Patent Publication Number: US-2020300522-A1

Title: Refrigerant-amount determination kit

Description:
TECHNICAL FIELD 
     The present disclosure relates to a refrigerant-amount determination kit that determines the amount of a refrigerant of a refrigeration cycle apparatus. 
     BACKGROUND ART 
     Conventionally, as disclosed in Patent Document 1 (Specification of Japanese Patent No. 5334909), there is a technology that controls the operational state (condensation temperature or evaporation temperature) of a refrigeration cycle apparatus to be under a constant condition and determines the amount of a refrigerant based on the value of the degree of subcooling or the like. Patent Document 1 (Specification of Japanese Patent No. 5334909) discloses that the refrigerant-amount determination technology is applied to a refrigerant packing operation or the like in the initial stage of equipment installation and that presence/absence of a refrigerant leak is determined based on a result of the refrigerant-amount determination. 
     SUMMARY OF THE INVENTION 
     It is, however, nearly impossible to perform refrigerant-amount determination in refrigeration cycle apparatuses loaded with a constant-speed compressor because such refrigeration cycle apparatuses have few sensors and the like although refrigeration cycle apparatuses loaded with an inverter compressor, such as that disclosed in Patent Document 1 (Specification of Japanese Patent No. 5334909), have a large number of sensors that measure the temperature or the pressure of refrigerants. Therefore, in refrigeration cycle apparatuses loaded with a constant-speed compressor, a service of determining a refrigerant amount has not been performed conventionally. 
     A refrigerant-amount determination kit according to a first aspect includes a sensor and a processor. The sensor is mounted at least temporarily on at least one of a portion of a refrigeration cycle apparatus and a periphery of the refrigeration cycle apparatus. The refrigeration cycle apparatus is an apparatus having a refrigerant circuit that includes a compressor, a condenser, and an evaporator. The processor determines the amount of a refrigerant in the refrigerant circuit based on a detection result detected by the sensor during operation of the refrigeration cycle apparatus. 
     The refrigerant-amount determination kit according to the first aspect is highly convenient because it is possible to perform refrigerant-amount determination easily even when the refrigerant cycle apparatus is not provided with a sensor required for refrigerant-amount determination. 
     A refrigerant-amount determination kit according to a second aspect is the refrigerant-amount determination kit of the first aspect, in which the sensor includes a temperature sensor that detects the temperature of a refrigerant flowing in the refrigerant circuit. 
     In the refrigerant-amount determination kit according to the second aspect, it is possible to perform refrigerant-amount determination with high accuracy by using a refrigerant temperature detected by the sensor. 
     A refrigerant-amount determination kit according to a third aspect is the refrigerant-amount determination kit of the second aspect, in which the refrigerant-amount determination kit further includes a heat insulation member that covers the periphery of the temperature sensor. 
     In the refrigerant-amount determination kit according to the third aspect, a refrigerant temperature can be detected with high accuracy, and it is possible to perform refrigerant-amount determination with high accuracy based on a detection result. 
     A refrigerant-amount determination kit according to a fourth aspect is the refrigerant-amount determination kit of the second aspect or the third aspect, in which the temperature sensor includes at least one of a first sensor group and a second sensor group. The first sensor group includes a first temperature sensor and a second temperature sensor. The first temperature sensor detects the condensation temperature of the refrigerant in the refrigerant circuit. The second temperature sensor detects the temperature of the refrigerant at an outlet of the condenser of the refrigerant circuit. The second sensor group includes a third temperature sensor and a fourth temperature sensor. The third temperature sensor detects the evaporation temperature of the refrigerant in the refrigerant circuit. The fourth temperature sensor detects the temperature of the refrigerant at an outlet of the evaporator of the refrigerant circuit. 
     In the refrigerant-amount determination kit according to the fourth aspect, it is possible to perform refrigerant-amount determination with high accuracy by utilizing a value of the degree of subcooling or the degree of superheating. 
     A refrigerant-amount determination kit according to a fifth aspect is the refrigerant-amount determination kit of any one of the first aspect to the fourth aspect, in which the sensor includes an outside-air temperature sensor that detects an outside air temperature at an installation place of the refrigeration cycle apparatus. 
     In the refrigerant-amount determination kit according to the fifth aspect, it is possible to perform refrigerant-amount determination with high accuracy by further using information on an actually measured outside air temperature. 
     A refrigerant-amount determination kit according to a sixth aspect is the refrigerant-amount determination kit of any one of the first aspect to the fifth aspect, in which the refrigerant-amount determination kit further includes a transmitter. The transmitter transmits a detection result detected during operation of the refrigeration cycle apparatus by the sensor to the processor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a refrigerant-amount determination kit according to a first embodiment of the present disclosure; 
         FIG. 2  is a schematic block diagram of an air conditioner that is a target of refrigerant-amount determination of the refrigerant-amount determination kit, illustrating a state in which sensors of the refrigerant-amount determination kit in  FIG. 1  are installed in a heat-source-side heat exchanger, a liquid-refrigerant pipe connected to the heat-source-side heat exchanger, and a measurement place of a heat-source air temperature; 
         FIG. 3  is an example of the flowchart of processing of refrigerant-amount determination of an air conditioner by the refrigerant-amount determination kit in  FIG. 1 ; 
         FIG. 4  is a block diagram of a refrigerant-amount determination kit according to a second embodiment of the present disclosure; 
         FIG. 5  illustrates a state in which sensors of the refrigerant-amount determination kit in  FIG. 4  are installed in a utilization-side heat exchanger, a gas-refrigerant pipe connected to the utilization-side heat exchanger, and a measurement place of a heat-source air temperature of an air conditioner that is a target of refrigerant-amount determination; 
         FIG. 6  is an example of the flowchart of processing of refrigerant-amount determination of an air conditioner by the refrigerant-amount determination kit in  FIG. 4 ; 
         FIG. 7  is a block diagram of a refrigerant-amount determination kit according to a modification A of the present disclosure; and 
         FIG. 8  is a block diagram of a refrigerant-amount determination kit according to a modification B of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS Embodiments of a refrigerant-amount determination kit of the present disclosure will be described. 
     First Embodiment 
     A refrigerant-amount determination kit  100  of a first embodiment will be described. 
     (1) Overall Configuration 
     The refrigerant-amount determination kit  100  will be described with reference to  FIG. 1 .  FIG. 1  is a block diagram of the refrigerant-amount determination kit  100 . 
     The refrigerant-amount determination kit  100  is a device for determining the amount of a refrigerant enclosed in a refrigerant circuit of a refrigeration cycle apparatus. Here, from the point of view of simplicity of expression, the expression “determines the amount of a refrigerant enclosed in a refrigerant circuit of a refrigeration cycle apparatus” is sometimes alternatively expressed as “determines the refrigerant amount of the refrigeration cycle apparatus”. The refrigerant-amount determination kit  100  is a unit that includes at least one sensor  10  and a determination device that determines the amount of a refrigerant enclosed in a refrigerant circuit of a refrigeration cycle apparatus based on a detection result of the sensor  10 . The sensor  10  is installed at least temporarily on at least one of the refrigeration cycle apparatus and the periphery of the refrigeration cycle apparatus. In the present embodiment, the determination device is a server  30  connected to the sensor  10  through a network NW, such as the Internet. The detailed configuration and operation of the refrigerant-amount determination kit  100  will be described later. 
     The refrigerant cycle apparatus that is a target of refrigerant-amount determination of the refrigerant-amount determination kit  100  is a vapor compression type apparatus having a refrigerant circuit that includes a compressor, a condenser, and an evaporator. Examples of the refrigeration cycle apparatus include an air conditioner, a hot water supply apparatus, a floor heating apparatus, and a refrigeration/freezing apparatus. Details of the refrigeration cycle apparatus will be described later by presenting an air conditioner  200  as an example. 
     The refrigeration cycle apparatus that is a target of refrigerant-amount determination of the refrigerant-amount determination kit  100  is an already-installed existing apparatus. By using the refrigerant-amount determination kit  100 , an administrator or the like of the refrigeration cycle apparatus is enabled to easily grasp a refrigerant amount, as necessary, even when the already-installed refrigeration cycle apparatus does not have a sensor required for performing refrigerant-amount determination. The target of refrigerant-amount determination of the refrigerant-amount determination kit  100  is, however, not limited to an existing refrigeration cycle apparatus and may be a new refrigeration cycle apparatus that is newly installed. 
     In the present embodiment, after the sensor  10  of the refrigerant-amount determination kit  100  is mounted on at least one of the refrigeration cycle apparatus and the periphery of the refrigeration cycle apparatus, the sensor  10  is left in a state of being mounted. In other words, the refrigerant-amount determination kit  100  of the present embodiment is configured to be able, after the sensor  10  is mounted, to determine, at any time, the refrigeration amount of the refrigeration cycle apparatus. 
     The use form of the refrigerant-amount determination kit  100  is, however, not limited to such a form. For example, the sensor  10  of the refrigerant-amount determination kit  100  may be mounted on at least one of the refrigeration cycle apparatus and the periphery of the refrigeration cycle apparatus only during refrigerant-amount determination. The refrigerant-amount determination kit  100  may be used repeatedly for refrigerant-amount determination of a plurality of refrigeration cycle apparatuses. 
     (2) Detailed Configuration of Air Conditioner 
     The air conditioner  200 , which is an example of the refrigeration cycle apparatus that is a target of refrigerant-amount determination of the refrigerant-amount determination kit  100 , will be described with reference to  FIG. 2 .  FIG. 2  is a schematic block diagram of the air conditioner  200 . An air temperature sensor  12 , a first refrigerant temperature sensor  14 , and a second refrigerant temperature sensor  16  drawn in  FIG. 2  are sensors of the refrigerant-amount determination kit  100  and not sensors originally installed in the air conditioner  200 . 
     The air conditioner  200  is an apparatus that performs cooling of an air conditioned space by utilizing a refrigeration cycle. The air conditioner  200 , however, may be an apparatus that performs heating of an air conditioned space in addition to cooling of the air conditioned space or instead of cooling of the air conditioned space. When the air conditioner  200  is an apparatus that performs both cooling and heating of an air conditioned space, a heat source unit  202  (described later) of the air conditioner  200  is provided with a mechanism, such as a four-way switching valve, for switching the flowing direction of a refrigerant. 
     The air conditioner  200  is provided with, mainly, the one heat source unit  202 , one utilization unit  204 , a liquid-refrigerant connection pipe  224   a  and a gas-refrigerant connection pipe  224   b,  and a control unit  280  (refer to  FIG. 2 ). The liquid-refrigerant connection pipe  224   a  and the gas-refrigerant connection pipe  224   b  are pipes that connect the heat source unit  202  and the utilization unit  204  to each other (refer to  FIG. 2 ). The control unit  280  controls operation of various devices of the heat source unit  202  and the utilization unit  204 . 
     The air conditioner  200  of the present embodiment includes one heat source unit  202  and one utilization unit  204  each other. The number of the heat source unit  202  and the utilization unit  204  is, however, not limited to one. The air conditioner  200  may include two or more of the heat source units  202  and may include two or more of the utilization units  204 . The air conditioner  200  may be an integration-type apparatus in which the heat source unit  202  and the utilization unit  204  are assembled into a single unit. 
     The heat source unit  202  and the utilization unit  204  are connected to each other via the liquid-refrigerant connection pipe  224   a  and the gas-refrigerant connection pipe  224   b,  thereby constituting a refrigerant circuit  220  (refer to  FIG. 2 ). A refrigerant is enclosed in the refrigerant circuit  220 . The refrigerant enclosed in the refrigerant circuit  220  is, for example, a fluorocarbon-based refrigerant, such as R32, but is not limited thereto. The refrigerant circuit  220  has a compressor  210 , a heat-source-side heat exchanger  230 , an expansion mechanism  250  of the heat source unit  202 , and a utilization-side heat exchanger  260  of the utilization unit  204  (refer to  FIG. 2 ). 
     (2-1) Utilization Unit 
     The utilization unit  204  is a unit to be installed in an air conditioned space. For example, the utilization unit  204  is a ceiling-embedded unit. The utilization unit  204  is, however, not limited to the ceiling-embedded unit and may be a unit of a ceiling suspension type, a wall mounted type, or a floor installation type. 
     The utilization unit  204  may be installed in a space other than an air conditioned space. For example, the utilization unit  204  may be installed in an attic, a machine room, a garage, or the like. In this case, an air passage through which air that has exchanged heat with a refrigerant in the utilization-side heat exchanger  260  is supplied from the utilization unit  204  to an air conditioned space is installed. The air passage is, for example, a duct. The type of the air passage is, however, not limited to a duct and is selectable, as appropriate. 
     The utilization unit  204  has, mainly, the utilization-side heat exchanger  260 , a utilization-side fan  270 , and a utilization-side control unit  284  (refer to  FIG. 2 ). 
     (2-1-1) Utilization-Side Heat Exchanger 
     The utilization-side heat exchanger  260  is a heat exchanger in which heat is exchanged between a refrigerant flowing in the utilization-side heat exchanger  260  and air of an air conditioned space. The utilization-side heat exchanger  260  is, for example, a fin-and-tube heat exchanger that has a plurality of heat transfer tubes and a plurality of fins (not illustrated); however, the type of the heat exchanger is not limited thereto. 
     The utilization-side heat exchanger  260  is connected at one end to a liquid-refrigerant pipe  226   a  and connected at the other end to a gas-refrigerant pipe  226   b.  The liquid-refrigerant pipe  226   a  is a pipe that is connected at one end to the liquid-refrigerant connection pipe  224   a  and connected at the other end to the utilization-side heat exchanger  260 . 
     The gas-refrigerant pipe  226   b  is a pipe connected at one end to the gas-refrigerant connection pipe  224   b  and connected at the other end to the utilization-side heat exchanger  260 . 
     During operation of the air conditioner  200 , the refrigerant flows in through the liquid-refrigerant pipe  226   a  to the liquid side of the utilization-side heat exchanger  260 , and the refrigerant flows out from the gas side of the utilization-side heat exchanger  260  into the gas-refrigerant pipe  226   b.  In the present embodiment, the utilization-side heat exchanger  260  functions as a refrigerant evaporator. 
     (2-1-2) Utilization-Side Fan 
     The utilization-side fan  270  is a mechanism that sucks air of an air conditioned space into a casing (not illustrated) of the utilization unit  204 , supplies the air to the utilization-side heat exchanger  260 , and blows out the air that has exchanged heat with the refrigerant in the utilization-side heat exchanger  260  into the air conditioned space. The utilization-side fan  270  is, for example, a turbo fan. The type of the utilization-side fan  270  is, however, not limited to the turbo fan and is selectable, as appropriate. 
     (2-1-3) Utilization-Side Control Unit 
     The utilization-side control unit  284  has a microcomputer, a memory in which a control program executable by the microcomputer is stored, and the like. Note that the configuration of the utilization-side control unit  284  described here is merely an example, and the function of the utilization-side control unit  284  may be realized by a software, may be realized by a hardware, and may be realized by a combination of a software and a hardware. 
     The utilization-side control unit  284  is electrically connected to the utilization-side fan  270  (refer to  FIG. 2 ). 
     The utilization-side control unit  284  is connected, through a transmission line  286 , to a heat-source-side control unit  282  of the heat source unit  202  in a state of being capable of performing an exchange of control signals and the like. The utilization-side control unit  284  and the heat-source-side control unit  282  may be communicably connected to each other wirelessly, instead of through a physical communication line. The utilization-side control unit  284  and the heat-source-side control unit  282  cooperate with each other to function as the control unit  280  that controls operation of the air conditioner  200 . The control unit  280  will be described later. 
     (2-2) Heat Source Unit 
     The heat source unit  202  is disposed outside the air conditioned space. The heat source unit  202  is installed, for example, on a roof floor of a building in which the air conditioner  200  is installed or adjacent to the building. 
     The heat source unit  202  has, mainly, the compressor  210 , the heat-source-side heat exchanger  230 , the expansion mechanism  250 , a heat-source-side fan  240 , and the heat-source-side control unit  282  (refer to  FIG. 2 ). 
     The heat source unit  202 , however, does not necessarily have all of the aforementioned constituent elements; the constituent elements of the heat source unit  202  are selectable, as appropriate. For example, the heat source unit  202  may not include the expansion mechanism  250  as a constituent, and the utilization unit  204 , instead of the heat source unit  202 , may have a similar expansion mechanism. 
     The heat source unit  202  has a suction pipe  222   a,  a discharge pipe  222   b,  and a liquid-refrigerant pipe  222   c  (refer to  FIG. 2 ). The suction pipe  222   a  connects the gas-refrigerant connection pipe  224   b  and the suction side of the compressor  210  to each other (refer to  FIG. 2 ). The discharge pipe  222   b  connects the discharge side of the compressor  210  and the gas side of the heat-source-side heat exchanger  230  to each other (refer to  FIG. 2 ). The liquid-refrigerant pipe  222   c  connects the liquid side of the heat-source-side heat exchanger  230  and the liquid-refrigerant connection pipe  224   a  to each other (refer to  FIG. 2 ). The liquid-refrigerant pipe  222   c  is provided with the expansion mechanism  250  (refer to  FIG. 2 ). 
     (2-2-1) Compressor 
     The compressor  210  is a device that sucks a low-pressure refrigerant of the refrigeration cycle through the suction pipe  222   a,  compresses the refrigerant with a compression mechanism (not illustrated), and discharges the compressed refrigerant into the discharge pipe  222   b.  In the present embodiment, the heat source unit  202  has one compressor  210 ; however, the number of the compressors  210  of the heat source unit  202  is not limited to one. The heat source unit  202  may have a plurality of the compressors  210 . 
     The compressor  210  is, for example, a displacement compressor of a rotary type or a scroll type; however, the type of the compressor  210  is not limited thereto. The compression mechanism (not illustrated) of the compressor  210  is driven by a motor  210   a  (refer to  FIG. 2 ). As a result of the compression mechanism (not illustrated) being driven by the motor  210   a,  the refrigerant is compressed by the compression mechanism. In the present embodiment, the motor  210   a  rotates at a constant speed. In other words, the compressor  210  of the present embodiment is a constant-speed compressor. 
     (2-2-2) Heat-source-Side Heat Exchanger 
     The heat-source-side heat exchanger  230  is a heat exchanger in which heat is exchanged between the refrigerant flowing in the heat-source-side heat exchanger  230  and air at an installation place of the heat source unit  202 . In the present embodiment, the heat-source-side heat exchanger  230  functions as a refrigerant condenser. The heat-source-side heat exchanger  230  is, for example, a fin-and-tube heat exchanger that has a plurality of heat transfer tubes and a plurality of fins (not illustrated); however, the type of the heat-source-side heat exchanger  230  is not limited thereto. 
     The heat-source-side heat exchanger  230  is connected at an end portion on the liquid side to the liquid-refrigerant pipe  222   c  and connected at an end portion on the gas side to the discharge pipe  222   b.    
     During operation of the air conditioner  200 , the refrigerant flows in through the discharge pipe  222   b  to the gas side of the heat-source-side heat exchanger  230 , and the refrigerant flows out from the liquid-side of the heat-source-side heat exchanger  230  into the liquid-refrigerant pipe  222   c.  In the present embodiment, the heat-source-side heat exchanger  230  functions as a refrigerant condenser. 
     (2-2-3) Expansion Mechanism 
     In the refrigerant circuit  220 , the expansion mechanism  250  is disposed in the liquid-refrigerant pipe  222   c  between the heat-source-side heat exchanger  230  and the utilization-side heat exchanger  260  (refer to  FIG. 2 ). When the utilization unit  204  has an expansion mechanism similar to the expansion mechanism  250 , instead of the expansion mechanism  250  included in the heat source unit  202 , the expansion mechanism is disposed in the liquid-refrigerant pipe  226   a  of the utilization unit  204 . 
     The expansion mechanism  250  adjusts the pressure and the flow rate of a refrigerant flowing in the liquid-refrigerant pipe  222   c.  In the present embodiment, the expansion mechanism  250  is a capillary tube. The expansion mechanism  250  is, however, not limited to a capillary tube and may be, for example, an expansion valve of a temperature sensitive cylinder type. 
     (2-2-4) Heat-Source-Side Fan 
     The heat-source-side fan  240  is a mechanism that sucks air around the heat source unit  202  into the casing (not illustrated) of the heat source unit  202 , supplies the air to the heat-source-side heat exchanger  230 , and blows out the air that has exchanged heat with the refrigerant in the heat-source-side heat exchanger  230  to the outside of the casing of the heat source unit  202 . The heat-source-side fan  240  is, for example, a propeller fan. The type of the fan of the heat-source-side fan  240  is, however, not limited to the propeller fan and is selectable, as appropriate. 
     (2-2-5) Heat-Source-Side Control Unit 
     The heat-source-side control unit  282  has a microcomputer, a memory in which a control program executable by the microcomputer is stored, and the like. Note that the configuration of the heat-source-side control unit  282  described here is merely an example, and the function of the utilization-side control unit  284  may be realized by a software, may be realized by a hardware, or may be realized by a combination of a software and a hardware. 
     The heat-source-side control unit  282  is electrically connected to the compressor  210  and the heat-source-side fan  240  (refer to  FIG. 2 ). 
     The heat-source-side control unit  282  is connected, through a transmission line  286 , to the utilization-side control unit  284  of the utilization unit  204  in a state of being capable of performing an exchange of control signals and the like. The heat-source-side control unit  282  and the utilization-side control unit  284  cooperate with each other to function as the control unit  280  that controls operation of the air conditioner  200 . The control unit  280  will be described later. 
     (2-3) Refrigerant Connection Pipe 
     The air conditioner  200  has, as connection pipes that connect the utilization unit  204  and the heat source unit  202  to each other, the liquid-refrigerant connection pipe  224   a  and the gas-refrigerant connection pipe  224   b.  The liquid-refrigerant connection pipe  224   a  and the gas-refrigerant connection pipe  224   b  are pipes that are to be constructed at an installation site of the air conditioner  200  during installation of the air conditioner  200 . As the liquid-refrigerant connection pipe  224   a  and the gas-refrigerant connection pipe  224   b,  pipes of various lengths and diameters are used depending on an installation place, installation conditions such as a combination of the heat source unit  202  and the utilization unit  204 , and the like. 
     (2-4) Control Unit 
     The control unit  280  is constituted by the heat-source-side control unit  282  of the heat source unit  202  and the utilization-side control unit  284  of the utilization unit  204  being communicably connected to each other through the transmission line  286 . In the control unit  280 , the microcomputers of the heat-source-side control unit  282  and the utilization-side control unit  284  control operation of the air conditioner  200  by executing the programs stored in the memories. Note that the configuration of the control unit  280  described here is merely an example, and the control unit  280  may be realized by a software, may be realized by a hardware, and may be realized by a combination of a software and a hardware. 
     In the present embodiment, the heat-source-side control unit  282  and the utilization-side control unit  284  constitute the control unit  280 . The configuration of the control unit  280  is, however, not limited to such a form. For example, in addition to the heat-source-side control unit  282  and the utilization-side control unit  284  or instead of the heat-source-side control unit  282  and the utilization-side control unit  284 , the air conditioner  200  may have a controller that realizes part of or all of the function of the control unit  280  described below. 
     As illustrated in  FIG. 2 , the control unit  280  is electrically connected to the compressor  210  and various devices of the heat source unit  202  and the utilization unit  204  including the heat-source-side fan  240  and the utilization-side fan  270 . 
     The control unit  280  is communicably connected to, for example, a thermostat (not illustrated). The thermostat is a temperature controller of the air conditioned space and is a device that transmits an operation command and a stop command of operation to the air conditioner  200  in accordance with the temperature of the air conditioned space. For example, the thermostat transmits the operation command to the air conditioner  200  when the temperature of the air conditioned space is higher than a first temperature and transmits the stop command to the air conditioner  200  when the temperature of the air conditioned space is lower than a second temperature. The second temperature is a temperature lower than the first temperature. On the basis of a command transmitted from the thermostat, the control unit  280  controls operation of the various devices of the air conditioner  200  such as the compressor  210 , the heat-source-side fan  240  and the utilization-side fan  270 . 
     The control unit  280  may stop the operation of the air conditioner  200  in response to, in addition to or instead of the command from the thermostat, an operation of a user to an operation switch (not illustrated). 
     During operation of the air conditioner  200 , the control unit  280  operates the compressor  210 , the heat-source-side fan  240 , and the utilization-side fan  270 . In this air conditioner  200 , the number of rotations of the motor  210   a  of the compressor  210  is constant. 
     During operation of the air conditioner  200 , the refrigerant flows in the refrigerant circuit  220  as follows. 
     When the compressor  210  is started, a low-pressure gas refrigerant of the refrigeration cycle is sucked into the compressor  210  and compressed in the compressor  210 , thereby becoming a high-pressure gas refrigerant of the refrigeration cycle. The high-pressure gas refrigerant is sent to the heat-source-side heat exchanger  230  and condensed by exchanging heat with a heat-source air supplied by the heat-source-side fan  240 , thereby becoming a high-pressure liquid refrigerant. The high-pressure liquid refrigerant flows in the liquid-refrigerant pipe  222   c,  becomes a gas-liquid two-phase state refrigerant by being decompressed in the expansion mechanism  250  to a pressure close to a suction pressure of the compressor  210 , and is sent to the utilization unit  204 . The gas-liquid two-phase state refrigerant that has been sent to the utilization unit  204  evaporates in the utilization-side heat exchanger  260  by exchanging heat with air of the air conditioned space supplied to the utilization-side heat exchanger  260  by the utilization-side fan  270 , thereby becoming a low-pressure gas refrigerant. The low-pressure gas refrigerant is sent to the heat source unit  202  via the gas-refrigerant connection pipe  224   b  and sucked into the compressor  210 . The temperature of the air supplied to the utilization-side heat exchanger  260  decreases by exchanging heat with the refrigerant flowing in the utilization-side heat exchanger  260 , and the air cooled in the utilization-side heat exchanger  260  is blown out into the air conditioned space. 
     (3) Refrigerant-Amount Determination Kit 
     The refrigerant-amount determination kit  100  has, mainly, the sensor  10 , a communication device  20 , and the server  30 . Preferably, the refrigerant-amount determination kit  100  further has heat insulation members  14   a  and  16   a.    
     (3-1) Sensor 
     The sensor  10  includes the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16 . The air temperature sensor  12  is a sensor that measures the temperature of heat-source air around the heat source unit  202 . The first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  are sensors that measure the temperature of the refrigerant. Hereinafter, the first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  are sometimes collectively referred to as a first sensor group  15 . The air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  are, for example, thermistors. 
     The air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  are communicably connected to the communication device  20 . The air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  each measures the temperature of a measurement target and transmits a measurement result to the communication device  20 . For example, the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  periodically measure the temperature of a measurement target and transmit measurement results to the communication device  20 . For example, the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  measure the temperature of the measurement target once per one minute and transmits measurement results to the communication device  20 . 
     The air temperature sensor  12  is mounted on the periphery of the heat source unit  202  of the air conditioner  200 . The air temperature sensor  12  may be mounted at an air intake port of the casing (not illustrated) of the heat source unit  202  of the air conditioner  200 . The air temperature sensor  12  measures the temperature of heat-source air. In other words, the air temperature sensor  12  measures the temperature of air around the heat source unit  202 . In the present embodiment, the air temperature sensor  12  detects the temperature of outside air at the installation place of the air conditioner  200 . 
     The first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  constituting the first sensor group  15  are each mounted on a portion of the air conditioner  200 . The first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  are mounted on the air conditioner  200  by using, for example, plate springs as metal fixtures. The fixing method is, however, not limited thereto. The first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  detect the temperature of a refrigerant flowing in the refrigerant circuit  220  of the air conditioner  200 . 
     In the present embodiment, the first refrigerant temperature sensor  14  is mounted on the heat-source-side heat exchanger  230  (refer to  FIG. 2 ). For example, the first refrigerant temperature sensor  14  is mounted on a heat transfer tube (not illustrated) of the heat-source-side heat exchanger  230  (refer to  FIG. 2 ). The first refrigerant temperature sensor  14  measures the temperature of the refrigerant flowing in the heat-source-side heat exchanger  230 . In other words, the first refrigerant temperature sensor  14  detects the condensation temperature of the refrigerant in the refrigerant circuit  220 . 
     In the present embodiment, the second refrigerant temperature sensor  16  is mounted, in the liquid-refrigerant pipe  222   c  of the heat source unit  202 , on the upstream side of the expansion mechanism  250  in a refrigerant flowing direction in the refrigerant circuit  220  (refer to  FIG. 2 ). In other words, the second refrigerant temperature sensor  16  is mounted on a portion of the liquid-refrigerant pipe  222   c,  the portion connecting the heat-source-side heat exchanger  230  and the expansion mechanism  250  to each other. The second refrigerant temperature sensor  16  detects the temperature of the refrigerant of the refrigerant circuit  220  at an outlet of the heat-source-side heat exchanger  230  as a condenser. 
     The first refrigerant temperature sensor  14  is preferably covered by the heat insulation member  14   a  to reduce direct contact between a temperature detection portion of the first refrigerant temperature sensor  14  and peripheral air and thereby reduce an influence applied on the measurement of the first refrigerant temperature sensor  14  by peripheral air. The second refrigerant temperature sensor  16  is preferably covered by the heat insulation member  16   a  to reduce direct contact between a temperature detection portion of the second refrigerant temperature sensor  16  and peripheral air and to thereby reduce an influence applied on the measurement of the second refrigerant temperature sensor  16  by the peripheral air. As the material of the heat insulation member  14   a  and the heat insulation member  16   a,  for example, expanded plastic is used. The material is, however, not limited thereto. 
     (3-2) Communication Device 
     The communication device  20  is a unit that transmits data detected by the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  to the server  30 . In other words, the communication device  20  functions as a gateway that performs relay processing between the sensor  10  and the server  30 . 
     The communication device  20  is communicably connected to the sensor  10  through, for example, a wireless network, such as wireless LAN, Bluetooth (registered trademark), or the like. The communication device  20  and the sensor  10 , however, do not necessarily communicate with each other wirelessly and may be communicably connected to each other by wire. The communication device  20  receives measurement data transmitted by the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16 . 
     The communication device  20  is communicably connected to the server  30  through the network NW such as the Internet. The communication device  20  transmits measurement data transmitted by the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  to the server  30  successively. Alternatively, the communication device  20  may transmit the measurement data transmitted by the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  collectively, as appropriate. For example, the communication device  20  may transmit measurement data transmitted every one minute by the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  to the server  30  collectively every one hour. 
     In the present embodiment, the refrigerant-amount determination kit  100  has the communication device  20  separately from the sensor  10  and transmits measurement data of the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  to the server  30  via the communication device  20 . The configuration of the refrigerant-amount determination kit  100  is, however, not limited thereto. Some or all of the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  may be devices directly connectable to the network NW, such as the Internet, and may transmit the measurement data directly to the server  30 . In other words, some or all of the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  may have a communication device capable of directly communicating with the server  30  through the network NW. 
     (3-3) Server 
     The server  30  is a computer connected to the sensor  10  through the network NW and the communication device  20 . The server  30  may be a single computer or may be constituted by a plurality of computers. 
     The server  30  functions as a determination device that determines, in response to a CPU  32  executing a program stored in a storage device  34 , the amount of the refrigerant in the refrigerant circuit  220  based on a detection result detected by the sensor  10  during operation of the air conditioner  200 . In the present embodiment, the server  30  functions as a determination device in the single refrigerant-amount determination kit  100 . The server  30 , however, may function as a determination device in a plurality of refrigerant-amount determination kits. 
     Operation of the server  30  as a determination device will be described with reference to the flowchart in  FIG. 3 . 
     In the server  30 , the measurement data of the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  transmitted from the communication device  20  is stored as time-series data in the storage device  34  (step S 1 ). 
     Next, when determined that conditions for executing refrigerant-amount determination are established (Yes in the step S 2 ), the server  30  starts determination of the amount of the refrigerant in the refrigerant circuit  220  of the air conditioner  200  (step S 3 ). 
     The server  30  determines that the conditions for executing refrigerant-amount determination are established, for example, at a following case. The server  30  determines that the conditions for executing refrigerant-amount determination are established, for example, at fixed intervals. Specifically, the server  30  determines that the conditions for executing refrigerant-amount determination are established, for example, every time point when three months have elapsed after a last refrigerant-amount determination. The server  30  may determine that the conditions for executing refrigerant-amount determination are established, for example, when received an execution instruction of a user of the refrigerant-amount determination kit  100  for refrigerant-amount determination processing. The execution instruction of the user is transmitted to the server  30  from, for example, a computer or a mobile device capable of communicating with the server  30  through the Internet. 
     Next, the server  30  determines the measurement data to be used in refrigerant-amount determination, for example, as follows (step S 4 ). 
     First, the server  30  identifies measurement data during operation of the air conditioner  200  among measurement data of the air temperature sensor  12 , the first refrigerant temperature sensor  14 , and the second refrigerant temperature sensor  16  during a latest predetermined period, the measurement data being stored in the storage device  34 . For example, the server  30  identifies the measurement data during operation of the air conditioner  200  among measurement data of the sensors  12 ,  14 , and  16  during latest one hour, the measurement data being stored in the storage device  34 . For example, the server  30  determines the measurement data of the sensors  12 ,  14 , and  16  at a time point when a temperature measured by the first refrigerant temperature sensor  14  is higher than a temperature measured by the air temperature sensor  12  by a predetermined temperature or more as the measurement data during operation of the air conditioner  200 . The method by which the server  30  identifies measurement data during operation of the air conditioner  200  among the measurement data of the sensors  12 ,  14 , and  16  is merely an example. For example, the server  30  may determine the measurement data of the sensors  12 ,  14 , and  16  at a time point when a temperature measured by the second refrigerant temperature sensor  16  is higher than a temperature measured by the air temperature sensor  12  by a predetermined temperature or more as measurement data during operation of the air conditioner  200 . In addition, the server  30  may acquire signals of an operation command and a stop command from the thermostat that transmits the operation command and the stop command to the air conditioner  200 , and the server  30  may identify the measurement data of the sensors  12 ,  14 , and  16  during operation of the air conditioner  200  based on the signals. 
     Further, the server  30  identifies measurement data of the sensors  12 ,  14 , and  16  during stable operation among the measurement data of the sensors  12 ,  14 , and  16  during operation of the air conditioner  200 . Here, “during stable operation” means a period during which a condensation temperature measured by the first refrigerant temperature sensor  14  or the temperature of a refrigerant measured by the second refrigerant temperature sensor  16  has little fluctuation. The server  30  determines the measurement data of the sensors  12 ,  14 , and  16  during stable operation of the air conditioner  200  as measurement data of the sensors  12 ,  14 , and  16  to be used in refrigerant-amount determination. 
     Next, the server  30  calculates the degree of subcooling in the refrigeration cycle by using a measurement value of the first refrigerant temperature sensor  14  and a measurement value of the second refrigerant temperature sensor  16  in the air conditioner  200  during stable operation (Step S 5 ). Specifically, the server  30  calculates the degree of subcooling by subtracting the measurement value of the second refrigerant temperature sensor  16  from the measurement value of the first refrigerant temperature sensor  14 . When the measurement data of the sensors  12 ,  14 , and  16  during stable operation of the air conditioner  200  includes measurement data at a plurality of time points, an average value, an intermediate value, or the like of the degrees of subcooling at the plurality of time points may be calculated as the degree of subcooling. 
     Next, the server  30  determines the refrigerant amount of the refrigerant circuit  220  based on an outside air temperature, which is a measurement value of the air temperature sensor  12  during stable operation of the air conditioner  200 , and the degree of subcooling calculated in the step S 5  (Step S 6 ). When the measurement data of the sensors  12 ,  14 , and  16  during stable operation of the air conditioner  200  includes measurement data at a plurality of time points, the server  30  may use, as the outside air temperature, an average value, an intermediate value, or the like of outside air temperatures at the plurality of time points. For example, when the measurement data of the sensors  12 ,  14 , and  16  during stable operation of the air conditioner  200  includes measurement data at a plurality of time points, the server  30  may determine the refrigerant amount of the refrigerant circuit  220  based on the average value of outside air temperatures at the plurality of time points and the average value of the degrees of subcooling at the plurality of time points. 
     An example of the refrigerant-amount determination method will be described in detail. 
     The storage device  34  of the server  30  stores a table or a formula in which the outside air temperature and a reference degree of subcooling of the air conditioner  200 , which is a degree of subcooling when the refrigerant amount of the refrigerant circuit  220  is proper, are in association with each other. For example, the table or formula in which the outside air temperature and the reference degree of subcooling are in association with each other may be theoretically calculated, or may be obtained based on a result of operation using an experimental apparatus of the air conditioner. The table or the formula in which the outside air temperature and the reference degree of subcooling are in association with each other may be generated by the server  30  based on the data that has been collected by using the sensor  10  during the past actual operation of the air conditioner  200  for which evaluation of the refrigerant amount is to be performed. The table or the formula in which an outside air temperature and the reference degree of subcooling are in association with each other may be generated by the server  30  based on the data of past actual operation of an air conditioner that differs from the air conditioner  200  for which evaluation of the refrigerant amount is to be performed. 
     The server  30  determines that the refrigerant amount of the refrigerant circuit  220  is small, for example, when the degree of subcooling calculated in the step S 5  is smaller than the value of (reference degree of subcooling—tolerance). When the degree of subcooling calculated in the step S 5  is more than or equal to the value of (reference degree of subcooling—tolerance), the server  30  determines that the refrigerant amount of the refrigerant circuit  220  is a proper amount. 
     When determined that the refrigerant amount of the air conditioner  200  is small, the server  30  preferably reports that the refrigerant amount of the air conditioner  200  is small to an operator of the refrigerant-amount determination kit  100 , a user of the air conditioner  200 , or the like. For example, the server  30  displays on a display (not illustrated) information reporting a shortage of the refrigerant amount. The server  30  may report the shortage of the refrigerant amount on a portable terminal or the like held by an operator of the refrigerant-amount determination kit  100  or a user of the air conditioner  200 . 
     The aforementioned flow of refrigerant-amount determination processing is merely an example. For example, according to the above description, the server  30  performs refrigerant-amount determination by using previously acquired measurement data of the sensors  12 ,  14 , and  16 . As an alternative to this, the server  30  may perform refrigerant-amount determination by using measurement data of the sensors  12 ,  14 , and  16  acquired after the conditions for executing the determination are established (after Yes is determined in the step S 2 ). 
     (4) Features 
     (4-1) 
     The refrigerant-amount determination kit  100  of the first embodiment includes the sensor  10  and the server  30  as an example of the determination device. The sensor  10  is mounted at least temporarily on at least one of a portion of the air conditioner  200  and the periphery of the air conditioner  200 . The air conditioner  200  is an apparatus that has the refrigerant circuit  220  including the compressor  210 , the heat-source-side heat exchanger  230  as a condenser, and the utilization-side heat exchanger  260  as an evaporator. The server  30  determines the amount of the refrigerant in the refrigerant circuit  220  based on a detection result detected by the sensor  10  during operation of the air conditioner  200 . 
     The refrigerant-amount determination kit  100  of the present embodiment is highly convenient because it is possible to perform refrigerant-amount determination easily even when the sensor  10  required for the refrigerant-amount determination is not provided in the air conditioner  200 . 
     (4-2) 
     In the refrigerant-amount determination kit  100  of the first embodiment, the sensor  10  includes the first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  that detect the temperature of the refrigerant flowing in the refrigerant circuit  220 . 
     In the refrigerant-amount determination kit  100  of the present embodiment, it is possible to perform refrigerant-amount determination with high accuracy by using a refrigerant temperature detected by the sensor  10 . 
     (4-3) 
     The refrigerant-amount determination kit  100  of the first embodiment includes the heat insulation members  14   a  and  16   a  that cover the peripheries of the first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16 . 
     In the refrigerant-amount determination kit  100  of the present embodiment, accurate detection of the refrigerant temperature is achieved, and it is possible to perform refrigerant-amount determination with high accuracy based on the detection result. 
     (4-4) 
     In the refrigerant-amount determination kit  100  of the first embodiment, the sensor  10  includes the first sensor group  15 . The first sensor group  15  includes the first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16 . The first refrigerant temperature sensor  14  detects the condensation temperature of the refrigerant in the refrigerant circuit  220 . The second refrigerant temperature sensor  16  detects the temperature of the refrigerant at the outlet of the heat-source-side heat exchanger  230 , which functions as the condenser of the refrigerant circuit  220 . 
     In the refrigerant-amount determination kit  100  of the present embodiment, it is possible to perform refrigerant-amount determination with high accuracy by utilizing the value of the degree of subcooling. 
     In particular, in the refrigerant-amount determination kit  100  of the first embodiment, the sensor  10  includes the air temperature sensor  12  that detects the outside air temperature at the installation place of the air conditioner  200 . 
     In the refrigerant-amount determination kit  100  of the present embodiment, the server  30  performs refrigerant-amount determination based on the value of the degree of subcooling measured by using the sensor  10  considering the actual measurement value of the outside air temperature. Therefore, the refrigerant-amount determination kit  100  of the present embodiment is able to perform refrigerant-amount determination with high accuracy. 
     Second Embodiment 
     A refrigerant-amount determination kit  100 ′ of a second embodiment will be described with reference to  FIG. 4  to  FIG. 6 .  FIG. 4  is a block diagram of the refrigerant-amount determination kit  100 ′.  FIG. 5  is a schematic block diagram of the air conditioner  200 .  FIG. 5  is similar to  FIG. 2  except for the attached position of the sensor  10  of the refrigerant-amount determination kit  100 ′.  FIG. 6  is an example of the flowchart of refrigerant-amount determination processing of the air conditioner  200  performed by the refrigerant-amount determination kit  100 ′. 
     The refrigerant-amount determination kit  100 ′ of the second embodiment is similar to the refrigerant-amount determination kit  100  of the first embodiment except for the position at which a first refrigerant temperature sensor  14 ′ and a second refrigerant temperature sensor  16 ′ are mounted on the air conditioner  200  and the refrigerant-amount determination processing of a server  30 ′. Description here will be thus provided mainly on the difference between the refrigerant-amount determination kit  100 ′ of the second embodiment and the refrigerant-amount determination kit  100  of the first embodiment, and description about features common therebetween are omitted. Description of the air conditioner  200  for which refrigerant-amount determination is to be performed by the refrigerant-amount determination kit  100 ′ is omitted here because the air conditioner  200  has already been described in the first embodiment. 
     (1) Sensor 
     In the present embodiment, the sensor  10  includes the air temperature sensor  12 , the first refrigerant temperature sensor  14 ′, and the second refrigerant temperature sensor  16 ′. 
     The air temperature sensor  12  is similar to the air temperature sensor  12  of the first embodiment. The first refrigerant temperature sensor  14 ′ and the second refrigerant temperature sensor  16 ′ are similar to the first refrigerant temperature sensor  14  and the second refrigerant temperature sensor  16  of the first embodiment respectively except for installation positions thereof with respect to the air conditioner  200 . Hereinafter, the first refrigerant temperature sensor  14 ′ and the second refrigerant temperature sensor  16 ′ are sometimes referred to as a second sensor group  15 ′. 
     The first refrigerant temperature sensor  14 ′ and the second refrigerant temperature sensor  16 ′ constituting the second sensor group  15 ′ are each mounted on a portion of the air conditioner  200 . 
     In the present embodiment, the first refrigerant temperature sensor  14 ′ is mounted on the utilization-side heat exchanger  260  (refer to  FIG. 5 ). For example, the first refrigerant temperature sensor  14 ′ is mounted on a heat transfer tube (not illustrated) of the utilization-side heat exchanger  260  (refer to  FIG. 5 ). The first refrigerant temperature sensor  14 ′ measures the temperature of the refrigerant flowing in the utilization-side heat exchanger  260 . In other words, the first refrigerant temperature sensor  14 ′ detects the evaporation temperature of the refrigerant in the refrigerant circuit  220 . 
     In the present embodiment, the second refrigerant temperature sensor  16 ′ is mounted on the gas-refrigerant pipe  226   b  of the utilization unit  204  (refer to  FIG. 5 ). The second refrigerant temperature sensor  16 ′ measures the temperature of a refrigerant flowing in the gas-refrigerant pipe  226   b.  In other words, the second refrigerant temperature sensor  16 ′ detects the temperature of the refrigerant at an outlet of the utilization-side heat exchanger  260  as an evaporator of the refrigerant circuit  220 . 
     As with the first embodiment, the first refrigerant temperature sensor  14 ′ and the second refrigerant temperature sensor  16 ′ are preferably provided with the heat insulation members  14   a  and  16   a,  respectively. 
     (2) Server 
     The server  30 ′ has a physical configuration identical to that in the first embodiment and partly differs from the first embodiment in terms of only an operation as a determination device. The operation of the server  30 ′ as a determination device will be described with reference to the flowchart in  FIG. 6 . 
     In the server  30 ′, the measurement data of the air temperature sensor  12 , the first refrigerant temperature sensor  14 ′, and the second refrigerant temperature sensor  16 ′ transmitted from the communication device  20  is stored in the storage device  34  as time-series data (step S 11 ). 
     Next, when determined that conditions for executing refrigerant-amount determination are established (Yes in the Step S 12 ), the server  30 ′ starts determination of the amount of the refrigerant in the refrigerant circuit  220  of the air conditioner  200  (step S 13 ). The conditions for executing refrigerant-amount determination are identical to those in the first embodiment, and thus, description thereof is omitted. 
     Next, the server  30 ′ determines the measurement data to be used in refrigerant-amount determination, for example, as follows (step S 14 ). 
     First, the server  30 ′ identifies measurement data during operation of the air conditioner  200  among measurement data of the air temperature sensor  12 , the first refrigerant temperature sensor  14 ′, and the second refrigerant temperature sensor  16 ′ during a latest predetermined period, the measurement data being stored in the storage device  34 . For example, the server  30 ′ identifies measurement data during operation of the air conditioner  200  among the measurement data of the sensors  12 ,  14 ′, and  16 ′ during latest one hour, the measurement data being stored in the storage device  34 . For example, the server  30 ′ determines the measurement data of the sensors  12 ,  14 ′, and  16 ′ at a time point when a temperature measured by the first refrigerant temperature sensor  14 ′ is lower than a predetermined temperature as the measurement data during operation of the air conditioner  200 . The method by which the server  30 ′ identifies measurement data during operation of the air conditioner  200  among the measurement data of the sensors  12 ,  14 ′, and  16 ′ is merely an example. The identification method may be selected, as appropriate, as with the first embodiment. 
     Further, the server  30 ′ identifies measurement data of the sensors  12 ,  14 ′, and  16 ′ during stable operation among the measurement data of the sensors  12 ,  14 ′, and  16 ′ during operation of the air conditioner  200 . Here, “during stable operation” means a period during which an evaporation temperature measured by the first refrigerant temperature sensor  14 ′ or the temperature of the refrigerant measured by the second refrigerant temperature sensor  16 ′ has little fluctuation. The server  30 ′ determines the measurement data of the sensors  12 ,  14 ′, and  16 ′ during stable operation of the air conditioner  200  as measurement data of the sensors  12 ,  14 ′, and  16 ′ to be used in refrigerant-amount determination. 
     Next, the server  30 ′ calculates the degree of superheating in the refrigeration cycle by using a measurement value of the first refrigerant temperature sensor  14 ′ and a measurement value of the second refrigerant temperature sensor  16 ′ in the air conditioner  200  during stable operation (step S 15 ). Specifically, the server  30 ′ calculates the degree of superheating by subtracting the measurement value of the first refrigerant temperature sensor  14 ′ from the measurement value of the second refrigerant temperature sensor  16 ′. When the measurement data of the sensors  12 ,  14 ′, and  16 ′ during stable operation of the air conditioner  200  includes measurement data at a plurality of time points, an average value, an intermediate value, or the like of the degrees of superheating at the plurality of time points may be calculated as the degree of superheating. 
     Next, the server  30 ′ determines the refrigerant amount of the refrigerant circuit  220  based on an outside air temperature, which is a measurement value of the air temperature sensor  12  during stable operation of the air conditioner  200 , and the degree of superheating calculated in the step S 15  (step S 16 ). When the measurement data of the sensors  12 ,  14 ′, and  16 ′ during stable operation of the air conditioner  200  includes measurement data at a plurality of time points, the server  30 ′ may use, as the outside air temperature, an average value, an intermediate value, or the like of outside air temperatures at the plurality of time points. For example, when the measurement data of the sensors  12 ,  14 ′, and  16 ′ during stable operation of the air conditioner  200  includes measurement data at a plurality of time points, the server  30 ′ may determine the refrigerant amount of the refrigerant circuit  220  based on the average value of outside air temperatures at the plurality of time points and the average value of the degrees of superheating at the plurality of time points. 
     An example of the refrigerant-amount determination method will be described in detail. 
     The storage device  34  of the server  30 ′ stores a table or a formula in which the outside air temperature and a reference degree of superheating of the refrigerant circuit  220  of the air conditioner  200 , which is a degree of superheating when the refrigerant amount of the refrigerant circuit  220  is proper, are in association with each other. For example, the table or formula in which the outside air temperature and the reference degree of superheating are in association with each other may be theoretically calculated, or may be obtained based on a result of operation using an experimental apparatus of the air conditioner. The table or the formula in which the outside air temperature and the reference degree of superheating are in association with each other may be generated by the server  30 ′ based on the data that has been collected by using a sensor  10 ′ during the past actual operation of the air conditioner  200  for which evaluation of the refrigerant amount is to be performed. The table or the formula in which an outside air temperature and the reference degree of superheating are in association with each other may be generated by the server  30 ′ based on the data of past actual operation of an air conditioner that differs from the air conditioner  200  for which evaluation of the refrigerant amount is to be performed. 
     The server  30 ′ determines that the refrigerant amount of the refrigerant circuit  220  is small, for example, when the degree of superheating calculated in the step S 15  is larger than the value of (reference degree of superheating +tolerance). When the degree of superheating calculated in the step S 15  is less than or equal to the value of (reference degree of superheating +tolerance), the server  30 ′ determines that the refrigerant amount of the refrigerant circuit  220  is proper amount. 
     As with the server  30  of the first embodiment, when determined that the refrigerant amount of the air conditioner  200  is small, the server  30 ′ preferably reports the determination that the refrigerant amount of the air conditioner  200  is small to an operator of the refrigerant-amount determination kit  100 , a user of the air conditioner  200 , or the like. 
     The aforementioned flow of refrigerant-amount determination processing is merely an example. For example, according to the above description, the server  30 ′ performs refrigerant-amount determination by using previously acquired measurement data of the sensors  12 ,  14 ′, and  16 ′. As an alternative to this, the server  30 ′ may perform refrigerant-amount determination by using measurement data of the sensors  12 ,  14 ′, and  16 ′ acquired after the conditions for executing the determination are established (after Yes is determined in the step S 12 ). 
     (3) Features 
     The refrigerant-amount determination kit  100 ′ of the second embodiment has features similar to those in (4-1) to (4-3) of the refrigerant-amount determination kit  100  of the first embodiment. In addition, the refrigerant-amount determination kit  100 ′ of the second embodiment has following features. 
     In the refrigerant-amount determination kit  100 ′ of the second embodiment, the sensor  10 ′ includes the second sensor group  15 ′. The second sensor group  15 ′ includes the first refrigerant temperature sensor  14 ′ and the second refrigerant temperature sensor  16 ′. The first refrigerant temperature sensor  14 ′ detects the evaporation temperature of the refrigerant in the refrigerant circuit  220 . The second refrigerant temperature sensor  16 ′ detects the temperature of the refrigerant at the outlet of the utilization-side heat exchanger  260 , which functions as an evaporator of the refrigerant circuit  220 . 
     In the refrigerant-amount determination kit  100 ′ of the present embodiment, it is possible to perform refrigerant-amount determination with high accuracy by utilizing the value of the degree of subheating measured by using the sensor  10 ′. 
     In particular, in the refrigerant-amount determination kit  100 ′ of the second embodiment, the sensor  10 ′ includes the air temperature sensor  12  that detects the outside air temperature at the installation place of the air conditioner  200 . 
     In addition, in the refrigerant-amount determination kit  100 ′ of the present embodiment, the server  30 ′ performs refrigerant-amount determination based on the value of the degree of superheating measured by using the sensor  10 ′ considering the actual measurement value of the outside air temperature. Therefore, the refrigerant-amount determination kit  100 ′ of the present embodiment is able to perform refrigerant-amount determination with high accuracy. 
     Modifications 
     Modifications of the aforementioned embodiments will be described. The following modifications may be combined together, as appropriate, within a scope that causes no inconsistency. 
     (1) Modification A 
     In the aforementioned embodiments, the refrigerant-amount determination kits  100  and  100 ′ have the sensors  10  and  10 ′ and the servers  30  and  30 ′ connected to the sensors  10  and  10 ′ through the network NW, respectively; the configurations of the refrigerant-amount determination kits  100  and  100 ′ are, however, not limited thereto. 
     For example, as illustrated in  FIG. 7 , a refrigerant-amount determination kit  100   a  may have the sensor  10  and a local computer  30   a  that has a function similar to that of the server  30  of the aforementioned embodiments. The computer  30   a  may be a mobile terminal, such as a smartphone. In the present modification, the computer  30   a  is connected to the sensor  10  through a signal line S, not through the network NW. The sensor  10  and the computer  30   a  may be communicably connected to each other through a wireless network, not through the physical signal line S. 
     The sensor  10  and the computer  30   a  are not limited to being communicably connected to each other. For example, measurement data of the sensor  10  may be inputted into the computer  30   a  by utilizing a medium, such as a memory card. 
     (2) Modification B 
     In the aforementioned embodiments, the refrigerant-amount determination kits  100  and  100 ′ each have the air temperature sensor  12  and measure the outside air temperature at the installation place of the air conditioner  200  by using the air temperature sensor  12 . 
     As illustrated in  FIG. 8 , a refrigerant-amount determination kit  100   b  may not include the air temperature sensor  12 . The server  30  of the refrigerant-amount determination kit  100   b  is connected through the network NW, such as the Internet, to a meteorological-data distribution server  40  that distributes meteorological data. The server  30  of the refrigerant-amount determination kit  100   b  uses, as an alternative to the outside air temperature measured by the air temperature sensor  12 , an outside air temperature distributed by the meteorological-data distribution server  40  in refrigerant-amount determination. 
     In addition, in another form, the server of the refrigerant-amount determination kit may use an outside air temperature inputted by a person in refrigerant-amount determination. 
     (3) Modification C 
     In the aforementioned embodiments, the refrigerant-amount determination kit  100  has the two refrigerant temperature sensors  14  and  16 , and the refrigerant-amount determination kit  100 ′ has the two refrigerant temperature sensors  14 ′ and  16 ′. 
     The refrigerant-amount determination kits are, however, not limited thereto and may have a single refrigerant temperature sensor. For example, the single refrigerant temperature sensor is a sensor that detects the condensation temperature in the heat-source-side heat exchanger  230 . In this case, the storage device of the server of the refrigerant-amount determination kit stores a table or a formula in which the outside air temperature and tendency of the temperature change of the condensation temperature of the air conditioner  200  when the refrigerant amount is proper are in association with each other. The server of the refrigerant-amount determination kit performs refrigerant-amount determination by comparing a change in the condensation temperature during operation of the air conditioner  200 , the change being obtained from a measurement result of the single refrigerant temperature sensor, with the tendency of the temperature change of the condensation temperature stored in the storage device. 
     The refrigerant-amount determination kit may perform refrigerant-amount determination by using a plurality of indicators (for example, the degree of subcooling, the degree of superheating, condensation temperature, evaporation temperature, and the like) obtained by using measurement data of three or more refrigerant temperature sensors. 
     (4) Modification D 
     In the aforementioned embodiments, the refrigerant-amount determination kits  100  and  100 ′ calculate, based on the measurement result of the sensor  10  or  10 ′, the degree of subcooling and the degree of superheating respectively in the air conditioner  200  that performs cooling of the air conditioned space and each performs refrigerant-amount determination based on the calculated value. 
     The refrigerant-amount determination kits  100  and  100 ′ are, however, not limited thereto and may calculate, based on the measurement result of the sensor  10  or  10 ′, the degree of subcooling and the degree of superheating respectively in an air conditioner that performs heating of the air conditioned space and may each perform refrigerant- amount determination based on the calculated value. In other words, the refrigerant-amount determination kits  100  and  100 ′ may calculate the degree of subcooling or the degree of superheating in an air conditioner that causes the utilization-side heat exchanger  260  to function as an evaporator and the heat-source-side heat exchanger  230  to function as an evaporator and may each perform refrigerant-amount determination based on the calculated value. 
     (5) Modification E 
     In the aforementioned embodiments, the refrigerant-amount determination kits  100  and  100 ′ utilize the degree of subcooling or the degree of superheating, and the measurement value of the air temperature sensor  12  in refrigerant-amount determination processing. The refrigerant-amount determination kits  100  and  100 ′ are, however, not limited by such a form and not limited to having the air temperature sensor  12 . The servers  30  and  30 ′ of the refrigerant-amount determination kits  100  and  100 ′ may each perform refrigerant-amount determination based on a result of comparison of the degree of subcooling or the degree of superheating with a predetermined reference value that does not depend on an outside air temperature. 
     Additional Remark 
     Although embodiments of the present disclosure have been described above, it should be understood that the form and details thereof can be variously changed without deviating from the spirit and the scope of the present disclosure.