JP4762797B2 - Multi-type air conditioning system - Google Patents

Description

  The present invention relates to a multi-type air conditioning system, and in particular, a plurality of indoor units having an expansion valve for expanding the refrigerant, an evaporator for evaporating the expanded refrigerant, and a refrigerant flow path for circulating the refrigerant through them. The present invention relates to a multi-type air conditioning system connected to an outdoor unit.

  As air conditioning equipment for office buildings, factories, etc., multiple indoor units are distributed in the air conditioning area, and a single outdoor unit performs air conditioning such as cooling, heating, dehumidification, and ventilation. Has become the mainstream. This multi-type air conditioning system has the advantage that the installation space for the outdoor unit can be saved.

  FIG. 4 shows a schematic configuration diagram of a general multi-type air conditioning system. In this configuration diagram, for the sake of explanation, the case where two indoor units 10 are connected to the outdoor unit 11 is illustrated. The multi-type air conditioning system 1 compresses refrigerant by a compressor 2, condenses the compressed refrigerant by a condenser 3 installed in an outdoor unit 11, and expands the condensed refrigerant by expansion valves 4a and 4b. Each room is air-conditioned by a refrigerant circulation cycle in which the refrigerant expanded by the evaporators 5a and 5b installed in the indoor unit 10 is evaporated. Further, this refrigerant circulation cycle is constituted by a refrigerant flow path 6 through which the refrigerant circulates through each device. The condenser 3 exchanges heat between the compressed and condensed refrigerant whose temperature has increased and the outside air, and the evaporators 5a and 5b have expanded and vaporized refrigerant whose temperature has decreased and the indoor air. Heat exchange between.

  The expansion valve 4 is incorporated in each indoor unit 10, performs expansion and condensation control of the refrigerant, and distributes the circulation amount of the refrigerant to each indoor unit 10. As the expansion valve 4, an electronic expansion valve 4 that opens and closes the valve with an operation force of an electromagnetic coil is generally used. Since the electronic expansion valve 4 has a narrow internal clearance, foreign matter mixed in the fluid may adhere to cause malfunction. When this malfunction occurs, it cannot be detected by the air conditioning system itself. This is because the air-conditioning system has means for detecting abnormalities in the drive electronic circuit and electric circuit of the electronic expansion valve 4, but the malfunction of the electronic expansion valve 4 itself is detected depending on the system itself. It is not possible.

  For example, when the indoor unit 10 is in a blowing operation state, if the electronic expansion valve 4 is closed and malfunctions (locked) and does not open, the indoor unit 10 has a reduced air conditioning capability, and the original cooling is not performed. Does not work. In addition, when the indoor unit 10 is in the blowing operation state, if the electronic expansion valve 4 is opened and malfunctions (locked) and does not close completely, the refrigerant leaks to the compressor 2 and is compressed by liquid compression. The compressor 2 may be damaged. Moreover, the indoor unit 10 is cooled by evaporation of the leaked refrigerant, and condensation due to water leakage occurs. Therefore, various methods for detecting an abnormality of the electronic expansion valve 4 have been proposed.

  Patent Document 1 discloses an air conditioner provided with failure diagnosis means for a flow control device that is an expansion valve. Patent Document 2 discloses an expansion valve abnormality detection method and an air conditioner.

  The failure diagnosing means of the flow control device of Patent Document 1 is provided with piping temperature detection means at the entrance / exit of the indoor heat exchanger, and performs failure diagnosis of the flow control device from a difference between a certain reference value and a temperature detected by the piping temperature detection means. Is. That is, in the cooling mode, the difference between the detected inlet temperature and outlet temperature of the indoor heat exchanger is ΔT1. Next, the electric expansion valve is closed, and the difference between the detected inlet temperature and outlet temperature of the indoor heat exchanger is set to ΔT2. When the electric expansion valve is normally closed, the inlet temperature becomes lower and the outlet temperature becomes higher, so that the value of ΔT2 becomes larger than the value of ΔT1. Based on this principle, the failure of the flow control device is determined.

  The abnormality detection method and air conditioner of the expansion valve disclosed in Patent Document 2 are detected by a temperature sensor S1 provided between the electronic expansion valve and the evaporator and detecting the temperature of the evaporator and a temperature sensor S2 detecting the intake air temperature. The abnormality of the electronic expansion valve is detected from the measured temperature. That is, in the cooling mode, when the electronic expansion valve is locked open due to a failure, the refrigerant also flows into the evaporator, and the detected temperature T1 of the temperature sensor S1 is a value sufficiently smaller than the detected temperature T2 of the temperature sensor S2. Become. Based on this principle, in the cooling OFF mode, it is detected by T2-T1> A (reference value) that the electronic expansion valve is locked open. In the cooling ON mode, it is detected that the electronic expansion valve is closed and locked by T2-T1 <B (reference value).

JP-A-7-55299 JP 2000-274896 A

  By the way, in the multi-type air conditioning system, when any electronic expansion valve malfunctions among a plurality of indoor units, the entire air conditioning system operates normally at first glance. It is difficult to identify and detect malfunctions.

  Conventionally, the malfunction of the expansion valve is detected from the inlet side refrigerant temperature and the outlet side refrigerant temperature of the evaporator of the indoor unit. However, in the multi-type air conditioning system, since the refrigerant temperature on the outlet side of the evaporator is particularly affected by the air conditioning load of each indoor unit, it cannot be accurately detected. Further, in the multi-type air conditioning system, the total amount of liquefied refrigerant required indoors changes every moment, and this affects the rotational speed of the compressor and the circulation amount of the refrigerant. The refrigerant temperature varies. Therefore, it is difficult to accurately identify and detect the malfunction of the electronic expansion valve only from the inlet side refrigerant temperature and the outlet side refrigerant temperature of the evaporator of the indoor unit.

  An object of the present application is to solve such a problem and provide a multi-type air conditioning system that accurately identifies and detects an operation failure of each electronic expansion valve for a plurality of indoor units.

In order to achieve the above object, a multi-type air conditioning system according to the present invention includes a plurality of expansion valves that expand a refrigerant, an evaporator that evaporates the expanded refrigerant, and a refrigerant flow path that causes the refrigerant to flow therethrough. In a multi-type air conditioning system in which an indoor unit is connected to an outdoor unit, an inlet side temperature sensor that measures the inlet side refrigerant temperature t1 of the evaporator of each indoor unit, and a refrigerant pressure that is installed in the refrigerant flow path and measures the refrigerant pressure and the sensor, when each indoor unit is in the cooling operation state, t1 of each indoor unit is determined for each indoor unit from the pipe resistance of the model and each indoor unit of the indoor unit to the evaporation temperature t4 calculated from the refrigerant pressure The reference temperature t6 is larger than the value obtained by adding the correction value t5 in consideration of the characteristics, and t1 of each indoor unit is the lowest value among t1 of each indoor unit, from the model of each indoor unit and the piping resistance of each indoor unit. each indoor unit When bets larger than a value characteristic plus the correction value t7 taking into account the determined the expansion valve is characterized in that it comprises, an expansion valve detection means for detecting an abnormal.

Also, multi type air conditioning system, and an outlet side temperature sensor for measuring the outlet side refrigerant temperature t2 of the evaporator of the indoor unit, an indoor temperature sensor for measuring the intake air temperature t3 of each indoor unit, the refrigerant flow path A refrigerant pressure sensor that measures the refrigerant pressure, and the expansion valve detection means is configured such that when each indoor unit is in a blowing operation state, t1 of each indoor unit is an evaporation temperature t4 calculated from the refrigerant pressure. Is smaller than a value obtained by adding a correction value t5 in consideration of characteristics determined for each indoor unit from the model of each indoor unit and the piping resistance of each indoor unit, and t2 of each indoor unit is equal to t1 of each indoor unit. It is preferable to detect that the expansion valve is abnormal when the value obtained by adding the intake air temperature t3 is smaller than the value obtained by dividing by 2 .

  In addition, the multi-type air conditioning system includes an operation control unit that controls the operation state of each indoor unit by switching to a cooling operation or an air blowing operation, and the operation control unit includes a plurality of indoor units during the first operation, The indoor units corresponding to approximately half of the air conditioning capacity are in the cooling operation state, the remaining indoor units are in the air blowing operation state, and during the second operation, the operation state of all the indoor units is changed from the cooling operation to the air blowing operation or It is preferable to reverse the operation to the cooling operation state.

  Furthermore, in the multi-type air conditioning system, when the operation control means is in the first operation, approximately half of the plurality of indoor units are in the cooling operation state and the remaining half are in the air blowing operation state, and in the second operation, all are It is preferable to reverse the operation state of the indoor unit from the cooling operation to the blowing operation or from the blowing operation to the cooling operation.

  With the above configuration, the multi-type air conditioning system detects not only the temperature difference between the inlet side temperature and the outlet side temperature of the evaporator but also the intake air temperature of each indoor unit for each indoor unit in the blowing operation state. Use. Thereby, it is possible to detect an abnormal state of the expansion valve in consideration of the load condition of the air conditioning for each indoor unit.

  In addition, the multi-type air conditioning system considers the characteristics determined for each indoor unit for each indoor unit in the cooling operation state, and the abnormality of each indoor unit is based on the lowest inlet side temperature among the inlet side temperatures of each indoor unit. Is detected. As a result, it is possible to detect an abnormal state of the expansion valve in consideration of characteristics such as pipe resistance of air conditioning that varies from indoor unit to indoor unit.

  As described above, according to the multi-type air conditioning system of the present invention, it is possible to accurately identify and detect the malfunction of each electronic expansion valve for a plurality of indoor units.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of one embodiment of a multi-type air conditioning system. The multi-type air conditioning system 1 compresses a refrigerant by a compressor 2, condenses the compressed refrigerant by a condenser 3 provided in the outdoor unit 11, and condenses the condensed refrigerant by the electronic expansion valves 4a and 4b. Each room is air-conditioned by a refrigerant circulation cycle in which the refrigerant expanded and evaporated by the evaporators 5a and 5b provided in the indoor unit 10 is evaporated. Further, this refrigerant circulation cycle is constituted by a refrigerant flow path 6 through which the refrigerant circulates through each device. The condenser 3 exchanges heat between the refrigerant that has been compressed and condensed to rise in temperature and the outside air, and the evaporators 5a and 5b are heated between the refrigerant that has been expanded and vaporized to fall in temperature, and the indoor air. Exchange. A four-way valve 14 is provided in the refrigerant flow path 6 of the outdoor unit 11. Moreover, the solid line shown in the four-way valve 14 shows the refrigerant flow path 6 in the case of cooling, and the broken line shows the refrigerant flow path 6 in the case of heating. Moreover, the arrow shown with the continuous line in FIG. 1 shows the refrigerant | coolant flow path 6 in the case of air_conditioning | cooling, and the arrow shown with the broken line shows the refrigerant | coolant flow path 6 in the case of heating.

  Each indoor unit 10 includes an evaporator 5, an electronic expansion valve 4, an inlet side temperature sensor 7, an outlet side temperature sensor 8, and an indoor temperature sensor 9. The expansion valve detection means 12 receives signals of the inlet side refrigerant temperature t1, the outlet side refrigerant temperature t2, and the intake air temperature t3 from the inlet side temperature sensor 7 and the indoor temperature sensor 9 of each indoor unit 10, respectively. A refrigerant pressure sensor 13 is attached to the outlet side of the condenser 3 to measure the refrigerant pressure p and transmit it to the expansion valve detection means 12. These indoor units 10 are divided into two groups, group A and group B. FIG. 1 shows a case where there are three indoor units 10 in each of the A group and the B group.

  Here, the abnormality detection method of the electronic expansion valve 4 when there is one indoor unit 10 will be described. FIG. 2 is an explanatory diagram showing how the refrigerant evaporates inside the evaporator 5 provided in the indoor unit 10 connected to the refrigerant flow path 6. In FIG. 2, the shaded portion indicates the amount of the liquefied refrigerant, and the portion without the hatched indicates the amount of the gasified refrigerant. The arrows in the figure indicate the flow directions of the liquefied refrigerant and the gasified refrigerant. In addition, an inlet side temperature sensor 7 and an outlet side temperature sensor 8 are attached to each refrigerant channel 6 to measure the inlet side refrigerant temperature t1 and the outlet side refrigerant temperature t2, respectively. Furthermore, an indoor temperature sensor 9 for measuring the intake air temperature t3 is attached to each indoor unit 10.

  FIG. 2A shows a case where the open / close state of the electronic expansion valve 4 is normal during the cooling operation. In this case, the electronic expansion valve 4 is opened, and the expanded liquefied refrigerant is appropriately evaporated and gasified in the evaporator 5. At this time, the inlet-side refrigerant temperature t1 and the outlet-side refrigerant temperature t2 of the indoor unit 10 are substantially constant temperatures, and the difference between the temperatures is small. FIG. 2B shows a case where the electronic expansion valve 4 is locked in the open state and is not completely closed when switching from the cooling operation to the air blowing operation. In this case, the liquefied refrigerant required inside the evaporator 5 is not supplied, and is completely evaporated in the middle of the evaporator 5. At this time, the inlet-side refrigerant temperature t1 of the evaporator 5 decreases due to the decrease in the refrigerant pressure p. Further, the outlet-side refrigerant temperature t2 of the evaporator 5 rises as the degree of superheat on the outlet side increases as the refrigerant flow rate decreases. Accordingly, the temperature difference between the inlet side refrigerant temperature t1 and the outlet side refrigerant temperature t2 becomes large. FIG. 2C shows a case where the electronic expansion valve 4 is locked in the open state during the cooling operation. In this case, since excessive liquefied refrigerant is supplied more than required inside the evaporator 5, the refrigerant is not completely gasified even when passing through the evaporator 5. At this time, the inlet-side refrigerant temperature t1 and the outlet-side refrigerant temperature t2 of the indoor unit 10 are substantially constant temperatures, and the difference between the temperatures is small.

  The change in temperature difference between the inlet side refrigerant temperature t1 and the outlet side refrigerant temperature t2 of the indoor unit 10 in the abnormal state of the electronic expansion valve 4 is as follows when the outdoor unit 11 and the indoor unit 10 are 1: 1. This is applied to the abnormality determination of the electronic expansion valve 4 as it is. However, the multi-type air conditioning system 1 cannot be applied as it is. This is not an accurate detection in the multi-type air conditioning system 1 because the outlet side refrigerant temperature t2 of the evaporator 5 is particularly affected by the air conditioning load of each indoor unit 10. Further, in the multi-type air conditioning system 1, the total amount of liquefied refrigerant required indoors changes every moment, and this affects the rotational speed of the compressor 2 and the circulation amount of the refrigerant. This is because the inlet side refrigerant temperature t1 varies.

(Abnormality detection method for multi-type air conditioning system)

  FIG. 3 is a flowchart showing one embodiment of the abnormality detection method in the case of the multi-type air conditioning system 1. In this abnormality detection method, the indoor units 10 are selected so that the air conditioning capacity is approximately half of each, and these are set as group A and group B, respectively. In the present embodiment, abnormality detection of the multi-type air conditioning system 1 is performed twice during the first operation and during the second operation. During the first operation, one group (for example, Group A) of the air conditioners 10 divided into two groups is set in a cooling operation state, and the other group (for example, Group B) is set in a blowing operation state (S1). After detecting the abnormality of the electronic expansion valves 4a and 4b of each indoor unit 10 in this state, all the indoor units 10 are once set in the cooling operation state (S4), and then divided into two groups during the second operation. Of the air conditioners 10, one group (for example, Group A) is set in the blowing operation state, and the other group (for example, Group B) is set in the cooling operation state (S5). The reason why the two groups are divided is that the compressor 2 is not temporarily stopped. Moreover, it is for keeping the circulation amount of the liquefied refrigerant of the whole multi-type air conditioning system 1 substantially constant. Therefore, it is desirable that the air conditioning capabilities of the group A indoor units 10 and the group B indoor units 10 are substantially equal. However, when the air conditioning capability of the indoor unit 10 can be regarded as almost the same in all the indoor units 10, the indoor unit 10 may be divided into the A group and the B group so as to be approximately half of each.

  At the time of the first operation, for the group A in the cooling operation state, it is determined whether or not the electronic expansion valve 4 is locked in the open state for all the indoor units 10 in the group according to the following criteria (S2). . Further, during the second operation, the same determination is performed for the group B in the cooling operation state (S7).

The first determination formula is to detect the abnormality when the electronic expansion valve 4 is normal when t1 <t4 + t5 is satisfied, and when not satisfied. Here, t1 is an inlet side refrigerant temperature, t4 is an evaporation temperature calculated from the refrigerant pressure p, and t5 is a correction value considering characteristics determined for each indoor unit 10, and each indoor unit The correction value is calculated from the ten models and the pipe resistance of the indoor unit 10. The determination equation is basically the evaporation temperature t 4 when calculated from the refrigerant pressure p of the refrigerant pressure sensor 13 provided on the outlet side is measured in the condenser 3, the inlet side refrigerant temperature t1 the corresponding It is a comparison. However, each indoor unit 10 of the multi-type air conditioning system 1 has, for example, a different pipe length from the outdoor unit 11 and a different temperature loss due to pipe resistance. Therefore, a more appropriate determination is made by considering a correction value (temperature) in consideration of the characteristics. Further, for example, when the models of the indoor units 10 are different, a more appropriate determination is made by considering a correction value (temperature) considering each characteristic. That is, the inlet side refrigerant temperature t1 of the indoor unit 10 is higher than the value obtained by adding a correction value t5 to evaporation temperature t4, the indoor unit 10 is lowered air conditioning capacity, become ineffective the inherent cooling Judge that And the abnormality of the electronic expansion valve 4 is detected as the factor . Evaporation temperature t4, in the air conditioning of a normal office building, is approximately 0 ℃.

  The second determination formula is to detect the abnormality when the electronic expansion valve 4 is normal when t1 <t6 + t7 is satisfied, and when not satisfied. Here, t6 is the lowest value of t1 of each indoor unit 10 and is a reference temperature. Further, t7 is a correction value considering characteristics determined for each indoor unit 10, but unlike t5 described above, it is a tolerance considering the variation of each indoor unit 10. This determination formula is used when the inlet refrigerant temperature having the lowest temperature among the indoor units 10 in the group is set as the reference temperature t6 and the characteristic value determined for each indoor unit 10 is higher than a value corrected in consideration of tolerance. Determines that the indoor unit 10 has a reduced air conditioning capability and the original cooling is no longer effective. And the abnormality of the electronic expansion valve 4 is detected as the factor.

  The first determination formula is satisfied not only when the electronic expansion valve 4 is abnormal, but also when the refrigerant leaks at the joint or valve of the refrigerant flow path 6 and is insufficient. In this case, because the refrigerant is insufficient, the cooling is not effective and the inlet side refrigerant temperature t1 rises. However, in this case, the second determination formula is not satisfied. This is because the inlet side refrigerant temperature t1 of the indoor unit 10 rises. Therefore, only the second determination formula may be applied, or two determination formulas may be applied together. The second determination formula is a basic determination formula for detecting an abnormality (decrease in air conditioning capability) of the electronic expansion valve 4 of each indoor unit 10 of the multi-type air conditioning system 1 during the cooling operation.

  At the time of the first operation, for the group B in the air blowing operation state, it is determined whether or not the electronic expansion valve 4 is locked in the open state for all the indoor units 10 in the group according to the following criteria (S3). . Further, during the second operation, the same determination is performed for the group A in the blowing operation state (S6).

The first determination formula is to detect the abnormality when the electronic expansion valve 4 is normal when t1> t4 + t5 is satisfied, and when not satisfied. Here, t1 is an inlet side refrigerant temperature, t4 is an evaporation temperature calculated from the refrigerant pressure p, and t5 is a correction value considering characteristics determined for each indoor unit 10, and each indoor unit The correction value is calculated from the ten models and the pipe resistance of the indoor unit 10. The determination equation is basically the evaporation temperature t 4 when calculated from the refrigerant pressure p of the refrigerant pressure sensor 13 provided on the outlet side is measured in the condenser 3, the inlet side refrigerant temperature t1 the corresponding It is a comparison. However, each indoor unit 10 of the multi-type air conditioning system 1 has, for example, different pipe lengths from the outdoor unit 11 and different temperature loss due to pipe resistance, and therefore adds a correction value (temperature) considering its characteristics. Therefore, make a more appropriate decision. For example, when the models of the indoor units 10 are different, a more appropriate determination is made by adding a correction value (temperature) considering each characteristic. Therefore, determining that an inlet side refrigerant temperature t1 of the indoor unit 10 is lower than the value obtained by adding a correction value t5 to evaporation temperature t4, the evaporator 5 of the indoor unit 10 is leaking refrigerant Is done. And the abnormality of the electronic expansion valve 4 is detected as the factor.

  The second determination formula is to detect the abnormality when the electronic expansion valve 4 is normal when t2> (t1 + t3) / 2 is satisfied, and when not satisfied. Here, t2 is the outlet side refrigerant temperature, and t3 is the intake air temperature. This determination formula basically determines the temperature difference between the inlet side refrigerant temperature t1 and the outlet side refrigerant temperature t2. However, each indoor unit 10 of the multi-type air conditioning system 1 cannot make an appropriate determination because the inlet side refrigerant temperature t1 and the outlet side refrigerant temperature t2 vary as described above. Therefore, the abnormality of the electronic expansion valve 4 is detected including the intake air temperature t3 of each indoor unit 10. Therefore, t2> t1 + f (t3) is set using the function f determined by the value of t3. In the present embodiment, this is (t1 + t3) / 2 in accordance with practical characteristics.

  The first judgment formula is the reverse of the first judgment formula at the time of cooling operation, and it is preferable to apply these judgment formulas together. The second judgment formula is improved so that the conventional judgment formula can be expanded and applied to the multi-type air conditioning system 1 during the air blowing operation. Therefore, these first and second determination formulas may be applied independently as determination formulas, or two determination formulas may be applied together.

It is a block diagram showing a schematic structure of one embodiment of a multi type air harmony system concerning the present invention. It is explanatory drawing which shows the mode of the evaporation of the refrigerant | coolant inside the evaporator of an indoor unit. It is. It is a flowchart which shows one Embodiment of the abnormality detection method in the case of a multi-type air conditioning system. It is a schematic block diagram of a general multi-type air conditioning system.

Explanation of symbols

  1 Multi-type air conditioning system, 2 compressor, 3 condenser, 4, 4a, 4b electronic expansion valve (expansion valve), 5, 5a, 5b evaporator, 6 refrigerant flow path, 7 inlet side temperature sensor, 8 outlet side Temperature sensor, 9 Indoor temperature sensor, 10 Indoor unit, 11 Outdoor unit, 12 Expansion valve detection means, 13 Refrigerant pressure sensor, 14 Four-way valve, t1 Inlet side refrigerant temperature, t2 Outlet side refrigerant temperature, t3 Intake air temperature, t4 Evaporation Temperature, t5 correction value, t6 reference temperature, t7 correction value (tolerance).

Claims (4)

In a multi-type air conditioning system for connecting a plurality of indoor units having an expansion valve for expanding a refrigerant, an evaporator for evaporating the expanded refrigerant, and a refrigerant flow path for circulating the refrigerant to the outdoor unit,
An inlet side temperature sensor for measuring an inlet side refrigerant temperature t1 of an evaporator of each indoor unit;
A refrigerant pressure sensor installed in the refrigerant flow path for measuring the refrigerant pressure;
When the indoor unit is in the cooling operation state, t1 of each indoor unit, taking into account the characteristics defined in the evaporation temperature t4 calculated from the refrigerant pressure from the pipe resistance of the model and the indoor unit of the indoor units for each indoor unit Each indoor unit has a reference temperature t6 that is greater than the value obtained by adding the corrected value t5 and the t1 of each indoor unit is the lowest value of t1 of each indoor unit, based on the model of each indoor unit and the piping resistance of each indoor unit. Expansion valve detection means for detecting that the expansion valve is abnormal when the value is larger than the value obtained by adding a correction value t7 in consideration of characteristics determined for each
A multi-type air conditioning system comprising: The multi-type air conditioning system according to claim 1,
An outlet side temperature sensor for measuring the outlet side refrigerant temperature t2 of the evaporator of each indoor unit;
An indoor temperature sensor for measuring the intake air temperature t3 of each indoor unit;
A refrigerant pressure sensor installed in the refrigerant flow path to measure the refrigerant pressure , and
When each indoor unit is in the air blowing operation state, the expansion valve detection means detects that each indoor unit t1 has an evaporation temperature t4 calculated from the refrigerant pressure based on the model of each indoor unit and the piping resistance of each indoor unit. Smaller than a value obtained by adding a correction value t5 in consideration of characteristics determined for each indoor unit, and t2 of each indoor unit is smaller than a value obtained by dividing the value obtained by adding the intake air temperature t3 of each indoor unit to t1 of each indoor unit by 2. Sometimes, the multi-type air conditioning system is characterized by detecting that the expansion valve is abnormal . 3. The multi-type air conditioning system according to claim 1 or 2 , further comprising operation control means for controlling the operation state of each indoor unit by switching to a cooling operation or an air blowing operation. During operation, among the plurality of indoor units, indoor units corresponding to approximately half of the air conditioning capacity are set in the cooling operation state, and the remaining indoor units are set in the blowing operation state. During the second operation, the operation state of all the indoor units is set. A multi-type air conditioning system that reverses from a cooling operation to a blowing operation or from a blowing operation to a cooling operation. The multi-type air conditioning system according to any one of claims 1 to 3, wherein during the first operation, the operation control means sets substantially half of the plurality of indoor units as a cooling operation state, Multi-type air conditioner characterized in that half of the air-conditioning operation is performed and the operation state of all indoor units is reversed from the cooling operation to the air-blowing operation or from the air-blowing operation to the air-cooling operation during the second operation. system.

Images