AIR CONDITIONER

Abstract

An air conditioner includes a pipe volume calculating section and a refrigerant circuit configured by the interconnection of a heat source unit and a utilization unit via a refrigerant communication pipe. The pipe volume calculating section calculates the volume of the refrigerant communication pipe based on an additional charging quantity which is a refrigerant quantity to be additionally charged after the refrigerant circuit is configured by interconnecting the heat source unit and the utilization unit via the refrigerant communication pipe.

Description

TECHNICAL FIELD

The present invention relates to a function to judge the adequacy of the refrigerant quantity in a refrigerant circuit of an air conditioner. More specifically, the present invention relates to a function to judge the adequacy of the refrigerant quantity in a refrigerant circuit of an air conditioner configured by the interconnection of a heat source unit and a utilization unit via a refrigerant communication pipe.

BACKGROUND ART

Conventionally, in a separate type air conditioner configured by the interconnection of a heat source unit and a utilization unit via a refrigerant communication pipe, information on the length and the like of the refrigerant communication pipe is input in order to accurately judge the excess or deficiency of the refrigerant quantity in a refrigerant circuit (for example, see Patent Document 1).

<Patent Document 1>

JP-A Publication No. H8-200905

DISCLOSURE OF THE INVENTION

However, the above described work to input information on the refrigerant communication pipe is extremely laborious work. In addition, there is a problem that an input error easily occurs.

An object of the present invention is to minimize the labor of inputting information on a refrigerant communication pipe before operating a separate type air conditioner, and at the same time, to enable a highly accurate judgment of the adequacy of the refrigerant quantity in a refrigerant circuit.

An air conditioner according to a first aspect of the present invention includes a refrigerant circuit configured by the interconnection of a heat source unit and a utilization unit via a refrigerant communication pipe, and a pipe volume calculating means. The pipe volume calculating means calculates the volume of the refrigerant communication pipe based on an additional charging quantity that is a refrigerant quantity to be additionally charged after the refrigerant circuit is configured by the interconnection of the heat source unit and the utilization unit via the refrigerant communication pipe.

In this air conditioner, the volume of the refrigerant communication pipe is calculated based on the additional charging quantity that is the refrigerant quantity to be additionally charged after the refrigerant circuit is configured by the interconnection of the heat source unit and the utilization unit via the refrigerant communication pipe. Thus, even when the volume of the refrigerant communication pipe is unknown, it is possible to calculate the volume of the refrigerant communication pipe by inputting a value of the additional charging quantity. Accordingly, it is possible to determine the volume of the refrigerant communication pipe while minimizing the labor of inputting information on the refrigerant communication pipe. As a result, it is possible to judge the adequacy of the refrigerant quantity in the refrigerant circuit with high accuracy.

An air conditioner according to a second aspect of the present invention is the air conditioner according to the first aspect of the present invention, further including a refrigerant quantity judging means to judge whether or not the refrigerant quantity charged in the refrigerant circuit has reached a target charging quantity based on an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in an automatic refrigerant charging operation in which the refrigerant is additionally charged into the refrigerant circuit. The additional charging quantity is the refrigerant quantity additionally charged into the refrigerant circuit in the automatic refrigerant charging operation.

In this air conditioner, whether or not the target charging quantity is reached can be judged based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit, so that it is possible to reliably perform additional refrigerant charging, and at the same time, it is possible to determine a value of the additional charging quantity required for the calculation of the volume of the refrigerant communication pipe by performing the automatic refrigerant charging operation.

An air conditioner according to a third aspect of the present invention includes a refrigerant circuit configured by the interconnection of a heat source unit and a utilization unit via a refrigerant communication pipe, and a pipe volume calculating means. The pipe volume calculating means calculates the volume of the refrigerant communication pipe based on a communication pipe refrigerant quantity that is a refrigerant quantity in the refrigerant communication pipe. The communication pipe refrigerant quantity is determined by subtracting an inside-unit refrigerant quantity that is a refrigerant quantity in the refrigerant circuit excluding the refrigerant communication pipe from a total charged refrigerant quantity that is a refrigerant quantity in the entire refrigerant circuit after the refrigerant is additionally charged thereinto.

In this air conditioner, the volume of the refrigerant communication pipe is calculated based on the communication pipe refrigerant quantity that is the refrigerant quantity in the refrigerant communication pipe. The communication pipe refrigerant quantity is determined by subtracting the inside-unit refrigerant quantity that is the refrigerant quantity in the refrigerant circuit excluding the refrigerant communication pipe from the total charged refrigerant quantity that is the refrigerant quantity in the entire refrigerant circuit after the refrigerant is additionally charged thereinto. Thus, even when the volume of the refrigerant communication pipe is unknown, it is possible to calculate the volume of the refrigerant communication pipe by inputting a value of the additional charging quantity. Accordingly, it is possible to determine the volume of the refrigerant communication pipe while minimizing the labor of inputting information on the refrigerant communication pipe. As a result, it is possible to judge the adequacy of the refrigerant quantity in the refrigerant circuit with high accuracy.

An air conditioner according to a fourth aspect of the present invention is the air conditioner according to the second aspect of the present invention, further including a refrigerant quantity calculating means to calculate an inside-unit refrigerant quantity that is a refrigerant quantity in the refrigerant circuit excluding the refrigerant pipe from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in the automatic refrigerant charging operation. The pipe volume calculating means determines a total charged refrigerant quantity that is a refrigerant quantity in the entire refrigerant circuit immediately after the automatic refrigerant charging operation, by adding the additional charging quantity to an initial charging quantity that is a refrigerant quantity charged in the refrigerant circuit before the automatic refrigerant charging operation. Then, the pipe volume calculating means determines a communication pipe refrigerant quantity that is a refrigerant quantity in the refrigerant communication pipe by subtracting the inside-unit refrigerant quantity from the total charged refrigerant quantity, and calculates a density of the refrigerant flowing through the refrigerant communication pipe from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit. Then, the pipe volume calculating means calculates the volume of the refrigerant communication pipe based on the communication pipe refrigerant quantity and the density.

In this air conditioner, it is possible to calculate the communication pipe refrigerant quantity present with high accuracy during the automatic refrigerant charging operation by subtracting the inside-unit refrigerant quantity calculated based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in the automatic refrigerant charging operation, from the total charged refrigerant quantity determined by adding the additional charging quantity to the initial charging quantity. Thus, the volume of the refrigerant communication pipe can be calculated with high accuracy.

An air conditioner according to a fifth aspect of the present invention is the air conditioner according to the fourth aspect of the present invention, wherein the refrigerant communication pipe includes a liquid refrigerant communication pipe and a gas refrigerant communication pipe. The pipe volume calculating means calculates a liquid refrigerant density that is a density of liquid refrigerant flowing through the liquid refrigerant communication pipe and a gas density that is a density of gas refrigerant flowing through the gas refrigerant communication pipe. Then, the pipe volume calculating means calculates the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe based on the communication pipe refrigerant quantity, a volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe, the liquid refrigerant density, and the gas refrigerant density.

The liquid refrigerant communication pipe and the gas refrigerant communication pipe are provided so as to interconnect the utilization unit and the heat source unit, so that these pipes have substantially the same pipe length but different pipe diameters, i.e., different flow passage cross-sectional areas, due to the different densities of the refrigerant flowing through the pipes. Therefore, the volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe will substantially correspond to a flow passage cross-sectional area ratio between these pipes, and furthermore, this volume ratio will be within a certain range because the flow passage cross-sectional area ratio is predetermined based on the capacities and models of the utilization unit and the heat source unit. Further, if the volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe is known, it will be possible to calculate both the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe, because a total value obtained by adding a value of the multiplication between the volume of the liquid refrigerant communication pipe and the liquid refrigerant density to a value of the multiplication between the volume of the gas refrigerant communication pipe and the gas refrigerant density will be equal to the communication pipe refrigerant quantity.

Consequently, in this air conditioner, it is possible to easily calculate both the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe by predetermining the volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe.

An air conditioner according to a sixth aspect of the present invention is the air conditioner according to the fourth or fifth aspect of the present invention, wherein the refrigerant quantity calculating means calculates a total calculated refrigerant quantity that is a refrigerant quantity in the entire refrigerant circuit based on the volume of the refrigerant communication pipe calculated by the pipe volume calculating means and based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in a refrigerant leak detection operation in which whether or not there is a refrigerant leak from the refrigerant circuit is judged. The refrigerant quantity judging means judges whether or not there is a refrigerant leak from the refrigerant circuit by comparing the total calculated refrigerant quantity with a reference refrigerant quantity that serves as a reference for judging whether or not there is a refrigerant leak from the refrigerant circuit.

In this air conditioner, the pipe volume calculating means can calculate the volume of the refrigerant communication pipe, so that even if the volume of the refrigerant communication pipe is unknown, it is possible to calculate the refrigerant quantity in the refrigerant circuit in the refrigerant leak detection operation using the volume of the refrigerant communication pipe calculated by the pipe volume calculating means. Accordingly, it is possible to determine, with high accuracy, whether or not there is a refrigerant leak from the refrigerant circuit while minimizing the labor of inputting information on the refrigerant communication pipe.

An air conditioner according to a seventh aspect of the present invention is the air conditioner according to the second aspect of the present invention, wherein the pipe volume calculating means calculates a density of the refrigerant flowing through the refrigerant communication pipe from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit, and calculates the volume of the refrigerant communication pipe based on the additional charging quantity and the density.

In this air conditioner, for example, the refrigerant whose quantity is substantially equal to an inside-unit refrigerant quantity that is a refrigerant quantity in the refrigerant circuit excluding the refrigerant communication pipe and that is present when the refrigerant quantity in the refrigerant circuit is reached the target charging quantity by the automatic refrigerant charging operation, is charged as an initial charging quantity into the refrigerant circuit before the automatic refrigerant charging operation is performed, and thereby the refrigerant quantity to be additionally charged into the refrigerant circuit in the automatic refrigerant charging operation can be regarded as a refrigerant quantity corresponding to the refrigerant quantity present in the refrigerant communication pipe. Accordingly, it is possible to calculate the volume of the refrigerant communication pipe with high accuracy based on the additional charging quantity and the density.

An air conditioner according to an eighth aspect of the present invention is the air conditioner according to the seventh aspect of the present invention, wherein the refrigerant communication pipe includes a liquid refrigerant communication pipe and a gas refrigerant communication pipe. The pipe volume calculating means calculates a liquid refrigerant density that is a density of liquid refrigerant flowing through the liquid refrigerant communication pipe and a gas refrigerant density that is a density of gas refrigerant flowing through the gas refrigerant communication pipe. Then, the pipe volume calculating means calculates the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe based on the additional charging quantity, a volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe, the liquid refrigerant density, and the gas refrigerant density.

The liquid refrigerant communication pipe and the gas refrigerant communication pipe are provided so as to interconnect the utilization unit and the heat source unit, so that these pipes have substantially the same pipe length but different pipe diameters, i.e., different flow passage cross-sectional areas, due to the different densities of the refrigerant flowing through the pipes. Therefore, the volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe substantially corresponds to a flow passage cross-sectional area ratio between these pipes, and further more, this volume ratio will be within a certain range because the flow passage cross-sectional area ratio is predetermined based on the capacities and models of the utilization unit and the heat source unit. Further, if the volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe is known, it will be possible to calculate both the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe because a total value obtained by adding a value of the multiplication between the volume of the liquid refrigerant communication pipe and the liquid refrigerant density to a value of the multiplication between the volume of the gas refrigerant communication pipe and the gas refrigerant density will be equal to the additional charging quantity.

Consequently, in this air conditioner, it is possible to easily calculate both the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe by predetermining the volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe.

An air conditioner according to a ninth aspect of the present invention is the air conditioner according to the seventh or eighth aspect of the present invention, further including a refrigerant quantity calculating means to calculate a total calculated refrigerant quantity that is a refrigerant quantity in the entire refrigerant circuit based on the volume of the refrigerant communication pipe calculated by the pipe volume calculating means and based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in a refrigerant leak detection operation in which whether or not there is a refrigerant leak from the refrigerant circuit is judged. The refrigerant quantity judging means judges whether or not there is a refrigerant leak from the refrigerant circuit by comparing the total calculated refrigerant quantity with a reference refrigerant quantity that serves as a reference for judging whether or not there is a refrigerant leak from the refrigerant circuit.

In this air conditioner, the pipe volume calculating means can calculate the volume of the refrigerant communication pipe, so that even when the volume of the refrigerant communication pipe is unknown, it is possible to calculate the refrigerant quantity in the refrigerant circuit in the refrigerant leak detection operation using the volume of the refrigerant communication pipe calculated by the pipe volume calculating means. Accordingly, it is possible to determine, with high accuracy, whether or not there is a refrigerant leak from the refrigerant circuit while minimizing the labor of inputting information on the refrigerant communication pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration view of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a control block diagram of the air conditioner.

FIG. 3 is a flowchart of a test operation mode.

FIG. 4 is a flowchart of an automatic refrigerant charging operation.

FIG. 5 is a schematic diagram to show a state of refrigerant flowing in a refrigerant circuit in a refrigerant quantity judging operation (illustrations of a four-way switching valve and the like are omitted).

FIG. 6 is a flowchart of a pipe volume calculation process.

FIG. 7 is a flowchart of a refrigerant leak detection operation mode.

DESCRIPTION OF THE REFERENCE SYMBOLS

• 1 Air conditioner
• 2 Outdoor unit (heat source unit)
• 4, 5 Indoor unit (utilization unit)
• 6 Liquid refrigerant communication pipe (refrigerant communication pipe)
• 7 Gas refrigerant communication pipe (refrigerant communication pipe)
• 10 Refrigerant circuit

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, an embodiment of an air conditioner according to the present invention is described based on the drawings.

(1) Configuration of the Air Conditioner

FIG. 1 is a schematic configuration view of an air conditioner 1 according to an embodiment of the present invention. The air conditioner 1 is a device that is used to cool and heat a room in a building and the like by performing a vapor compression-type refrigeration cycle operation. The air conditioner 1 mainly includes one outdoor unit 2 as a heat source unit, indoor units 4 and 5 as a plurality (two in the present embodiment) of utilization units connected in parallel thereto, and a liquid refrigerant communication pipe 6 and a gas refrigerant communication pipe 7 as refrigerant communication pipes which interconnect the outdoor unit 2 and the indoor units 4 and 5. In other words, the vapor compression-type refrigerant circuit 10 of the air conditioner 1 in the present embodiment is configured by the interconnection of the outdoor unit 2, the indoor units 4 and 5, and the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7.

<Indoor Unit>

The indoor units 4 and 5 are installed by being embedded in or hung from a ceiling of a room in a building and the like or by being mounted or the like on a wall surface of a room. The indoor units 4 and 5 are connected to the outdoor unit 2 via the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7, and configure a part of the refrigerant circuit 10.

Next, the configurations of the indoor units 4 and 5 are described. Note that, because the indoor units 4 and 5 have the same configuration, only the configuration of the indoor unit 4 is described here, and in regard to the configuration of the indoor unit 5, reference numerals in the 50s are used instead of reference numerals in the 40s representing the respective portions of the indoor unit 4, and descriptions of those respective portions are omitted.

The indoor unit 4 mainly includes an indoor side refrigerant circuit 10a (an indoor side refrigerant circuit 10b in the case of the indoor unit 5) that configures a part of the refrigerant circuit 10. The indoor side refrigerant circuit 10a mainly includes an indoor expansion valve 41 as an expansion mechanism and an indoor heat exchanger 42 as a utilization side heat exchanger.

In the present embodiment, the indoor expansion valve 41 is an electrically powered expansion valve connected to a liquid side of the indoor heat exchanger 42 in order to adjust the flow rate or the like of the refrigerant flowing in the indoor side refrigerant circuit 10a.

In the present embodiment, the indoor heat exchanger 42 is a cross fin-type fin-and-tube type heat exchanger configured by a heat transfer tube and numerous fins, and is a heat exchanger that functions as an evaporator for the refrigerant during a cooling operation to cool the room air and functions as a condenser for the refrigerant during a heating operation to heat the room air.

In the present embodiment, the indoor unit 4 includes an indoor fan 43 as a ventilation fan for taking in room air into the unit, causing the air to heat exchange with the refrigerant in the indoor heat exchanger 42, and then supplying the air to the room as supply air. The indoor fan 43 is a fan capable of varying an air flow rate Wr of the air which is supplied to the indoor heat exchanger 42, and in the present embodiment, is a centrifugal fan, multi-blade fan, or the like, which is driven by a motor 43a comprising a DC fan motor.

In addition, various types of sensors are disposed in the indoor unit 4. A liquid side temperature sensor 44 that detects the temperature of the refrigerant (i.e., the refrigerant temperature corresponding to a condensation temperature Tc during the heating operation or an evaporation temperature Te during the cooling operation) is disposed at the liquid side of the indoor heat exchanger 42. A gas side temperature sensor 45 that detects a temperature Teo of the refrigerant is disposed at a gas side of the indoor heat exchanger 42. A room temperature sensor 46 that detects the temperature of the room air that flows into the unit (i.e., a room temperature Tr) is disposed at a room air intake side of the indoor unit 4. In the present embodiment, the liquid side temperature sensor 44, the gas side temperature sensor 45, and the room temperature sensor 46 comprise thermistors. In addition, the indoor unit 4 includes an indoor side controller 47 that controls the operation of each portion constituting the indoor unit 4. Additionally, the indoor side controller 47 includes a microcomputer and a memory and the like disposed in order to control the indoor unit 4, and is configured such that it can exchange control signals and the like with a remote controller (not shown) for individually operating the indoor unit 4 and can exchange control signals and the like with the outdoor unit 2 via a transmission line 8a.

<Outdoor Unit>

The outdoor unit 2 is installed outside of a building and the like, is connected to the indoor units 4 and 5 via the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7, and configures the refrigerant circuit 10 with the indoor units 4 and 5.

Next, the configuration of the outdoor unit 2 is described. The outdoor unit 2 mainly includes an outdoor side refrigerant circuit 10c that configures a part of the refrigerant circuit 10. This outdoor side refrigerant circuit 10c mainly includes a compressor, a four-way switching valve 22, an outdoor heat exchanger 23 as a heat source side heat exchanger, an outdoor expansion valve 38 as an expansion mechanism, an accumulator 24, a subcooler 25 as a temperature adjustment mechanism, a liquid side stop valve 26, and a gas side stop valve 27.

The compressor 21 is a compressor whose operation capacity can be varied, and in the present embodiment, is a positive displacement-type compressor driven by a motor 21a whose rotation frequency Rm is controlled by an inverter. In the present embodiment, only one compressor 21 is provided, but it is not limited thereto, and two or more compressors may be connected in parallel according to the number of connected units of indoor units and the like.

The four-way switching valve 22 is a valve for switching the direction of the flow of the refrigerant such that, during the cooling operation, the four-way switching valve 22 is capable of connecting a discharge side of the compressor 21 and a gas side of the outdoor heat exchanger 23 and connecting a suction side of the compressor 21 (specifically, the accumulator 24) and the gas refrigerant communication pipe 7 (see the solid lines of the four-way switching valve 22 in FIG. 1) to cause the outdoor heat exchanger 23 to function as a condenser for the refrigerant compressed in the compressor 21 and to cause the indoor heat exchangers 42 and 52 to function as evaporators for the refrigerant condensed in the outdoor heat exchanger 23; and such that, during the heating operation, the four-way switching valve 22 is capable of connecting the discharge side of the compressor 21 and the gas refrigerant communication pipe 7 and connecting the suction side of the compressor 21 and the gas side of the outdoor heat exchanger 23 (see the dotted lines of the four-way switching valve 22 in FIG. 1) to cause the indoor heat exchangers 42 and 52 to function as condensers for the refrigerant compressed in the compressor 21 and to cause the outdoor heat exchanger 23 to function as an evaporator for the refrigerant condensed in the indoor heat exchangers 42 and 52.

In the present embodiment, the outdoor heat exchanger 23 is a cross-fin type fin-and-tube type heat exchanger configured by a heat transfer tube and numerous fins, and is a heat exchanger that functions as a condenser for the refrigerant during the cooling operation and as an evaporator for the refrigerant during the heating operation. The gas side of the outdoor heat exchanger 23 is connected to the four-way switching valve 22, and the liquid side thereof is connected to the liquid refrigerant communication pipe 6.

In the present embodiment, the outdoor expansion valve 38 is an electrically powered expansion valve connected to a liquid side of the outdoor heat exchanger 23 in order to adjust the pressure, flow rate, or the like of the refrigerant flowing in the outdoor side refrigerant circuit 10c.

In the present embodiment, the outdoor unit 2 includes an outdoor fan 28 as a ventilation fan for taking in outdoor air into the unit, causing the air to exchange heat with the refrigerant in the outdoor heat exchanger 23, and then exhausting the air to the outside. The outdoor fan 28 is a fan capable of varying an air flow rate Wo of the air which is supplied to the outdoor heat exchanger 23, and in the present embodiment, is a propeller fan or the like driven by a motor 28a comprising a DC fan motor.

The accumulator 24 is connected between the four-way switching valve 22 and the compressor 21, and is a container capable of accumulating excess refrigerant generated in the refrigerant circuit 10 in accordance with the change in the operation load of the indoor units 4 and 5 and the like.

In the present embodiment, the subcooler 25 is a double tube heat exchanger, and is disposed to cool the refrigerant sent to the indoor expansion valves 41 and 51 after the refrigerant is condensed in the outdoor heat exchanger 23. In the present embodiment, the subcooler 25 is connected between the outdoor expansion valve 38 and the liquid side stop valve 26.

In the present embodiment, a bypass refrigerant circuit 61 as a cooling source of the subcooler 25 is disposed. Note that, in the description below, a portion corresponding to the refrigerant circuit 10 excluding the bypass refrigerant circuit 61 is referred to as a main refrigerant circuit for convenience sake.

The bypass refrigerant circuit 61 is connected to the main refrigerant circuit so as to cause a portion of the refrigerant sent from the outdoor heat exchanger 23 to the indoor expansion valves 41 and 51 to branch from the main refrigerant circuit and return to the suction side of the compressor 21. Specifically, the bypass refrigerant circuit 61 includes a branch circuit 61a connected so as to branch a portion of the refrigerant sent from the outdoor expansion valve 38 to the indoor expansion valves 41 and 51 at a position between the outdoor heat exchanger 23 and the subcooler 25, and a merging circuit 61b connected to the suction side of the compressor 21 so as to return a portion of refrigerant from an outlet on a bypass refrigerant circuit side of the subcooler 25 to the suction side of the compressor 21. Further, the branch circuit 61a is disposed with a bypass expansion valve 62 for adjusting the flow rate of the refrigerant flowing in the bypass refrigerant circuit 61. Here, the bypass expansion valve 62 comprises an electrically operated expansion valve. In this way, the refrigerant sent from the outdoor heat exchanger 23 to the indoor expansion valves 41 and 51 is cooled in the subcooler 25 by the refrigerant flowing in the bypass refrigerant circuit 61 which has been depressurized by the bypass expansion valve 62. In other words, performance of the subcooler 25 is controlled by adjusting the opening degree of the bypass expansion valve 62.

The liquid side stop valve 26 and the gas side stop valve 27 are valves disposed at ports connected to external equipment and pipes (specifically, the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7). The liquid side stop valve 26 is connected to the outdoor heat exchanger 23. The gas side stop valve 27 is connected to the four-way switching valve 22.

In addition, various sensors are disposed in the outdoor unit 2. Specifically, disposed in the outdoor unit 2 are an suction pressure sensor 29 that detects a suction pressure Ps of the compressor 21, a discharge pressure sensor 30 that detects a discharge pressure Pd of the compressor 21, a suction temperature sensor 31 that detects a suction temperature Ts of the compressor 21, and a discharge temperature sensor 32 that detects a discharge temperature Td of the compressor 21. The suction temperature sensor 31 is disposed at a position between the accumulator 24 and the compressor 21. A heat exchanger temperature sensor 33 that detects the temperature of the refrigerant flowing through the outdoor heat exchanger 23 (i.e., the refrigerant temperature corresponding to the condensation temperature Tc during the cooling operation or the evaporation temperature Te during the heating operation) is disposed in the outdoor heat exchanger 23. A liquid side temperature sensor 34 that detects a refrigerant temperature Tco is disposed at the liquid side of the outdoor heat exchanger 23. A liquid pipe temperature sensor 35 that detects the temperature of the refrigerant (i.e., a liquid pipe temperature T1p) is disposed at the outlet on the main refrigerant circuit side of the subcooler 25. The merging circuit 61b of the bypass refrigerant circuit 61 is disposed with a bypass temperature sensor 63 for detecting the temperature of the refrigerant flowing through the outlet on the bypass refrigerant circuit side of the subcooler 25. An outdoor temperature sensor 36 that detects the temperature of the outdoor air that flows into the unit (i.e., an outdoor temperature Ta) is disposed at an outdoor air intake side of the outdoor unit 2. In the present embodiment, the suction temperature sensor 31, the discharge temperature sensor 32, the heat exchanger temperature sensor 33, the liquid side temperature sensor 34, the liquid pipe temperature sensor 35, the outdoor temperature sensor 36, and the bypass temperature sensor 63 comprise thermistors. In addition, the outdoor unit 2 includes an outdoor side controller 37 that controls the operation of each portion constituting the outdoor unit 2. Additionally, the outdoor side controller 37 includes a microcomputer and a memory disposed in order to control the outdoor unit 2, an inverter circuit that controls the motor 21a, and the like, and is configured such that it can exchange control signals and the like with the indoor side controllers 47 and 57 of the indoor units 4 and 5 via the transmission line 8a. In other words, a controller 8 that performs the operation control of the entire air conditioner 1 is configured by the indoor side controllers 47 and 57, the outdoor side controller 37, and the transmission line 8a that interconnects the controllers 37, 47, and 57.

As shown in FIG. 2, the controller 8 is connected so as to be able to receive detection signals of sensors 29 to 36, 44 to 46, 54 to 56, and 63 and also to be able to control various equipment and valves 21, 22, 24, 28a, 38, 41, 43a, 51, 53a, and 62 based on these detection signals and the like. In addition, the controller 8 is provided with an input unit 9a such that a set value for each type of control can be input and changed and such that the total charged refrigerant quantity including the refrigerant quantity additionally charged into the refrigerant circuit 10 in an automatic refrigerant charging operation (described later) and an initial charging quantity can be input. In addition, a display 9b comprising LEDs and the like is connected to the controller 8. The display 9b is configured to indicate that additional charging is completed in the automatic refrigerant charging operation (described later) and that a refrigerant leak is detected in a refrigerant leak detection operation (described later). Here, FIG. 2 is a control block diagram of the air conditioner 1. Note that the input unit 9a is not limited to the one provided to the controller 8, but may be the one that is connected to the controller 8 as needed when inputting the additional charging quantity and the total charged refrigerant quantity.

<Refrigerant Communication Pipe>

The refrigerant communication pipes 6 and 7 are refrigerant pipes that are arranged on site when installing the air conditioner 1 at an installation site such as a building. As the refrigerant communication pipes 6 and 7, pipes having various lengths and diameters are used according to the installation conditions such as an installation site, combination of an outdoor unit and an indoor unit, and the like. Accordingly, for example, when installing a new air conditioner, in order to calculate the additional charging quantity of the refrigerant, it is necessary to obtain accurate information regarding the lengths, diameters and the like of the refrigerant communication pipes 6 and 7. However, such information management and the calculation itself of the refrigerant quantity are difficult. In addition, when utilizing an existing pipe to renew an indoor unit and an outdoor unit, information regarding the lengths, diameters and the like of the refrigerant communication pipes 6 and 7 may have been lost in some cases.

As described above, the refrigerant circuit 10 of the air conditioner 1 is configured by the interconnection of the indoor side refrigerant circuits 10a and 10b, the outdoor side refrigerant circuit 10c, and the refrigerant communication pipes 6 and 7. In addition, it can also be that this refrigerant circuit 10 is configured by the bypass refrigerant circuit 61 and the main refrigerant circuit excluding the bypass refrigerant circuit 61. Additionally, the controller 8 constituted by the indoor side controllers 47 and 57 and the outdoor side controller 37 allows the air conditioner 1 in the present embodiment to switch and operate between the cooling operation and the heating operation by the four-way switching valve 22 and to control each equipment of the outdoor unit 2 and the indoor units 4 and 5 according to the operation load of each of the indoor units 4 and 5.

(2) Operation of the Air Conditioner

Next, the operation of the air conditioner 1 in the present embodiment is described.

The operation modes of the air conditioner 1 in the present embodiment include: a normal operation mode where control of constituent equipment of the outdoor unit 2 and the indoor units 4 and 5 is performed according to the operation load of each of the indoor units 4 and 5; a test operation mode where a test operation is performed after installation of constituent equipment of the air conditioner 1 is performed (specifically, it is not limited to after the first installation of equipment: it also includes, for example, after modification by adding or removing constituent equipment such as an indoor unit, after repair of damaged equipment); and a refrigerant leak detection operation mode where, after the test operation is finished and the normal operation has started, whether or not there is a refrigerant leak from the refrigerant circuit 10 is judged. The normal operation mode mainly includes the cooling operation for cooling the room and the heating operation for heating the room. In addition, the test operation mode mainly includes the automatic refrigerant charging operation to charge refrigerant into the refrigerant circuit 10, and a pipe volume calculation process to calculate the volumes of the refrigerant communication pipes 6 and 7.

Operation in each operation mode of the air conditioner 1 is described below.

<Normal Operation Mode>

(Cooling Operation)

First, the cooling operation in the normal operation mode is described with reference to FIGS. 1 and 2.

During the cooling operation, the four-way switching valve 22 is in the state represented by the solid lines in FIG. 1, i.e., a state where the discharge side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23 and also the suction side of the compressor 21 is connected to the gas sides of the indoor heat exchangers 42 and 52 via the gas side stop valve 27 and the gas refrigerant communication pipe 7. The outdoor expansion valve 38 is in a fully opened state. The liquid side stop valve 26 and the gas side stop valve 27 are in an opened state. The opening degree of each of the indoor expansion valves 41 and 51 is adjusted such that a superheat degree SHr of the refrigerant at the outlets of the indoor heat exchangers 42 and 52 (i.e., the gas sides of the indoor heat exchangers 42 and 52) becomes constant at a target superheat degree SHrs. In the present embodiment, the superheat degree SHr of the refrigerant at the outlet of each of the indoor heat exchangers 42 and 52 is detected by subtracting the refrigerant temperature (which corresponds to the evaporation temperature Te) detected by the liquid side temperature sensors 44 and 54 from the refrigerant temperature detected by the gas side temperature sensors 45 and 55, or is detected by converting the suction pressure Ps of the compressor 21 detected by the suction pressure sensor 29 to saturated temperature corresponding to the evaporation temperature Te, and subtracting this saturated temperature of the refrigerant from the refrigerant temperature detected by the gas side temperature sensors 45 and 55. Note that, although it is not employed in the present embodiment, a temperature sensor that detects the temperature of the refrigerant flowing through each of the indoor heat exchangers 42 and 52 may be disposed such that the superheat degree SHr of the refrigerant at the outlet of each of the indoor heat exchangers 42 and 52 is detected by subtracting the refrigerant temperature corresponding to the evaporation temperature Te which is detected by this temperature sensor from the refrigerant temperature detected by the gas side temperature sensors 45 and 55. In addition, the opening degree of the bypass expansion valve 62 is adjusted such that a superheat degree SHb of the refrigerant at the outlet on the bypass refrigerant circuit side of the subcooler 25 becomes a target superheat degree SHbs. In the present embodiment, the superheat degree SHb of the refrigerant at the outlet on the bypass refrigerant circuit side of the subcooler 25 is detected by converting the suction pressure Ps of the compressor 21 detected by the suction pressure sensor 29 to saturated temperature corresponding to the evaporation temperature Te, and subtracting this saturated temperature of the refrigerant from the refrigerant temperature detected by the bypass temperature sensor 63. Note that, although it is not employed in the present embodiment, a temperature sensor may be disposed at an inlet on the bypass refrigerant circuit side of the subcooler 25 such that the superheat degree SHb of the refrigerant at the outlet on the bypass refrigerant circuit side of the subcooler 25 is detected by subtracting the refrigerant temperature detected by this temperature sensor from the refrigerant temperature detected by the bypass temperature sensor 63.

When the compressor 21, the outdoor fan 28, the indoor fans 43 and 53 are started in this state of the refrigerant circuit 10, low-pressure gas refrigerant is sucked into the compressor 21 and compressed into high-pressure gas refrigerant. Subsequently, the high-pressure gas refrigerant is sent to the outdoor heat exchanger 23 via the four-way switching valve 22, exchanges heat with the outdoor air supplied by the outdoor fan 28, and becomes condensed into high-pressure liquid refrigerant. Then, this high-pressure liquid refrigerant passes through the outdoor expansion valve 38, flows into the subcooler 25, exchanges heat with the refrigerant flowing in the bypass refrigerant circuit 61, is further cooled, and becomes subcooled. At this time, a portion of the high-pressure liquid refrigerant condensed in the outdoor heat exchanger 23 is branched into the bypass refrigerant circuit 61 and is depressurized by the bypass expansion valve 62. Subsequently, it is returned to the suction side of the compressor 21. Here, the refrigerant that passes through the bypass expansion valve 62 is depressurized close to the suction pressure Ps of the compressor 21 and thereby a portion of the refrigerant evaporates. Then, the refrigerant flowing from the outlet of the bypass expansion valve 62 of the bypass refrigerant circuit 61 toward the suction side of the compressor 21 passes through the subcooler 25 and exchanges heat with high-pressure liquid refrigerant sent from the outdoor heat exchanger 23 on the main refrigerant circuit side to the indoor units 4 and 5.

Then, the high-pressure liquid refrigerant that has become subcooled is sent to the indoor units 4 and 5 via the liquid side stop valve 26 and the liquid refrigerant communication pipe 6. The high-pressure liquid refrigerant sent to the indoor units 4 and 5 is depressurized close to the suction pressure Ps of the compressor 21 by the indoor expansion valves 41 and 51, becomes refrigerant in a low-pressure gas-liquid two-phase state, is sent to the indoor heat exchangers 42 and 52, exchanges heat with the room air in the indoor heat exchangers 42 and 52, and is evaporated into low-pressure gas refrigerant.

This low-pressure gas refrigerant is sent to the outdoor unit 2 via the gas refrigerant communication pipe 7, and flows into the accumulator 24 via the gas side stop valve 27 and the four-way switching valve 22. Then, the low-pressure gas refrigerant that flowed into the accumulator 24 is again sucked into the compressor 21.

(Heating Operation)

Next, the heating operation in the normal operation mode is described.

During the heating operation, the four-way switching valve 22 is in a state represented by the dotted lines in FIG. 1, i.e., a state where the discharge side of the compressor 21 is connected to the gas sides of the indoor heat exchangers 42 and 52 via the gas side stop valve 27 and the gas refrigerant communication pipe 7 and also the suction side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23. The opening degree of the outdoor expansion valve 38 is adjusted so as to be able to depressurize the refrigerant that flows into the outdoor heat exchanger 23 to a pressure where the refrigerant can evaporate (i.e., evaporation pressure Pe) in the outdoor heat exchanger 23. In addition, the liquid side stop valve 26 and the gas side stop valve 27 are in an opened state. The opening degree of the indoor expansion valves 41 and 51 is adjusted such that a subcooling degree SCr of the refrigerant at the outlets of the indoor heat exchangers 42 and 52 becomes constant at the target subcooling degree SCrs. In the present embodiment, a subcooling degree SCr of the refrigerant at the outlets of the indoor heat exchangers 42 and 52 is detected by converting the discharge pressure Pd of the compressor 21 detected by the discharge pressure sensor 30 to saturated temperature corresponding to the condensation temperature Tc, and subtracting the refrigerant temperature detected by the liquid side temperature sensors 44 and 54 from this saturated temperature of the refrigerant. Note that, although it is not employed in the present embodiment, a temperature sensor that detects the temperature of the refrigerant flowing through each of the indoor heat exchangers 42 and 52 may be disposed such that the subcooling degree SCr of the refrigerant at the outlets of the indoor heat exchangers 42 and 52 is detected by subtracting the refrigerant temperature corresponding to the condensation temperature Tc which is detected by this temperature sensor from the refrigerant temperature detected by the liquid side temperature sensors 44 and 54. In addition, the bypass expansion valve 62 is closed.

When the compressor 21, the outdoor fan 28, the indoor fans 43 and 53 are started in this state of the refrigerant circuit 10, low-pressure gas refrigerant is sucked into the compressor 21, compressed into high-pressure gas refrigerant, and sent to the indoor units 4 and 5 via the four-way switching valve 22, the gas side stop valve 27, and the gas refrigerant communication pipe 7.

Then, the high-pressure gas refrigerant sent to the indoor units 4 and 5 exchanges heat with the room air in the indoor heat exchangers 42 and 52 and is condensed into high-pressure liquid refrigerant. Subsequently, it is depressurized according to the opening degree of the indoor expansion valves 41 and 51 when passing through the indoor expansion valves 41 and 51.

The refrigerant that passed through the indoor expansion valves 41 and 51 is sent to the outdoor unit 2 via the liquid refrigerant communication pipe 6, is further depressurized via the liquid side stop valve 26, the subcooler 25, and the outdoor expansion valve 38, and then flows into the outdoor heat exchanger 23. Then, the refrigerant in a low-pressure gas-liquid two-phase state that flowed into the outdoor heat exchanger 23 exchanges heat with the outdoor air supplied by the outdoor fan 28, is evaporated into low-pressure gas refrigerant, and flows into the accumulator 24 via the four-way switching valve 22. Then, the low-pressure gas refrigerant that flowed into the accumulator 24 is again sucked into the compressor 21.

Such operation control as described above in the normal operation mode is performed by the controller 8 (more specifically, the indoor side controllers 47 and 57, the outdoor side controller 37, and the transmission line 8a that connects between the controllers 37, 47 and 57) that functions as a normal operation controlling means to perform the normal operation that includes the cooling operation and the heating operation.

<Test Operation Mode>

Next, the test operation mode is described with reference to FIGS. 1 to 3. Here, FIG. 3 is a flowchart of the test operation mode. In the present embodiment, in the test operation mode, first, the automatic refrigerant charging operation in Step S1 is performed, and subsequently, the pipe volume calculation process in Step S2 is performed.

In the present embodiment, an example of a case is described where, the outdoor unit 2 in which the refrigerant is charged in advance and the indoor units 4 and 5 are installed at an installation site such as a building, and the outdoor unit 2, the indoor units 4, 5 are interconnected via the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7 to configure the refrigerant circuit 10, and subsequently additional refrigerant is charged into the refrigerant circuit 10 whose refrigerant quantity is insufficient according to the volumes of the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7.

(STEP S1: Automatic Refrigerant Charging Operation)

First, the liquid side stop valve 26 and the gas side stop valve 27 of the outdoor unit 2 are opened and the refrigerant circuit 10 is filled with the refrigerant that is charged in the outdoor unit 2 in advance.

Next, when a worker performing the test operation connects a refrigerant cylinder for additional charging to a service port (not shown) of the refrigerant circuit 10 and issues a command to start the test operation directly to the controller 8 or remotely by a remote controller (not shown) and the like, the controller 8 starts the process from Step S11 to Step S13 shown in FIG. 4. Here, FIG. 4 is a flowchart of the automatic refrigerant charging operation.

(STEP S11: Refrigerant Quantity Judging Operation)

When a command to start the automatic refrigerant charging operation is issued, the refrigerant circuit 10, with the four-way switching valve 22 of the outdoor unit 2 in the state represented by the solid lines in FIG. 1, becomes a state where the indoor expansion valves 41 and 51 of the indoor units 4 and 5 and the outdoor expansion valve 38 are opened. Then, the compressor 21, the outdoor fan 28, and the indoor fans 43 and 53 are started, and the cooling operation is forcibly performed in all of the indoor units 4 and 5 (hereinafter referred to as “all indoor unit operation”).

Consequently, as shown in FIG. 5, in the refrigerant circuit 10, the high-pressure gas refrigerant compressed and discharged in the compressor 21 flows along a flow path from the compressor 21 to the outdoor heat exchanger 23 that functions as a condenser (see the portion from the compressor 21 to the outdoor heat exchanger 23 in the hatching area indicated by the diagonal line in FIG. 5); the high-pressure refrigerant that undergoes phase-change from a gas state to a liquid state by heat exchange with the outdoor air flows in the outdoor heat exchanger 23 that functions as a condenser (see the portion corresponding to the outdoor heat exchanger 23 in the hatching area indicated by the diagonal line and the black-lacquered hatching area in FIG. 5); the high-pressure liquid refrigerant flows along a flow path from the outdoor heat exchanger 23 to the indoor expansion valves 41 and 51 including the outdoor expansion valve 38, the portion corresponding to the main refrigerant circuit side of the subcooler 25 and the liquid refrigerant communication pipe 6, and a flow path from the outdoor heat exchanger 23 to the bypass expansion valve 62 (see the portions from the outdoor heat exchanger 23 to the indoor expansion valves 41 and 51 and to the bypass expansion valve 62 in the area indicated by the black hatching in FIG. 5); the low-pressure refrigerant that undergoes phase-change from a gas-liquid two-phase state to a gas state by heat exchange with the room air flows in the portions corresponding to the indoor heat exchangers 42 and 52 that function as evaporators and the portion corresponding to the bypass refrigerant circuit side of the subcooler 25 (see the portions corresponding to the indoor heat exchangers 42 and 52 and the portion corresponding to the subcooler 25 in the area indicated by the lattice hatching and the hatching indicated by the diagonal line in FIG. 5); and the low-pressure gas refrigerant flows along a flow path from the indoor heat exchangers 42 and 52 to the compressor 21 including the gas refrigerant communication pipe 7 and the accumulator 24 and a flow path from the portion corresponding to the bypass refrigerant circuit side of the subcooler 25 to the compressor 21 (see the portion from the indoor heat exchangers 42 and 52 to the compressor 21 and the portion from the portion corresponding to the bypass refrigerant circuit side of the subcooler 25 to the compressor 21 in the hatching area indicated by the diagonal line in FIG. 5). FIG. 5 is a schematic diagram to show a state of the refrigerant flowing in the refrigerant circuit 10 in a refrigerant quantity judging operation (illustrations of the four-way switching valve 22 and the like are omitted).

Next, equipment control as described below is performed to proceed to operation to stabilize the state of the refrigerant circulating in the refrigerant circuit 10. Specifically, the indoor expansion valves 41 and 51 are controlled such that the superheat degree SHr of the indoor heat exchangers 42 and 52 that function as evaporators becomes constant (hereinafter referred to as “super heat degree control”); the operation capacity of the compressor 21 is controlled such that an evaporation pressure Pe becomes constant (hereinafter referred to as “evaporation pressure control”); the air flow rate Wo of outdoor air supplied to the outdoor heat exchanger 23 by the outdoor fan 28 is controlled such that a condensation pressure Pc of the refrigerant in the outdoor heat exchanger 23 becomes constant (hereinafter referred to as “condensation pressure control”); the operation capacity of the subcooler 25 is controlled such that the temperature of the refrigerant sent from the subcooler 25 to the indoor expansion valves 41 and 51 becomes constant (hereinafter referred to as “liquid pipe temperature control”); and the air flow rate Wr of room air supplied to the indoor heat exchangers 42 and 52 by the indoor fans 43 and 53 is maintained constant such that the evaporation pressure Pe of the refrigerant is stably controlled by the above described evaporation pressure control.

Here, the reason to perform the evaporation pressure control is that the evaporation pressure Pe of the refrigerant in the indoor heat exchangers 42 and 52 that function as evaporators is greatly affected by the refrigerant quantity in the indoor heat exchangers 42 and 52 where low-pressure refrigerant flows while undergoing a phase change from a gas-liquid two-phase state to a gas state as a result of heat exchange with the room air (see the portions corresponding to the indoor heat exchangers 42 and 52 in the area indicated by the lattice hatching and hatching indicated by the diagonal line in FIG. 5, which is hereinafter referred to as “evaporator portion C”). Consequently, here, a state is created in which the refrigerant quantity in the evaporator portion C changes mainly by the evaporation pressure Pe by causing the evaporation pressure Pe of the refrigerant in the indoor heat exchangers 42 and 52 to become constant and by stabilizing the state of the refrigerant flowing in the evaporator portion C as a result of controlling the operation capacity of the compressor 21 by the motor 21a whose rotation frequency Rm is controlled by an inverter. Note that, the control of the evaporation pressure Pe by the compressor 21 in the present embodiment is achieved in the following manner: the refrigerant temperature (which corresponds to the evaporation temperature Te) detected by the liquid side temperature sensors 44 and 54 of the indoor heat exchangers 42 and 52 is converted to saturation pressure; the operation capacity of the compressor 21 is controlled such that the saturation pressure becomes constant at a target low pressure Pes (in other words, the control to change the rotation frequency Rm of the motor 21a is performed); and then a refrigerant circulation flow rate Wc flowing in the refrigerant circuit 10 is increased or decreased. Note that, although it is not employed in the present embodiment, the operation capacity of the compressor 21 may be controlled such that the suction pressure Ps of the compressor 21 detected by the suction pressure sensor 29, which is the operation state quantity equivalent to the pressure of the refrigerant at the evaporation pressure Pe of the refrigerant in the indoor heat exchangers 42 and 52, becomes constant at the target low pressure Pes, or the saturation temperature (which corresponds to the evaporation temperature Te) corresponding to the suction pressure Ps becomes constant at a target low pressure Tes. Also, the operation capacity of the compressor 21 may be controlled such that the refrigerant temperature (which corresponds to the evaporation temperature Te) detected by the liquid side temperature sensors 44 and 54 of the indoor heat exchangers 42 and 52 becomes constant at the target low pressure Tes.

Then, by performing such evaporation pressure control, the state of the refrigerant flowing in the refrigerant pipes from the indoor heat exchangers 42 and 52 to the compressor 21 including the gas refrigerant communication pipe 7 and the accumulator 24 (see the portion from the indoor heat exchangers 42 and 52 to the compressor 21 in the hatching area indicated by the diagonal line in FIG. 5, which is hereinafter referred to as “gas refrigerant distribution portion D”) becomes stabilized, creating a state where the refrigerant quantity in the gas refrigerant distribution portion D changes mainly by the evaporation pressure Pe (i.e., the suction pressure Ps), which is the operation state quantity equivalent to the pressure of the refrigerant in the gas refrigerant distribution portion D.

In addition, the reason to perform the condensation pressure control is that the condensation pressure Pc of the refrigerant is greatly affected by the refrigerant quantity in the outdoor heat exchanger 23 where high-pressure refrigerant flows while undergoing a phase change from a gas state to a liquid state as a result of heat exchange with the outdoor air (see the portions corresponding to the outdoor heat exchanger 23 in the area indicated by the diagonal line hatching and the black hatching in FIG. 5, which is hereinafter referred to as “condenser portion A”). The condensation pressure Pc of the refrigerant in the condenser portion A greatly changes due to the effect of the outdoor temperature Ta. Therefore, the air flow rate Wo of the room air supplied from the outdoor fan 28 to the outdoor heat exchanger 23 is controlled by the motor 28a, and thereby the condensation pressure Pc of the refrigerant in the outdoor heat exchanger 23 is maintained constant and the state of the refrigerant flowing in the condenser portion A is stabilized, creating a state where the refrigerant quantity in condenser portion A changes mainly by a subcooling degree SCo at the liquid side of the outdoor heat exchanger 23 (hereinafter regarded as the outlet of the outdoor heat exchanger 23 in the description regarding the refrigerant quantity judging operation). Note that, for the control of the condensation pressure Pc by the outdoor fan 28 in the present embodiment, the discharge pressure Pd of the compressor 21 detected by the discharge pressure sensor 30, which is the operation state quantity equivalent to the condensation pressure Pc of the refrigerant in the outdoor heat exchanger 23, or the temperature of the refrigerant flowing through the outdoor heat exchanger 23 (i.e., the condensation temperature Tc) detected by the heat exchanger temperature sensor 33 is used.

Then, by performing such condensation pressure control, the high-pressure liquid refrigerant flows along a flow path from the outdoor heat exchanger 23 to the indoor expansion valves 41 and 51 including the outdoor expansion valve 38, the portion on the main refrigerant circuit side of the subcooler 25, and the liquid refrigerant communication pipe 6 and a flow path from the outdoor heat exchanger 23 to the bypass expansion valve 62 of the bypass refrigerant circuit 61; the pressure of the refrigerant in the portions from the outdoor heat exchanger 23 to the indoor expansion valves 41 and 51 and to the bypass expansion valve 62 (see the area indicated by the black hatching in FIG. 5, which is hereinafter referred to as “liquid refrigerant distribution portion B”) also becomes stabilized; and the liquid refrigerant distribution portion B is sealed by the liquid refrigerant, thereby becoming a stable state.

In addition, the reason to perform the liquid pipe temperature control is to prevent a change in the density of the refrigerant in the refrigerant pipes from the subcooler 25 to the indoor expansion valves 41 and 51 including the liquid refrigerant communication pipe 6 (see the portion from the subcooler 25 to the indoor expansion valves 41 and 51 in the liquid refrigerant distribution portion B shown in FIG. 5). Performance of the subcooler 25 is controlled by increasing or decreasing the flow rate of the refrigerant flowing in the bypass refrigerant circuit 61 such that the refrigerant temperature T1p detected by the liquid pipe temperature sensor 35 disposed at the outlet on the main refrigerant circuit side of the subcooler 25 becomes constant at a target liquid pipe temperature T1ps, and by adjusting the quantity of heat exchange between the refrigerant flowing through the main refrigerant circuit side and the refrigerant flowing through the bypass refrigerant circuit side of the subcooler 25. Note that, the flow rate of the refrigerant flowing in the bypass refrigerant circuit 61 is increased or decreased by adjustment of the opening degree of the bypass expansion valve 62. In this way, the liquid pipe temperature control is achieved in which the refrigerant temperature in the refrigerant pipes from the subcooler 25 to the indoor expansion valves 41 and 51 including the liquid refrigerant communication pipe 6 becomes constant.

Then, by performing such liquid pipe temperature constant control, even when the refrigerant temperature Tco at the outlet of the outdoor heat exchanger 23 (i.e., the subcooling degree SCo of the refrigerant at the outlet of the outdoor heat exchanger 23) changes along with a gradual increase in the refrigerant quantity in the refrigerant circuit 10 by charging refrigerant into the refrigerant circuit 10, the effect of a change in the refrigerant temperature Tco at the outlet of the outdoor heat exchanger 23 will remain only within the refrigerant pipes from the outlet of the outdoor heat exchanger 23 to the subcooler 25, and the effect will not extend to the refrigerant pipes from the subcooler 25 to the indoor expansion valves 41 and 51 including the liquid refrigerant communication pipe 6 in the liquid refrigerant distribution portion B.

Further, the reason to perform the superheat degree control is because the refrigerant quantity in the evaporator portion C greatly affects the quality of wet vapor of the refrigerant at the outlets of the indoor heat exchangers 42 and 52. The superheat degree SHr of the refrigerant at the outlets of the indoor heat exchangers 42 and 52 is controlled such that the superheat degree SHr of the refrigerant at the gas sides of the indoor heat exchangers 42 and 52 (hereinafter regarded as the outlets of the indoor heat exchangers 42 and 52 in the description regarding the refrigerant quantity judging operation) becomes constant at the target superheat degree SHrs (in other words, the gas refrigerant at the outlets of the indoor heat exchangers 42 and 52 is in a superheat state) by controlling the opening degree of the indoor expansion valves 41 and 51, and thereby the state of the refrigerant flowing in the evaporator portion C is stabilized.

Consequently, by performing such superheat degree control, a state is created in which the gas refrigerant reliably flows into the gas refrigerant communication portion D.

By various control described above, the state of the refrigerant circulating in the refrigerant circuit 10 becomes stabilized, and the distribution of the refrigerant quantity in the refrigerant circuit 10 becomes constant. Therefore, when refrigerant starts to be charged into the refrigerant circuit 10 by additional refrigerant charging, which is subsequently performed, it is possible to create a state where a change in the refrigerant quantity in the refrigerant circuit 10 mainly appears as a change of the refrigerant quantity in the outdoor heat exchanger 23 (hereinafter this operation is referred to as “refrigerant quantity judging operation”).

Such operation control as described above is performed as the process in Step S11 by the controller 8 (more specifically, the indoor side controllers 47, 57, the outdoor side controller 37, and the transmission line 8a that connects between the controllers 37, 47 and 57) that functions as a normal operation controlling means to perform the refrigerant quantity judging operation.

(STEP S12: Refrigerant Quantity Calculation)

Next, additional refrigerant is charged into the refrigerant circuit 10 during performing the above described refrigerant quantity judging operation. At this time, the controller 8 that functions as refrigerant quantity calculating means calculates the refrigerant quantity in the refrigerant circuit 10 from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 during additional refrigerant charging in Step S12.

First, the refrigerant quantity calculating means in the present embodiment is described. The refrigerant quantity calculating means divides the refrigerant circuit 10 into a plurality of portions, calculates the refrigerant quantity for each divided portion, and thereby calculates the refrigerant quantity in the refrigerant circuit 10. More specifically, a relational expression between the refrigerant quantity in each portion and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is set for each divided portion, and the refrigerant quantity in each portion can be calculated by using these relational expressions. In the present embodiment, in a state where the four-way switching valve 22 is represented by the solid lines in FIG. 1, i.e., a state where the discharge side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23 and where the suction side of the compressor 21 is connected to the outlets of the indoor heat exchangers 42 and 52 via the gas side stop valve 27 and the gas refrigerant communication pipe 7, the refrigerant circuit 10 is divided into the following portions and a relational expression is set for each portion: a portion corresponding to the compressor 21 and a portion from the compressor 21 to the outdoor heat exchanger 23 including the four-way switching valve 22 (not shown in FIG. 5) (hereinafter referred to as “high-pressure gas pipe portion E”); a portion corresponding to the outdoor heat exchanger 23 (i.e., the condenser portion A); a portion from the outdoor heat exchanger 23 to the subcooler 25 and an inlet side half of the portion corresponding to the main refrigerant circuit side of the subcooler 25 in the liquid refrigerant distribution portion B (hereinafter referred to as “high temperature side liquid pipe portion B1”); an outlet side half of a portion corresponding to the main refrigerant circuit side of the subcooler 25 and a portion from the subcooler 25 to the liquid side stop valve 26 (not shown in FIG. 5) in the liquid refrigerant distribution portion B (hereinafter referred to as “low temperature side liquid pipe portion B2”); a portion corresponding to the liquid refrigerant communication pipe 6 in the liquid refrigerant distribution portion B (hereinafter referred to as “liquid refrigerant communication pipe portion B3”); a portion from the liquid refrigerant communication pipe 6 in the liquid refrigerant distribution portion B to the gas refrigerant communication pipe 7 in the gas refrigerant distribution portion D including portions corresponding to the indoor expansion valves 41 and 51 and the indoor heat exchangers 42 and 52 (i.e., the evaporator portion C) (hereinafter referred to as “indoor unit portion F”); a portion corresponding to the gas refrigerant communication pipe 7 in the gas refrigerant distribution portion D (hereinafter referred to as “gas refrigerant communication pipe portion G”); a portion from the gas side stop valve 27 (not shown in FIG. 5) in the gas refrigerant distribution portion D to the compressor 21 including the four-way switching valve 22 and the accumulator 24 (hereinafter referred to as “low-pressure gas pipe portion H”); and a portion from the high temperature side liquid pipe portion B1 in the liquid refrigerant distribution portion B to the low-pressure gas pipe portion H including the bypass expansion valve 62 and a portion corresponding to the bypass refrigerant circuit side of the subcooler 25 (hereinafter referred to as “bypass circuit portion I”). Next, the relational expressions set for each portion described above are described.

In the present embodiment, a relational expression between a refrigerant quantity Mog1 in the high-pressure gas pipe portion E and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mog1=Vog1×ρd,

which is a function expression in which a volume Vog1 of the high-pressure gas pipe portion E in the outdoor unit 2 is multiplied by the density ρd of the refrigerant in high-pressure gas pipe portion E. Note that, the volume Vog1 of the high-pressure gas pipe portion E is a value that is known prior to installation of the outdoor unit 2 at the installation site and is stored in advance in the memory of the controller 8. In addition, a density pd of the refrigerant in the high-pressure gas pipe portion E is obtained by converting the discharge temperature Td and the discharge pressure Pd.

A relational expression between a refrigerant quantity Mc in the condenser portion A and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mc=kc1×Ta+kc2×Tc+kc3×SHm+kc4×Wc+kc5×ρc+kc6×ρco+kc7,

which is a function expression of the outdoor temperature Ta, the condensation temperature Tc, a compressor discharge superheat degree SHm, the refrigerant circulation flow rate Wc, the saturated liquid density ρc of the refrigerant in the outdoor heat exchanger 23, and the density ρco of the refrigerant at the outlet of the outdoor heat exchanger 23. Note that, the parameters kc1 to kc7 in the above described relational expression are derived from a regression analysis of results of tests and detailed simulations and are stored in advance in the memory of the controller 8. In addition, the compressor discharge superheat degree SHm is a superheat degree of the refrigerant at the discharge side of the compressor, and is obtained by converting the discharge pressure Pd to refrigerant saturation temperature and subtracting this refrigerant saturation temperature from the discharge temperature Td. The refrigerant circulation flow rate Wc is expressed as a function of the evaporation temperature Te and the condensation temperature Tc (i.e., Wc=f(Te, Tc)). A saturated liquid density ρc of the refrigerant is obtained by converting the condensation temperature Tc. A density ρco of the refrigerant at the outlet of the outdoor heat exchanger 23 is obtained by converting the condensation pressure Pc which is obtained by converting the condensation temperature Tc and the refrigerant temperature Tco.

A relational expression between a refrigerant quantity Mol1 in the high temperature liquid pipe portion B1 and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mol1=Vol1×ρco,

which is a function expression in which a volume Vol1 of the high temperature liquid pipe portion B1 in the outdoor unit 2 is multiplied by the density ρco of the refrigerant in the high temperature liquid pipe portion B1 (i.e., the above described density of the refrigerant at the outlet of the outdoor heat exchanger 23). Note that, the volume Vol1 of the high-pressure liquid pipe portion B1 is a value that is known prior to installation of the outdoor unit 2 at the installation site and is stored in advance in the memory of the controller 8.

A relational expression between a refrigerant quantity Mol2 in the low temperature liquid pipe portion B2 and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mol2=Vol2×ρlp,

which is a function expression in which a volume Vol2 of the low temperature liquid pipe portion B2 in the outdoor unit 2 is multiplied by a density ρ12p of the refrigerant in the low temperature liquid pipe portion B2. Note that, the volume Vol2 of the low temperature liquid pipe portion B2 is a value that is known prior to installation of the outdoor unit 2 at the installation site and is stored in advance in the memory of the controller 8. In addition, the density ρlp of the refrigerant in the low temperature liquid pipe portion B2 is the density of the refrigerant at the outlet of the subcooler 25, and is obtained by converting the condensation pressure Pc and the refrigerant temperature T1p at the outlet of the subcooler 25.

A relational expression between a refrigerant quantity M1p in the liquid refrigerant communication pipe portion B3 and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

M1p=V1p×ρ1p,

which is a function expression in which a volume V1p of the liquid refrigerant communication pipe 6 is multiplied by the density ρ1p of the refrigerant in the liquid refrigerant communication pipe portion B3 (i.e., the density of the refrigerant at the outlet of the subcooler 25).

A relational expression between a refrigerant quantity Mr in the indoor unit portion F and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mr=kr1×T1p+kr2×ΔT+kr3×SHr+kr4×Wr+kr5,

which is a function expression of the refrigerant temperature T1p at the outlet of the subcooler 25, a temperature difference ΔT in which the evaporation temperature Te is subtracted from the room temperature Tr, the superheat degree SHr of the refrigerant at the outlets of the indoor heat exchangers 42 and 52, and the air flow rate Wr of the indoor fans 43 and 53. Note that, the parameters kr1 to kr5 in the above described relational expression are derived from a regression analysis of results of tests and detailed simulations and are stored in advance in the memory of the controller 8. Note that, here, the relational expression for the refrigerant quantity Mr is set for each of the two indoor units 4 and 5, and the total refrigerant quantity in the indoor unit portion F is calculated by adding the refrigerant quantity Mr in the indoor unit 4 to the refrigerant quantity Mr in the indoor unit 5. Note that relational expressions in each portion having parameters kr1 to kr5 with different values will be used when the indoor unit 4 and the indoor unit 5 are different in terms of the model and the capacity.

A relational expression between a refrigerant quantity Mgp in the gas refrigerant communication pipe portion G and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mgp=Vgp×ρgp,

which is a function expression in which a volume Vgp of the gas refrigerant communication pipe 7 is multiplied by a density ρgp of the refrigerant in the gas refrigerant communication pipe portion H. In addition, the density ρgp of the refrigerant in the gas refrigerant communication pipe portion G is an average value between a density ρs of the refrigerant at the suction side of the compressor 21 and a density ρeo of the refrigerant at the outlets of the indoor heat exchangers 42 and 52 (i.e., the inlet of the gas refrigerant communication pipe 7). The density ρs of the refrigerant is obtained by converting the suction pressure Ps and the suction temperature Ts, and a density ρeo of the refrigerant is obtained by converting the evaporation pressure Pe, which is a converted value of the evaporation temperature Te, and the outlet temperature Teo of the indoor heat exchangers 42 and 52.

A relational expression between a refrigerant quantity Mog2 in the low-pressure gas pipe portion H and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mog2=Vog2×ρs,

which is a function expression in which a volume Vog2 of the low-pressure gas pipe portion H in the outdoor unit 2 is multiplied by the density ρs of the refrigerant in the low-pressure gas pipe portion H. Note that, the volume Vog2 of the low-pressure gas pipe portion H is a value that is known prior to shipment to the installation site and is stored in advance in the memory of the controller 8.

A relational expression between a refrigerant quantity Mob in the bypass circuit portion I and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 is, for example, expressed by

Mob=kob1×ρco+kob2×ρs+kob3×Pe+kob4,

which is a function expression of a density ρco of the refrigerant at the outlet of the outdoor heat exchanger 23, and the density ρs and evaporation pressure Pe of the refrigerant at the outlet on the bypass circuit side of the subcooler 25. Note that, the parameters kob1 to kob3 in the above described relational expression are derived from a regression analysis of results of tests and detailed simulations and are stored in advance in the memory of the controller 8. In addition, the refrigerant quantity Mob of the bypass circuit portion I may be calculated using a simpler relational expression because the refrigerant quantity there is smaller compared to the other portions. For example, it is expressed as follows:

Mob=Vob×ρe×kob5,

which is a function expression in which a volume Vob of the bypass circuit portion I is multiplied by the saturated liquid density ρe at the portion corresponding to the bypass circuit side of the subcooler 25 and a correct coefficient kob 5. Note that, the volume Vob of the bypass circuit portion I is a value that is known prior to installation of the outdoor unit 2 at the installation site and is stored in advance in the memory of the controller 8. In addition, the saturated liquid density ρe at the portion corresponding to the bypass circuit side of the subcooler 25 is obtained by converting the suction pressure Ps or the evaporation temperature Te.

Note that, in the present embodiment, one outdoor unit 2 is provided. However, when a plurality of outdoor units are connected, as for the refrigerant quantity in the outdoor unit such as Mog1, Mc, Mol1, Mol2, Mog2, and Mob, the relational expression for the refrigerant quantity in each portion is set for each of the plurality of outdoor units, and the entire refrigerant quantity in the outdoor units is calculated by adding the refrigerant quantity in each portion of the plurality of the outdoor units.

As described above, in the present embodiment, by using the relational expressions for each portion in the refrigerant circuit 10, the refrigerant quantity in each portion is calculated from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the refrigerant quantity judging operation, and thereby the refrigerant quantity in the refrigerant circuit 10 can be calculated.

Further, this Step S12 is repeated until the condition for judging the adequacy of the refrigerant quantity in the below described Step S13 is satisfied. Therefore, in the period from the start to the completion of additional refrigerant charging, the refrigerant quantity in each portion is calculated from the operation state quantity during refrigerant charging by using the relational expressions for each portion in the refrigerant circuit 10. More specifically, a refrigerant quantity Mo in the outdoor unit 2 and the refrigerant quantity Mr in each of the indoor units 4 and 5 (i.e., the refrigerant quantity in each portion in the refrigerant circuit 10 excluding the refrigerant communication pipes 6 and 7) necessary for judgment of the adequacy of the refrigerant quantity in the below described Step S13 are calculated. Here, the refrigerant quantity Mo in the outdoor unit 2 is calculated by adding Mog1, Mc, Mol1, Mol2, Mog2, and Mob described above, each of which is the refrigerant quantity in each portion in the outdoor unit 2.

In this way, the process in Step S12 is performed by the controller 8 that functions as the refrigerant quantity calculating means for calculating the refrigerant quantity in each portion in the refrigerant circuit 10 from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the automatic refrigerant charging operation.

(STEP S13: Judgment of the Adequacy of the Refrigerant Quantity)

As described above, when additional refrigerant charging into the refrigerant circuit 10 starts, the refrigerant quantity in the refrigerant circuit 10 gradually increases. Here, when the volumes of the refrigerant communication pipes 6 and 7 are unknown, the refrigerant quantity that should be charged into the refrigerant circuit 10 after additional refrigerant charging cannot be prescribed as a total charging refrigerant quantity Mt that is a refrigerant quantity in the entire refrigerant circuit 10. However, when the focus is placed only on the outdoor unit 2 and the indoor units 4 and 5 (i.e., the refrigerant circuit 10 excluding the refrigerant communication pipes 6 and 7), it is possible to know in advance the optimal refrigerant quantity Mo in the outdoor unit 2 and the optimal refrigerant quantities Mr in the indoor units 4 and 5 by tests and detailed simulations. Therefore, additional refrigerant can be charged by the following manner: a refrigerant quantity that satisfies these optimal refrigerant quantities is stored in advance in the memory of the controller 8 as a target charging value Ms; the refrigerant quantity Mo in the outdoor unit 2 and the refrigerant quantities Mr in the indoor units 4 and 5 are calculated from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the automatic refrigerant charging operation by using the above described relational expressions; and additional refrigerant is charged until a value (hereinafter referred to as an inside-unit refrigerant quantity Mu) of the refrigerant quantity obtained by adding the refrigerant quantity Mo to the refrigerant quantities Mr (i.e., the refrigerant quantity in the refrigerant circuit 10 excluding the refrigerant communication pipes 6 and 7) reaches the target charging value Ms. In other words, Step S13 is a process to judge the adequacy of the refrigerant quantity charged in the refrigerant circuit 10, by additional refrigerant charging by judging whether or not the inside-unit refrigerant quantity Mu in the automatic refrigerant charging operation has reached the target charging value Ms.

Further, in Step S13, when a value of the inside-unit refrigerant quantity Mu is smaller than the target charging value Ms and additional refrigerant charging has not been completed, the process in Step S13 is repeated until the target charging value Ms is reached. In addition, when the inside-unit refrigerant quantity Mu reaches the target charging value Ms, the display 9b displays a message indicating that the additional refrigerant charging is completed, the refrigerant supply from the refrigerant cylinder is stopped, and Step S1 as the automatic refrigerant charging operation process is completed.

In this way, the process in Step S13 is performed by the controller 8 that functions as an automatic refrigerant charging judging means which is one of the refrigerant quantity judging means to judge the adequacy of the refrigerant quantity in the refrigerant circuit 10 in the refrigerant quantity judging operation of the automatic refrigerant charging operation (i.e., to judge whether or not the refrigerant quantity has reached the target charging value Ms). Then, by this automatic refrigerant charging operation, a state is reached where the total charged refrigerant quantity Mt is charged in the refrigerant circuit 10. the total charged refrigerant quantity Mt is the refrigerant quantity obtained by adding an additional charging quantity Ma that is a refrigerant quantity additionally charged to an initial charging quantity Mi that is a refrigerant quantity that has been charged into the refrigerant circuit 10 before the automatic refrigerant charging operation (i.e., the refrigerant quantity charged in the outdoor unit 2 in advance).

(STEP S2: Pipe Volume Calculation)

When the above described automatic refrigerant charging operation in Step S1 is completed, the process proceeds to the pipe volume calculation process in Step S2. In this pipe volume calculation process, the process from Steps S21 to S24 shown in FIG. 6 is performed by the controller 8 that functions as a pipe volume calculating means that calculates the volumes of the refrigerant communication pipes 6 and 7 based on the additional charging quantity Ma. Here, FIG. 6 is a flowchart of the pipe volume calculation process.

(STEPS S21, S22: Storing Data from the Automatic Refrigerant Charging Operation and Inputting Additional Charging Quantity)

In Step S21, the operation data from the above described automatic refrigerant charging operation is stored in the memory of the controller 8 such that the density of the refrigerant flowing through the refrigerant communication pipes 6 and 7 can be calculated in the below described Step S23. Here, the data stored in the memory of the controller 8 includes: condensation pressure Pc and temperature T1p of the refrigerant at the outlet of the subcooler 25 required for the calculation of the density pip of the refrigerant in the liquid refrigerant communication pipe portion B3; suction pressure Ps, suction temperature Ts, evaporation pressure Pe, and outlet temperature Teo required for the calculation of the density ρgp of the refrigerant in the gas refrigerant communication pipe portion H; and the inside-unit refrigerant quantity Mu at the time of completion of the automatic refrigerant charging operation.

In Step S22, a value of the additional charging quantity Ma or a value of the total charged refrigerant quantity Mt including the additional charging quantity Ma is input in the memory of the controller 8 through the input unit 9a. Here, the additional charging quantity Ma is a value of the refrigerant quantity obtained from the change in the weight of the refrigerant cylinder and the like in the automatic refrigerant charging operation. The additional charging quantity Ma may be manually input in the memory of the controller 8 through the input unit 9a provided in the controller 8 by an operator or the like who performs additional charging, or may be automatically input in the memory of the controller 8 by connecting a scale for measuring the change in the weight of the refrigerant cylinder as the input unit 9a to the controller 8.

Note that, here, the process of Steps S21 and S22 is performed in the process of the pipe volume calculation, however, the process may be performed in the process of the above described automatic refrigerant charging operation.

(STEPS S23, S24: Calculation of Communication Pipe Refrigerant Quantity, Calculation of Density, Calculation of Pipe Volume)

In Step S23, first, the total charged refrigerant quantity Mt, which is the refrigerant quantity in the entire refrigerant circuit 10 immediately after the automatic refrigerant charging operation, is obtained by adding the additional charging quantity Ma input in the controller 8 in Step S22 to the initial charging quantity Mi that is the refrigerant quantity that has been charged in the refrigerant circuit 10 before the automatic refrigerant charging operation. Here, the initial charging quantity Mi is stored in the memory of the controller 8. Next, the inside-unit refrigerant quantity Mu (or the target charging quantity Ms) stored in the controller 8 in Step S21 is subtracted from the total charged refrigerant quantity Mt, and thereby the communication pipe refrigerant quantity Mp that is the refrigerant quantity in the refrigerant communication pipes 6 and 7 is determined.

In addition, in Step S23, based on the condensation pressure Pc and the temperature T1p of the refrigerant at the outlet of the subcooler 25 stored in the controller 8 in Step S21, the density ρ1p of liquid refrigerant flowing through the liquid refrigerant communication pipe portion B 3 (i.e., the liquid refrigerant communication pipe 6) during the automatic refrigerant charging operation is determined. In addition, based on the suction pressure Ps, the suction temperature Ts, the evaporation pressure Pe, and the outlet temperature Teo stored in the controller 8 in Step S21, the density ρgp of gas refrigerant flowing through the gas refrigerant communication pipe portion H (i.e., the gas refrigerant communication pipe 7) during the automatic refrigerant charging operation is determined (note that the calculation of these densities ρ1p and ρgp is the same as the calculation of the densities ρ1p and ρgp for the calculation of the refrigerant quantity in Step S12 of the above described automatic refrigerant charging operation, and thus the description thereof is omitted here).

In Step S24, the volumes of the refrigerant communication pipes 6 and 7 (more specifically, the volume V1p of the liquid refrigerant communication pipe 6 and the volume Vgp of the gas refrigerant communication pipe) are calculated based on the communication pipe refrigerant quantity Mp and the densities ρ1p and ρgp determined in Step S23.

Here, first, the calculation method of the volumes of the refrigerant communication pipes 6 and 7 in the present embodiment is described.

The liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7 are provided so as to interconnect the indoor units 4 and 5 and the outdoor unit 2, so that these pipes have substantially the same pipe length but different pipe diameters, i.e., different flow passage cross-sectional areas, due to the different densities of the refrigerant flowing through the pipes. Therefore, the volume ratio between the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7 (in the description below, a value of Vgp/V1p in which the gas refrigerant communication pipe Vgp is divided by the volume V1quid refrigerant communication pipe 6 is referred to as a volume ratio Rv) will substantially correspond to the flow passage cross-sectional area ratio between these pipes, and furthermore, this volume ratio Rv will be within a certain range because the flow passage cross-sectional area ratio is predetermined based on the capacities and models of the indoor units 4 and 5 and the outdoor unit 2.

Further, if the volume ratio Rv between the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7 is known, a total value obtained by adding a value of the multiplication between the volume V1e liquid refrigerant communication pipe 6 and the liquid refrigerant density ρ1of the multiplication between the volume Vgp of the gas refrigerant communication pipe 7 and the gas refrigerant density ρwill be equal to the communication pipe refrigerant quantity Mp, as in the following expression:

$\begin{array}{c}\mathrm{Vlp}\times \rho \mathrm{lp}+\mathrm{Vgp}\times \rho \mathrm{gp}=\mathrm{Vlp}\times \rho \mathrm{lp}+\left(\mathrm{Vlp}\times \mathrm{Rv}\right)\times \rho \mathrm{gp}\\ =\mathrm{Vlp}\times \left(\rho \mathrm{lp}+\mathrm{Rv}\times \rho \mathrm{gp}\right)\\ =\mathrm{Mp}.\end{array}$

Thereby, the volume V1e liquid refrigerant communication pipe can be calculated as follows:

V1p=Mp/(ρ1p+Rv×ρgp),

and the volume Vgp of the gas refrigerant communication pipe 7 can be calculated as follows:

Vg p=V1p×Rv.

In addition, in the present embodiment, the volume ratio Rv between the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7 is stored in the memory of the controller 8 in advance as a value corresponding to the capacities and models of the indoor units 4, 5 and the outdoor unit 2, then the volumes of the refrigerant communication pipes 6 and 7 (more specifically, the volume V1e liquid refrigerant communication pipe 6 and the volume Vgp of the gas refrigerant communication pipe) are calculated using the above described calculation equations, based on the communication pipe refrigerant quantity Mp, the densities ρ1and ρgp determined in Step S23 and the volume ratio Rv.

<Refrigerant Leak Detection Operation Mode>

Next, the refrigerant leak detection operation mode is described with reference to FIGS. 1, 2, 5, and 7. Here, FIG. 7 is a flowchart of the refrigerant leak detection operation mode.

In the present embodiment, an example of a case is described where, whether or not the refrigerant in the refrigerant circuit 10 is leaking to the outside due to an unforeseen factor is detected periodically (for example, during a period of time such as on a holiday or in the middle of the night when air conditioning is not needed).

(STEP S31: Refrigerant Quantity Judging Operation)

First, when operation in the normal operation mode such as the above described cooling operation and heating operation has gone on for a certain period of time (for example, half a year to a year), the normal operation mode is automatically or manually switched to the refrigerant leak detection operation mode, and as is the case with the refrigerant quantity judging operation of the initial refrigerant quantity detection operation, the refrigerant quantity judging operation, including the all indoor unit operation, condensation pressure control, liquid pipe temperature control, superheat degree control, and evaporation pressure control, is performed. Here, as a rule, values that are the same as the target values in Step S11 of the refrigerant quantity judging operation of the automatic refrigerant charging operation are used for the target liquid pipe temperature T1ps in the liquid pipe temperature control, the target superheat degree SHrs in the superheat degree control, and the target low pressure Pes in the evaporation pressure control.

Note that, this refrigerant quantity judging operation is performed for each time the refrigerant leak detection operation is performed. Even when the refrigerant temperature Tco at the outlet of the outdoor heat exchanger 23 fluctuates due to the different operating conditions, for example, such as when the condensation pressure Pc is different or when there is a refrigerant leak, the refrigerant temperature T1p in the liquid refrigerant communication pipe 6 is maintained constant at the same target liquid pipe temperature T1ps by the liquid pipe temperature control.

In this way, the process in Step S31 is performed by the controller 8 that functions as the refrigerant quantity judging operation controlling means for performing the refrigerant quantity judging operation, including the all indoor unit operation, condensation pressure control, liquid pipe temperature control, superheat degree control, and evaporation pressure control.

(STEP S32: Refrigerant Quantity Calculation)

Next, the refrigerant quantity in the refrigerant circuit 10 is calculated from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the refrigerant leak detection operation in Step S32 by the controller 8 that functions as the refrigerant quantity calculating means during performing the above described refrigerant quantity judging operation. Calculation of the refrigerant quantity in the refrigerant circuit 10 is performed by using the above described relational expression between the refrigerant quantity in each portion in the refrigerant circuit 10 and the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10. However, at this time, the volumes V1p and Vgp of the refrigerant communication pipes 6 and 7, which were unknown at the time of after installation of constituent equipment of the air conditioner 1, have been calculated and the values thereof are known by the above described pipe volume calculation process. Thus, by multiplying the volumes V1p and Vgp of the refrigerant communication pipes 6 and 7 by the density of the refrigerant, the refrigerant quantities M1p, Mgp in the refrigerant communication pipes 6 and 7 can be calculated, and further by adding the refrigerant quantity in each of the other portions (for the calculation of the refrigerant in each of other portions, see Step S12 of the automatic refrigerant charging operation), the refrigerant quantity in the entire refrigerant circuit 10 (hereinafter referred to as “total calculated refrigerant quantity M”) can be calculated.

Here, as described above, the refrigerant temperature T1p in the liquid refrigerant communication pipe 6 is maintained constant at the target liquid pipe temperature T1ps by the liquid pipe temperature control. Therefore, regardless the difference in the operating conditions for the refrigerant leak detection operation, the refrigerant quantity M1p in the liquid refrigerant communication pipe portion B3 will be maintained constant even when the refrigerant temperature Tco at the outlet of the outdoor heat exchanger 23 changes.

In this way, the process in Step S32 is performed by the controller 8 that functions as the refrigerant quantity calculating means for calculating the refrigerant quantity at each portion in the refrigerant circuit 10 from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the refrigerant leak detection operation.

(STEPS S33, S34: Adequacy Judgment of the Refrigerant Quantity, Warning Display)

When refrigerant leaks from the refrigerant circuit 10, the refrigerant quantity in the refrigerant circuit 10 decreases. Then, when the refrigerant quantity in the refrigerant circuit 10 decreases, mainly, a tendency of a decrease in the subcooling degree SC_o at the outlet of the outdoor heat exchanger 23 appears. Along with this, the refrigerant quantity Mc in the outdoor heat exchanger 23 decreases, and the refrigerant quantities in other portions tend to be maintained substantially constant. Consequently, when there is a refrigerant leak from the refrigerant circuit 10, the total calculated refrigerant quantity M calculated in the above described Step S32 is smaller than the total charged refrigerant quantity Mt that is the refrigerant quantity in the entire refrigerant circuit 10 immediately after the automatic refrigerant charging operation is completed and that serves as a reference refrigerant quantity for judging whether or not there is a refrigerant leak; whereas when there is no refrigerant leak from the refrigerant circuit 10, the total calculated refrigerant quantity M has substantially the same value as the total charged refrigerant quantity Mt.

By utilizing the above described characteristics, whether or not there is a refrigerant leak is judged in Step S33. When it is judged in Step S33 that there is no refrigerant leak from the refrigerant circuit 10, the refrigerant leak detection operation mode is finished.

On the other hand, when it is judged in Step S33 that there is a refrigerant leak from the refrigerant circuit 10, the process proceeds to Step S34, and a warning indicating that a refrigerant leak is detected is displayed on the display 9b. Subsequently, the refrigerant leak detection operation mode is finished.

In this way, the process from Steps S32 to S34 is performed by the controller 8 that functions as the refrigerant leak detection means, which is one of the refrigerant quantity judging means, and which detects whether or not there is a refrigerant leak by judging the adequacy of the refrigerant quantity in the refrigerant circuit 10 during performing the refrigerant quantity judging operation in the refrigerant leak detection operation mode.

As described above, in the air conditioner 1 in the present embodiment, the controller 8 functions as the refrigerant quantity judging operation means, the refrigerant quantity calculating means, the refrigerant quantity judging means, and the pipe volume calculating means, and thereby configures the refrigerant quantity judging system for judging the adequacy of the refrigerant quantity charged into the refrigerant circuit 10.

(3) Characteristics of the Air Conditioner

The air conditioner 1 in the present embodiment has the following characteristics.

(A)

In the air conditioner 1 of the present embodiment, the volume of each of the refrigerant communication pipes 6 and 7 is calculated based on the additional charging quantity Ma that is the refrigerant quantity to be additionally charged after the refrigerant circuit 10 is configured by the interconnection of the outdoor unit 2 and the indoor units 4 and 5 via the refrigerant communication pipes 6 and 7. Thus, even if the volumes of the refrigerant communication pipes 6 and 7 are unknown, it is possible to calculate the volumes of the refrigerant communication pipes 6 and 7 by inputting a value of the additional charging quantity Ma. Accordingly, it is possible to determine the volume of each of the refrigerant communication pipes 6 and 7 while minimizing the labor of inputting information on the refrigerant communication pipes 6 and 7. As a result, it is possible to judge the adequacy of the refrigerant quantity in the refrigerant circuit 10 with high accuracy. More specifically, it is possible to judge whether or not there is a refrigerant leak from the refrigerant circuit 10 with high accuracy.

(B)

In the air conditioner 1 of the present embodiment, the automatic refrigerant charging operation can be performed in which whether or not the target charging quantity Ms is reached is judged based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10, so that it is possible to reliably perform additional refrigerant charging, and at the same time, it is possible to determine a value of the additional charging quantity Ma required for the calculation of the volumes of the refrigerant communication pipes 6 and 7 by performing the automatic refrigerant charging operation.

(C)

In the air conditioner 1 of the present embodiment, it is possible to calculate the communication pipe refrigerant quantity Mp that is present with high accuracy during the automatic refrigerant charging operation by subtracting the inside-unit refrigerant quantity Mu calculated based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the automatic refrigerant charging operation from the total charged refrigerant quantity Mt determined by adding the additional charging quantity Ma to the initial charging quantity Mi that is the refrigerant quantity that has been charged in the refrigerant circuit 10 before the automatic refrigerant charging operation. Thus, the volumes of the refrigerant communication pipes 6 and 7 can be calculated with high accuracy. In addition, in the air conditioner 1 of the present embodiment, it is possible to easily calculate both the volume V1p of the liquid refrigerant communication pipe 6 and the volume Vgp of the gas refrigerant communication pipe 7 by predetermining the volume ratio Rv between the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7 as a value corresponding to the capacities and models of the indoor units 4, 5 and the outdoor unit 2.

(4) Alternative Embodiment

In the above described embodiment, the communication pipe refrigerant quantity Mp required for the calculation of the volumes of the refrigerant communication pipes 6 and 7 is determined by calculating the inside-unit refrigerant quantity Mu determined by the calculation above from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the automatic refrigerant charging operation and subtracting the inside-unit refrigerant quantity Mu from the total charged refrigerant quantity Mt. However, the refrigerant whose quantity is substantially equal to the inside-unit refrigerant quantity Mu that is present when the refrigerant quantity in the refrigerant circuit 10 is reached the target charging quantity Ms by the automatic refrigerant charging operation may be charged as the initial charging quantity Mi into the refrigerant circuit 10 before the automatic refrigerant charging operation (in other words, into the indoor units 4, 5 and the outdoor unit 2 to be shipped to the installation site) is performed.

In this case, although a slight error will be generated depending on the capacities and models of the indoor units 4 and 5 or the number of units and the like, the additional charging quantity Ma that is the refrigerant quantity to be additionally charged into the refrigerant circuit 10 in the automatic refrigerant charging operation can be regarded as being corresponding to the communication pipe refrigerant quantity Mp that is refrigerant quantity present in the refrigerant communication pipes 6 and 7. Therefore, unlike the above described embodiment, the need to calculate the communication pipe refrigerant quantity Mp using the inside-unit refrigerant quantity Mu and the total charged refrigerant quantity Mt will be eliminated, and thus the volumes of the refrigerant communication pipes 6 and 7 can be easily calculated.

Meanwhile, even if the refrigerant whose quantity is different from the refrigerant quantity corresponding to the inside-unit refrigerant quantity Mu that is present when the refrigerant quantity in the refrigerant circuit 10 is reached the target charging quantity Ms by the automatic refrigerant charging operation is charged as the initial charging quantity Mi in the refrigerant circuit 10 before the automatic refrigerant charging operation (in other words, into the indoor units 4 and 5 and the outdoor unit 2 to be shipped to the installation site), in the above described embodiment, as described above, the inside-unit refrigerant quantity Mu is calculated from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit 10 in the automatic refrigerant charging operation. Therefore, even under various conditions of the initial charging quantity Mi, it is possible to determine a correct value of the communication pipe refrigerant quantity Mp, and it is possible to calculate the volumes of the refrigerant communication pipes 6 and 7 with high accuracy.

(5) Other Embodiment

While a preferred embodiment of the present invention has been described with reference to the figures, the scope of the present invention is not limited to the above embodiment, and the various changes and modifications may be made without departing from the scope of the present invention.

For example, in the above described embodiment, an example in which the present invention is applied to an air conditioner capable of switching and performing the cooling operation and heating operation is described. However, it is not limited thereto, and the present invention may be applied to different types of air conditioners such as a cooling only air conditioner and the like. In addition, in the above described embodiment, an example in which the present invention is applied to an air conditioner including a single outdoor unit is described. However, it is not limited thereto, and the present invention may be applied to an air conditioner including a plurality of outdoor units.

INDUSTRIAL APPLICABILITY

When the present invention is used, the labor of inputting information on the refrigerant communication pipe before the operation of a separate type air conditioner is minimized, and at the same time, the adequacy of the refrigerant quantity in the refrigerant circuit can be judged with high accuracy.

Claims

1. An air conditioner comprising:

a refrigerant circuit including a refrigerant communication pipe interconnecting a heat source unit and a utilization unit; and

a pipe volume calculating section configured to calculate volume of the refrigerant communication pipe based on an additional charging quantity, the additional charging quantity being a refrigerant quantity additionally charged after interconnecting the refrigerant communication pipe to the heat source unit and the utilization unit.

2. The air conditioner according to claim 1, further comprising

a refrigerant quantity judging section configured to judge whether or not refrigerant quantity charged in the refrigerant circuit has reached a target charging quantity based on an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in an automatic refrigerant charging operation in which refrigerant is additionally charged into the refrigerant circuit,

the additional charging quantity being the refrigerant quantity additionally charged into the refrigerant circuit in the automatic refrigerant charging operation.

3. An air conditioner comprising:

a refrigerant circuit including a refrigerant communication pipe interconnecting a heat source unit and a utilization unit; and

a pipe volume calculating section configured to calculate volume of the refrigerant communication pipe based on a communication pipe refrigerant quantity that is a refrigerant quantity in the refrigerant communication pipe,

the communication pipe refrigerant quantity being determined by subtracting an inside-unit refrigerant quantity from a total charged refrigerant quantity, and

the inside-unit refrigerant quantity being a refrigerant quantity in the refrigerant circuit excluding the refrigerant communication pipe, and the total charged refrigerant quantity being a refrigerant quantity in the entire refrigerant circuit after the refrigerant is additionally charged thereinto.

4. The air conditioner according to claim 2, further comprising

a refrigerant quantity calculating means section configured to calculate an inside-unit refrigerant quantity, the inside-unit refrigerant quantity a refrigerant quantity in the refrigerant circuit excluding the refrigerant pipe from an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in the automatic refrigerant charging operation,

the pipe volume calculating section being further configured to determine a total charged refrigerant quantity, the total charged refrigerant being a refrigerant quantity in the entire refrigerant circuit immediately after the automatic refrigerant charging operation by adding the additional charging quantity to an initial charging quantity, and the initial charging quantity being a refrigerant quantity charged in the refrigerant circuit before the automatic refrigerant charging operation,

the pipe volume calculating section being further configured to determine a communication pipe refrigerant quantity, the communication pipe refrigerant quantity being a refrigerant quantity in the refrigerant communication pipe determined by subtracting the inside-unit refrigerant quantity from the total charged refrigerant quantity,

the pipe volume calculating section being further configured to calculate a density of the refrigerant flowing through the refrigerant communication pipe from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit, and

the pipe volume calculating section being further configured to calculate the volume of the refrigerant communication pipe based on the communication pipe refrigerant quantity and the density.

5. The air conditioner according to claim 4, wherein

the refrigerant communication pipe includes a liquid refrigerant communication pipe and a gas refrigerant communication pipe,

the pipe volume calculating section is further configured to calculate a liquid refrigerant density and a gas refrigerant density, the liquid refrigerant density is a density of liquid refrigerant flowing through the liquid refrigerant communication pipe, and the gas refrigerant density is a density of gas refrigerant flowing through the gas refrigerant communication pipe, and

the pipe volume calculating section is further configured to calculate the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe based on the communication pipe refrigerant quantity, a volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe, the liquid refrigerant density, and the gas refrigerant density.

6. The air conditioner according claim 5, wherein

the refrigerant quantity calculating means section is configured to calculate a total calculated refrigerant quantity, the total calculated refrigerant quantity being a refrigerant quantity in the entire refrigerant circuit based on the volume of the refrigerant communication pipe calculated by the pipe volume calculating section and based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in a refrigerant leak detection operation in which whether or not there is a refrigerant leak from the refrigerant circuit is judged, and

the refrigerant quantity judging section is further configured to judge whether or not there is a refrigerant leak from the refrigerant circuit by comparing the total calculated refrigerant quantity with a reference refrigerant quantity that serves as a reference for judging whether or not there is a refrigerant leak from the refrigerant circuit.

7. The air conditioner according to claim 2, wherein

the pipe volume calculating section is configured to calculate a density of the refrigerant flowing through the refrigerant communication pipe from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit, and

the pipe volume calculating section is further configured to calculate the volume of the refrigerant communication pipe based on the additional charging quantity and the density.

8. The air conditioner according to claim 7, wherein

the refrigerant communication pipe includes a liquid refrigerant communication pipe and a gas refrigerant communication pipe, and

the pipe volume calculating section is configured to calculate a liquid refrigerant density and a gas refrigerant density, the liquid refrigerant density is a density of liquid refrigerant flowing through the liquid refrigerant communication pipe, and the gas refrigerant density is a density of gas refrigerant flowing through the gas refrigerant communication pipe, and

the pipe volume calculating section is further configured to calculate the volume of the liquid refrigerant communication pipe and the volume of the gas refrigerant communication pipe based on the additional charging quantity, a volume ratio between the liquid refrigerant communication pipe and the gas refrigerant communication pipe, the liquid refrigerant density, and the gas refrigerant density.

9. The air conditioner according to claim 8, further comprising

a refrigerant quantity calculating section configured to calculate a total calculated refrigerant quantity, the total calculated refrigerant quantity being a refrigerant quantity in the entire refrigerant circuit based on the volume of the refrigerant communication pipe calculated by the pipe volume calculating section and based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in a refrigerant leak detection operation in which whether or not there is a refrigerant leak from the refrigerant circuit is judged,

the refrigerant quantity judging section being further configured to judge whether or not there is a refrigerant leak from the refrigerant circuit by comparing the total calculated refrigerant quantity with a reference refrigerant quantity that serves as a reference for judging whether or not there is a refrigerant leak from the refrigerant circuit.

10. The air conditioner according to claim 7, further comprising

a refrigerant quantity calculating section configured to calculate a total calculated refrigerant quantity, the total calculated refrigerant quantity being a refrigerant quantity in the entire refrigerant circuit based on the volume of the refrigerant communication pipe calculated by the pipe volume calculating section and based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in a refrigerant leak detection operation in which whether or not there is a refrigerant leak from the refrigerant circuit is judged,

the refrigerant quantity judging section being further configured to judge whether or not there is a refrigerant leak from the refrigerant circuit by comparing the total calculated refrigerant quantity with a reference refrigerant quantity that serves as a reference for judging whether or not there is a refrigerant leak from the refrigerant circuit.

11. The air conditioner according claim 4, wherein

the refrigerant quantity calculating section is configured to calculate a total calculated refrigerant quantity, the total calculated refrigerant quantity being a refrigerant quantity in the entire refrigerant circuit based on the volume of the refrigerant communication pipe calculated by the pipe volume calculating section and based on the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in a refrigerant leak detection operation in which whether or not there is a refrigerant leak from the refrigerant circuit is judged, and

the refrigerant quantity judging section is further configured to judge whether or not there is a refrigerant leak from the refrigerant circuit by comparing the total calculated refrigerant quantity with a reference refrigerant quantity that serves as a reference for judging whether or not there is a refrigerant leak from the refrigerant circuit.