JP2011085320A - Heat pump device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pump device defrosting in a short period of time and improving startability in restarting heating. <P>SOLUTION: When a frost formation detecting means 15 detects frost formation on an outdoor heat exchanger 10, a reverse cycle defrosting operation for switching a four-way switch valve 6 to a cooling side is carried out. A pump-down operation for switching the four-way switch valve 6 to a heating side and closing a throttle means 9 is carried out when a refrigerant temperature near an indoor heat exchanger 10 becomes lower than a prescribed temperature. A hot gas bypass defrosting operation for opening a bypass valve 13 is carried out when a liquid refrigerant discharge detecting means 14 detects discharge of liquid refrigerant from the outdoor heat exchanger 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat pump device that performs heat exchange by forming a refrigeration cycle that circulates refrigerant, and more particularly, to a heat pump device that performs a defrosting operation for melting frost adhering to an evaporator.

  In a heat pump device such as an air conditioner that collects heat from the outside air and heats the indoor space, in the case of an outside air condition that forms frost on the outdoor heat exchanger that operates as an evaporator, the heating operation is temporarily stopped to defrost Although the operation is performed, a decrease in room temperature due to the heating operation being stopped is often a problem.

  The defrosting method includes a hot gas bypass method in which the high-temperature discharged gas refrigerant discharged from the compressor flows directly into the evaporator inlet, and the refrigerant circuit is switched in the same way as the cooling operation to operate the outdoor heat exchanger as a condenser. There is a reverse cycle method, and a method of combining these two defrosting methods for the purpose of shortening the defrosting time is known (for example, see Patent Document 1).

  In addition, when defrosting is performed using the reverse cycle method, the amount of heat stored in the refrigerant piping that is the defrosting heat source is detected and switched to the hot gas bypass method at an appropriate timing, in addition to shortening the defrosting time. There is known a method for improving the rising performance of the heating capacity after returning to the heating operation (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 6-201233 (paragraph [0008], FIG. 1) Japanese Patent Laying-Open No. 2008-96033 (paragraph [0010], FIG. 3)

  However, in the defrosting method of the heat pump device as in Patent Document 1, the outdoor heat exchanger is in a high temperature state to some extent in the situation immediately before the frost is completely melted by reverse cycle defrosting. As a result, the refrigerant no longer condenses and liquefies, and the entire refrigerant circuit circulates in a gas-liquid two-phase state. As a result, the gas refrigerant pushes out the liquid refrigerant in the refrigerant circuit, and a large amount of liquid refrigerant returns to the compressor, which impairs reliability.

  Even if the defrosting operation is switched from the reverse cycle method to the hot gas bypass method so as to keep the gas piping at a high temperature as in Patent Document 2, the discharge pressure of the compressor is close to the ice temperature of 0 ° C. immediately after the switching. In addition, there is a problem that the liquid refrigerant returns to the compressor just before the defrosting is finished, and the compressor itself becomes a low temperature and the rising property at the time of returning to heating is impaired.

  An object of the present invention is to solve the above-described problems, and an object of the present invention is to obtain a heat pump device that can perform defrosting in a short time and has improved start-up performance when returning to heating. It is said.

  A heat pump device according to the present invention includes a refrigerant circuit formed by sequentially connecting a compressor, a four-way switching valve, an indoor heat exchanger, an expansion means, and an outdoor heat exchanger to a pipe for circulating the refrigerant, Detecting frost formation on an outdoor heat exchanger in a heat pump device comprising a bypass pipe connecting the discharge side of the machine and an inlet on the throttle means side of the outdoor heat exchanger and a bypass valve opening and closing the bypass pipe A frosting detection means, a liquid refrigerant discharge detection means for detecting that the liquid refrigerant has been discharged from the outdoor heat exchanger, a four-way switching valve, and a control unit for controlling the throttling means, the control unit, When the frosting detection means detects frosting of the outdoor heat exchanger, the reverse cycle defrosting operation for switching the four-way switching valve to the cooling side, and the refrigerant temperature near the indoor heat exchanger became lower than the predetermined temperature. When the four-way selector valve is on the heating side The pump down operation for switching and closing the throttle means and the hot gas bypass defrosting operation for opening the bypass valve when the liquid refrigerant discharge detecting means detects the discharge of the liquid refrigerant from the outdoor heat exchanger. is there.

  During the defrosting operation of the heat pump device, the gas side connection pipe is kept at a high temperature and the compressor can also be kept at a high temperature, so that the defrosting can be performed in a short time and the start-up property at the time of heating return is improved. A heat pump device can be obtained.

3 is a refrigerant circuit diagram of the heat pump device according to Embodiment 1. FIG. It is a flowchart figure which shows the flow of the defrost operation control of the heat pump apparatus which concerns on Embodiment 1. FIG. 4 is a refrigerant circuit diagram of a heat pump device according to Embodiment 2. FIG.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram of the heat pump device according to the first embodiment. The heat pump device according to Embodiment 1 includes an outdoor unit 1, an indoor unit 2, a gas side connection pipe 3 connecting them, and a liquid side connection pipe 4.

  To the outdoor unit 1, a compressor 5, a four-way switching valve 6, an outdoor heat exchanger 10, and an expansion valve 9 as a throttle means are sequentially connected by piping. The four-way switching valve 6 is connected to a pipe as shown by the solid line in FIG. 1 during heating operation. That is, the discharge side of the compressor 5 is connected to the connection pipe 3 via the four-way switching valve 6, and the suction side of the compressor 5 is routed via the four-way switching valve 6, the outdoor heat exchanger 10, and the expansion valve 9. Connected to the connecting pipe 4.

  In the following description, for the sake of convenience, the inlet or outlet of the outdoor heat exchanger 10 and an indoor heat exchanger 7 described later is defined based on the refrigerant flow during the heating operation. That is, in the outdoor heat exchanger 10, since the refrigerant flows from the bottom to the top during the heating operation, the lower side in the figure is the inlet and the upper side in the figure is the outlet. Further, in the indoor heat exchanger 7 to be described later, since the refrigerant flows from the top to the bottom of the figure, the upper side of the figure is the inlet and the lower side of the figure is the outlet.

  The bypass pipe 12 branched on the discharge side of the compressor 5 is connected to the vicinity of the inlet of the outdoor heat exchanger 10 via the bypass valve 13. The bypass valve 13 opens and closes the bypass pipe 12. A temperature sensor 14 is provided near the discharge side of the compressor 5, a temperature sensor 15 is provided near the inlet of the outdoor heat exchanger 10, and a temperature sensor 16 is provided near the outlet of the outdoor heat exchanger 10. Detect the refrigerant temperature. An outdoor fan 11 for blowing air to the outdoor heat exchanger 10 is provided in the vicinity of the outdoor heat exchanger 10.

  The indoor unit 2 is provided with an indoor heat exchanger 7 whose inlet is connected to the connecting pipe 3 and whose outlet is connected to the connecting pipe 4. A temperature sensor 17 for detecting the refrigerant temperature is provided in the vicinity of the outlet of the indoor heat exchanger 7. An indoor fan 8 for sending air to the indoor heat exchanger 7 is provided in the vicinity of the indoor heat exchanger 7.

  In the refrigerant circuit thus configured, for example, R410A is sealed as a refrigerant and circulates in the refrigerant circuit.

  Although not shown, the outdoor unit 1 is provided with a control unit. The control unit reads information from each temperature sensor described above and controls the compressor 5, the four-way switching valve 6, the bypass valve 13, the expansion valve 9, the outdoor fan 11, and the indoor fan 8. The control unit does not necessarily have to be provided in the outdoor unit 1 and may be provided anywhere as long as the above control can be performed.

  Next, the operation | movement at the time of the heating operation of a heat pump apparatus is demonstrated.

  The four-way switching valve 6 is set on the heating side, that is, in the direction in which the gas refrigerant discharged from the compressor 5 flows into the indoor heat exchanger 7. The bypass valve 13 is closed. The high-temperature and high-pressure gas refrigerant discharged from the compressor 5 and flowing into the indoor heat exchanger 7 via the connection pipe 3 exchanges heat with the indoor air blown by the indoor fan 8 to be condensed and liquefied to be high-pressure liquid refrigerant. It becomes.

  This high-pressure liquid refrigerant returns to the outdoor unit 1 through the connection pipe 4, is decompressed by the expansion valve 9, and becomes a gas-liquid two-phase refrigerant. This gas-liquid two-phase refrigerant flows into the outdoor heat exchanger 10, receives heat from the outdoor air blown from the outdoor fan 11, evaporates, and becomes a low-pressure gas refrigerant. This low-pressure gas refrigerant is again sucked into the compressor 5 via the four-way switching valve 6.

  In this heating operation, the compressor 5 is adjusted in rotation speed so that the indoor air temperature becomes the temperature required by the occupant, and the expansion valve 9 is a low-pressure gas refrigerant on the outlet side of the outdoor heat exchanger 10. The flow resistance is adjusted so that the degree of superheat is about 2 [deg]. Or you may adjust so that the supercooling degree of about 10 [deg] may be attached to the exit side of the indoor heat exchanger 7.

  Here, under an operating condition where the outdoor air temperature is as low as less than 5 ° C., the evaporation temperature of the outdoor heat exchanger 10 operating as an evaporator becomes 0 ° C. or less, and frost grows on the surface of the outdoor heat exchanger 10. The growth of frost hinders heat collection from outdoor air to lower the heating operation efficiency, and further lowers the evaporation temperature to accelerate the growth of frost. Therefore, when the evaporator is frosted, it is necessary to perform a defrosting operation.

  Then, the operation | movement at the time of a defrost operation is demonstrated.

  FIG. 2 is a flowchart showing a flow of defrosting operation control of the heat pump device according to the first embodiment. The operation during the defrosting operation will be described with reference to FIGS. 1 and 2.

  S1 is a state in which the heating operation is performed, and S2 is a step in which the start determination of the defrosting operation is performed. In the example of FIG. 2, the temperature sensor 15 or the temperature sensor 16 is used as frost detection means. That is, as a determination condition for starting the defrosting operation, the state where the temperature sensor 15 or the temperature sensor 16 is −5 ° C. or lower continues for a predetermined time (5 minutes in FIG. 2), and the control unit satisfies this condition. When it is done, it is determined that frost has been formed, and the defrosting operation mode is entered. Note that the determination condition for starting the defrosting operation is not limited to this, and it is determined whether or not frost formation has occurred in consideration of the state in which the outside air temperature is equal to or lower than the predetermined temperature for a predetermined period of time or the compressor rotation speed. May be.

  S3 is a step for performing a reverse cycle defrosting operation. The control unit stops the indoor fan 8 and the outdoor fan 11, and turns the four-way switching valve 6 to the cooling side, that is, the direction in which the gas refrigerant discharged from the compressor 5 flows into the outdoor heat exchanger 10 (the direction of the broken line in FIG. 1). ). At this time, the suction side of the compressor 5 is connected to the connection pipe 3 via the four-way switching valve 6. The compressor rotation speed is set to a rotation speed suitable for performing the defrosting operation.

  S4 is a step for determining the end of the reverse cycle defrosting. The reverse cycle defrosting operation is terminated before the connection pipe 3 becomes low temperature. In the example of FIG. 2, the end determination of the reverse cycle defrosting is based on the fact that the outlet temperature sensor 17 of the indoor heat exchanger 7 has detected a low temperature (in FIG. 2, less than 0 ° C.). That is, the reverse cycle defrosting is terminated when the low-pressure two-phase refrigerant reaches the indoor heat exchanger 7.

The reason for determining the end of the reverse cycle defrosting in this way will be described below.
The refrigerant state immediately after the start of the reverse cycle defrosting is such that the high-temperature discharge gas refrigerant that has exited the compressor 5 flows into the outdoor heat exchanger 10 that is covered with frost, so that the discharge gas refrigerant pressure is saturated at 0 ° C. It drops at a stretch to the vicinity. Along with this, the suction side pressure of the compressor 5 also decreases to a saturation temperature of −20 ° C. or lower. However, the connection pipe 4, the indoor heat exchanger 7, and the connection pipe 3 are still hot because the high-temperature and high-pressure refrigerant has circulated until immediately before the start of defrosting, and the refrigerant once liquefied in the outdoor heat exchanger 10 is the indoor unit 2 The refrigerant returns to the compressor 5 as a low-pressure gas refrigerant having a large degree of superheat again.

  As the defrosting progresses, the condensation in the outdoor heat exchanger 10 is gradually not performed, and the liquid refrigerant pushed out of the outdoor heat exchanger 10 passes through the expansion valve 9 and has a low-temperature gas-liquid two-phase refrigerant. It goes to the connection pipe 4 and the indoor heat exchanger 7. Therefore, the connection pipe 4 that has been at a high temperature gradually reaches a low pressure saturation temperature of about −20 ° C., and this low-temperature liquid refrigerant proceeds to the indoor unit 2.

  If the reverse cycle defrosting continues and the temperature of the connection pipe 3 becomes low, the liquid refrigerant will eventually return to the compressor 5 to deteriorate the reliability, and the defrosting is completed and the heating operation is resumed. After a while, the heat of the discharged gas refrigerant is consumed for heating the connection pipe 3, and the heating capacity is not exhibited, thereby deteriorating the comfort of the indoor space.

  In order to prevent this, in the reverse cycle defrosting end determination S4, the outlet temperature sensor 17 of the indoor heat exchanger 7 detects the lower temperature than the predetermined temperature so that at least the connection pipe 3 can maintain a high temperature state. End of cycle defrosting. The means for detecting the refrigerant temperature of the indoor heat exchanger 7 is not necessarily required by the temperature sensor on the outlet side, and may be provided on the inlet side. In this case, in order to maintain the connection pipe 3 in a high temperature state, a temperature that is a criterion for determining whether or not the connection pipe 3 is low may be set higher than when the outlet temperature sensor 17 is used.

  S5 is a step for performing a pump-down operation. As an operation, while the operation of the compressor 5 is continued, the control unit switches the four-way switching valve 6 to the heating side (in the direction of the solid line in FIG. 1) and closes the expansion valve 9 which is a throttle means.

  By performing the pump-down operation, the refrigerant that has been present in the outdoor heat exchanger 10 is pushed into the indoor unit 2 side, so that the pressure on the compressor high-pressure side once reduced by reverse cycle defrosting increases again.

  At this time, the outdoor fan 11 may be operated. By promoting the heat exchange with the outside air by the operation of the outdoor fan 11, the liquid refrigerant that may remain in the outdoor heat exchanger 10 can be completely evaporated.

  S6 is a step for determining the end of the pump-down operation. The end determination of the pump-down operation is based on the fact that no liquid refrigerant is present in the outdoor heat exchanger 10. As the refrigerant on the low-pressure side of the compressor 5 decreases, the pressure on the low-pressure side approaches the vacuum level, and the temperature of the discharged gas refrigerant rises due to an increase in the compression ratio and a decrease in the amount of refrigerant circulating as the coolant. By measuring the temperature on the discharge side of the compressor 5, it can be determined that the liquid refrigerant no longer exists in the outdoor heat exchanger 10.

  In the determination condition shown in FIG. 2, the temperature sensor 14 detects a temperature exceeding 100 ° C. as the liquid refrigerant discharge detecting means. However, the present invention is not limited to this, and a pressure sensor is installed on the low pressure side. It may be detected that the pressure is not more than the predetermined pressure directly, or the time for which the refrigerant recovery can be completed is considered in consideration of the internal volume of the outdoor heat exchanger 10, the displacement volume of the compressor 5 and the rotational speed. It may be set. In this way, it is detected that the liquid refrigerant has been discharged from the outdoor heat exchanger 10.

  In this pump-down operation, since the connection pipe 4 is cooled to about −20 ° C., the refrigerant is quickly condensed from the high pressure side. Further, even in the outdoor heat exchanger 10 communicating with the low pressure, the defrosting proceeds to some extent and has a high temperature portion, so that a large amount of liquid refrigerant does not remain. finish.

  S7 is a step for performing a hot gas bypass defrosting operation. As an operation, the bypass valve 13 is opened by the control unit. The expansion valve 9 is kept closed. By this operation, the discharged gas refrigerant having a high temperature flows in from the inlet side of the outdoor heat exchanger 10.

  The hot gas bypass defrosting is performed in order to completely end the defrosting of the outdoor heat exchanger 10. That is, since the above-described reverse cycle defrosting end determination is that the liquid refrigerant has reached the indoor unit 2, it is not guaranteed that the defrosting of the outdoor heat exchanger 10 has been completely completed. Therefore, the frost residue is avoided here by flowing the discharge gas refrigerant from the inlet side of the outdoor heat exchanger 10 where the possibility of frost residue is high, that is, the opposite side to the reverse cycle defrosting.

  Due to the pump-down operation described above, both the discharge-side pressure and temperature of the compressor 5 are sufficiently high immediately before the bypass valve 13 is opened, so that the discharge gas refrigerant temperature for defrosting tends to maintain a high temperature. . Further, immediately after the bypass valve 13 is opened, the gas refrigerant is appropriately supplied to the hot gas bypass defrosting cycle side by the boiling of the high-temperature liquid refrigerant on the indoor unit 2 side, so that the refrigerant shortage operation is unlikely.

  In addition, when a refrigerant | coolant runs short in a hot gas bypass defrost operation, you may move to such an extent that the malfunction by a liquid back does not arise. As a specific method, the expansion valve 9 is slightly opened. By this operation, a part of the liquid refrigerant stored in the connection pipe 4 can be moved to the hot gas bypass cycle side.

  In normal hot gas bypass defrosting, since there is no evaporation heat source, the refrigerant condensed and liquefied by melting the frost returns to the compressor 5 as it is, and the reliability is deteriorated. Further, at the end of the defrosting operation, the compressor 5 becomes low temperature due to the liquid back, so that it takes time to increase the high-pressure side pressure after returning to the heating operation.

  However, in this embodiment, since the refrigerant is recovered to the indoor unit 2 immediately before the hot gas bypass defrosting operation by the above-described pump down operation, the hot gas bypass defrosting operation is performed for a relatively long time. However, there is no fear that the liquid refrigerant returns to the compressor 5, and the heating start-up time is shortened while maintaining high reliability.

  S8 is a step for determining the end of hot gas bypass defrosting. The hot gas bypass defrosting operation is based on the end determination condition that the defrosting of the outdoor heat exchanger 10 has been completely removed. In the example shown in FIG. 2, the hot gas bypass defrosting operation is installed on the outlet side of the outdoor heat exchanger 10. It is assumed that the temperature sensor 16 has detected a temperature exceeding 10 ° C. This is because the high-temperature discharged gas refrigerant flows from the bypass pipe 12 into the outdoor heat exchanger 10 and proceeds while melting the frost, but when the refrigerant flows out of the outdoor heat exchanger 10, a temperature of 10 ° C. or higher is still secured. This is because it can be determined that frost has been almost completely removed.

  S9 is a step of completing the defrosting and returning to the heating operation. The bypass valve 13 is closed by the control unit, and the control of the expansion valve 9 is returned to the control of the heating operation.

  At this time, the above-described pump-down operation ensures sufficient liquid refrigerant in the connecting pipe 4 and the indoor heat exchanger 7, while the outdoor heat exchanger 10 has almost no liquid refrigerant, and the compressor 5 Since the connecting pipe 3 maintains a sufficiently high temperature, the heating capacity after heating starts up quickly.

  According to the first embodiment, the reverse cycle defrosting can be completed while keeping the gas-side connection pipe 3 at a high temperature, and the liquid refrigerant is obtained by performing the pump-down operation before the hot gas bypass defrosting. Since it can collect | recover in the indoor unit 2 and the compressor 5 can also hold | maintain high temperature, while being able to perform a defrost in a short time, the heat pump apparatus which improved the standup property at the time of heating return can be obtained. effective.

Embodiment 2. FIG.
FIG. 3 is a refrigerant circuit diagram illustrating the heat pump device according to the second embodiment. This is a configuration example of a large-scale heat pump apparatus in which a plurality of indoor units 2 are connected in parallel to one outdoor unit 1.

  Differences from FIG. 1 will be described. In a large-scale heat pump device, the amount of refrigerant flowing through the refrigerant circuit also increases. In order to prevent the lubricating oil of the compressor 5 from being diluted by this refrigerant, an accumulator 21 is provided on the suction side of the compressor 5. In addition, in order to perform control for each indoor heat exchanger 7, an expansion valve 9 is provided for each indoor heat exchanger 7. In order to prevent liquid refrigerant from flowing into the outdoor heat exchanger 10 from the connection pipe 4 during the pump-down operation described above, an electromagnetic as a throttle means is provided between the outlet of the outdoor heat exchanger 10 and the connection pipe 4. A valve 22 is provided.

  The difference in the defrosting operation in the configuration of FIG. 3 is that the expansion valve 9 is closed instead of the expansion valve 9 during the pump-down operation, and the rest is the same as in the first embodiment. Even if the expansion valve 9 is provided for each indoor heat exchanger 7, the liquid refrigerant can be prevented from flowing into the outdoor heat exchanger 10 by closing the electromagnetic valve 22 during the pump-down operation.

  In a heat pump apparatus having a large scale as shown in FIG. 3, when a liquid back is generated immediately before the end of the defrosting and the liquid refrigerant once accumulates in the accumulator, heat for evaporating it is obtained even after heating is restored. It is difficult, and the refrigerant shortage will continue for a while after returning to heating. However, according to the present invention, liquid back does not occur before completion of defrosting, and such a refrigerant shortage state does not occur. Therefore, the merit of applying the present invention to a large-scale heat pump device is great.

  According to the second embodiment, the same effect as in the first embodiment can be obtained even in a large-scale heat pump apparatus.

  The heat pump device according to the present invention is not limited to an air conditioner and can be applied to other products using a heat pump such as a hot water supply device and a refrigerator.

DESCRIPTION OF SYMBOLS 1 Outdoor unit 2 Indoor unit 3, 4 Connection piping 5 Compressor 6 Four-way switching valve 7 Indoor heat exchanger 8 Indoor fan 9 Expansion valve 10 Outdoor heat exchanger 11 Outdoor fan 12 Bypass piping 13 Bypass valves 14-17 Temperature sensor 21 Accumulator 22 Solenoid valve

Claims (7)

A refrigerant circuit formed by sequentially connecting a compressor, a four-way switching valve, an indoor heat exchanger, a throttle means, and an outdoor heat exchanger to a pipe for circulating the refrigerant;
A bypass pipe connecting the discharge side of the compressor and the inlet of the throttle means side of the outdoor heat exchanger;
In a heat pump device comprising a bypass valve that opens and closes the bypass pipe,
Frost detection means for detecting frost formation of the outdoor heat exchanger;
Liquid refrigerant discharge detecting means for detecting that liquid refrigerant has been discharged from the outdoor heat exchanger;
A controller for controlling the four-way switching valve and the throttle means;
With
The control unit, when the frost detection means detects frost formation of the outdoor heat exchanger, reverse cycle defrosting operation for switching the four-way switching valve to the cooling side,
A pump-down operation for switching the four-way switching valve to a heating side and closing the throttle means when the refrigerant temperature in the vicinity of the indoor heat exchanger becomes lower than a predetermined temperature;
A heat pump device that performs a hot gas bypass defrosting operation that opens the bypass valve when the liquid refrigerant discharge detecting means detects the discharge of the liquid refrigerant from the outdoor heat exchanger. 2. The heat pump device according to claim 1, wherein the frost detection means detects frost on the condition that a state in which the refrigerant temperature in the vicinity of the outdoor heat exchanger has become equal to or lower than a predetermined temperature continues for a predetermined time or longer. 2. The heat pump device according to claim 1, wherein the frost detection means detects frost on the condition that a state in which an air temperature in the vicinity of the outdoor heat exchanger has become equal to or lower than a predetermined temperature continues for a predetermined time or longer. The heat pump device according to any one of claims 1 to 3, wherein the liquid refrigerant discharge detection means detects liquid refrigerant discharge on the condition that the discharge temperature of the compressor has become a predetermined temperature or higher. The heat pump device according to any one of claims 1 to 3, wherein the liquid refrigerant discharge detecting means detects liquid refrigerant discharge on the condition that the suction pressure of the compressor is equal to or lower than a predetermined pressure. The liquid refrigerant discharge detecting means detects liquid refrigerant discharge on the condition that a product of a displacement volume per rotation of the compressor and a rotation speed of the compressor becomes a predetermined value or more. The heat pump device according to any one of 1 to 3. An outdoor fan that is disposed in the vicinity of the outdoor heat exchanger and blows air to the outdoor heat exchanger;
The heat pump device according to any one of claims 1 to 6, wherein the control unit performs control for operating the outdoor fan during the pump-down operation.

Images