Refrigerant leak sensor measurement adjustment systems and methods

A refrigerant measurement adjustment system includes: a refrigerant sensor for a building and configured to measure an amount of refrigerant present in air outside of a refrigeration system of the building; and an adjustment module configured to: adjust the amount of refrigerant measured based on an adjustment to produce an adjusted amount; and determine the adjustment based on at least one of: an air temperature; an air pressure; a relative humidity of air; a mode of operation of the refrigeration system; a change in the measurements of the refrigerant sensor over time; and whether a blower that blows air across a heat exchanger of the refrigeration system located within the building is on.

FIELD

The present disclosure relates to refrigerant leak sensors and more particularly to systems and methods for controlling measurements of refrigerant leak sensors.

BACKGROUND

Refrigeration and air conditioning applications are under increased regulatory pressure to reduce the global warming potential of the refrigerants they use. In order to use lower global warming potential refrigerants, the flammability of the refrigerants may increase.

Several refrigerants have been developed that are considered low global warming potential options, and they have an ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) classification as A2L, meaning mildly flammable. The UL (Underwriters Laboratory) 60335-2-40 standard, and similar standards, specifies a predetermined (M1) level for A2L (or mildly flammable) refrigerants and indicates that A2L refrigerant charge levels below the predetermined level do not require leak detection and mitigation.

SUMMARY

In a feature, a refrigerant measurement adjustment system includes: a refrigerant sensor for a building and configured to measure an amount of refrigerant present in air outside of a refrigeration system of the building; and an adjustment module configured to: adjust the amount of refrigerant measured based on an adjustment to produce an adjusted amount; and determine the adjustment based on at least one of: an air temperature; an air pressure; a relative humidity of air; a mode of operation of the refrigeration system; a change in the measurements of the refrigerant sensor over time; and whether a blower that blows air across a heat exchanger of the refrigeration system located within the building is on.

In further features, a leak module is configured to indicate whether a refrigerant leak is present based on the adjusted measurement.

In further features, the adjustment module is configured to determine the adjustment based on the air temperature.

In further features, the adjustment module is configured to determine the adjustment based on a change in the air temperature.

In further features, the adjustment module is configured to determine the adjustment based on the air pressure.

In further features, the adjustment module is configured to determine the adjustment based on a change in the air pressure.

In further features, the adjustment module is configured to determine the adjustment based on the relative humidity.

In further features, the adjustment module is configured to determine the adjustment based on a change in the relative humidity.

In further features, the adjustment module is configured to set the adjustment based on the amount of refrigerant measured when the mode of operation is in a heating mode for a predetermined period.

In further features, the adjustment module is configured to set the adjustment based on the amount of refrigerant measured after a pumpout of refrigerant from within the building has been performed.

In further features, the adjustment module is configured to set the adjustment based on the amount of refrigerant measured when the mode of operation transitions from a cooling mode to a heating mode and a pumpout of refrigerant from within the building has been performed.

In further features, the adjustment module is configured to set the adjustment based on the amount of refrigerant measured when the blower has been on for at least a predetermined period.

In further features, the adjustment module is configured to: adjust the amount of refrigerant further based on a second adjustment to produce the adjusted measurement; and determine the second adjustment based on the change in the amount of refrigerant measured by the refrigerant sensor over time.

In further features, the adjustment module is configured to set the adjusted amount based on one of (a) the amount of refrigerant measured plus the adjustment and (b) the amount of refrigerant measured minus the adjustment.

In further features, the adjustment module is configured to set the adjusted amount based on the amount of refrigerant measured multiplied by the adjustment.

In further features, the adjustment module is configured to adjust the amount based on at least two adjustments determined based on at least two of: the air temperature; the air pressure; the relative humidity of air; the mode of operation of the refrigeration system; the change in the measurements of the refrigerant sensor over time; and whether the blower that blows air across the heat exchanger of the refrigeration system located within the building is on.

In further features, the adjustment module is configured to adjust the amount based on adjustments determined based on each of: the air temperature; the air pressure; the relative humidity of air; the mode of operation of the refrigeration system; the change in the measurements of the refrigerant sensor over time; and whether the blower that blows air across the heat exchanger of the refrigeration system located within the building is on.

In further features: the adjustment module is configured to adjust the amount of refrigerant measured based on the change in the measurements of the refrigerant sensor over time; and the refrigerant measurement adjustment system further includes an end of life module configured to indicate that the refrigerant sensor is at an end of its useful life when a magnitude of the change is greater than a predetermined value.

In further features: the adjustment module is configured to adjust the amount of refrigerant measured based on the change in the measurements of the refrigerant sensor over time; and the refrigerant measurement adjustment system further includes an end of life module configured to indicate that the refrigerant sensor is at an end of its useful life when a magnitude of the change increases on at least a predetermined number of consecutive instances.

In a feature, a refrigerant measurement adjustment method includes: by a refrigerant sensor for a building, measuring an amount of refrigerant present in air outside of a refrigeration system of the building; adjusting the amount of refrigerant measured based on an adjustment to produce an adjusted amount; determining the adjustment based on at least one of: an air temperature; an air pressure; a relative humidity of air; a mode of operation of the refrigeration system; a change in the measurements of the refrigerant sensor over time; and whether a blower that blows air across a heat exchanger of the refrigeration system located within the building is on.

DETAILED DESCRIPTION

Some refrigerants used in refrigeration systems may be classified as mildly flammable (e.g., A2L refrigerants). Refrigeration systems using mildly flammable refrigerant may include a refrigerant leak sensor configured to measure an amount of refrigerant that is present in air outside of the refrigeration system within a building served by the refrigeration system. This amount of refrigerant corresponds to an amount of refrigerant that has leaked out of the refrigeration system.

The measurements of a refrigerant leak sensor may naturally change over time as the refrigerant leak sensor ages. For example, the measurements of the refrigerant leak sensor may drift over time. The measurements of the refrigerant leak sensor may also vary due to one or more operating conditions, such as a mode of operation of a refrigeration system, whether a blower is on, and/or a relative humidity, a temperature, or a pressure of air at the refrigerant leak sensor.

The present application involves adjusting the measurements of the refrigerant leak sensor in view of the above. This increases accuracy of the measurements and increase a lifetime of the refrigerant leak sensor.

FIG.1is a functional block diagram of an example refrigeration system100including a compressor102, a condenser104, an expansion valve106, and an evaporator108. The refrigeration system100may include additional and/or alternative components, such as a reversing valve or a filter-drier. In addition, the present disclosure is applicable to other types of refrigeration systems including, but not limited to, heating, ventilating, and air conditioning (HVAC), heat pump, refrigeration, and chiller systems. For example, the refrigeration system100may include a reversing valve (not shown) that is configured to reverse a direction of refrigerant flow in a heat pump system.

The compressor102receives refrigerant in vapor form and compresses the refrigerant. The compressor102provides pressurized refrigerant in vapor form to the condenser104. The compressor102includes an electric motor that drives a pump. For example only, the pump of the compressor102may include a scroll compressor and/or a reciprocating compressor.

All or a portion of the pressurized refrigerant is converted into liquid form within the condenser104. The condenser104transfers heat away from the refrigerant, thereby cooling the refrigerant. When the refrigerant vapor is cooled to a temperature that is less than a saturation temperature, the refrigerant transforms into a liquid (or liquefied) refrigerant. The condenser104may include an electric fan that increases the rate of heat transfer away from the refrigerant.

The condenser104provides the refrigerant to the evaporator108via the expansion valve106. The expansion valve106controls the flow rate at which the refrigerant is supplied to the evaporator108. The expansion valve106may include a thermostatic expansion valve or may be controlled electronically by, for example, a control module130. A pressure drop caused by the expansion valve106may cause a portion of the liquefied refrigerant to transform back into the vapor form. In this manner, the evaporator108may receive a mixture of refrigerant vapor and liquefied refrigerant.

The refrigerant absorbs heat in the evaporator108. Liquid refrigerant transitions into vapor form when warmed to a temperature that is greater than the saturation temperature of the refrigerant. The evaporator108may include an electric fan that increases the rate of heat transfer to the refrigerant.

A utility120provides power to the refrigeration system100. For example only, the utility120may provide single-phase alternating current (AC) power at approximately 230 Volts root mean squared (VRMS). In other implementations, the utility120may provide three-phase AC power at approximately 400 VRMS, 480 VRMS, or 600 VRMSat a line frequency of, for example, 50 or 60 Hz. When the three-phase AC power is nominally 600 VRMS, the actual available voltage of the power may be 575 VRMS.

The utility120may provide the AC power to the control module130via an AC line, which includes two or more conductors. The AC power may also be provided to a drive132via the AC line. The control module130controls the refrigeration system100. For example only, the control module130may control the refrigeration system100based on user inputs and/or parameters measured by various sensors (not shown). The sensors may include pressure sensors, temperature sensors, current sensors, voltage sensors, etc. The sensors may also include feedback information from the drive control, such as motor currents or torque, over a serial data bus or other suitable data buses.

A user interface134provides user inputs to the control module130. The user interface134may additionally or alternatively provide the user inputs directly to the drive132. The user inputs may include, for example, a desired temperature, requests regarding operation of a fan (e.g., a request for continuous operation of the evaporator fan), and/or other suitable inputs. The user interface134may take the form of a thermostat, and some or all functions of the control module (including, for example, actuating a heat source) may be incorporated into the thermostat.

The control module130may control operation of the fan of the condenser104, the fan of the evaporator108, and the expansion valve106. The control module130may also control actuation of the reversing valve.

The drive132may control the compressor102based on commands from the control module130. For example only, the control module130may instruct the drive132to operate the motor of the compressor102at a certain speed or to operate the compressor102at a certain capacity. In various implementations, the drive132may also control the condenser fan.

The evaporator108may be located within a building served by the refrigeration system. The condenser104may be located outside of the building. In heat pump systems, the functions of the evaporator108and the condenser104are switched depending on whether heating is to be performed within the building or cooling is to be performed within the building. When cooling is performed, the condenser104and the evaporator108perform as described above. When heating is performed, coolant flow is reversed, and the condenser104and the evaporator108operate oppositely. The condenser104and the evaporator108may therefore be more generally referred to as heat exchangers.

A refrigerant leak sensor140is disposed inside of the building and measures an amount (e.g., concentration) of refrigerant in air (outside of the refrigeration system) present at the refrigerant leak sensor. The refrigerant leak sensor140may be located, for example, near the evaporator108, such as downstream of a blower that blows air across the evaporator108and into the building through ducts. The refrigerant leak sensor140may also be located downstream of evaporator108.

The refrigerant leak sensor140generates a signal based on the amount of refrigerant measured. For example, the refrigerant leak sensor140may transmit the amount of refrigerant to the control module130. Alternatively, the refrigerant leak sensor140may set the signal to a first state when the amount is greater than a predetermined amount and set the signal to a second state when the amount is less than the predetermined amount. The predetermined amount may be, for example, 25 percent of a lower flammability level of the refrigerant or another suitable value. In various implementations, the refrigerant is classified under one or more standards as being mildly flammable. For example only, the refrigerant may be classified as an A2L refrigerant or more generally mildly flammable as discussed above. The classification may be, for example, by a standard of ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), UL (Underwriters Laboratory) 60335-2-40 standard, or in another standard which may be by ASHRAE, UL, or another regulatory body.

The control module130receives the output of the refrigerant leak sensor140and determines whether a refrigerant leak is present based on the output. For example, the control module130may determine that a leak is present when the output is in the first state or when the amount is greater than the predetermined amount. If the amount is less than the predetermined amount or the output is in the second state, the control module130may determine that no leak is present.

One or more remedial actions may be taken when a refrigerant leak is present (e.g., the signal indicates that the amount is greater than the predetermined value or the signal is in the first state). For example, the control module130may turn on the blower (that blows air across the evaporator108) when a leak is present. Turning on the blower may disperse leaked refrigerant. Additionally, the control module130may turn off the compressor102and maintain the compressor102off until the leak is remediated (e.g., for a predetermined period). Additionally, the control module130may actuate lockout devices to prevent ignition by one or more ignition devices within the building. Additionally or alternatively, the control module130may close one or more isolation valves to isolate the refrigerant outside of the building. In various implementations, a first isolation valve may be implemented directly between the condenser104and the expansion valve106. The control module130may close the first isolation valve when a leak is detected. A second isolation valve may be implemented directly between the evaporator108and the compressor102. The control module130may maintain the second isolation valve open while the compressor102is on and the first isolation valve is closed to pump refrigerant out from within the building. The control module130may close the second isolation valve after operation of the compressor102for a predetermined period with the first isolation valve closed.

Additionally or alternatively, the control module130may generate one or more indicators when a leak is present. For example, the control module130may transmit an indicator to one or more external devices, generate one or more visual indicators (e.g., turn on one or more lights, display information on one or more displays, etc.), and/or generate one or more audible indicators, such as via one or more speakers.

The refrigerant leak sensor140may be, for example, non dispersive infrared (NDIR) refrigerant sensor, a thermal conductivity refrigerant sensor, a quartz crystal microbalance (QCM) sensor, or another suitable type of refrigerant leak sensor. NDIR sensors include an infrared (IR) lamp that transmits light through a tube. A fan or blower may push or pull gas (e.g., air and, if a leak is present, refrigerant) through the tube. An optical sensor receives light from the IR lamp through the tube and measures the amount of refrigerant in the gas based on one or more characteristics of the light. A thermal conductivity sensor includes conductive plates between which the gas may be pushed or pulled by a blower or a fan. The blower or fan may be omitted in various implementations. Different amounts of refrigerant have different thermal conductivities. Thermal conductivity sensors include two temperature sensors (e.g., one before and one after a heating element). A thermal conductivity sensor determines a temperature difference between the measurements from the two sensors. Given a known heating input from the heating element, the thermal conductivity sensor determines the amount of the refrigerant based on the temperature difference. Different amounts of refrigerant have different densities and may therefore cause different vibrations. QCM sensors measure the amount of refrigerant in the gas based on the vibration. Other examples of refrigerant leak sensors140include metal oxide refrigerant sensors, acoustic refrigerant sensors, quartz resonation (e.g., QCM) refrigerant sensors, and carbon nanotube refrigerant sensors. Metal oxide refrigerant sensors measure a resistance across a surface oxidizer heated by a hotplate. In the presence of the refrigerant, the resistance of the oxidizing layer may decrease. As refrigerant dissipates, the resistance of the oxidizing layer may increase. A metal oxide refrigerant sensor may determine the amount of refrigerant based on the resistance.

The amount of refrigerant measured by the refrigerant leak sensor140may naturally deviate from the actual amount of refrigerant present over time. For example, the amount of refrigerant measured may drift over time. One or more ambient conditions (e.g., temperature, pressure, humidity) may cause inaccuracy in the amount of refrigerant measured by the refrigerant leak sensor140. The blower being on may also cause the amount of refrigerant measured to be inaccurate. The response of the refrigerant leak sensor140to change in one or more ambient conditions (e.g., temperature, pressure, humidity) may also slow or speed up over time.

The present application involves adjusting the amount of refrigerant measured by the refrigerant leak sensor140to account for the above. For example, an adjustment for drift may be determined and used to adjust the amount of refrigerant measured. Additionally or alternatively, one or more adjustments may be determined based on one or more ambient conditions and used to adjust the amount of refrigerant measured. Additionally or alternatively, an adjustment for when a change in an ambient condition occurs may be determined and used to adjust the amount of refrigerant measured. Additionally or alternatively, an adjustment may be determined for when the blower is on and used to adjust the amount of refrigerant measured. Additionally or alternatively, an adjustment may be determined based on a difference between measurements during heating and cooling mode operation and used to adjust the amount of refrigerant measured.

FIG.2is a functional block diagram of an example portion of the refrigeration system ofFIG.1. When on, a blower204draws air in from within the building through one or more return air ducts. The blower204forces air past the evaporator108. The evaporator108transfers heat to or from the air as the air passes the evaporator108. Heated or cooled air flows from the evaporator108to within the building through one or more supply air ducts.

One or more sensors may be implemented in addition to the refrigerant leak sensor140. For example, a motor current sensor208may measure current to the blower204and more specifically to an electric motor of the blower204. The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the current is greater than a predetermined current.

Additionally or alternatively, a voltage sensor may measure a voltage applied to the electric motor of the blower204. The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the voltage is greater than a predetermined voltage.

Additionally or alternatively, a power sensor may measure a power consumption of the electric motor of the blower204. The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the power consumption is greater than a predetermined power.

Additionally or alternatively, a speed sensor212may measure a rotational speed of the electric motor of the blower204. The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the speed is greater than a predetermined speed.

Additionally or alternatively, one or more sensors may be implemented downstream of the evaporator108. For example, a pressure sensor216may measure a pressure of air downstream of the evaporator108(e.g., in a supply air duct). The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the pressure is greater than a predetermined pressure (e.g., a barometric pressure). The pressure may approach barometric pressure when the blower204is off. The pressure may increase relative to barometric pressure when the blower204is on.

Additionally or alternatively, a temperature sensor220may measure a temperature of air downstream of the evaporator108(e.g., in a supply air duct). The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the temperature is greater than a predetermined temperature (e.g., a setpoint pressure of the thermostat) during heating or less than the predetermined temperature during cooling. The temperature measured by the temperature sensor220may be an ambient temperature while the blower204is off.

Additionally or alternatively, a relative humidity sensor224may measure a relative humidity (RH) of air downstream of the evaporator108(e.g., in a supply air duct). The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the relative humidity is greater than or less than a predetermined relative humidity. Different predetermined relative humidities may be used for heating mode and cooling mode. The relative humidity measured by the relative humidity sensor224may be an ambient relative humidity while the blower204is off.

Additionally or alternatively, an air flowrate (e.g., mass air flowrate (MAF)) sensor228may measure a flowrate (e.g., a mass flowrate) of air downstream of the evaporator108(e.g., in a supply air duct). The control module130may determine that the blower204is on (and turn off the refrigerant leak sensor140) when the air flowrate is greater than a predetermined air flowrate.

While example locations of sensors are provided inFIG.2, the sensors may be located in other suitable locations. Additionally, one or more of the sensors ofFIG.2may be omitted or duplicated.

FIG.3is a functional block diagram of an example implementation of the control module130. A compressor control module304controls operation of the compressor102. For example, the compressor control module304may turn on the compressor102in response to receipt of a command (e.g., cool mode command) from a thermostat308. The thermostat308may generate the command, for example, when a temperature of air within the building is greater than a setpoint temperature (in the example of cooling) or less than the setpoint temperature (in the example of heating). The compressor control module304may vary a speed and/or capacity of the compressor102when the compressor102is on. The compressor control module304may turn the compressor102off when the thermostat308stops generating the command.

A fan control module312controls operation of the condenser fan316. The condenser fan316increases airflow past the condenser104when the condenser fan316is on. For example, the fan control module312may turn on the condenser fan316in response to receipt of the command from the thermostat308. The fan control module312may turn the condenser fan316off when the thermostat308stops generating the command. In various implementations, the fan control module312may turn the condenser fan316on before the compressor102is turned on and maintain the condenser fan316on for a predetermined period after the compressor102is turned off.

A blower control module320controls operation of the blower204. For example, the blower control module320may turn on the blower204in response to receipt of the command from the thermostat308. The blower control module320may also turn on the blower204in response to receipt of a command for heating from the thermostat308. The blower control module320may also turn on the blower204in response to receipt of a command to turn the blower204on (Fan On command) from the thermostat308. The blower control module320may turn the blower204off when the thermostat308is not generating any of the commands. In various implementations, the blower control module320may turn the blower204on before the compressor102is turned on and maintain the blower204on for a predetermined period after the compressor102is turned off.

The control modules discussed herein turn a device on by applying power to the device. The control modules turn a device off by disconnecting the device from power.

The blower control module320may also turn the blower204on when a refrigerant leak is detected using the refrigerant leak sensor140. For example, a leak module324may determine that a refrigerant leak is present in the refrigeration system when the amount of refrigerant measured outside of the refrigeration system by the refrigerant leak sensor140is greater than a predetermined amount. The leak module324may determine that a refrigerant leak is not present when the amount is less than the predetermined amount.

One or more other remedial actions may be taken when a refrigerant leak is present in the refrigeration system, such as described above. For example, the compressor control module304may turn the compressor102off and maintain the compressor102off for a predetermined period when a refrigerant leak is present. One or more isolation valves may also be closed, such as to pump refrigerant out from within the building and to trap the refrigerant outside of the building.

As discussed above, the amount of refrigerant measured by the refrigerant leak sensor140may vary from the actual amount of refrigerant present at the refrigerant leak sensor140. An adjustment module328adjusts the amount of refrigerant measured by the refrigerant leak sensor before the (adjusted) amount of refrigerant is used, such as by the leak module324. The adjustment module328may determine one or more adjustments based on measurements from one or more other sensors332, such as the temperature sensor220, the relative humidity sensor224, the pressure sensor216, and/or one or more other types of sensors. While the adjusting module328is illustrated as being implemented within the control module130, the adjustment module328may be implemented within the refrigerant leak sensor140or a portion of the functionality of the adjustment module328may be implemented within the refrigerant leak sensor140and a portion (e.g., the remainder) of the functionality of the adjustment module328may be implemented within the control module130.

FIG.4is a functional block diagram of an example implementation of the adjustment module328. A first adjusting module404receives the measurement of the refrigerant leak sensor140. The measurement includes the amount of refrigerant measured by the refrigerant leak sensor140.

The first adjusting module404adjusts the measurement based on a drift adjustment to produce a first adjusted measurement. For example, the first adjusting module404may set the first adjusted measurement based on or equal to a sum (addition) of the drift adjustment and the measurement or a product (multiplication) of the drift adjustment and the measurement.

A drift module408determines the drift adjustment based on a difference between two of the measurements taken at two different times. For example, the drift module408may set the drift adjustment based on or equal to a first measurement from a first time minus a second measurement from a second time. The first measurement may be, for example, stored in the refrigerant leak sensor140, a first measurement received from refrigerant leak sensor140by the first adjusting module404, a measurement from a previous time (relative to a present time), or another suitable measurement. The second measurement may be a measurement received after the first measurement, the present measurement, or another suitable measurement.

A second adjusting module412receives the first adjusted measurement (first adjusted measured amount of refrigerant). The second adjusting module412adjusts the first adjusted measurement based on an ambient adjustment to produce a second adjusted measurement. For example, the second adjusting module412may set the second adjusted measurement based on or equal to a sum (addition) of the ambient adjustment and the first adjusted measurement or a product (multiplication) of the ambient adjustment and the first adjusted measurement.

An ambient module416determines the ambient adjustment based on an ambient parameter, such as an ambient temperature, an ambient pressure, or an ambient relative humidity. The ambient temperature may be measured by the temperature sensor220while the blower204is off. The ambient pressure may be measured by the pressure sensor216while the blower204is off. The ambient relative humidity may be measured by relative humidity sensor224while the blower204is off. The ambient module416may determine the ambient adjustment, for example, using one of a lookup table and an equation that relates values of the ambient parameter to ambient adjustments.

In various implementations, the ambient module416may determine multiple ambient adjustments, such as a first ambient adjustment based on the ambient temperature, a second ambient adjustment based on the ambient pressure, and a third ambient adjustment based on the ambient relative humidity. In such implementations, the second adjusting module412may adjust the first adjustment measurement based on each of the ambient adjustments, such as by adding or multiplying each.

The ambient module416may also include inputs signaling blower power state and mode (e.g., heating, cooling, off). This allows the ambient module416to anticipate/predict what the changes will be seen in ambient conditions. For instance, if the thermostat is in cooling mode and the blower is on, the ambient module416may expect to see a decrease in temperature, and increase in humidity, and an increase in barometric pressure. If these expected changes are reflected in all but one of the sensors, it could signal that that sensor is not operating properly or at the end of its life.

A third adjusting module420receives the second adjusted measurement (second adjusted measured amount of refrigerant). The third adjusting module420adjusts the second adjusted measurement based on a change adjustment to produce a third adjusted measurement. For example, the third adjusting module420may set the third adjusted measurement based on or equal to a sum (addition) of the change adjustment and the second adjusted measurement or a product (multiplication) of the change adjustment and the second adjusted measurement.

A change module424determines the change adjustment based on a change in the measurements that occurred in response to a change in a parameter, such as temperature, pressure, or relative humidity. The temperature may be measured by the temperature sensor220. The pressure may be measured by the pressure sensor216. The relative humidity may be measured by relative humidity sensor224. The change module424may determine the change adjustment, for example, using one of a lookup table and an equation that relates measurement changes of the parameter to change adjustments.

In various implementations, the change module424may determine multiple change adjustments, such as a first change adjustment based on a change in temperature, a second change adjustment based on a change in pressure, and a third change adjustment based on a change in relative humidity. In such implementations, the third adjusting module420may adjust the second adjustment measurement based on each of the change adjustments, such as by adding or multiplying each.

In various implementations, the change module424may determine the change adjustment(s) based on the final adjusted measurement output by the adjusting module328. The change module424may disable each of the adjustments, however, to determine the change adjustment(s).

A fourth adjusting module428receives the third adjusted measurement (third adjusted measured amount of refrigerant). The fourth adjusting module428adjusts the third adjusted measurement based on a blower adjustment to produce a fourth adjusted measurement. For example, the fourth adjusting module428may set the fourth adjusted measurement based on or equal to a sum (addition) of the blower adjustment and the third adjusted measurement (e.g., in the example of the blower adjustment being a negative value) or a product (multiplication) of the blower adjustment and the third adjusted measurement (e.g., in the example of the blower adjustment being a positive value) or a difference (subtraction) between the third adjusted measurement and the blower adjustment (e.g., in the example of the blower adjustment being a positive value).

A blower adjustment module432determines the blower adjustment based on whether the blower204is on. When the blower204is on for at least a predetermined period, any refrigerant leak should be mitigated, so the measurements from the refrigerant leak sensor140should be zero. The measurements may increase or decrease, however, as the refrigerant leak sensor140ages. The measurements may become negative in some implementations. The blower adjustment module432may therefore set the blower adjustment based on or equal to the measurement (a positive value) from the refrigerant leak sensor140when the blower204transitions from on to off after being on for at least the predetermined period (such that the measurement should be zero). The blower adjustment module432may make the blower adjustment negative (e.g., -measurement) to produce a negative value.

A fifth adjusting module436receives the fourth adjusted measurement (fourth adjusted measured amount of refrigerant). The fifth adjusting module436adjusts the fourth adjusted measurement based on a mode adjustment to produce a (final) adjusted measurement. For example, the fifth adjusting module436may set the adjusted measurement based on or equal to a sum (addition) of the mode adjustment and the fourth adjusted measurement (e.g., in the example of the mode adjustment being a negative value) or a product (multiplication) of the mode adjustment and the fourth adjusted measurement (e.g., in the example of the mode adjustment being a positive value) or a difference (subtraction between the mode adjustment and the fourth adjusted measurement (e.g., in the example of the mode adjustment being a positive value). The leak module324determines whether a refrigerant leak is present, as discussed above, based on the adjusted measurement output by the adjustment module328.

A mode module438determines the mode adjustment based on the present mode of operation of the refrigeration system. The thermostat308sets the mode of operation to one of heating mode, cooling mode, or off. A pumpout may be performed to pump refrigerant out of the indoor section of the refrigeration system when the refrigeration system is off or transitioned to the heating mode. Therefore, even if a refrigerant leak is present, the measurements of the refrigerant leak sensor140should be zero. The mode module438may therefore set the mode adjustment based on or equal to a measurement of the refrigerant leak sensor140when the mode transitions to the heating mode or otherwise when a pumpout has been performed. The mode module438may make the mode adjustment negative (e.g., -measurement) to produce a negative value or a positive value if the measurement has drifted negatively.

While an example order of applying adjustments is provided inFIG.4, the adjustments may be made in another order. Also, one or more of the adjustments discussed above may be omitted.

Referring back toFIG.3, an end of life module440may indicate whether the refrigerant leak sensor140is at or nearing an end of its useful life. The measurements of refrigerant leak sensor140may have an accuracy that is less than a predetermined value when the refrigerant leak sensor140is at or nearing the end of its useful life. The refrigeration leak sensor140should be replaced when the refrigeration leak sensor140is at or nearing the end of its useful life.

The end of life module440may determine whether the refrigerant leak sensor140is at or near the end of its useful life when a change in the measurements in response to a change in relative humidity is greater than or less than a predetermined expected value bounds associated with the change in relative humidity. The change adjustment above may help increase the useful life of the refrigerant leak sensor140. Additionally or alternatively, the end of life module440may determine whether the refrigerant leak sensor140is at or near the end of its useful life when a change in the measurements in response to a change in temperature is greater than or less than a predetermined expected value bounds associated with the change in temperature. The end of life module440may determine whether the refrigerant leak sensor140is at or near the end of its useful life when a change in the measurements in response to a change in pressure is less than a predetermined expected value associated with the change in pressure. The end of life module440may additionally determine that the refrigerant leak sensor140is at or near the end of its useful life when the mode adjustment (determined based on the difference between the first and second measurements) is greater than or less than a predetermined value.

The end of life module440may additionally or alternatively determine that the refrigerant leak sensor140is at or near the end of its useful life when one or more of the adjustments (e.g., the blower adjustment, the drift adjustment, the mode adjustment, etc.) is greater than or less than a predetermined value.

The end of life module440may take one or more remedial actions when the refrigerant leak sensor140is at or near the end of its useful life. For example, the end of life module440may illuminate a light, store a predetermined code in memory, transmit a message to one or more computing devices via a network, or perform one or more other remedial actions when the refrigerant leak sensor140is at or near the end of its useful life.

FIG.5is a flowchart depicting an example method of adjusting the measurements of the refrigerant leak sensor140and performing leak detection and remediation. Control begins with504, where the adjustment module328receives a measurement from the refrigerant leak sensor140. The adjustment module328also obtains or determines the adjustments, as described above.

At508, the first adjusting module404may determine the first adjusted measurement based on the measurement (from504) and the drift adjustment. At512the second adjusting module412determines the second adjusted measurement based on the first adjusted measurement and the ambient adjustment(s). At516, the third adjusting module420determines the third adjusted measurement based on the second adjusted measurement and the change adjustment(s). At520, the fourth adjusting module determines the fourth adjusted measurement based on the third adjusted measurement and the blower adjustment. At524, the fifth adjusting module436determines the adjusted measurement based on the fourth adjusted measurement and the mode adjustment. As described above, one or more of the adjustments may be omitted, and a different order of adjustment may be used.

At528, the leak module324determines whether the adjusted measurement is greater than the predetermined amount of refrigerant. If528is false, the leak module324indicates that no refrigerant leak is present at532, and control returns to504for a next measurement. If528is true, control continues with536.

At536, the leak module324indicates that a refrigerant leak is present. At540, in response to the diagnosis of the presence of a refrigerant leak, one or more remedial actions are performed. For example, the blower control module320may turn the blower204on for a predetermined period to dissipate any leaked refrigerant. The compressor control module304may also turn the compressor102off for the predetermined period. Before turning the compressor off, the compressor control module304may leave the compressor102on to pump refrigerant out from within the building. One or more valves may be actuated to trap the refrigerant outside of the building.

FIG.6is a flowchart depicting an example method of determining the drift adjustment and determining whether the refrigerant leak sensor140is at or near the end of its useful life. Control begins with601where the adjustment module328determines whether an indication that the refrigerant leak sensor140is at or near the end of its useful life has been generated. If601is true, control transfers to602. IF601is false, control continues with604. At602, the adjustment module328determines whether a predetermined period has passed since the indication was generated. If602is false, mitigation of a leak is performed at603. For example, the blower control module320may turn on the blower204. Additionally, the control module130may lockout one or more lockout devices to prevent ignition within the building. If602is false, control may return to601. The predetermined period may be, for example, 24 hours (1 day) or another suitable period.

At604, the adjustment module328determines whether the refrigeration system is on such that heating or cooling of the building is being performed. If604is true, control continues with608. If604is false, the adjustment module328may leave the drift adjustment unchanged and return to601.

At608, the adjustment module328determines the present mode of operation of the refrigeration system. If the refrigeration system is operating in the heating mode, control continues with616. If the refrigeration system is operating in the cooling mode, control continues with612.

At612, the adjustment module328determines whether the refrigeration system has been operating in the cooling mode for at least a predetermined period, such as approximately 5 minutes or another suitable period that is greater than zero. If612is true, control continues with618. If612is false, control returns to601and the adjustment module328leaves the drift adjustment unchanged. At616, the adjustment module328determines whether the refrigeration system has been operating in the heating mode for at least a predetermined period, such as approximately 5 minutes or another suitable period that is greater than zero. If616is true, control continues with620. If616is false, control returns to601and the adjustment module328leaves the drift adjustment unchanged.

At618, the drift module408determines a baseline measurement, such as the present measurement of the refrigerant leak sensor140or an average (e.g., a standard average, a moving average, or a weighted moving average) of the last X measurements of the refrigerant leak sensor140. X may be, for example, the last 10 measurements or another suitable number of measurements or all of the measurements from the refrigerant leak sensor140obtained over the last X units of time (e.g., seconds, minutes, etc.). Last may refer to the temporal sense relative to a present time.

At620, the drift module408determines a baseline clean measurement, such as the present measurement of the refrigerant leak sensor140or an average (e.g., a standard average, a moving average, or a weighted moving average) of the last X measurements of the refrigerant leak sensor140. X may be, for example, the last 10 measurements or another suitable number of measurements or all of the measurements from the refrigerant leak sensor140obtained over the last X units of time (e.g., seconds, minutes, etc.). Last may refer to the temporal sense relative to a present time. Control continues with624after618and620.

At624, the drift module408determines the drift adjustment based on the baseline clean measurement (from620) and the baseline measurement (from618). The initial measurement may be stored in memory. The drift module408may set the drift adjustment based on or equal to a difference between the baseline measurement and the baseline clean measurement, such as the baseline measurement minus the baseline clean measurement.

At628, the end of life module440may determine whether the drift adjustment (e.g., a magnitude) is greater than a predetermined value. If628is true, the end of life module440may indicate that the refrigerant leak sensor is at or near the end of its useful life and take one or more remedial actions at632. The end of life module440may also reset the period (compared at602) at632. If628is false, control may transfer to636. At636, the end of life module440may determine whether the drift adjustment (e.g., the magnitude) has increased by more than a predetermined amount relative to an initial drift adjustment or increased during each of the last Y number of updates (at624). Y is an integer greater than or equal to 2. If636is true, the end of life module440may indicate that the refrigerant leak sensor140is at or near the end of its useful life and take one or more remedial actions at632. If636is false, the end of life module440may indicate that the refrigerant leak sensor140is not at or near the end of its useful life at640, and control may return to601.