the condition of the air filter. In contrast to a conventional monitoring system, which only provides an indication of the condition of an air filter every eight weeks to six months. Further, the EFCM system 150 embodiments reliably record and verify the air filter is in an acceptable and proper condition. In contrast, there is no reliable way in a conventional monitoring system of confirming that the air filters have been inspected and properly cleaned. As such, the EFCM system 150 embodiments provide significant improvements in the field.

It should be appreciated that a computing system can be associated with the EFCM system

150. For example, the EFCM system 150 may be interfaced with a separate computing system running application software via a wired or wireless network. In at least one embodiment, a plurality of devices or systems may be interfaced over a standard wired serial bus or may independently communicate with the application wirelessly, such as over Wi-Fi, GPRS or any other suitable wireless technology.

Accordingly, Figures 1 and 2 and the corresponding text illustrate or otherwise describe one or more components, modules, and/or mechanisms for monitoring the condition of an air filter 120 based on feedback from one or more sensing devices 130, 140 that measure current through and voltage across a blower 110 of the HVAC system 100. One will appreciate that implementations of the present disclosure can also be described in terms of computer-executable instructions within a computing system that when executed comprise one or more acts for accomplishing a particular result. For instance, Figure 3 and the corresponding text illustrate or otherwise describe a sequence of acts from instructions within a computing system for monitoring the condition of an air filter based on feedback from one or more sensing devices. The acts of Figure 3 are described below with reference to the components and modules illustrated in Figures 1 and 2.

Figure 3 illustrates a flowchart 300 of an embodiment of a method for monitoring the air filter in an HVAC system including step 310 of measuring current through a blower 110 of an HVAC system 100. Step 310 includes measuring, with a current sensing device 130, an instantaneous current traveling through a blower of the HVAC system 100. For instance, Figures 1 and 2 and the accompanying description depict and describe a current sensing device 130 measuring current through a blower 110.

Figure 3 also shows that the method includes the step 320 of comparing a measured current to a baseline. Step 320 includes comparing, with the one or more processors, the instantaneous current with a baseline current that was previously measured traveling through the blower. For instance, Figure 2 and the accompanying description depict and describe processor(s) 210 that receive sensor readings from the sensors 280. During calibration the processor determines baseline voltage and current values, which are stored in the memory store 200. The processor(s) 210 then compare instantaneous current values to the stored baseline current values.

Additionally, Figure 3 shows that the method includes a step 330 of generating a filter condition indicator. Step 330 includes based upon the comparison, generating a filter condition indicator related to the cleanliness of the air filter. For instance, Figure 2 and the accompanying description depict and describe a communications module 270 arranged to communicate at least a portion of the filter condition information to an intended recipient. In at least one embodiment, the intended recipient comprises a graphical user interface associated with a computer system. Further, the methods may be practiced by a computer system including one or more processors and computer-readable media such as computer memory. In particular, the computer memory may store computer-executable instructions that when executed by one or more processors cause various functions to be performed, such as the acts recited in the embodiments.

Embodiments of the present invention may comprise or utilize a special purpose or general-purpose computer including computer hardware, as discussed in greater detail below. Embodiments within the scope of the present invention also include physical and other computer- readable media for carrying or storing computer-executable instructions and/or data structures. Such computer-readable media can be any available media that can be accessed by a general purpose or special purpose computer system. Computer-readable media that store computer- executable instructions are physical storage media. Computer-readable media that carry computer- executable instructions are transmission media. Thus, by way of example, and not limitation, embodiments of the invention can comprise at least two distinctly different kinds of computer- readable media: physical computer-readable storage media and transmission computer-readable media.

Physical computer-readable storage media includes RAM, ROM, EEPROM, CD-ROM or other optical disk storage (such as CDs, DVDs, etc.), magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store desired program code means in the form of computer-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer.

A "network" is defined as one or more data links that enable the transport of electronic data between computer systems and/or modules and/or other electronic devices. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a computer, the computer properly views the connection as a transmission medium. Transmissions media can include a network and/or data links which can be used to carry program code in the form of computer-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer. Combinations of the above are also included within the scope of computer-readable media.

Further, upon reaching various computer system components, program code means in the form of computer-executable instructions or data structures can be transferred automatically from transmission computer-readable media to physical computer-readable storage media (or vice versa). For example, computer-executable instructions or data structures received over a network or data link can be buffered in RAM within a network interface module (e.g., a "NIC"), and then eventually transferred to computer system RAM and/or to less volatile computer-readable physical storage media at a computer system. Thus, computer-readable physical storage media can be included in computer system components that also (or even primarily) utilize transmission media.

Computer-executable instructions comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. The computer-executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, or even source code. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the described features or acts described above. Rather, the described features and acts are disclosed as example forms of implementing the claims.

Those skilled in the art will appreciate that the invention may be practiced in network computing environments with many types of computer system configurations, including, personal computers, desktop computers, laptop computers, message processors, hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, mobile telephones, PDAs, pagers, routers, switches, and the like. The invention may also be practiced in distributed system environments where local and remote computer systems, which are linked (either by hardwired data links, wireless data links, or by a combination of hardwired and wireless data links) through a network, both perform tasks. In a distributed system environment, program modules may be located in both local and remote memory storage devices.

Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Program- specific Integrated Circuits (ASICs), Program- specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc.

The present invention may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

CLAIMS What is claimed is:

1. A computer system for monitoring the condition of an air filter in a heating, ventilation, and air conditioning (HVAC) system comprising:

one or more processors; and

one or more computer-readable media having stored thereon executable instructions that when executed by the one or more processors configure the computer system to perform at least the following:

measure, with a current sensing device, an instantaneous current value traveling through a blower of the HVAC system;

compare, with the one or more processors, the measured instantaneous current value with a baseline current value that was previously measured traveling through the blower; and

based upon the comparison, generate a filter condition indicator related to the cleanliness of the air filter.

2. The computer system as recited in claim 1, wherein the computer system includes an analog-to-digital converter and a microcontroller.

3. The computer system as recited in claim 2, wherein the analog-to-digital converter is integrated with the microcontroller.

4. The computer system as recited in 1, wherein the computer system comprises a plurality of electronic filter-condition monitoring ("EFCM") systems networked or grouped together.

5. The system as recited in 1, wherein the computer system includes a signal processor arranged to process signals sent from the current sensing device.

6. The computer system as recited in claim 1, wherein the current sensing device includes a Hall-effect device.

7. The computer system as recited in claim 1, wherein the executable instructions include instructions that are executable to configure the computer system to:

measure, with a voltage sensing device, an instantaneous voltage value across the blower of the HVAC system.

8. The system as recited in claim 7, wherein the voltage sensing device includes a Hall- effect device.

9. The system as recited in claim 7, wherein the executable instructions include instructions that are executable to configure the computer system to: measure, with the voltage sensing device, a baseline voltage value across the blower of the HVAC system.

10. The computer system as recited in claim 9, wherein the executable instructions include instructions that are executable to configure the computer system to:

calculate a ratio between the instantaneous voltage value and the baseline voltage value that was previously measured across the blower;

adjust the measured instantaneous current by the calculated ratio; and use the adjusted instantaneous current value in place of the measured instantaneous current value when comparing the measured instantaneous current value with the baseline current value.

11. The computer system as recited in claim 1, wherein the executable instructions include instructions that are executable to configure the computer system to:

adjust the baseline current value, wherein adjusting the baseline current value comprises:

measuring, with the current sensing device, a calibration current value traveling through a blower of the HVAC system; and

updating the baseline current value to reflect the calibration current value.

12. The computer system as recited in claim 11, wherein the calibration current value is measured when a clean air filter is installed within the HVAC system.

13. The computer system as recited in claim 11, wherein the calibration current value is measured when a dirty air filter is installed within the HVAC system.

14. The computer system as recited in claim 1, wherein the baseline current value comprises a current level associated with a low blower speed.

15. The computer system as recited in claim 1, wherein the baseline current value comprises a current level associated with a high blower speed.