Apparatus, System and Method for Monitoring Air Conditioning Condenser Cleanliness

Abstract

A device is described herein comprising an electrical circuit board containing a micro-controller using software commands to determine the cleanliness of an air conditioning system condensing unit with the input of two temperature sensors and optionally a pressure sensor for determining lo/hi refrigerant charge by means of determining refrigerant sub-cooling.

Description

BACKGROUND

A residential or commercial air conditioning system utilizing a refrigerant vapor compression cycle typically has high power requirements during the summer months, depending on location. Comfort settings can be adjusted by the control thermostat within the dwelling to accommodate lower system usage, however hotter climates may still require the air conditioning system to operate several hours daily on a continuous basis. Several factors can contribute to an air conditioning system not operating at peak efficiency. These factors include, but are not limited to, outside condenser heat exchanger cleanliness, limited or excess refrigerant charge, and air handler filter cleanliness. Some homeowners opt for annual service calls to professional HVAC technicians that may check the aforementioned issues. For many homeowners the cost for this service is not an option on an annual basis.

In lieu of annual cost for professional maintenance the homeowner can assume responsibility for cleaning the outside condenser heat exchanger. These condensers induce heat transfer with an internal fan pulling in ambient air through the condenser's aluminum fins that surround the coils or pipes carrying the refrigerant. The hot discharge gas from the compressor will cool to a saturation point from this heat transfer, where the gas is on the threshold of converting to a liquid. This energy transfer is the greatest when this gas condenses to a liquid.

Heat transfer from a heat exchanger is highly dependent on the surface area exposed to the medium to which heat is being transferred. As the internal fan continuously operates when the system is operating, the air passing through the coils/fins may contain dirt particles or other foreign objects. The dirt particles can collect on the coils/fins surface to inhibit flow and reduce air flow. Both the reduction in heat transfer surface area and a reduced flow rate influence the rate of heat transfer of the refrigerant gas to the ambient air. Reducing the heat transfer of the condenser negatively affects the efficiency of the system.

Diminished efficiency of an air conditioning system results in additional power being supplied to receive the same output compared to a clean condenser coil. Additional power input to the compressor is needed to increase the refrigerant gas pressure, so the refrigerant may condense to a liquid at a higher temperature. The refrigerant will condense at a higher temperature from the increased temperature difference between the condenser and the ambient temperature. If the heat transfer surface is decreased, the temperature difference from the hot surface to the environment must be increased to satisfy overall demand. Within this document this characteristic of the system is referred to as condensing temperature over ambient (CTOA). The increase of this parameter directly relates to air flow rate through a condenser coil/fins and to the reduced surface area on the coil/fins from dirt or foreign matter accumulation.

An air conditioning system can also operate below normal efficiency due to low refrigerant charge, resulting from a leak of the closed circuit to the ambient environment. Leaks can occur at the location of an access fitting, a valve, or the evaporator heat exchange coil. Air conditioning systems are designed to operate with an optimal amount of refrigerant within the circuit, predicated on the target amount of cooling load for the installation site. The refrigerant charge can be directly measured by evacuating the system to a pressure vessel and weighing it on a scale. This method can be impractical as it requires a trained technician, which is costly and only shows one instance in time. The refrigerant charge can be theoretically estimated by calculating the sub-cooling of the liquid refrigerant as it exits the condenser. Low sub-cooling indicates low refrigerant charge, whereas high sub-cooling indicates refrigerant over-charge.

It would be useful to develop an improved system and method for maintaining air conditioning efficiency over time.

SUMMARY OF THE INVENTION

One embodiment described herein is a device comprising an electrical circuit board containing a micro-controller using software commands to determine the cleanliness of an air conditioning system condensing unit with the input of two temperature sensors and optionally a pressure sensor for determining lo/hi refrigerant charge by means of determining refrigerant sub-cooling. In embodiments, the device is configured to communicate with a cloud server to allow for alerts transmitted to a mobile device. In some cases, the device is powered from an available power source commonly included in air conditioning condensing units. In certain cases, the device is calibrated to a clean condenser to establish a baseline for comparing future measurements.

Another embodiment is an apparatus for monitoring the cleanliness of the coils and/or fins of an air conditioner condenser, the apparatus comprising a first temperature sensor configured to periodically measure ambient air temperature proximate the condenser, second temperature sensor configured to periodically measure a temperature of a refrigerant liquid line downstream from the condenser, and a housing disposed proximate the condenser. The housing contains a controller connected to a processor configured to receive periodic temperature measurements from the first temperature sensor and periodic temperature measurements from the second temperature sensor, and based on the periodic temperature measurements from the first temperature sensor and the second temperature sensor, determine when the system efficiency is sufficiently reduced due to accumulated debris on the condenser coils or fins in order that the coils or fins of the condenser should be cleaned. In embodiments, the apparatus further comprises a first pressure sensor configured to periodically measure the pressure in the liquid line downstream from the condenser, the processor being further configured to receive periodic pressure measurements from the first pressure sensor and use the periodic pressure measurements along with the periodic temperature measurements to determine when the system efficiency is sufficiently reduced due to accumulated debris on the condenser coils or fins in order that the coils or fins of the condenser should be cleaned and/or the refrigerant charge is in need of adjustment. In some cases, the apparatus includes a microcontroller contained within the housing, the microcontroller determining condenser efficiency. In embodiments, the apparatus is calibrated to the condenser when it is clean in order to establish a baseline for comparing future measurements.

Yet another embodiment is an air conditioning system comprising a compressor, a condenser, an expansion device, an evaporator, and an apparatus for monitoring the cleanliness of the coils and/or fins of the condenser. The apparatus comprises a first temperature sensor configured to periodically measure ambient air temperature proximate the condenser, a second temperature sensor configured to periodically measure a temperature of a refrigerant liquid line downstream from the condenser, and a housing disposed proximate the condenser. The housing contains a controller connected to a processor configured to receive periodic temperature measurements from the first temperature sensor and periodic temperature measurements from the second temperature sensor, and based on the periodic temperature measurements from the first temperature sensor and the second temperature sensor, determine when the system efficiency is sufficiently reduced due to accumulated debris on the coils or fins of the condenser in order that the coils or fins should be cleaned. In embodiments, the system further comprises a first pressure sensor configured to periodically measure the pressure in the liquid line downstream from the condenser. The processor is further configured to receive periodic pressure measurements from the first pressure sensor and use the periodic pressure sensor measurements, along with the periodic temperature sensor measurements, to determine when the system efficiency is sufficiently reduced due to accumulated debris on the condenser coils or fins in order that the coils or fins of the condenser should be cleaned and/or the refrigerant charge is in need of adjustment.

A further embodiment is a method of monitoring the cleanliness of a condenser in an air conditioning system, the method comprising taking periodic temperature measurements of a condensed liquid refrigerant stream downstream from the condenser, taking periodic ambient temperature measurements proximate the condenser, determining when the difference between the temperature of the condensed liquid refrigerant stream and the ambient temperature is sufficient to recommend cleaning of coils and/or fins of the condenser in order to improve condenser efficiency, and providing an alert to a supervisor of the air conditioning system when cleaning is recommended.

In some cases, the method further comprises taking periodic pressure measurements of the condensed liquid refrigerant stream downstream from the condenser and utilizing the periodic pressure measurements in determining when to recommend cleaning of the coils and/or fins of the condenser and/or adjusting the charge of the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts a condenser layout showing a monitoring device and sensor placement according to a first embodiment described herein.

FIG. 1B shows details of the temperature sensor on the condenser liquid line.

FIG. 1C shows details of the optional pressure sensor on the condenser liquid line.

FIG. 2 shows a condenser layout displaying air flow.

FIG. 3 illustrates the electronics of the monitoring device.

FIG. 4 shows the vapor compression cycle.

FIG. 5 shows a top view of the monitoring device.

FIG. 6 illustrates a side view of the monitoring device.

FIG. 7 shows an experimental data relationship of measured compressor amps vs the CTOA when the condenser surface area is artificially reduced by 20% to simulate a dirty condenser.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

If maintenance of an air conditioning air-cooled condenser is neglected, this can lead to diminished heat exchange of the high temperature refrigerant gas with the ambient air. The reduction in heat exchange then requires the refrigerant compressor to increase the saturation pressure of the refrigerant to induce condensation to a liquid state. This increase in pressure results in the compressor consuming more energy. The embodiments described herein alert the owner or supervisor to this occurrence so that the heat exchange coils may be cleaned.

More specifically, the embodiments described herein provide continuous monitoring of parameters that will be impacted from reduced efficiency of a residential and/or commercial air conditioning system. These parameters include the liquid line temperature at the condenser exit, and the ambient temperature, i.e. the heat sink. This heat sink is considered infinite and not influenced by the heat addition from the heat source.

During periods of air conditioning operation, the system described herein collects data for the necessary parameters. Utilizing the two temperature inputs of (1) the liquid refrigerant line at or proximate the condenser exit and (2) ambient air, the device collects data points when the liquid line temperature is 5° F. higher (or more) than the ambient temperature. The purpose of the 5° F. higher than the ambient temperature indicates the compressor is operating, therefore the device collects relevant data points. The monitoring device saves measurements of these parameters at predetermined intervals. In some cases these intervals are uniform intervals ranging from constant monitoring to about every 5 minutes, or at intervals ranging from about 30 seconds to about 4 minutes, or at intervals of about 1 minute to about 2 minutes. In other cases, the measurements are taken at longer intervals, such as once per day or once per hour. In some cases, the data is momentarily saved on the monitoring device as overall averages over the operating cycle. After the temperature difference between the liquid line and ambient fall below 5° F., the monitoring device sends the average values of the parameters obtained to a processor. The processor is responsible for analyzing the data to determine the status of the air conditioning condenser cleanliness. If the status falls within pre-determined guidelines that warrant attention, an alert is sent to the building owner or supervisor. In embodiments, the alert is sent to a mobile device.

With this device the refrigerant charge can also be estimated to need adjustment, refrigerant charge increased or decreased. Either situation may cause degradation in performance, therefore require additional energy input to meet comfort levels of the dwelling. To determine sub-cooling, both temperature and pressure measurements of the condenser liquid line are required. Thus, the sub-cooling calculation requires the optional pressure sensor to be installed. Every refrigerant has a temperature-pressure relationship, where if one parameter is known the other may be found from the refrigerant manufacturer as a data table. This data table may be saved on the microcontroller so the algorithm may verify the pressure-temperature relationship versus what is being measured with the temperature and pressure sensors. After an averaging time frame the algorithm may determine if the refrigerant charge is potentially above or below the manufacturer's recommended charge amount.

In embodiments, the processor is part of a remote cloud server and the data is transmitted by wireless communications. In other cases the processor is local.

The alerts received by the owner or supervisor may include pre-emptive warnings of system efficiency degradation or other faults that may require attention due to a dirty condenser heat exchanger.

Referring to FIGS. 1A-6, one embodiment of a system described herein is shown. The system includes a monitoring device 1, which is associated with, and preferably mounted on, the condenser heat exchanger 15 within an air conditioning system such as that shown in FIG. 4. The condenser 15 is responsible for condensing high pressure, hot discharge gas from the compressor 22. The refrigerant is then expanded to a lower pressure, lower temperature liquid in the expansion device 23. The refrigerant is then evaporated in the evaporator 24 producing a net cooling effect for air passing through the evaporator coils. The air is distributed by the air handling system within the building or private dwelling.

FIG. 1A shows the monitoring device 1 located close in proximity to the condenser heat exchanger 15. In the embodiment shown in FIGS. 1A-3 and 5-6, the device 1 is powered through wire 7 which is attached to a power supply 30 on the condenser 15. The device 1 contains two temperature sensors, namely a first temperature sensor 3 for measuring ambient air 18 temperature, and a second temperature sensor 2 for measuring the temperature on the outer surface of the liquid line 17 exiting the condenser 15. Utilizing these two temperatures the electrical micro-controller 13 of the monitoring device 1 can calculate the difference between these two temperatures, i.e. the condensing temperature over ambient (CTOA), and then utilize algorithms to determine when the system efficiency is sufficiently decreasing due to accumulated debris on the heat exchanger fins/coil 15 in order that the system should be cleaned. Post cleaning of the heat exchanger fins/coil 25, a clean calibration process is completed. The clean calibration is utilized by the internal algorithms of the electrical micro-controller 13 to then determine the presence of decreased air flow as the heat exchanger fins/coil 25 becomes fouled by surrounding debris. Optionally a pressure sensor 21 is attached to a threaded port 32 on or near the condenser liquid line piping 17 provided by the condenser unit manufacturer. The pressure sensor 21 measures the refrigerant pressure within the condenser 15. The device may have the refrigerant pressure and temperature relationship saved on the micro-controller 13.

FIG. 2 shows the air inlet flow 19 into the condenser 15, passing the fins/coil 25 and the air outlet flow 20 through the top of the condenser 15.

FIG. 3 schematically shows the data processing system associated with the monitoring device 1. Inputs include a first temperature sensor 3, a second temperature sensor 2 and optionally a pressure sensor 21. The first temperature sensor 3 and the second temperature sensor 2 input analog signals to the micro-controller 13. The signals are converted to digital signals by an analog to digital converter. Data is routed to a processing device 42 on a cloud server 40 through a wireless circuit 27 using a wireless external antenna 14 or the like. The server 40 can be in communication with a remote computer 44 through which a homeowner or supervisor can receive data indicative of the condition of the condenser 15, such as condenser 15 efficiency.

FIG. 5 displays a top view of the monitoring device 1. Inputs as temperature are via the first sensor 3 and the second sensor 2, where there is a multi-conductor cable 28 supporting connections to the two temperature sensors. Optionally cable 26 is utilized for connection of the pressure sensor 21. LED lights in the center of the monitoring device 1 are positioned on the top cover 8 of the monitoring device 1 to indicate the status of the condenser coil 25. The top cover 8 is secured with screws 12 on the corners to a case 9, which can be made of a thermoplastic material, a thermoset material, a metal, or another suitable material. LED 4 is green, LED 5 is yellow, and LED 6 is red. As the condenser coil 25 collects more debris and system efficiency is degraded, the yellow LED 5 is illuminated, then finally the red LED 6 is illuminated. Only one LED is illuminated at any given time. Power supply for the electrical circuit for the LEDs is provided by a cable 7.

FIG. 6 shows a side view of the monitoring device 1. The input connector 50 and the power supply connector 52 are secured to the top cover 8 by nuts 11, which may be made of plastic or metal, and said connectors attach to the cables by a threaded portion 10.

FIG. 7 shows a data comparison of measured compressor amps [A] vs. the condenser temperature data [D] collected by the device. Data points (shown in minutes on the X-axis) were collected every 4 minutes. Only time durations of the compressor in the ON state are shown. The horizontal line [B] is the clean calibrated level or base CTOA. This average baseline would typically be established over a 2 week period to account for temperature variations between night and day. To dynamically show the result of a dirty condenser, at point [C] the condenser coils were artificially blocked by 20%. The subsequent increase in CTOA can be noted along with the increase in compressor amps from straight trend line [E]. As the condenser fins collect more debris, the passage for air flows decreases, therefore allowing smaller debris to collect. This compounding effect could quickly impair the efficiency of the system to which this device is installed. Further collection of debris on the condenser fins will elevate the CTOA away from the baseline. Pre-configured deltas of the CTOA—baseline will serve as warning points that may be sent to the user indicating the condenser fins should be cleaned. In embodiments, this delta could be between 4° F. and 6° F. for an initial warning and 6° F. and 8° F. for second warning, or between 5° F. and 7° F. for initial warning and 7° F. and 9° F. for second warning. These data points demonstrate how the device can validate a fouled or dirty A/C condenser.

• • A number of alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.

COMPONENTS SHOWN IN THE FIGURES

• • 1. Whole monitoring device
  • 2. 1^st temperature input sensor, connected to condenser liquid line 17
  • 3. 2^nd temperature input sensor, measuring surrounding ambient air 18
  • 4. LED indicator, clean (green)
  • 5. LED indicator, condenser coil beginning to show debris collection (yellow)
  • 6. LED indicator, condenser coil needs to be cleaned immediately (red)
  • 7. Power input cable
  • 8. Top plastic cover
  • 9. Bottom case
  • 10. Plastic connector connected to circuit controller 13
  • 11. Plastic nut connected to 10, with gasket connected to 8
  • 12. Screws in four corners to retain 8 to 9
  • 13. Circuit controller
  • 14. Wireless external antenna
  • 15. Air conditioning condensing unit
  • 16. Condenser liquid line 17 with temperature sensor 2
  • 17. Condenser liquid line
  • 18. Ambient air
  • 19. Air flow entering condenser heat exchanger fins
  • 20. Air flow exiting condenser heat exchanger fins
  • 21. Pressure sensor on liquid line 17
  • 22. Compressor
  • 23. Expansion device
  • 24. Evaporator
  • 25. Condenser heat exchanger fins/coil surrounding the condensing unit 15
  • 26. Pressure sensor 21 wire from device 1
  • 27. Wireless circuit
  • 28. Multi-conductor cable
  • 30. Power supply
  • 32. Threaded port
  • 40. Server
  • 42. Processor
  • 44. Remote computer
  • 50. Input connector
  • 52. Power supply connector

Claims

1. An apparatus for monitoring the cleanliness of the coils and/or fins of an air conditioner condenser, the apparatus comprising:

a first temperature sensor configured to periodically measure ambient air temperature proximate the condenser,

a second temperature sensor configured to periodically measure a temperature of a refrigerant liquid line downstream from the condenser, and

a housing disposed proximate the condenser, the housing containing a controller connected to a processor configured to: receive periodic temperature measurements from the first temperature sensor and periodic temperature measurements from the second temperature sensor, and based on the periodic temperature measurements from the first temperature sensor and the second temperature sensor, determine when the system efficiency is sufficiently reduced due to accumulated debris on the condenser coils or fins in order that the coils or fins of the condenser should be cleaned.

2. The apparatus of claim 1, further comprising a first pressure sensor configured to periodically measure the pressure in the liquid line downstream from the condenser, the processor being further configured to receive periodic pressure measurements from the first pressure sensor and use the periodic pressure sensor measurements, along with the periodic temperature sensor measurements, to determine when the system efficiency is sufficiently reduced due to accumulated debris on the condenser coils or fins in order that the coils or fins of the condenser should be cleaned and/or the refrigerant charge is in need of adjustment.

3. The apparatus of claim 1, wherein the apparatus includes a microcontroller contained within the housing, the microcontroller determining condenser efficiency.

4. The apparatus of claim 2, wherein the apparatus includes a microcontroller contained within the housing, the microcontroller determining condenser efficiency.

5. The apparatus of claim 1, wherein the apparatus is calibrated to the condenser when it is clean in order to establish a baseline for comparing future measurements.

6. The apparatus of claim 1, wherein the apparatus is configured to provide an initial warning when a condensing temperature over ambient (CTOA) is in the range of about 4° F. to about 7° F.

7. The apparatus of claim 6, wherein the apparatus is configured to provide a secondary warning when a condensing temperature over ambient (CTOA) is in the range of about 6° F. to about 9° F.

8. A system comprising the apparatus of claim 1 and a condenser for an air conditioner.

9. An air conditioning system comprising a compressor, a condenser, an expansion device, an evaporator, and an apparatus for monitoring the cleanliness of the coils and/or fins of the condenser, the apparatus comprising:

a first temperature sensor configured to periodically measure ambient air temperature proximate the condenser,

a second temperature sensor configured to periodically measure a temperature of a refrigerant liquid line downstream from the condenser, and

a housing disposed proximate the condenser, the housing containing a controller connected to a processor configured to: receive periodic temperature measurements from the first temperature sensor and periodic temperature measurements from the second temperature sensor, and based on the periodic temperature measurements from the first temperature sensor and the second temperature sensor, determine when the system efficiency is sufficiently reduced due to accumulated debris on the coils or fins of the condenser in order that the coils or fins should be cleaned.

10. The system of claim 9, further comprising a first pressure sensor configured to periodically measure the pressure in the liquid line downstream from the condenser, the processor being further configured to receive periodic pressure measurements from the first pressure sensor and use the periodic pressure sensor measurements, along with the periodic temperature sensor measurements, to determine when the system efficiency is sufficiently reduced due to accumulated debris on the condenser coils or fins in order that the coils or fins of the condenser should be cleaned and/or the refrigerant charge is in need of adjustment.

11. A method of monitoring the cleanliness of a condenser in an air conditioning system, comprising:

taking periodic temperature measurements of a condensed liquid refrigerant stream downstream from the condenser,

taking periodic ambient temperature measurements proximate the condenser,

determining when the difference between the temperature of the condensed liquid refrigerant stream and the ambient temperature is sufficient to recommend cleaning of coils and/or fins of the condenser in order to improve condenser efficiency, and

providing an alert to a supervisor of the air conditioning system when cleaning is recommended.

12. The method of claim 11, further comprising taking periodic pressure measurements of the condensed liquid refrigerant stream downstream from the condenser and utilizing the periodic pressure measurements, along with the periodic temperature measurements, in determining when to recommend cleaning of the coils and/or fins of the condenser, and/or adjusting the charge of the refrigerant.

13. The method of claim 11, wherein the alert is provided when the difference between the temperature of the condensed liquid refrigerant stream and the ambient temperature is in the range of about 4° F. to about 7° F.

14. The method of claim 11, wherein the alert is provided when the difference between the temperature of the condensed liquid refrigerant stream and the ambient temperature is in the range of about 6° F. to about 9° F.