Indoor unit of refrigeration apparatus

An indoor unit of a refrigeration apparatus includes: a drain pan that includes four wall surfaces including a first wall surface, and has a quadrangle shape in a plan view; a heat exchanger disposed above the drain pan and through which a combustible refrigerant, having a larger specific gravity than air, flows; a fan that generates air flow to the heat exchanger; a gas sensor that detects a refrigerant leakage; and a casing accommodating the drain pan, the heat exchanger, the fan, and the gas sensor.

TECHNICAL FIELD

The present disclosure relates to an indoor unit of a refrigeration apparatus configured to detect refrigerant leakage.

BACKGROUND

In recent years, an air conditioner adopting a refrigerant having low global warming potential (GWP) (hereinafter, called low GWP refrigerants) is introduced into a market in view of environmental protection. Examples of the low GWP refrigerant include a flammable refrigerant disclosed in Patent Literature 1 (JP 2019-11914 A).

SUMMARY

An indoor unit of a refrigeration apparatus according to one or more embodiments of the present disclosure includes a drain pan, a heat exchanger, a fan, a gas sensor, and a casing. The drain pan has four wall surfaces including a first wall surface and has a quadrangle shape in a plan view. The heat exchanger is installed above the drain pan, and a combustible refrigerant having a larger specific gravity than air flows through the heat exchanger. The fan generates an air flow to the heat exchanger. The gas sensor detects leakage of the refrigerant. The casing accommodates the drain pan, the heat exchanger, the fan, and the gas sensor. The casing has a plurality of side plates, a partition plate, and a blow-out port. The plurality of side plates constitutes side surfaces of an outer contour. The partition plate divides an internal space surrounded by the plurality of side plates into a first chamber and a second chamber. The drain pan is installed in the first chamber. The fan is installed in the second chamber. The blow-out port is formed on a first side plate, which is one of the plurality of side plates. The first side plate faces the first wall surface of the drain pan. The wall surfaces other than the first wall surface of the drain pan are arranged along the side plates or the partition plate. An installation position of the gas sensor is above the drain pan, and a height H from an upper end of the drain pan to the gas sensor satisfies a relational expression represented by
L·W{C1·H1/Q+C2·H/(Q−C3·L·H{circumflex over ( )}(3/2))}≤90, where

L [m]: a length of the first wall surface of the drain pan,

W [m]: a length of the wall surface of the drain pan intersecting the first wall surface,

H1 [m]: a depth of the drain pan, and

Q [m{circumflex over ( )}3/s]: a refrigerant leakage flow rate.

DETAILED DESCRIPTION

Description will be made herein about an air conditioner10as an exemplary refrigeration apparatus.

FIG. 1is a piping diagram depicting a configuration of a refrigerant circuit C in the air conditioner10according to one or more embodiments of the present disclosure. The air conditioner10depicted inFIG. 1cools and heats air in a room. As depicted inFIG. 1, the air conditioner10includes an outdoor unit11disposed outdoors and an indoor unit20installed in the room. The outdoor unit11and the indoor unit20are connected to each other by two connection pipes2and3. The refrigerant circuit C is accordingly constituted in the air conditioner10. The refrigerant circuit C is filled with a refrigerant that circulates to achieve a vapor compression refrigeration cycle.

The refrigerant sealed in the refrigerant circuit C is a flammable refrigerant. Examples of the flammable refrigerant include refrigerants categorized in Class 3 (higher flammability), Class 2 (lower flammability), and Subclass 2L (slight flammability) in the standards according to ASHRAE 34 Designation and safety classification of refrigerant in the U.S.A. or the standards according to ISO 817 Refrigerants—Designation and safety classification.

One or more embodiments employ R32 as the refrigerant.

The outdoor unit11is provided with a compressor12, an outdoor heat exchanger13, an outdoor expansion valve14, and a four-way switching valve15.

The compressor12compresses a low-pressure refrigerant and discharges a high-pressure refrigerant obtained by compression. The compressor12includes any one of a compression mechanism of a scroll type, a rotary type, or the like driven by a compressor motor12a. An operating frequency of the compressor motor12ais variable by means of an inverter device.

As depicted inFIG. 1, there is provided a discharge pipe121connecting a refrigerant discharge port of the compressor12and the four-way switching valve15. There is further provided a suction pipe122connecting a suction port of the compressor12and the four-way switching valve15.

The outdoor heat exchanger13is of a fin-and-tube heat exchanger. There is installed an outdoor fan16adjacent to the outdoor heat exchanger13. The outdoor heat exchanger13causes heat exchange between air conveyed by the outdoor fan16and a refrigerant flowing in the outdoor heat exchanger13.

As depicted inFIG. 1, there is provided a first pipe131connecting a refrigerant inflow port of the outdoor heat exchanger13and the four-way switching valve15during cooling operation.

The outdoor expansion valve14is an electronic expansion valve having a variable opening degree. The outdoor expansion valve14is installed downstream of the outdoor heat exchanger13in a refrigerant flow direction in the refrigerant circuit C during cooling operation.

The opening degree of the outdoor expansion valve14is fully opened during cooling operation. In contrast, during heating operation, the opening degree of the outdoor expansion valve14is adjusted such that a refrigerant flowing into the outdoor heat exchanger13is decompressed up to a pressure enabling evaporation (evaporation pressure) in the outdoor heat exchanger13.

The four-way switching valve15has first to fourth ports. At the four-way switching valve15, a first port P1is connected to the discharge pipe121of the compressor12, a second port P2is connected to the suction pipe122of the compressor12, a third port P3is connected to the first pipe131of the outdoor heat exchanger13, and a fourth port P4is connected to a gas shutoff valve5.

The four-way switching valve15is switched between a first state (state indicated by solid lines inFIG. 1) and a second state (state indicated by broken lines inFIG. 1). At the four-way switching valve15in the first state, the first port P1and the third port P3communicate with each other and the second port P2and the fourth port P4communicate with each other. At the four-way switching valve15in the second state, the first port P1and the fourth port P4communicate with each other and the second port P2and the third port P3communicate with each other.

The outdoor fan16is composed of a propeller fan driven by an outdoor fan motor16a. An operating frequency of the outdoor fan motor16ais variable by means of an inverter device.

The two connection pipes include the liquid connection pipe2and the gas connection pipe3. The liquid connection pipe2has one end connected to a liquid shutoff valve4and the other end connected to a liquid connection tube6of an indoor heat exchanger32. As depicted inFIG. 1, the liquid connection tube6is connected directly or indirectly to a refrigerant inlet of the indoor heat exchanger32during cooling operation.

The gas connection pipe3has one end connected to the gas shutoff valve5and the other end connected to a gas connection tube7of the indoor heat exchanger32. As depicted inFIG. 1, the gas connection tube7is connected directly or indirectly to a refrigerant outlet of the indoor heat exchanger32during cooling operation.

FIG. 2is a perspective view of the indoor unit20of an air conditioner according to one or more embodiments of the present disclosure, in which an upper surface of the casing22is removed.FIG. 3is a side view of the indoor unit20of the air conditioner, and the casing22is indicated by a chain double-dashed line.

InFIGS. 2 and 3, the indoor unit20is installed in an attic space of a building or the like, and includes the casing22, an indoor fan30, the indoor heat exchanger32, a drain pan36, and a gas sensor55. The casing22has a ventilation space. InFIG. 3, the ventilation space is an internal space in which air flows from a fourth side plate27of the casing22toward a first side plate23of the casing22. In the ventilation space, the indoor fan30and the indoor heat exchanger32are arranged in order from the fourth side plate27to the first side plate23of the casing.

The casing22has a box shape and has the first side plate23, a second side plate24, a third side plate26, and the fourth side plate27that form side surfaces of an outer contour of the casing22.

The fourth side plate27is located on a back surface of the casing22, and the fourth side plate27is provided with a suction port21. The suction port21sucks air into the casing22through an inlet duct (indicated by an alternate long and short dash line inFIG. 3).

Further, the first side plate23is located on a front surface of the casing22, and the first side plate23is provided with a blow-out port37. The blow-out port37blows air that has passed through the indoor heat exchanger32to outside of the casing22through an outlet duct (indicated by an alternate long and short dash line inFIG. 3).

The second side plate24is provided with an opening241. The opening241is used for replacing a drain pump (not shown) that discharges condensed water accumulated in the drain pan36. The opening241is also used for replacing the gas sensor55. The opening241is closed by a lid25except when the drain pump or the gas sensor is replaced.

The partition plate28divides the ventilation space into a first chamber R1and a second chamber R2. The second chamber R2communicates with the suction port21. The indoor fan30is installed in the second chamber R2. The first chamber R1communicates with the blow-out port37. The indoor heat exchanger32and the drain pan36are installed in the first chamber R1.

Further, the partition plate28is plate-shaped and is installed so as to be parallel to the front surface and the back surface of the casing22. The partition plate28is provided with three openings28a,28b, and28caligned side by side. The three openings28a,28b, and28care aligned parallel to the front surface and the back surface of the casing22.

The indoor fan30is disposed in the second chamber R2. The indoor fan30sucks air into the second chamber R from the suction port21and blows air into the first chamber R1through the openings28a,28b, and28cof the partition plate28. The indoor fan30is a double-suction sirocco fan. The indoor fan30includes three impellers301a,301b, and301c, three scroll casings302a,302b, and302caccommodating the impellers301a,301b, and301c, respectively, and a motor30athat drives the impellers301a,301b, and301c.

The impellers301a,301b, and301care aligned side by side toward a side of the casing22. The scroll casings302a,302b, and302chave three scroll suction ports303a,303b, and303c, respectively, formed on both side surfaces, and scroll blow-out ports304a,304b, and304c, respectively, formed on the front surface. The scroll blow-out ports304a,304b, and304care arranged so as to respectively correspond to the openings28a,28b, and28cof the partition plate28.

The motor30ais disposed between the scroll casing302aand the scroll casing302bin a plan view of the casing22, and a shaft is connected to the two impellers301aand301b. The impeller301band the impeller301care connected to each other by a shaft.

The indoor fan30is not limited to a configuration in which a plurality of double-suction sirocco fans are driven by one motor30aas described above. The number of sirocco fans may be two, and the number of motors may be different. Alternatively, the indoor fan30may be a fan other than a sirocco fan.

The indoor heat exchanger32is disposed in the first chamber R1. The indoor heat exchanger32exchanges heat between the air blown from the scroll blow-out ports304a,304b, and304cinto the first chamber R1and the refrigerant flowing through the indoor heat exchanger32.

The indoor heat exchanger32is a cross-fin-tube heat exchanger. The indoor heat exchanger32has a plurality of fins321, a plurality of heat transfer tubes322, a collection tube323(FIG. 3), and a connection tube324. The fins321are rectangular thin plates including a metal having high thermal conductivity, for example, aluminum or an aluminum alloy. The fins321are each provided with a plurality of through holes penetrating in a plate thickness direction. The plurality of fins321are layered at regular intervals.

The heat transfer tubes322are copper tubes. The heat transfer tubes322are inserted into the through holes of the fins321and then expanded to come into close contact with the fins321. The collection tube323is connected to one end of the plurality of heat transfer tubes322. The connection tube324connects the heat transfer tubes322to each other at the other end of the plurality of heat transfer tubes322(i.e., the connection tube324is connected to the other end of the plurality of heat transfer tubes322).

For convenience of explanation, among ends of the indoor heat exchanger32, an end on a side where the collection tubes323are located is referred to as a first end32a, and an end on a side where the connection tube324is located is referred to as a second end32b.

The indoor heat exchanger32is inclined toward the front surface of the casing22from a lower end to an upper end. Further, a combustible refrigerant having a larger specific gravity than air, for example, R32 refrigerant, flows through the indoor heat exchanger32.

The indoor heat exchanger32is not limited to a cross-fin-tube heat exchanger.

The drain pan36has a first wall surface361, a second wall surface362, a third wall surface363, and a fourth wall surface364, and has a quadrangle shape in a plan view. The indoor heat exchanger32is installed above the drain pan36, and the drain pan36receives water condensed by the indoor heat exchanger32.

The first wall surface361of the drain pan36faces the first side plate23of the casing22, and as a result, the blow-out port37formed in the first side plate23is along the first wall surface361of the drain pan36. The second wall surface362of the drain pan36is along the second side plate24of the casing22, the third wall surface363of the drain pan36is along the third side plate26of the casing22, and the fourth wall surface364of the drain pan36is along the partition plate28.

An electric component box50is installed along the side plate24of the casing22or the partition plate28. The electric component box50includes a control board501, and the control board501is also installed along the side plate24or the partition plate28.

The control board501controls devices such as the indoor fan30in response to signals from various sensors. The control board501is closer to the first end32awhere the collection tubes323of the indoor heat exchanger32are located than to the second end32bwhere the connection tube324of the indoor heat exchanger32is located.

FIG. 4Ais a perspective view of the gas sensor55to be covered with a case56.FIG. 4Bis a perspective view of the gas sensor55covered with the case56. The gas sensor55depicted inFIG. 4AandFIG. 4Bdetects refrigerant leakage. The gas sensor55includes a substrate551, a sensor unit552, and a wiring unit553. The sensor unit552includes a sensor element552a, and a cylindrical pipe552bcovering the sensor element552a.

The sensor element552ais mounted on the substrate551and detects presence or absence of refrigerant gas. The cylindrical pipe552bhas an upper end surface provided with a hole552callowing entry of refrigerant gas.

The wiring unit553includes a female connector553amounted on the substrate551, a male connector553bfitted to the female connector553a, and a cable553cconnected to the male connector553b. The wiring unit553electrically connects the sensor element552aand the substrate551to each other.

At least the sensor unit552of the gas sensor55is covered with the case56for protection. The case56has a first opening561for ventilation. The first opening561is provided in a surface called a ventilation surface56a.

The ventilation surface56aaccording to one or more embodiments crosses a side surface56bprovided with a second opening562.

When a refrigerant leaks, part of refrigerant gas entered through the first opening561can flow to the sensor unit552of the gas sensor55and the remainder can exit through the second opening562. Alternatively, when the refrigerant leaks, part of refrigerant gas entered through the second opening562can flow to the sensor unit552of the gas sensor55and the remainder can exit through the first opening561.

In one or more embodiments, the ventilation surface56ahas a plurality of first openings561and the side surface56bhas a plurality of second openings562. There may alternatively be provided a 1 first opening561and a 1 second opening562.

The case56exerts two functions of protecting the sensor unit552and introducing refrigerant gas as a leaking refrigerant.

FIG. 4Cis an enlarged side view of an installation position of the gas sensor55. InFIG. 4C, the cable553cof the wiring unit553is curved to be positioned below the sensor unit552and is then introduced into the electric component box50. This is to prevent water droplets from entering the substrate551along the electric wire553cwhen the water droplets adhere to the electric wire for some reason.

The air conditioner10according to one or more embodiments will be described next in terms of its operation. The air conditioner10switches between cooling operation and heating operation.

(2-1) Cooling Operation

During cooling operation, the four-way switching valve15depicted inFIG. 1is in the state indicated by solid lines, and the compressor12, the indoor fan30, and the outdoor fan16are in an operating state. The refrigerant circuit C thus achieves a refrigeration cycle in which the outdoor heat exchanger13functions as a radiator and the indoor heat exchanger32functions as an evaporator.

Specifically, a high-pressure refrigerant compressed by the compressor12flows in the outdoor heat exchanger13to exchange heat with outdoor air. The high-pressure refrigerant radiates heat to the outdoor air in the outdoor heat exchanger13. A refrigerant condensed by the outdoor heat exchanger13is sent to the indoor unit20. The refrigerant in the indoor unit20is decompressed by the indoor expansion valve39and then flows in the indoor heat exchanger32.

In the indoor unit20, indoor air blown out of the indoor fan30passes the indoor heat exchanger32to exchange heat with the refrigerant. The refrigerant in the indoor heat exchanger32is evaporated by absorbing heat from the indoor air. The indoor air is cooled by the refrigerant.

The air cooled by the indoor heat exchanger32is supplied into an indoor space. The refrigerant evaporated in the indoor heat exchanger32is sucked into the compressor12to be compressed again.

(2-2) Heating Operation

During heating operation, the four-way switching valve15depicted inFIG. 1is in the state indicated by broken lines, and the compressor12, the indoor fan30, and the outdoor fan16are in the operating state. The refrigerant circuit C thus achieves a refrigeration cycle in which the indoor heat exchanger32functions as a condenser and the outdoor heat exchanger13functions as an evaporator.

Specifically, a high-pressure refrigerant compressed by the compressor12flows in the indoor heat exchanger32of the indoor unit20. In the indoor unit20, indoor air blown out of the indoor fan30passes the indoor heat exchanger32to exchange heat with the refrigerant. The refrigerant in the indoor heat exchanger32radiates heat to the indoor air. The indoor air is heated by the refrigerant.

The air heated in the indoor heat exchanger32is supplied into the indoor space. The refrigerant condensed in the indoor heat exchanger32is decompressed by the outdoor expansion valve14and then flows in the outdoor heat exchanger13. The refrigerant in the outdoor heat exchanger13absorbs heat from outdoor air to be evaporated. The refrigerant evaporated in the outdoor heat exchanger13is sucked into the compressor12to be compressed again.

(3) Installation Position of Gas Sensor

(3-1) Relationship Between Height Position of Gas Sensor55and Time Until Leakage Detection

The conditions of the installation position of the gas sensor55are 1) maintenance is possible and 2) refrigerant leakage can be detected.

Regarding 1), in one or more embodiments, an optimal installation position is where a service person can work, the control board501is in vicinity, and the opening241is in vicinity.

Regarding 2), when a refrigerant having a higher specific density than air leaks from the indoor heat exchanger32, it can be easily estimated that the refrigerant will stay in the drain pan36below the indoor heat exchanger32, and thus the gas sensor55may be installed in the drain pan36. However, in order to prevent water from splashing on the gas sensor55, it is conceivable to install the gas sensor55above the wall surface of the drain pan36.

In such a case, when the height position of the gas sensor55is inappropriate, it is assumed that time from a start of the refrigerant leak until the leaked refrigerant reaches the height position of the gas sensor55becomes long, or the leaked refrigerant does not reach the height position of the gas sensor55and is not detected by the gas sensor55.

Therefore, the applicant(s) identifies a relational expression between the height position of the gas sensor55and the time from the start of the refrigerant leakage until the leaked refrigerant reaches the height position of the gas sensor55, and, the height position of the gas sensor55is set on the basis of the relational expression.

Specifically, the gas sensor55is installed above the drain pan36, and a height H from an upper end of the drain pan36to the gas sensor55is set to satisfy a relational expression represented by
L·W{C1·H1/Q+C2·H/(Q−C3·L·H{circumflex over ( )}(3/2))}≤90, where

L [m]: a length of the first wall surface of the drain pan36,

W [m]: a length of the wall surface of the drain pan36intersecting the first wall surface,

H1 [m]: a depth of the drain pan36, and

Q [m{circumflex over ( )}3/s]: a refrigerant leakage flow rate.

In the above expression, L·W·H1/Q represents time until the inside of the drain pan36is filled with the refrigerant, and is a value obtained by dividing an internal volume of the drain pan36[L·W·H1] by a “refrigerant leakage flow rate Q per unit time of the leaked refrigerant”. The flow rate is a volumetric flow rate. Q=1.90131×10−5, which is a value obtained by converting a lower limit of a leakage rate of R32, 0.42 g/s, with a density of R32 at a temperature of 0° C., 22.09 [kg/m{circumflex over ( )}3].

L·W·H/(Q−L·H{circumflex over ( )}(3/2)) represents time from when the inside of the drain pan36is filled with the refrigerant until the refrigerant overflowing from the drain pan36reaches the height H. Constants C1, C2, and C3 are flow rate coefficients.

The refrigerant overflowing from the drain pan36accumulates along the side plate of the casing22, but since the casing22is opened to the blow-out port37, the refrigerant converts its potential energy into kinetic energy and flows out.

The refrigerant located at a higher position than the drain pan36is an accumulation of a refrigerant corresponding to a flow rate obtained by subtracting [a flow rate q of the outflowing refrigerant per unit time] from the “refrigerant leakage flow rate Q per unit time of the leaked refrigerant”.

Here, [the flow rate q of the outflowing refrigerant per unit time] differs depending on an amount the refrigerant accumulated on the drain pan, and is thus obtained by integration.

The “height H to the gas sensor55” is a vertical distance from the upper end of the drain pan36to a center of the cylindrical pipe552bprotecting the sensor element.

The depth H1 of the drain pan36may not be uniquely identified because shapes of a bottom surface and an opening surface of the drain pan36do not match in some cases. In this case, the depth H1 is substituted by an average depth.

The numerical value 90 on the right side of the inequality sign in the relational expression adopts an upper limit of allowable time until a gas concentration at the position of the gas sensor after the start of leakage exceeds a set value in the IEC standards (IEC60335-2-40).

FIG. 5is a graph showing a relationship between the height position (height H) of the gas sensor55and time T until leakage detection, a horizontal axis represents the height H from the upper end of the drain pan36to the gas sensor55, and a vertical axis represents time from the start of the refrigerant leakage until the leaked refrigerant is detected by the gas sensor55.

According to the graph inFIG. 5, the time T until leakage detection is 90 seconds or less in a range where the height H is 110 mm or less. In one or more embodiments, the height H is set to 80 mm or less while ensuring a margin of 20% of a theoretical value.

By setting the gas sensor to satisfy a relationship between representative dimensions of the drain pan36(length L, width W, and average depth H1), the refrigerant leakage flow rate Q, and the time until the leaked refrigerant reaches the position of the gas sensor55(height H) represented by the relational expression, the refrigerant leakage can be detected at an early stage.

In the indoor unit20, the relationship between the representative dimensions of the drain pan36(length L, width W, and average depth H1), the refrigerant leakage flow rate Q, and the time until the leaked refrigerant reaches the position of the gas sensor (height H) is clear. Therefore, the position of the gas sensor (height H) can be set appropriately.

Especially, when the gas sensor55is installed above the drain pan36, the refrigerant leakage can be detected at an early stage by setting the height position (height H) of the gas sensor55to satisfy a relationship represented by the above expression.

In the indoor unit20, an installation location of the gas sensor55is close to the control board501. In general, the control board501is installed at a place where the service person can easily work in consideration of work efficiency during maintenance such as replacement. Therefore, by installing the gas sensor55close to the control board501, the work efficiency during maintenance such as replacement of the gas sensor55is improved.

Further, since the installation location of the gas sensor55is close to the control board501, a length of a wire electrically connecting the gas sensor55and the control board501is shortened, which has an advantage of reducing a material cost.

The control board501is installed closer to the collection tube than the connection tube324of the indoor heat exchanger32.

The control board501is disposed along the side plate24or the partition plate28.

The gas sensor55is installed at a position where the service person can attach and detach the gas sensor55through the opening241when the lid25is opened, and the service person can replace the gas sensor55through the opening241without removing the second side plate24of the casing22from the casing22, which improves maintainability.

The gas sensor55is installed below the indoor heat exchanger32.

The indoor unit20further includes a plurality of gas sensors55, and the plurality of gas sensors55are installed at a plurality of different locations.

The gas sensor55is covered with the case56provided with the first opening561for ventilation. The case56can exert two functions of protecting the gas sensor55and introducing the leaking refrigerant.

The gas sensor55includes the sensor unit552and the wiring unit553. The gas sensor55is installed such that at least a part of the wiring unit553is below the sensor unit552.

(5-1) First Modification

The above embodiments relate to installing the single gas sensor55. However, the present disclosure should not be limited to this aspect. Alternatively, the indoor unit20may further include a plurality of gas sensors55, which are installed at a plurality of different positions.

FIG. 6Ais a perspective view of the indoor unit20according to a first modification when viewed from above, and shows the installation position of each gas sensor55when the plurality of gas sensors55are installed.FIG. 6Bis a schematic front view of the drain pan36when viewed from the blow-out port37, and shows the installation position of each gas sensor55when a plurality of gas sensors55are installed.

InFIGS. 6A and 6B, the four gas sensors55are installed at different locations along the partition plate28in the first chamber R1.

For easier description, the four gas sensors55include a first gas sensor55A, a second gas sensor55B, a third gas sensor55C, and a fourth gas sensor55D.

Here, the first gas sensor55A is installed at a height position of h1(for example, 60 mm) from the upper end of the drain pan36at a location close to the electric component box50. The second gas sensor55B is installed at a height position of h2(for example, 20 mm) from the upper end of the drain pan36at a location close to the collection tube323of the indoor heat exchanger32. The third gas sensor55C is installed at a height position of h2from the upper end of the drain pan36at a center of the drain pan36. The fourth gas sensor55D is installed at a height position of h2from the upper end of the drain pan36at a location close to the connection tube324of the indoor heat exchanger32.

In such a case, any of the gas sensors can detect the refrigerant within 90 seconds after the start of the refrigerant leakage.

The first gas sensor55A and the second gas sensor55B are closer to the control board501and the opening241of the second side plate24than the third gas sensor55C and the fourth gas sensor55D.

Thus, the service person can replace the first gas sensor55A and the second gas sensor55B through the opening241.

The service person can replace the first gas sensor55A and the second gas sensor55B without removing the second side plate24from the casing22, which improves maintainability.

The third gas sensor55C and the fourth gas sensor55D are installed along the blow-out port37while maintaining the height position of h2from the upper end of the drain pan36, and thus are located below the indoor heat exchanger32and above the upper end of the drain pan36.

(5-2) Second Modification

The above first modification exemplifies the installation position of the plurality of gas sensors55, but there is no need to simultaneously use all the gas sensors55thus installed. With exemplary reference toFIGS. 6A and 6B, only the first gas sensor55A may be used initially and the second gas sensor55B may be switchingly used before the first gas sensor55A terminates its durability life cycle.

The first gas sensor55A can be switched at timing that can be exemplarily determined in accordance with guarantee years of the gas sensor55A. The first gas sensor55A may alternatively be switched to a subsequent gas sensor55when abnormality different from refrigerant leakage is assumed in accordance with an output signal of the first gas sensor55A.

In a similar manner, the second gas sensor55B, the third gas sensor55C, and the fourth gas sensor55D may be used in that order.

(5-3) Third Modification

The plurality of gas sensors55may alternatively be installed vertically.FIG. 6Cis a schematic front view of the drain pan36in the indoor unit20according to a third modification when viewed from the blow-out port37, and the first gas sensor55A, the second gas sensor55B, the third gas sensor55C, and the fourth gas sensor55D are installed vertically.

However, the first gas sensor55A installed at a highest position is to be capable of detecting the refrigerant within 90 seconds after the start of the refrigerant leakage. Therefore, the first gas sensor55A is installed at the height position of h1(for example, 60 mm) from the upper end of the drain pan36.

Assumed examples of a method of use include a first aspect of connecting each of the first gas sensor55A, the second gas sensor55B, the third gas sensor55C, and the fourth gas sensor55D to the control board501to be in use, and a second aspect of connecting only one of the gas sensors to the control board501to be in use.

(5-3-1) First Aspect

In the first aspect, when a refrigerant leaks, any of the first gas sensor55A, the second gas sensor55B, the third gas sensor55C, or the fourth gas sensor55D installed vertically detects a refrigerant leakage. Thus, in case any of the gas sensors is in trouble, the other gas sensors detect the refrigerant leakage. This configuration achieves early detection of refrigerant leakage.

Furthermore, in the first aspect, when the refrigerant leaks, after elapse of a predetermined period from occurrence of refrigerant leakage, all the gas sensors operating normally detect refrigerant leakage. Any gas sensor not detecting refrigerant leakage after elapse of the predetermined period can thus be determined as being abnormal.

(5-3-2) Second Aspect

In the second aspect, only the first gas sensor55A among the first gas sensor55A, the second gas sensor55B, the third gas sensor55C, and the fourth gas sensor55D is exemplarily connected to the control board501to be in use, whereas the other gas sensors are not in use.

Since the second gas sensor55B, the third gas sensor55C, and the fourth gas sensor55D are stored below the first gas sensor55A, when the first gas sensor55A is in failure, a service person has only to connect any of the gas sensors55B to55D to the control board501in place of the first gas sensor55A to complete replacement of the gas sensor.

The service person can thus replace the gas sensor when visiting for repair without carrying any gas sensor for replacement.

The embodiments and the modifications described above refer to the air conditioner as an exemplary refrigeration apparatus. However, the present disclosure should not be limited thereto. Examples of the refrigeration apparatus include, as well as the air conditioner, a low temperature warehouse storing articles that need to be frozen, refrigerated, or kept at low temperature.

REFERENCE SIGNS LIST

PATENT LITERATURE

Patent Literature 1: JP 2019-11914 A