AIR CONDITIONER AND METHOD FOR CONTROLLING AIR CONDITIONER

Abstract

 An air conditioner in which a compressor (10) provided with a crankcase heater (40), and energizing the crankcase heater (40) allows the compressor to be heated. In addition, when the compressor (10) is stopped and before the compressor (10) is started, a control unit (41) determines the timing for starting the crankcase heater (40) on the basis of a degree of superheating, which is a parameter having a correlation with the temperature of the refrigerant. Thus, it is possible to further reduce standby power consumption resulting from energization of the crankcase heater (40) while the compressor (10) is stopped.

Description

TECHNICAL FIELD

[0001] The present invention relates to an air conditioner and a method for controlling an air conditioner.

BACKGROUND ART

[0002] When an air conditioner is stopped for a long period, the refrigerant is liquefied and is accumulated inside the compressor. When the compressor is started in this state, there is a risk that the compressor will be damaged as a result of liquid compression. Hence, in air conditioners for use in cold regions, the compressor is provided with a crankcase heater, which is energized before operating the air conditioner to heat the compressor and thereby prevents the liquid compression caused by the accumulation of liquid refrigerant.

[0003] However, if the crankcase heater is energized continuously while the compressor is stopped, power consumed by the crankcase heater will increase, thus increasing the standby power consumption of the air conditioner.

[0004] To solve this problem, Patent Document 1 discloses an air conditioner in which, while a compressor is stopped, a crankcase heater is caused to operate and, upon a refrigerating machine oil temperature reaching a predetermined temperature, the operation of the crankcase heater is stopped to prepare for the restart of the compressor.

CITATION LIST

Patent Literature(s)

[0005] Patent Document 1: Japanese Patent No. 3799940B

SUMMARY OF INVENTION

Technical Problem

[0006] However, the air conditioner disclosed in Patent Document 1 needs to energize the crankcase heater every time the refrigerating machine oil temperature decreases lower than the predetermined temperature, thus limiting the reduction in standby power consumption.

[0007] The present invention has been conceived in view of such circumstances, and an object of the present invention is to provide an air conditioner and a method for controlling an air conditioner capable of further reducing the standby power consumption that occurs as a result of the crankcase heater being energized while the compressor is stopped.

Solution to Problem

[0008] To solve the above described problem, the air conditioner and the method for controlling an air conditioner of the present invention employ the following means.

[0009] In the air conditioner according to a first aspect of the present invention, a compressor is provided with a crankcase heater, and energizing the crankcase heater allows the compressor to be heated. Such an air conditioner includes control means that determine, on the basis of a parameter having a correlation with a temperature of a refrigerant, a timing for starting to energize the crankcase heater while the compressor is stopped and before the compressor is started.

[0010] According to this configuration, the air conditioner is configured so that the compressor is provided with the crankcase heater, and energizing the crankcase heater allows the compressor to be heated. In the air conditioner, the crankcase heater is energized to heat the compressor before the stopped compressor is started. Accordingly, the liquid refrigerant is heated and vaporized, preventing liquid compression due to an accumulation of the liquid refrigerant.

[0011] However, unless the energization of the crankcase heater is started at an appropriate timing, the crankcase heater will be energized more than necessary and standby power consumption will increase.

[0012] Hence, the timing for starting to energize the crankcase heater is determined on the basis of the parameter having the correlation with the temperature of the refrigerant while the compressor is stopped and before the compressor is started. Specifically, the timing for starting to energize the crankcase heater is determined so that the above-described parameter reaches a preset target value when the compressor is started.

[0013] To be more specific, the timing for starting to energize the crankcase heater is set to be earlier as the value of the parameter having the correlation with the temperature of the refrigerant decreases so that the refrigerant reaches a temperature at which the accumulation thereof can be eliminated by the start time of the compressor. On the other hand, as the value of the parameter having the correlation with the temperature of the refrigerant increases, the timing for starting to energize the crankcase heater is delayed. Accordingly, the period of energizing the crankcase heater is suppressed from being longer than necessary.

[0014] Therefore, according to this configuration, the standby power consumption that occurs due to the energization of the crankcase heater while the compressor is stopped can be reduced.

[0015] In the above-described first aspect, it is preferable that the parameter be a degree of superheating of the refrigerant.

[0016] The accumulation of liquid refrigerant is small when the degree of superheating is sufficiently high. Moreover, when a temperature of a lower portion of the compressor is sufficiently high, the accumulation of liquid refrigerant is small. However, the temperature of the lower portion of the compressor is easily affected by outside air temperature; thus, the state of the refrigerant may not always be measured correctly. On the other hand, the degree of superheating of the refrigerant is a parameter that has a correlation not only with the temperature of the refrigerant, but also with the pressure of the refrigerant. Hence, measuring the degree of superheating of the refrigerant allows the state of the refrigerant to be more correctly measured than measuring the temperature of the lower portion of the compressor.

[0017] Therefore, according to this configuration, the timing for energizing the crankcase heater can be more accurately determined.

[0018] In the above-described first aspect, it preferable that the control means determine, on the basis of the parameter and outside air temperature, the timing for starting to energize the crankcase heater while the compressor is stopped and before the compressor is started.

[0019]  Even when the crankcase heater is energized, the temperature of the compressor, specifically the degree of an increase in temperature of the refrigerant, will differ depending on differences in the outside air temperature.

[0020] Hence, according to this configuration, the timing for starting to energize the crankcase heater is determined on the basis of the parameter having the correlation with the temperature of the refrigerant and the outside air temperature. Specifically, even if the parameter values are the same, the timing for starting to energize the crankcase heater becomes earlier as the outside air temperature decreases. Similarly, the timing for starting to energize the crankcase heater becomes later as the outside temperature increases.

[0021] Therefore, according to this configuration, the timing for energizing the crankcase heater can be more accurately determined.

[0022] In the above-described first aspect, it is preferable the compressor be started according to a preset schedule.

[0023] According to this configuration, the timing for energizing the crankcase heater can be more accurately determined.

[0024] In the above-described first aspect, it is preferable that a control board be provided with an indicator light that indicates a control status and that the indicator light turn off when control is stable for at least a predetermined period.

[0025] According to this configuration, the power consumption of the air conditioner can be further reduced.

[0026] In a method for controlling an air conditioner according to a second aspect of the present invention, a compressor is provided with a crankcase heater, and energizing the crankcase heater allows the compressor to be heated. Such a method includes the step of determining, on the basis of a parameter having a correlation with a temperature of a refrigerant, a timing for starting to energize the crankcase heater while the compressor is stopped and before the compressor is started.

Advantageous Effects of Invention

[0027]  The present invention exhibits the advantageous effect of allowing a further reduction in the standby power consumption that occurs as a result of the crankcase heater being energized while the compressor is stopped.

Brief Description of Drawing(s)

[0028] 

FIG. 1 is a schematic configuration diagram of a multiple air conditioner according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of surroundings of a compressor including a crankcase heater of the multiple air conditioner of the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a degree of superheating and a heater-on period according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating the steps of CH energization processing according to the first embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a degree of superheating and a heater-on period according to a second embodiment of the present invention.

Description of Embodiments

[0029] The following describes an embodiment of an air conditioner and a method for controlling an air conditioner according to the present invention, with reference to the drawings.

First Embodiment

[0030] The following describes a first embodiment of the present invention.

[0031] FIG. 1 is a schematic configuration diagram of a multiple air conditioner according to a first embodiment of the present invention, and FIG. 2 is a configuration diagram of the surroundings of a compressor including a crankcase heater of the multiple air conditioner.

[0032] In a multiple air conditioner 1, a plurality of inside units 3A and 3B are connected to a single outside unit 2 in parallel via branching devices 6 between gas-side piping 4 and liquid-side piping 5 leading from the outside unit 2.

[0033] The outside unit 2 includes an inverter-driven compressor 10 that compresses a refrigerant, an oil separator 11 that separates lubricating oil from the refrigerant gas, a four-way selector valve 12 that switches circulating directions of the refrigerant, an outside heat exchanger 13 that allows the refrigerant to exchange heat with the outside air, a supercooling coil 14 that is integrally constituted with the outside heat exchanger 13, an outside expansion valve (EEVH) 15, a receiver 16 that stores liquid refrigerant, a supercooling heat exchanger 17 that supercools the liquid refrigerant, a supercooling expansion valve (EEVSC) 18 that controls the amount of refrigerant to be branched to the supercooling heat exchanger 17, an accumulator 19 that separates a liquid component from the refrigerant gas to be sucked into the compressor 10 so as to allow only a gas component to be sucked into the compressor 10, a gas-side control valve 20, and a liquid-side control valve 21.

[0034] The above-described devices on the outside unit 2 side are connected in a well-known manner via refrigerant piping 22, thereby configuring an outside refrigerant circuit 23. Further, the outside unit 2 is provided with an outside fan 24 that makes outside air flow to the outside heat exchanger 13, and an oil return circuit 25 between the oil separator 11 and intake piping of the compressor 10. The oil return circuit 25 returns, by a predetermined amount, the lubricating oil separated from the discharged refrigerant gas in the oil separator 11 to the compressor 10.

[0035] The gas-side piping 4 and the liquid-side piping 5 are cooling piping connected to the gas-side control valve 20 and the liquid-side control valve 21 of the outside unit 2. At the time of installation on site, the length of this piping is set according the distance between the outside unit 2 and the plurality of inside units 3A and 3B connected to the outside unit 2. An appropriate number of branching devices 6 is provided part way along the gas-side piping 4 and the liquid-side piping 5, and an appropriate number of the inside units 3A and 3B is connected via the branching devices 6. As a result, a single sealed system of refrigeration cycle (refrigeration circuit) 7 is formed.

[0036] The inside units 3A and 3B include respective inside heat exchangers 30 that are used for inside air conditioning to cause the inside air to exchange heat with the refrigerant, an inside expansion valve (EEVC) 31, and an inside fan 32 that causes the inside air to circulate in the inside heat exchanger 30. The inside units 3A and 3B are connected to the branching devices 6 via the inside branching gas-side piping 4A and 4B and the branching liquid-side piping 5A and 5B.

[0037] Further, the pressure of the refrigerant discharged from the compressor 10 is measured by a pressure sensor 33.

[0038] In the above-described air conditioner 1, cooling operation is performed as follows.

[0039] The refrigerant gas compressed by the compressor 10 and discharged at high temperature and high pressure has the lubricating oil contained therein separated by the oil separator 11. Thereafter, the refrigerant gas is circulated to the outside heat exchanger 13 via the four-way selector valve 12 and is condensed and liquefied in the outside heat exchanger 13 as a result of heat exchange with the outside air that is blown through by the outside fan 24. This liquid refrigerant is further cooled by the supercooling coil 14, then passed through an outside expansion valve 15 and stored in the receiver 16.

[0040] The liquid refrigerant that has its circulation flow adjusted by the receiver 16, is split away from the liquid refrigerant piping while being circulated through a liquid refrigerant side piping via the supercooling heat exchanger 17, and undergoes supercooling through heat exchange with a portion of the refrigerant that has undergone adiabatic expansion in the supercooling expansion valve (EEVSC) 18. This liquid refrigerant is introduced from the outside unit 2 to the liquid-side piping 5 via the liquid-side control valve 21. Further, the liquid refrigerant introduced to the liquid-side piping 5 is split by the branching devices 6 and flows to branching liquid-side piping 5A and 5B of the inside units 3A and 3B.

[0041] The liquid refrigerant flowing in the respective branching liquid-side piping 5A and 5B is introduced to the inside units 3A and 3B, undergoes adiabatic expansion in the inside expansion valve (EEVC) 31, and is introduced to the inside heat exchanger 30 as a gas-liquid two-phase flow. In the inside heat exchanger 30, the inside air being circulated by the inside fan 32 exchanges heat with the refrigerant so that the inside air is cooled, thereby cooling the room. Meanwhile, the refrigerant is vaporized and sent to the branching devices 6 through the branching gas-side piping 4A and 4B, and is merged in the gas-side piping 4 with the refrigerant gas form another inside unit.

[0042]  The refrigerant gas merged in the gas-side piping 4 is again returned to the outside unit 2, passed through the gas-side control valve 20 and the four-way selector valve 12 to merge with the refrigerant gas from the supercooling heat exchanger 17, and then introduced to the accumulator 19. In the accumulator 19, the liquid component contained in the refrigerant gas is separated out, and the gas component alone is introduced to the compressor 10. This refrigerant is compressed again by the compressor 10. The cooling operation is performed through repetition of the above-described cycle.

[0043] Heating operation, on the other hand, is performed as follows.

[0044] Refrigerant gas, after being compressed by the compressor 10 and discharged at high temperature and high pressure, has the lubricating oil contained therein separated by the oil separator 11, and is then circulated to the gas-side control valve 20 via the four-way selector valve 12. The refrigerant circulated to the gas-side control valve 20 is introduced from the outside unit 2 through the gas-side piping 4, and then introduced to a plurality of the inside units 3A and 3B via the branching devices 6 and the inside branching gas-side piping 4A and 4B.

[0045] The high pressure and high temperature refrigerant gas introduced to the inside units 3A and 3B exchanges heat with the inside air being circulated in the inside heat exchanger 30 via the inside fan 32, thus heating the inside air and providing heating in the room. The liquid refrigerant condensed by the inside heat exchanger 30 is passed through the inside expansion valve (EEVC) 31 and the branching liquid-side piping 5A and 5B to the branching devices 6, and is merged with refrigerant from another inside unit before being returned through the liquid-side piping 5 to the outside unit 2. Note that, during heating, an opening degree of the inside expansion valve (EEVC) 31 in the inside units 3A and 3B is controlled so that the refrigerant outlet temperature or the degree of supercooling of the refrigerant in the inside heat exchanger 30, which functions as a condenser, reach a target value.

[0046] The refrigerant that has returned to the outside unit 2 is passed through the liquid-side control valve 21 to the supercooling heat exchanger 17 and undergoes supercooling in the same way as in the case of cooling, before being introduced to the receiver 16 and temporarily stored therein to adjust circulation flow. After being supplied to the outside expansion valve (EEVH) 15 and undergoing adiabatic expansion, the liquid refrigerant is passed through the supercooling coil 14 and introduced to the outside heat exchanger 13.

[0047] In the outside heat exchanger 13, the outside air blown in via the outside fan 24 exchanges heat with the refrigerant, thereby causing the refrigerant to absorb heat from the outside air and then to be vaporized. The refrigerant gas is passed from the outside heat exchanger 13 via the four-way selector valve 12 to merge with the refrigerant gas from the supercooling heat exchanger 17, and then introduced to the accumulator 19. In the accumulator 19, the liquid component contained in the refrigerant gas is separated out, and the gas component alone is introduced to the compressor 10 and compressed again in the compressor 10. The heating operation is performed through repetition of the above-described cycle.

[0048] Further, as illustrated in FIG. 2, in the air conditioner 1, the compressor 10 is provided with a crankcase heater (referred to hereinafter as "CH") 40 on the periphery of a sealed housing 10A. The CH 40 is provided to prevent damage to the compressor 10, which occurs when the refrigerant is liquefied and accumulated in the compressor 10 while the compressor 10 is stopped and is then sucked in when the compressor 10 is started, causing the compressor 10 to attempt liquid compression. The CH 40, by being energized to heat the compressor 10 before the air conditioner 1 is operated, removes the liquid refrigerant from the compressor 10; thus, the CH 40 plays a role of preventing liquid compression.

[0049] The CH 40 is turned ON/OFF via a control unit 41. The control unit 41 includes a normal operation mode control unit 42 that performs normal energization control of the CH 40 on the basis of a preset specification while the compressor 10 is stopped and a reduced operation mode control unit 43 that calculates an ON timing for the CH 40 and turns CH 40 ON/OFF. The control unit 41 includes switching means 44 that allow the control mode to be selectively switched to either a normal operation mode or a reduced operation mode. The switching means 44 are, for example, configured so that switching operation can be performed from a remote control 45.

[0050] Note that the control unit 41 is configured of, for example, a central processing unit (CPU), a random access memory (RAM), and a computer-readable storage medium, and the like. A sequence of processing to realize various functions is, for example, recorded in a recording medium or the like in program form. The CPU then reads this program into RAM or the like and executes processing and calculation on the information to realize the various functions.

[0051] Further, the control unit 41 includes, on a control board, an indicator light 50 that indicates a control status of the air conditioner 1. The indicator light 50 is used to indicate when the air conditioner 1 requires maintenance or the like. The indicator light 50 is, for example, a 7-segment display, but is not limited to this, and may be a single or plurality of LED lamps.

[0052] Further, the control unit 41 receives measurement values from an under-dome temperature sensor 52 that measures a temperature of a lower portion of the compressor 10 (hereinafter referred to as "under-dome temperature"), measurement values from an outside air temperature sensor 46 that measures an outside air temperature, and measurement values from a pressure sensor 33.

[0053] If an ON condition for the CH 40 in the preset specification is satisfied, the normal operation mode control unit 42 constantly energizes the CH 40 while the compressor 10 is stopped, thus keeping the CH 40 ON and heating the compressor 10. In this case, when the compressor 10 is started up, the CH 40 is kept OFF while the compressor 10 is running. When the compressor 10 is stopped, the CH 40 is kept ON while the compressor 10 is stopped.

[0054] Thus, in the air conditioner 1, the CH 40 is energized to heat the compressor 10 before the stopped compressor 10 is started. As a result, the refrigerant is heated and vaporized; thus, liquid compression due to the accumulation of refrigerant is prevented.

[0055] However, unless the energization of the CH40 is started at an appropriate timing, the CH 40 will be energized more than necessary and standby power consumption will increase.

[0056] Thus, the reduced operation mode control unit 43 according to the first embodiment determines, on the basis of a parameter having a correlation with the temperature of the refrigerant, the timing for starting to energize the CH 40 while the compressor 10 is stopped and before the compressor 10 is started. Specifically, the timing for starting to energize the CH40 is determined so that the above-described parameter reaches a preset target value when the compressor 10 is started.

[0057] Note that in the above-described parameter in the first embodiment is the degree of superheating of the refrigerant. This is because the accumulation of liquid refrigerant is small when the degree of superheating is sufficiently high. The degree of superheating is calculated by subtracting a saturation temperature, which is calculated on the basis of measurement values of the pressure sensor 33, from the under-dome temperature measured by the under-dome temperature sensor 52.

[0058] The reduced operation mode control unit 43 then calculates the period for energizing the CH 40 from the relationship between the degree of superheating shown in the graph in FIG. 3 and an ON period of the CH 40 (hereinafter referred to as the "heater-ON period").

[0059] Specifically, the timing for starting to energize the CH 40 is set to be earlier as the degree of superheating decreases, so that the refrigerant reaches the degree of superheating at which the accumulation thereof can be eliminated by the start time of the compressor 10. Conversely, the timing for starting to energize the CH 40 is set later as the degree of superheating increases. Furthermore, if the degree of superheating is sufficiently high, the energization of the CH 40 is not performed while the compressor 10 is stopped.

[0060] Accordingly, the period of energizing the CH 40 is suppressed from being longer than necessary.

[0061] The relationship between the degree of superheating and the heater-ON period is expressed by a function f as in equation (1); however, the relationship is not necessarily the linear relationship illustrated in FIG. 3.

[0062] The function f is determined in advance on the basis of a heat capacity of the compressor 10, output from the CH 40, the amount of heat radiated from the compressor 10, and the like. Note that the degree of superheating at which the compressor 10 can be started may, for example, be 10 to 15°C.

[0063] Further, the control unit 41 according to the first embodiment includes a so-called schedule timer function whereby starting and stopping of the air conditioner 1, specifically the starting, stopping, and the like of various sub-assemblies such as the compressor 10, are performed in accordance with a preset schedule. If the schedule timer has been set, the control unit 41 cuts off unnecessary electric power to various sub-assemblies while the air conditioner 1 is stopped, in accordance with the preset schedule, and puts the air conditioner 1 in a sleep state.

[0064] The reduced operation mode control unit 43 then calculates the time for energizing the CH 40 (hereinafter referred to as the "CH energization start time"). For example, when the heater-ON period is calculated as being 3 hours if the air conditioner 1 is to be started at 8 a.m. according to the schedule timer, the CH energization start time is set to 5 a.m.

[0065] Note that, when the under-dome temperature is sufficiently high, the accumulation of liquid is small. Hence, as expressed in equation (2), the reduced operation mode control unit 43 may calculate the heater-ON period using the function of Heater-ON period = f(under-dome temperature).

[0066] However, because the under-dome temperature is easily affected by the outside air temperature, the state of the refrigerant may not always be correctly measured. On the other hand, the degree of superheating of the refrigerant is a parameter that correlates not only with the temperature of the refrigerant, but also with the pressure of the refrigerant. Hence, measuring the degree of superheating of the refrigerant allows the state of the refrigerant to be correctly measured comparing with measuring the temperature of the lower portion of the compressor 10.

[0067] Thus, by using the degree of superheating as the parameter having a correlation with the temperature of the refrigerant, the timing for energizing the CH 40 can more accurately calculated.

[0068] FIG. 4 is a flowchart illustrating the flow of processing for energizing the CH 40 (hereinafter referred to as "CH energization processing"), which is executed by the reduced operation mode control unit 43 while the compressor 10 is stopped and before the compressor 10 is started. Note that the CH energization processing is executed while the compressor 10 is stopped.

[0069] First, in step 100, the degree of superheating is calculated.

[0070] Next, in step 102, the heater-ON period is calculated on the basis of the calculated degree of superheating.

[0071]  Next, in step 104, the CH energization start time is calculated on the basis of the calculated heater-ON period.

[0072] Next, in step 106, it is determined whether or not the current time has reached the CH energization start time. When the determination is affirmative, the processing proceeds to step 108. When the determination is negative, the processing returns to step 100.

[0073] In step 108, the energization of the CH 40 is started.

[0074] Note that, in the case in which the processing returns from step 106 to step 100, a new CH energization start time is calculated on the basis of a newly calculated degree of superheating and heater-ON period.

[0075] Further, the control unit 41 according to the present embodiment turns off the indicator light 50 when the control is stable for at least a predetermined period. Here, "control is stable" means that, for example, there has been no operation on the remote control 45, there has been no change in the capabilities of the outside unit 2, and there has been no change in the stopping and starting of the compressor 10. Further, the indicator light 50 turns off in accordance with the schedule timer.

[0076] As a result the power consumption of the air conditioner 1 is reduced.

[0077] As described above, in the air conditioner 1 according to the first embodiment, the compressor 10 is provided with the CH 40, the energization of the CH 40 allows the compressor 10 to be heated. Then, while the compressor 10 is stopped and before the compressor 10 is started, the control unit 41 determines the timing for starting the CH 40 on the basis of the degree of superheating, which is a parameter having a correlation with the temperature of the refrigerant.

[0078] Hence, the air conditioner 1 according to the first embodiment is capable of further reducing standby power consumption that occurs due to the energization of the CH 40 while the compressor 10 is stopped.

Second Embodiment

[0079] The following describes a second embodiment of the present invention.

[0080] Note that because the configuration of the air conditioner 1 according to the second embodiment is similar to that of the air conditioner 1 according to the first embodiment illustrated in FIGS. 1 and 2, the repetition explanation will be omitted.

[0081] Even when the CH 40 is energized while the compressor 10 is stopped and before the compressor 10 is started, the temperature of the compressor 10, specifically the degree of an increase in temperature of the refrigerant, will differ depending on differences in the outside air temperature.

[0082] Thus, the reduced operation mode control unit 43 according to the second embodiment determines, on the basis of the degree of superheating and the outside air temperature, the timing for starting to energize the CH 40 while the compressor 10 is stopped and before the compressor 10 is started.

[0083] Specifically, the heater-ON period may be represented as in Equation (2).

[0084] FIG. 5 is graph showing a relationship between the degree of superheating and the heater-ON period according to the second embodiment. The solid line indicates a case in which the outside air temperature is low compared with that indicated by the dashed line. Thus, even for the same degree of superheating, the timing for starting to energize the CH 40 becomes earlier as the outside air temperature decreases. Conversely, the timing for starting to energize the CH 40 becomes later as the outside air temperature increases.

[0085] Hence, the air conditioner 1 according to the second embodiment can more accurately determine the timing for energizing the crankcase heater.

[0086] Thus far, while the present invention has been explained with reference to the above embodiments, it is to be noted that the technical scope of the present invention shall not be limited by these embodiments. Various modifications or improvements to the above embodiments can be made without departing from the spirit of the invention, and embodiments resulting from such modifications or improvements shall be included in the present invention.

[0087] Further, the flow of the CH energization processing described in the above embodiments is also an example; thus an unnecessary step may be removed, a new step may be added, and processing order may be changed without departing from the spirit of the present invention.

Reference Signs List

[0088] 

1

Air conditioner

10

Compressor

40

Crankcase heater

41

Control unit

50

Indicator light

Claims

1. An air conditioner in which a compressor is provided with a crankcase heater, and energizing the crankcase heater allows the compressor to be heated, the air conditioner comprising:

control means that determine, on the basis of a parameter having a correlation with a temperature of a refrigerant, a timing for starting energizing the crankcase heater while the compressor is stopped and before the compressor is started.

2. The air conditioner according to claim 1, wherein the parameter is a degree of superheating of the refrigerant.

3. The air conditioner according to claim 1 or 2, wherein the control means determine, on the basis of the parameter and an outside air temperature, the timing for starting to energize the crankcase heater while the compressor is stopped and before the compressor is started.

4. The air conditioner according to any one of claims 1 to 3, wherein the compressor is started in accordance with a preset schedule.

5. The air conditioner according to any one of claims 1 to 4, further comprising an indicator light provided on a control board, the indicator light indicating a control status, wherein
the indicator light turns off when control is stable for at least a predetermined period.

6. A method for controlling an air conditioner in which a compressor is provided with a crankcase heater, and energizing the crankcase heater allows the compressor to be heated, the method comprising the step of:

determining, on the basis of a parameter having a correlation with a temperature of a refrigerant, a timing for starting to energize the crankcase heater while the compressor is stopped and before the compressor is started.

Drawing