Industrial air conditioner control method

Abstract

The invention relates to an industrial air conditioner control method and belongs to the technical field of industrial air conditioners. According to the method, a user only needs to select the working mode, the air conditioning system can automatically detect the environmental parameters and make corresponding adjustment, frequent manual intervention is not needed, the use convenience and comfort are improved, the energy efficiency ratio of the air conditioner is increased, and unnecessary energy waste is avoided. And meanwhile, various working modes such as refrigeration, dehumidification, air supply and heating are provided, the use requirements under different seasons and different weather conditions can be met, and the diversified requirements of industrial places for the air conditioning system are met.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial air conditioners, and in particular relates to an industrial air conditioner control method. Background Art

[0002] Industrial air conditioning refers to air conditioning equipment that provides environmental temperature, humidity, and cleanliness guarantees for the reliable operation of industrial product production processes or industrial process equipment. However, since different industries and different equipment have different requirements for the production environment, there is an urgent need for an industrial air conditioning control method that can cope with a variety of usage scenarios. Summary of the invention

[0003] In order to solve at least one of the above problems existing in the prior art, the present invention provides an industrial air conditioning control method.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] An industrial air conditioner control method is applied to the industrial air conditioner, the industrial air conditioner includes a compressor, a steam side fan, a condensing side fan, a water pumping motor and a four-way valve; the control method includes:

[0006] S101: Select working mode and set working parameters;

[0007] S102: Detect environmental parameters;

[0008] S103: Control equipment operation;

[0009] Among them, the working modes include cooling mode, dehumidification mode, air supply mode and heating mode.

[0010] In some embodiments of the present invention, when the working mode is the cooling mode, the control method includes:

[0011] S201: Detect the outlet air temperature. When the outlet air temperature is not less than the sum of the set temperature and the temperature control hysteresis, execute step S202; when the outlet air temperature is not greater than the difference between the set temperature and the temperature control hysteresis, execute step S203;

[0012] S202: Turn on the compressor and execute step S204;

[0013] S203: Turn off the compressor and execute step S205;

[0014] S204: Turn on the condensing side fan and the water pumping motor, and execute step S206;

[0015] S205: Turn off the condensing side fan and the water pumping motor, and execute step S201;

[0016] S206: Turn on the evaporation side fan, forcefully close the four-way valve, and execute step S201.

[0017] In some embodiments of the present invention, when the working mode is a dehumidification mode, the control method includes:

[0018] S301: Detecting the ambient humidity. When the ambient humidity is not less than the sum of the set humidity and the humidity control hysteresis, executing step S302; when the ambient humidity is not greater than the difference between the set humidity and the humidity control hysteresis, executing step S303;

[0019] S302: Turn on the compressor and run step S304;

[0020] S303: Turn off the compressor and run step S305;

[0021] S304: Turn on the condensation side fan and execute step S306;

[0022] S305: Turn off the condensation side fan and execute step S301;

[0023] S306: Forcefully close the water pumping motor and the four-way valve, and execute step S301.

[0024] In some embodiments of the present invention, refrigeration and defrosting must be completed before turning on the compressor, and during refrigeration and defrosting, the compressor is immediately turned off;

[0025] Among them, the conditions for opening the refrigeration defrost are: the continuous operation time of the compressor is not less than the defrost interval time and the coil temperature is detected to be no greater than the refrigeration defrost opening temperature for three consecutive seconds;

[0026] The shut-down conditions for refrigeration defrost are: the compressor defrost time is not less than the defrost running time or the compressor defrost time is not less than three minutes and the coil temperature is detected to be not less than the refrigeration defrost exit temperature for three consecutive seconds.

[0027] In some embodiments of the present invention, when the working mode is the air supply mode, the control method includes:

[0028] S401: Forced shutdown of the compressor, condensing side fan and four-way valve;

[0029] S402: Turn on the steam side fan.

[0030] In some embodiments of the present invention, when the working mode is a heating mode, the control method includes:

[0031] S501: Detect the outlet air temperature. When the outlet air temperature is not greater than the difference between the set temperature and the temperature vacancy return difference, execute step S502; when the outlet air temperature is not less than the sum of the set temperature and the temperature vacancy return difference, execute step S503;

[0032] S502: Turn on the compressor and execute step S504;

[0033] S503: Turn off the compressor and execute step S505;

[0034] S504: Turn on the condensing side fan, turn on the evaporating side fan after five seconds, and execute step S506;

[0035] S505: Turn off the condensing side fan and the steam side fan, open the four-way valve after two minutes, and execute step S501;

[0036] S506: forcibly shut down the water pumping motor and execute step S501;

[0037] Among them, when the working mode is switched from heating mode to other modes, the four-way valve is closed after a delay of two minutes.

[0038] In some embodiments of the present invention, heating and defrosting must be completed before turning on the compressor. During heating and defrosting, the compressor is turned off, and after fifty seconds, the evaporation side fan, the condensation side fan and the four-way valve are turned off, and after another ten seconds, the compressor is turned on;

[0039] The heating and defrosting start conditions are: the continuous operation time of the compressor is not less than the defrosting interval time and the coil temperature is not greater than the heating and defrosting start temperature for three consecutive seconds;

[0040] The end condition of heating defrost is: the compressor defrost time is not less than the defrost operation time or the coil temperature is detected to be not less than the heating defrost exit temperature for three consecutive seconds when the compressor defrost time is not less than three minutes.

[0041] In some embodiments of the present invention, it is characterized in that before starting the compressor, the compressor three-minute start-stop protection, system high-pressure protection and system low-pressure protection need to be met; wherein, the compressor three-minute start-stop protection is: without power outage, the compressor must stop running for no less than three minutes before it can be started again.

[0042] In some embodiments of the present invention, the system high-pressure protection includes: the compressor can only be turned on when the high-pressure switch is detected to be connected for five consecutive seconds; the high-pressure switch is detected to be disconnected for five consecutive seconds, entering the high-pressure protection state, shutting down the compressor and the condensing side fan, and closing the four-way valve after a delay of two minutes; if the high-pressure protection state is entered three times within thirty minutes, the compressor and the condensing side fan will be shut down and the power must be turned off before recovery.

[0043] In some embodiments of the present invention, the system low-pressure protection includes: after the compressor has been running for three minutes, if the low-pressure switch is detected to be disconnected for five consecutive seconds, the system enters the low-pressure protection state, shuts down the compressor and the condensing side fan, and closes the four-way valve after a delay of two minutes; if the system enters the low-pressure protection state three times within thirty minutes, the compressor and the condensing side fan are shut down and the power cannot be restored without power failure;

[0044] Among them, when the compressor is in defrosting state, the low pressure fault is not detected.

[0045] The beneficial effects of the present invention are:

[0046] 1. Users only need to select the working mode, and the air conditioning system can automatically detect environmental parameters and make corresponding adjustments without frequent manual intervention, which improves the convenience and comfort of use, improves the energy efficiency of the air conditioner, and avoids unnecessary energy waste.

[0047] 2. By introducing cooling / heating defrost mechanism, three-minute compressor start / stop protection, system high / low pressure protection and other measures, the stable operation of the air-conditioning system under various working conditions is ensured, which can extend the service life of the equipment and improve the safety and reliability of the air-conditioning system.

[0048] 3. It provides multiple working modes such as refrigeration, dehumidification, air supply, heating, etc., which can adapt to the usage needs in different seasons and weather conditions, and meet the diverse requirements of industrial sites for air-conditioning systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0050] Figure 1 This is a flow chart of overall air conditioning control provided in one embodiment of the present invention;

[0051] Figure 2 A cooling mode control flow chart provided in one embodiment of the present invention;

[0052] Figure 3 A dehumidification mode control flow chart provided in one embodiment of the present invention;

[0053] Figure 4 A flow chart of air supply mode control provided in one embodiment of the present invention;

[0054] Figure 5 A heating mode control flow chart provided in one embodiment of the present invention;

[0055] Figure 6 A circuit diagram of a control system provided in one embodiment of the present invention;

[0056] Figure 7A circuit diagram of a control system provided in one embodiment of the present invention;

[0057] Figure 8 This is a schematic diagram of a main control chip of a control system provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0059] The present embodiment provides an industrial air conditioner control method, which is applied to an industrial air conditioner. The industrial air conditioner includes a compressor, a steam side fan, a condensing side fan, a water pumping motor, and a four-way valve. The control method includes:

[0060] S101: Select working mode and set working parameters;

[0061] S102: Detect environmental parameters;

[0062] S103: Control equipment operation;

[0063] Among them, the working modes include cooling mode, dehumidification mode, air supply mode and heating mode.

[0064] The parameters that need to be set include but are not limited to: temperature, temperature control hysteresis, humidity, humidity control hysteresis and evaporation side fan speed.

[0065] In this embodiment, the air conditioning system automatically detects environmental parameters and controls the operation of each component according to preset logic by selecting the working mode and setting the working parameters by the user. By accurately detecting environmental parameters and automatically adjusting the working state of each component according to actual needs, unnecessary energy waste is avoided and the energy efficiency ratio of the air conditioner is improved.

[0066] In a further embodiment of the present invention, when the working mode is a cooling mode, the control method includes:

[0067] S201: Detect the outlet air temperature or the inlet air temperature. When the outlet air temperature or the inlet air temperature is not less than the sum of the set temperature and the temperature control hysteresis, execute step S202; when the outlet air temperature or the inlet air temperature is not greater than the difference between the set temperature and the temperature control hysteresis, execute step S203;

[0068] S202: Turn on the compressor and execute step S204;

[0069] S203: Turn off the compressor and execute step S205;

[0070] S204: Turn on the condensing side fan and the water pumping motor, and execute step S206;

[0071] S205: Turn off the condensing side fan and the water pumping motor, and execute step S201;

[0072] S206: Turn on the evaporation side fan, forcefully close the four-way valve, and execute step S201.

[0073] Among them, the temperature, temperature control hysteresis and evaporation side fan speed are user preset values; the condensation side fan and water pumping motor are started and stopped synchronously with the compressor. When the evaporation side fan is at high or medium wind, the condensation side fan runs at high wind; when the evaporation side fan is at low wind, the condensation side fan runs at low wind.

[0074] In this embodiment, the system controls the switch status of the compressor, condensing side fan, water pumping motor and evaporating side fan according to the difference between the outlet air temperature and the set temperature, and automatically adjusts the working status of the compressor and other components according to the difference between the outlet air temperature and the set temperature, thereby achieving precise temperature control, improving the comfort and stability of the indoor temperature, and reducing energy consumption. At the same time, a temperature control hysteresis is set to set the target temperature within a certain range to avoid frequent start and stop of the compressor and thus reduce the life of the compressor.

[0075] In a further embodiment of the present invention, when the working mode is a dehumidification mode, the control method includes:

[0076] S301: Detecting the ambient humidity. When the ambient humidity is not less than the sum of the set humidity and the humidity control hysteresis, executing step S302; when the ambient humidity is not greater than the difference between the set humidity and the humidity control hysteresis, executing step S303;

[0077] S302: Turn on the compressor and run step S304;

[0078] S303: Turn off the compressor and run step S305;

[0079] S304: Turn on the condensation side fan and execute step S306;

[0080] S305: Turn off the condensation side fan and execute step S301;

[0081] S306: Forcefully close the water pumping motor and the four-way valve, and execute step S301.

[0082] Among them, the humidity and humidity control hysteresis are user preset values, the condensing side fan and the compressor start and stop synchronously, the evaporating side fan is forced to run at low wind speed, and the condensing side fan is forced to run at high wind speed.

[0083] In this embodiment, the switch status of the compressor, condensing side fan and water pumping motor are controlled according to the difference between the ambient humidity and the set humidity, so as to control the ambient humidity, prevent the equipment from getting damp, improve the ambient air quality and protect the normal operation of the industrial equipment.

[0084] In a further embodiment of the present invention, refrigeration and defrosting must be completed before turning on the compressor, and during refrigeration and defrosting, the compressor is immediately turned off;

[0085] Among them, the conditions for opening the refrigeration defrost are: the continuous operation time of the compressor is not less than the defrost interval time and the coil temperature is detected to be no greater than the refrigeration defrost opening temperature for three consecutive seconds;

[0086] The shut-down conditions for refrigeration defrost are: the compressor defrost time is not less than the defrost running time or the compressor defrost time is not less than three minutes and the coil temperature is detected to be not less than the refrigeration defrost exit temperature for three consecutive seconds.

[0087] Among them, the defrost interval time, the refrigeration defrost start temperature and the refrigeration defrost exit temperature are user preset values; at the same time, if the sensor for detecting the coil temperature fails and cannot detect the coil temperature, the compressor will enter refrigeration defrost if the continuous running time is not less than the defrost detection time.

[0088] In this embodiment, setting the refrigeration mode can effectively prevent the compressor from freezing during the refrigeration process and affecting the refrigeration effect. By detecting the compressor operating time, coil temperature and defrost time, the defrost function is automatically turned on or off. It can automatically detect and handle icing problems that may occur during the refrigeration process, ensure the continuous and efficient operation of the air-conditioning system, extend the service life of air-conditioning components, and improve the stability and reliability of the system.

[0089] In a further embodiment of the present invention, when the working mode is the air supply mode, the control method includes:

[0090] S401: Forced shutdown of the compressor, condensing side fan and four-way valve;

[0091] S402: Turn on the steam side fan.

[0092] In this embodiment, the air conditioning system is controlled to only provide air flow when cooling or heating is not needed, thereby improving indoor air quality by supplying air, saving energy, and improving indoor air circulation.

[0093] In a further embodiment of the present invention, when the working mode is a heating mode, the control method includes:

[0094] S501: Detect the outlet air temperature. When the outlet air temperature is not greater than the difference between the set temperature and the temperature vacancy return difference, execute step S502; when the outlet air temperature is not less than the sum of the set temperature and the temperature vacancy return difference, execute step S503;

[0095] S502: Turn on the compressor and execute step S504;

[0096] S503: Turn off the compressor and execute step S505;

[0097] S504: Turn on the condensing side fan, turn on the evaporating side fan after five seconds, and execute step S506;

[0098] S505: Turn off the condensing side fan and the steam side fan, open the four-way valve after two minutes, and execute step S501;

[0099] S506: forcibly shut down the water pumping motor and execute step S501;

[0100] Among them, when the working mode is switched from heating mode to other modes, the four-way valve is closed after a delay of two minutes.

[0101] In this embodiment, the temperature, temperature control hysteresis and speed of the evaporation side fan are user preset values, and the condensation side fan and the compressor start and stop synchronously. If the evaporation side fan is at high or medium wind, the condenser fan runs at high wind. If the evaporation side fan is at low wind, the condenser fan runs at low wind.

[0102] According to the difference between the outlet temperature and the set temperature, the switch status of the compressor, condensing side fan, steam side fan and four-way valve is controlled, and the working status of the compressor and other components is automatically adjusted according to the difference between the outlet temperature and the set temperature, realizing precise temperature control. At the same time, a temperature control hysteresis is set to set the target temperature within a certain range to avoid frequent start and stop of the compressor and thus reduce the life of the compressor.

[0103] In a further embodiment of the present invention, heating and defrosting must be completed before turning on the compressor. During heating and defrosting, the compressor is turned off, and after fifty seconds, the evaporation side fan, the condensation side fan and the four-way valve are turned off, and after another ten seconds, the compressor is turned on;

[0104] The heating and defrosting start conditions are: the continuous operation time of the compressor is not less than the defrosting interval time and the coil temperature is not greater than the heating and defrosting start temperature for three consecutive seconds;

[0105] The end condition of heating defrost is: the compressor defrost time is not less than the defrost operation time or the coil temperature is detected to be not less than the heating defrost exit temperature for three consecutive seconds when the compressor defrost time is not less than three minutes.

[0106] In this embodiment, heating defrosting is used to prevent the outdoor unit from freezing in the heating mode, which affects the heating effect. At the same time, the defrosting function is automatically turned on or off according to the compressor running time and the coil temperature, and the icing problem that may occur during the heating process is automatically detected and processed, ensuring the continuous and efficient operation of the air-conditioning system, extending the service life of the air-conditioning components, and improving the stability and reliability of the system.

[0107] In a further embodiment of the present invention, before starting the compressor, the compressor three-minute start-stop protection, system high-pressure protection and system low-pressure protection need to be met; among which, the compressor three-minute start-stop protection is: without power outage, the compressor must stop running for no less than three minutes before it can be started again.

[0108] In this embodiment, after the compressor stops running, it is necessary to wait for at least three minutes before starting again, thereby protecting the compressor from damage caused by frequent starts and stops, preventing the compressor from being damaged due to frequent starts and stops, extending the service life of the compressor, and reducing maintenance costs.

[0109] In a further embodiment of the present invention, the system high-pressure protection includes: the compressor can only be turned on when the high-pressure switch is detected to be connected for five consecutive seconds; the high-pressure switch is detected to be disconnected for five consecutive seconds, entering the high-pressure protection state, shutting down the compressor and the condensing side fan, and closing the four-way valve after a delay of two minutes; if the high-pressure protection state is entered three times within thirty minutes, the compressor and the condensing side fan will be shut down and the power must be cut off before recovery.

[0110] In this embodiment, when the air conditioning system is running at high load, the pressure may be too high. In order to prevent safety accidents and component damage caused by excessive system pressure, a high-pressure switch is provided. The high-pressure switch detects the pressure in the system. When the system pressure is too high, the high-pressure switch is disconnected. By detecting the state of the high-pressure switch, the compressor and the condensing side fan are controlled to enter the protection state when necessary. By detecting the state of the high-pressure switch, timely measures are taken to protect the air conditioning system from damage, thereby improving the safety and reliability of the air conditioning system and reducing the downtime caused by failures.

[0111] In a further embodiment of the present invention, the system low-pressure protection includes: after the compressor has been running for three minutes, if the low-pressure switch is detected to be disconnected for five consecutive seconds, the system enters the low-pressure protection state, shuts down the compressor and the condensing side fan, and closes the four-way valve after a delay of two minutes; if the system enters the low-pressure protection state three times within thirty minutes, the compressor and the condensing side fan are shut down and the power cannot be restored without power failure;

[0112] Among them, when the compressor is defrosting, the low-pressure fault is not detected. In some cases, the air-conditioning system may have a low pressure, such as refrigerant leakage; in order to prevent the system from having poor refrigeration effect and component damage due to low low pressure, a low-pressure switch is provided. The low-pressure switch detects the pressure in the system. When the pressure in the system is too low, the low-pressure switch is disconnected; by detecting the state of the low-pressure switch, the compressor and the condensing side fan are controlled to enter the protection state when necessary; at the same time, during the defrosting of the compressor, the low-pressure fault is not detected to avoid false alarms. By detecting the state of the low-pressure switch, timely measures can be taken to protect the air-conditioning system from damage, thereby improving the safety and reliability of the air-conditioning system and reducing the downtime caused by faults.

[0113] Please refer to Figure 6-8 In another aspect, the present invention provides an industrial air conditioning control system in an embodiment, and the control system uses the above-mentioned industrial air conditioning control method to control the industrial air conditioning.

[0114] In a further embodiment of the present invention, the system is further provided with:

[0115] Automatic drying function: when the system is turned off, the user presses and holds the "mute" button: the fans on the evaporation and condensation sides are all forced to run and maintain for 3 minutes.

[0116] The alarm output function is to turn on the alarm output when the system is turned on and there is any unresolved fault in the device and the fault silencer is not set; the alarm output is turned off when the system is turned off or the fault silencer is set or there is no unresolved fault in the machine.

[0117] Coil temperature query: When the system is turned on, the user presses and holds the "wind speed" button to enter the coil temperature query state; after no operation for 5 seconds, the coil temperature query state is exited.

[0118] Interlocking switch protection function: When the system detects that the interlocking switch is closed for 3 consecutive seconds, the equipment can be turned on or operated normally; when the system detects that the interlocking switch is disconnected for 3 consecutive seconds, it enters the interlocking locking state: the "lock" prompt light of the system flashes, and the whole machine shuts down the load in sequence and stops running.

[0119] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An industrial air conditioning control method, characterized in that: Applied to industrial air conditioners, the industrial air conditioners include a compressor, a steam side fan, a condensing side fan, a water pumping motor and a four-way valve; the control method includes: S101: Select working mode and set working parameters; S102: Detect environmental parameters; S103: Control equipment operation; Among them, the working modes include cooling mode, dehumidification mode, air supply mode and heating mode.

2. An industrial air conditioning control method according to claim 1, characterized in that: When the working mode is the cooling mode, the control method includes: S201: Detect the outlet air temperature. When the outlet air temperature is not less than the sum of the set temperature and the temperature control hysteresis, execute step S202; when the outlet air temperature is not greater than the difference between the set temperature and the temperature control hysteresis, execute step S203; S202: Turn on the compressor and execute step S204; S203: Turn off the compressor and execute step S205; S204: Turn on the condensing side fan and the water pumping motor, and execute step S206; S205: Turn off the condensing side fan and the water pumping motor, and execute step S201; S206: Turn on the evaporation side fan, forcefully close the four-way valve, and execute step S201.

3. The industrial air conditioning control method according to claim 1, characterized in that: When the working mode is the dehumidification mode, the control method includes: S301: Detecting the ambient humidity. When the ambient humidity is not less than the sum of the set humidity and the humidity control hysteresis, executing step S302; when the ambient humidity is not greater than the difference between the set humidity and the humidity control hysteresis, executing step S303; S302: Turn on the compressor and run step S304; S303: Turn off the compressor and run step S305; S304: Turn on the condensation side fan and execute step S306; S305: Turn off the condensation side fan and execute step S301; S306: Forcefully close the water pumping motor and the four-way valve, and execute step S301.

4. An industrial air conditioning control method according to claim 2 or 3, characterized in that: Refrigeration and defrosting must be completed before turning on the compressor. During refrigeration and defrosting, the compressor must be turned off immediately; Among them, the conditions for opening the refrigeration defrost are: the continuous operation time of the compressor is not less than the defrost interval time and the coil temperature is detected to be no greater than the refrigeration defrost opening temperature for three consecutive seconds; The shut-down conditions for refrigeration defrost are: the compressor defrost time is not less than the defrost running time or the compressor defrost time is not less than three minutes and the coil temperature is detected to be not less than the refrigeration defrost exit temperature for three consecutive seconds.

5. The industrial air conditioning control method according to claim 1, characterized in that: When the working mode is the air supply mode, the control method includes: S401: Forced shutdown of the compressor, condensing side fan and four-way valve; S402: Turn on the steam side fan.

6. The industrial air conditioning control method according to claim 1, characterized in that: When the working mode is the heating mode, the control method includes: S501: Detect the outlet air temperature. When the outlet air temperature is not greater than the difference between the set temperature and the temperature vacancy return difference, execute step S502; when the outlet air temperature is not less than the sum of the set temperature and the temperature vacancy return difference, execute step S503; S502: Turn on the compressor and execute step S504; S503: Turn off the compressor and execute step S505; S504: Turn on the condensing side fan, turn on the evaporating side fan after five seconds, and execute step S506; S505: Turn off the condensing side fan and the steam side fan, open the four-way valve after two minutes, and execute step S501; S506: forcibly shut down the water pumping motor and execute step S501; Among them, when the working mode is switched from heating mode to other modes, the four-way valve is closed after a delay of two minutes.

7. An industrial air conditioning control method according to claim 5 or 6, characterized in that: Before turning on the compressor, heating and defrosting must be completed. During heating and defrosting, turn off the compressor, turn off the evaporation side fan, condensation side fan and four-way valve after fifty seconds, and turn on the compressor after another ten seconds; The heating and defrosting start conditions are: the continuous operation time of the compressor is not less than the defrosting interval time and the coil temperature is not greater than the heating and defrosting start temperature for three consecutive seconds; The end condition of heating defrost is: the compressor defrost time is not less than the defrost operation time or the coil temperature is detected to be not less than the heating defrost exit temperature for three consecutive seconds when the compressor defrost time is not less than three minutes.

8. An industrial air conditioning control method according to claim 2, 3 or 6, characterized in that: Before starting the compressor, the compressor three-minute start-stop protection, system high-pressure protection and system low-pressure protection must be met; among which, the compressor three-minute start-stop protection is: without power outage, the compressor must stop running for no less than three minutes before it can be started again.

9. An industrial air conditioning control method according to claim 8, characterized in that: The system high-pressure protection includes: the compressor can only be turned on when the high-pressure switch is detected to be connected for five consecutive seconds; the high-pressure switch is detected to be disconnected for five consecutive seconds, entering the high-pressure protection state, shutting down the compressor and the condensing side fan, and closing the four-way valve after a delay of two minutes; if the high-pressure protection state is entered three times within thirty minutes, the compressor and the condensing side fan will be shut down and the power will not be restored unless the power is cut off.

10. An industrial air conditioning control method according to claim 8, characterized in that: The system low-pressure protection includes: after the compressor has been running for three minutes, if the low-pressure switch is detected to be disconnected for five consecutive seconds, it will enter the low-pressure protection state, shut down the compressor and the condensing side fan, and close the four-way valve after a delay of two minutes; if it enters the low-pressure protection state three times within thirty minutes, the compressor and the condensing side fan will be shut down and the power will not be restored unless it is powered off; Among them, when the compressor is in defrosting state, the low pressure fault is not detected.

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