Building fresh air system and fresh air system control method

Abstract

The invention discloses a building fresh air system and a fresh air system control method, the building fresh air system comprises an air conditioning unit, the air conditioning unit comprises an air mixing box, and an air treatment device is installed in the air mixing box; an air mixing box pressure sensor is arranged in the air mixing box; the air return unit comprises an air return box, the air return box is provided with a second inlet and a second outlet, and an air return fan is installed in the air return box; the second outlet is connected with an exhaust pipe, and an exhaust valve is mounted in the exhaust pipe; an air return valve is mounted in the air return pipe; the return air pressure sensor is mounted in the return air pipe; the controller is connected with the air mixing box pressure sensor and the return air pressure sensor; the controller controls the states of the air return valve and the air return fan according to information of the pressure sensor. The fresh air system is suitable for a double-fan air conditioning system, low in manufacturing cost, high in feasibility, convenient to install, high in universality, capable of ensuring fresh air of indoor air, capable of bringing good energy-saving and economic benefits, wide in application and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of heating, ventilation and air conditioning, and in particular relates to a building fresh air system and a fresh air system control method. Background Art

[0002] In large-space buildings, air conditioning systems are usually used to provide a suitable environment in order to meet the requirements of indoor air quality and temperature. The fresh air and return air systems in the air conditioning system are particularly important. The fresh air is used to provide the fresh air required indoors, while the return air is used to return the indoor air to the air conditioning system for processing. However, in actual use, especially in large-space air conditioning systems, due to the complexity of the system and various operating environment factors, the mixing process of fresh air and return air often faces some problems, especially in terms of pressure control.

[0003] The air conditioning system of large-space buildings usually adopts a full air system. When the return air system is long and has large resistance, or for energy saving and consumption reduction, a dual-fan system is often used. The air pressure of the supply fan and return fan of the dual-fan air conditioning system is designed according to the most unfavorable working conditions. Due to the factors such as the certain margin of the equipment selection air pressure and the dynamic change of the system resistance, the actual air system resistance often differs from the fan pressure head. These differences cause the pressure of the mixing box of the fresh air and return air of the air conditioning unit to be unstable. Affected by the air pressure of the return fan, when the mixing box has a positive pressure, the fresh air cannot be inhaled, and even the return air is discharged from the fresh air outlet, which not only affects the indoor air quality, but also causes the fan energy loss. There is a conversion and adjustment of the fresh air and exhaust air volume in the transition season. In the transition season, when the fresh air working condition is full, the return fan outlet must have a certain residual pressure, such as 50Pa residual pressure or more, to overcome the resistance of the exhaust duct, air valve, and exhaust louver, so that the air can be discharged. In winter and summer, the return air from the return fan outlet directly returns to the air mixing box of the air conditioning unit. In this working condition, the return air inlet of the mixing box can be kept at 0 pressure. If effective control measures are not taken and only the return air valve is used for throttling adjustment, it will inevitably cause energy loss of the fan.

[0004] In view of the above problems, in order to solve the problem of stabilizing the pressure of the mixing box of the new and return air in the dual-fan air-conditioning system, ensuring that the fresh air can be introduced as needed, and reducing the energy loss of the fan, this patented technology is proposed. Summary of the invention

[0005] The object of the present invention is to provide a building fresh air system and a fresh air system control method.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A building fresh air system, comprising: An air conditioning unit, the air conditioning unit comprises an air mixing box, the air mixing box comprises an air mixing part, an air processing part and an air supply part which are connected in sequence, an air processing device is installed in the air processing part, and a blower is installed in the air supply part; the air mixing part is provided with a first inlet, and the air supply part is provided with a first outlet; the air mixing part is connected to an air inlet pipe, and a fresh air valve is installed in the air inlet pipe; a mixing box pressure sensor is provided in the mixing box, and the mixing box pressure sensor is arranged at a position close to the air inlet pipe; A return air unit, the return air unit comprises a return air box, the return air box is provided with a second inlet and a second outlet, a return air fan is installed in the return air box; the second outlet is connected to an exhaust duct, an exhaust valve is installed in the exhaust duct; one end of the return air duct is connected to the exhaust duct, the other end of the return air duct is connected to the first inlet of the air mixing box, and a return air valve is installed in the return air duct; a return air pressure sensor is installed in the return air duct, located at the air inlet side of the return air valve; A controller is connected to the air mixing box pressure sensor and the return air pressure sensor; the controller controls the status of the return air valve and the return air fan according to the pressure sensor information.

[0007] The building fresh air system of the present invention as described above, further, an air guide vane is provided in the air mixing box of the air conditioning unit, and the air guide vane is installed at the first inlet position of the air mixing box, and the air guide vane guides the return air in a direction away from the pressure sensor of the air mixing box.

[0008] The building fresh air system of the present invention as described above, further, the angle between the air guide plate and the top plate of the air mixing box is 30 degrees to 59 degrees.

[0009] The building fresh air system of the present invention as described above, further, the return fan of the return air unit is connected to the return fan frequency conversion controller, and the return fan frequency conversion controller is connected to the controller.

[0010] A method for controlling a fresh air system, wherein the fresh air system is a fresh air system as described in any of the above items; the fresh air system is in a minimum fresh air operating condition: the exhaust valve is in a closed state, and the return air valve and the fresh air valve are in an open state; the controller controls the return air fan operating state through a first pressure value range of a mixing box pressure sensor to keep a negative pressure in the mixing box; when the pressure value of the mixing box pressure sensor is higher than the maximum value of the first pressure value range, the controller controls the return air fan to reduce the operating power, thereby reducing the wind pressure at the return air fan outlet; when the pressure value of the mixing box pressure sensor is lower than the minimum value of the first pressure value range, the controller controls the return air fan to increase the operating power, thereby increasing the wind pressure at the return air fan outlet; the pressure value of the return air pressure sensor is set to 0±10Pa, and the return air pressure sensor is in a monitoring state.

[0011] In the fresh air system control method of the present invention as described above, preferably, the first pressure value range is -50±10Pa; the controller monitors whether the pressure value of the return air pressure sensor is within 0±10Pa, and the controller monitors whether the return air system is faulty according to the pressure value of the return air pressure sensor.

[0012] According to the fresh air system control method of the present invention as described above, preferably, the fresh air system is in a fresh air operating condition: the exhaust valve is in an open state, the return air valve is closed, and the fresh air valve is in an open state; the controller controls the return air fan operating state through the second pressure value range of the return air pressure sensor to maintain a positive pressure at the return air fan outlet; when the pressure value of the return air pressure sensor is higher than the maximum value of the second pressure value range, the controller controls the return air fan to reduce the operating power, thereby reducing the wind pressure; when the pressure value of the return air pressure sensor is higher than the minimum value of the second pressure value range, the controller controls the return air fan to reduce or increase the operating power, thereby increasing the wind pressure.

[0013] In the fresh air system control method of the present invention as described above, preferably, the second pressure value range is 50±10Pa; the controller monitors whether the pressure value of the mixing box pressure sensor is -50±10Pa, and the controller monitors whether the air supply system is faulty according to the pressure value of the mixing box pressure sensor.

[0014] In the fresh air system control method of the present invention as described above, preferably, the fresh air system is in a variable fresh air operation condition: the exhaust valve, the return air valve, and the fresh air valve are all in an adjustment state; The controller controls the operating state of the return fan through the third pressure value range of the return air pressure sensor to keep the return fan outlet at positive pressure; when the pressure value of the return air pressure sensor is higher than the maximum value of the third pressure value range, the controller controls the return fan to reduce the operating power, thereby reducing the wind pressure; when the pressure value of the return air pressure sensor is higher than the minimum value of the third pressure value range, the controller controls the return fan to reduce or increase the operating power, thereby increasing the wind pressure; The controller controls the opening of the return air valve through the fourth pressure value range of the mixing box pressure sensor to maintain a negative pressure in the mixing box; when the pressure value of the mixing box pressure sensor is higher than the maximum value of the fourth pressure value range, the controller controls the opening of the return air valve to become smaller; when the pressure value of the mixing box pressure sensor is lower than the minimum value of the fourth pressure value range, the controller controls the opening of the return air valve to become larger.

[0015] In the fresh air system control method of the present invention as described above, preferably, the third pressure value range is 50±10Pa, and the fourth pressure value range is -50±10Pa.

[0016] The fresh air system of the present invention is suitable for a dual-fan air-conditioning system, has low manufacturing cost, strong feasibility, easy installation, and strong universality, and while ensuring fresh air in the room, can bring good energy saving and economic benefits, is widely used, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or other advantages of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings, which are only exemplary and do not limit the present invention, wherein: Figure 1 A schematic diagram of a building fresh air system and a fresh air system control method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the connection between a controller and a pressure sensor according to an embodiment of the present invention.

[0018] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. Mixing box; 2. Mixing box pressure sensor; 3. Return air valve; 4. Return air duct; 5. Exhaust valve; 6. Exhaust duct; 7. Controller; 8. Control line; 9. Return air fan; 10. Return air fan frequency conversion controller; 11. Return air pressure sensor; 12. Supply air fan; 13. Air handling unit; 14. Fresh air valve; 15. Fresh air duct; 16. Air conditioning unit; 17. Return air unit; 18. Air guide vane. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of a building fresh air system and a fresh air system control method of the present invention will be described with reference to the accompanying drawings.

[0020] The embodiments described herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention, are illustrative and exemplary, and should not be construed as limiting the embodiments of the present invention and the scope of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the claims and the contents disclosed in the specification of this application, including technical solutions that adopt any obvious replacement and modification of the embodiments described herein.

[0021] The drawings of this specification are schematic diagrams, which assist in explaining the concept of the present invention and schematically show the shapes of various parts and their mutual relationships. Please note that in order to clearly show the structures of various components of the embodiments of the present invention, the drawings are not drawn according to the same scale. The same reference numerals are used to represent the same parts.

[0022] The following combination Figure 1 and Figure 2 A building fresh air system according to an embodiment of the present invention is shown, which comprises: Air conditioning unit 16, the air conditioning unit 16 includes a mixing air box, the mixing air box includes a mixing air part, an air treatment part 13 and a air supply part which are sequentially communicated. An air treatment device is installed in the air treatment part 13, and a air supply fan is installed in the air supply part; The mixing air part is provided with a first inlet, and the air supply part is provided with a first outlet; The mixing air part is communicated with an air inlet pipe, and a fresh air valve is installed in the air inlet pipe; A mixing air box pressure sensor is arranged in the mixing air box, and the mixing air box pressure sensor is arranged at a position close to the air inlet pipe; In a preferred embodiment, a wind guiding vane 18 is further arranged in the mixing air box of the air conditioning unit 16, the wind guiding vane 18 is installed at the first inlet position of the mixing air box, and the wind guiding vane 18 guides the return air away from the mixing air box pressure sensor. For example, the included angle between the wind guiding vane 18 and the top plate of the mixing air box is 30 degrees to 59 degrees, and a better angle is 45 degrees.

[0023] Return air unit 17, the return air unit 17 includes a return air box, the return air box is provided with a second inlet and a second outlet, and a return air fan is installed in the return air box; The second outlet is connected to an exhaust pipe, and an exhaust valve is installed in the exhaust pipe; One end of the return air pipe 4 is communicated with the exhaust pipe, and the other end of the return air pipe 4 is communicated with the first inlet of the mixing air box, and a return air valve is installed in the return air pipe 4; A return air pressure sensor is installed in the return air pipe 4, on the air inlet side of the return air valve; Controller, the controller is connected to the mixing air box pressure sensor and the return air pressure sensor; The controller controls the states of the return air valve and the return air fan according to the pressure sensor information. In Figure 2 It shows the connection states of the air valve, the sensor and the controller. In order to better control the operating state of the return air fan, the return air fan of the return air unit 17 is connected to a return air fan frequency converter controller, and the return air fan frequency converter controller is connected to the controller.

[0024] The fresh air system of the present invention is applicable to an air conditioning system with double fans, has low manufacturing cost, strong feasibility, convenient installation, strong universality, can ensure fresh air in the room, and can bring good energy-saving and economic benefits, has wide application, and has good application prospects.

[0025] The control method of the fresh air system of the present invention is described below. The fresh air system is the fresh air system as described in any one of the above; The above-mentioned building fresh air system of the present invention operates in any one of the following states.

[0026] Status 1, the fresh air system is in the minimum fresh air operation condition: the exhaust valve is in the closed state, and the return air valve and the fresh air valve are in the open state; the controller controls the operating state of the return air fan through the first pressure value range of the mixing box pressure sensor to keep the mixing box in a negative pressure; when the pressure value of the mixing box pressure sensor is higher than the maximum value of the first pressure value range, the controller controls the return air fan to reduce the operating power, thereby reducing the air pressure at the outlet of the return air fan; when the pressure value of the mixing box pressure sensor is lower than the minimum value of the first pressure value range, the controller controls the return air fan to increase the operating power, thereby increasing the air pressure at the outlet of the return air fan; the pressure value of the return air pressure sensor is set to 0 ± 10 Pa, and the return air pressure sensor is in the monitoring state. For the fresh air system control method as described above in the present invention, preferably, the first pressure value range is -50 ± 10 Pa; the controller monitors whether the pressure value of the return air pressure sensor is within 0 ± 10 Pa, and the controller monitors whether the return air system fails according to the pressure value of the return air pressure sensor.

[0027] In a specific embodiment, in winter and summer, the air conditioning system is in the minimum fresh air operation condition: the exhaust valve 5 is installed on the exhaust duct 6 and is in the closed state; the return air valve 3 is open; the fresh air valve 14 is installed on the fresh air duct 15 and is in the open state. At this time, it is necessary to keep a certain negative pressure in the mixing box 1 so that fresh air can be introduced, and the negative pressure is generated by the supply air fan 12. By setting the pressure value of the mixing box pressure sensor 2, such as -50 ± 10 Pa, to keep the mixing box 1 in a negative pressure. When the pressure value of the mixing box pressure sensor 2 is higher than -40 Pa, the frequency converter controller 10 of the return air fan is controlled through the air pressure controller 7 to reduce the operating frequency of the return air fan 9, thereby reducing the air pressure at the outlet of the return air fan 9 and reducing the energy consumption of the return air fan 9. Ensure that the mixing box 1 has enough negative pressure to introduce fresh air. When the pressure value of the mixing box pressure sensor 2 is lower than -60 Pa, increase the operating frequency of the return air fan 9, thereby increasing the air pressure and ensuring the return air volume. In this condition, the exhaust duct 6 does not need to exhaust air, and it is not necessary to maintain a positive pressure at the outlet of the return air fan 9. The pressure value of the return air pressure sensor 11 is set to 0 ± 10 Pa and is in the monitoring state. When the return air fan 9 runs at full frequency and still cannot meet the pressure value of the return air pressure sensor 11, an alarm signal is issued to indicate that the resistance of the return air system is too large and maintenance or cleaning is required.

[0028] Status 2, the fresh air system is in the all-fresh air operation mode: the exhaust valve is in the open state, the return air valve is closed, and the fresh air valve is in the open state; the controller controls the operation state of the return air fan through the second pressure value range of the return air pressure sensor to keep the outlet of the return air fan under positive pressure; when the pressure value of the return air pressure sensor is higher than the maximum value of the second pressure value range, the controller controls the return air fan to reduce the operating power, thereby reducing the air pressure; when the pressure value of the return air pressure sensor is higher than the minimum value of the second pressure value range, the controller controls the return air fan to increase the operating power, thereby increasing the air pressure. For the fresh air system control method as described above in the present invention, preferably, the second pressure value range is 50±10 Pa; the controller monitors whether the pressure value of the mixing box pressure sensor is within -50±10 Pa, and the controller monitors whether the air supply system is faulty according to the pressure value of the mixing box pressure sensor.

[0029] In a specific embodiment, during the transitional season, the air conditioner operates in the all-fresh air operation mode: the exhaust valve 5 is in the open state, the return air valve 3 is closed, and the fresh air valve 14 is in the open state. At this time, a certain positive pressure needs to be maintained at the outlet of the return air fan 9 to discharge the return air. By setting the pressure value of the return air pressure sensor 11, such as 50±10 Pa, to keep the outlet of the return air fan 9 under positive pressure, when the pressure value of the return air pressure sensor 11 is higher than 60 Pa, the air pressure controller 7 controls the return air fan frequency converter controller 10 (as Figure 1 shown, the air pressure controller 7 and the return air fan frequency converter controller 10 are connected through the control line 8), reducing the operating frequency of the return air fan 9, thereby reducing the air pressure and the energy consumption of the return air fan 9. When the pressure value of the return air pressure sensor 11 is lower than 40 Pa, the operating frequency of the return air fan 9 is increased, thereby increasing the air pressure to ensure that the return air can be discharged. In this condition, the mixing box 1 is in a negative pressure state, such as less than -50±10 Pa, and the mixing box pressure sensor 2 is in the monitoring state, and the air supply fan 12 adjusts according to the air supply demand. When the air supply fan operates at full frequency and still cannot meet the pressure value of the mixing box pressure sensor 2, an alarm signal is issued, indicating that the resistance of the air supply system is too large and maintenance or cleaning is required.

[0030] Status 3, the fresh air system is in the variable fresh air operation condition: the exhaust air valve, the return air valve, and the fresh air valve are all in the adjustment state; the controller controls the operation state of the return air fan through the third pressure value range of the return air pressure sensor to keep the outlet of the return air fan under positive pressure; when the pressure value of the return air pressure sensor is higher than the maximum value of the third pressure value range, the controller controls the return air fan to reduce the operation power, thereby reducing the wind pressure; when the pressure value of the return air pressure sensor is higher than the minimum value of the third pressure value range, the controller controls the return air fan to increase the operation power, thereby increasing the wind pressure; the controller controls the opening of the return air valve through the fourth pressure value range of the air mixing box pressure sensor to keep the air mixing box under negative pressure; when the pressure value of the air mixing box pressure sensor is higher than the maximum value of the fourth pressure value range, the controller controls the opening of the return air valve to become smaller; when the pressure value of the air mixing box pressure sensor is lower than the minimum value of the fourth pressure value range, the controller controls the opening of the return air valve to become larger. For the fresh air system control method of the present invention as described above, preferably, the third pressure value range is 50±10Pa, and the fourth pressure value range is -50±10Pa.

[0031] In a specific embodiment, the air conditioning system is in the variable fresh air operation condition: the exhaust air valve 5, the return air valve 3, and the fresh air valve 14 are all in the adjustment state. At this time, a certain positive pressure needs to be maintained at the outlet of the return air fan 9 to discharge the return air. By setting the pressure value of the return air pressure sensor 11, such as 50±10Pa, the outlet of the return air fan 9 is kept under positive pressure. When the pressure value of the return air pressure sensor 11 is higher than 60Pa, the frequency conversion controller 10 of the return air fan is controlled by the wind pressure controller 7 to reduce the operating frequency of the return air fan 9, thereby reducing the wind pressure and the energy consumption of the return air fan 9. When the pressure value of the return air pressure sensor 11 is lower than 40Pa, the operating frequency of the return air fan 9 is increased, thereby increasing the wind pressure to ensure that the return air can be discharged. In this condition, the air mixing box 1 is in a negative pressure state, such as less than -50±10Pa. When the pressure of the air mixing box pressure sensor 2 becomes larger or smaller, the opening of the return air valve 3 is controlled and adjusted by the wind pressure controller 7 to ensure that the air mixing box 1 is in a constant negative pressure state, thereby ensuring that fresh air can be introduced.

[0032] The above building fresh air system and fresh air system control method of the present invention have the following advantages: 1. Adaptability to multi-condition operation modes The system can enter three different operating conditions according to actual needs - minimum fresh air, full fresh air, and variable fresh air: Minimum fresh air condition: In this condition, the mixing box maintains negative pressure, and the controller adjusts the power of the return air fan according to the pressure value to ensure the introduction of the minimum fresh air volume, which is suitable for low-load operation in winter and summer. Full fresh air condition: By closing the return air valve and opening the exhaust air valve, the controller maintains positive pressure at the outlet of the return air fan to ensure effective exhaust air volume, which is suitable for seasons with poor air quality (such as transitional seasons). Variable fresh air condition: This mode combines the dual control of the return air pressure sensor and the mixing box pressure sensor to accurately adjust the introduction of fresh air volume and maintain negative pressure in the mixing box. By adjusting the opening degree of the return air valve, the system can be flexibly adjusted according to the indoor air demand. Technical effect: The flexible switching of these three conditions greatly improves the adaptability of the system and meets the requirements for indoor air quality in different seasons and different usage conditions. At the same time, through the intelligent adjustment of the control system, the energy consumption and maintenance cost of the system are also greatly reduced.

[0033] 2. Precise pressure monitoring and fault diagnosis By monitoring the system status through pressure sensors (mixing box pressure sensor and return air pressure sensor), the system can issue an alarm in a timely manner when a fault occurs: Pressure monitoring: The pressure sensors can accurately monitor the pressure values of the return air duct and the mixing box to ensure that the system is within the normal operating range. When the detected pressure value exceeds the range, the controller can immediately adjust the working state of the return air fan or the return air valve. Technical effect: This intelligent monitoring function can not only ensure the normal operation of the air conditioning system, but also timely detect system faults and make adjustments, avoiding potential fault hazards in traditional systems, and significantly improving the reliability of the system and the user experience.

[0034] 3. Energy-saving effect and energy efficiency improvement Through precise air pressure control and intelligent adjustment, the system can dynamically adjust the operating state of the fan according to the load demand: Energy-saving operation: In the case of light load, the power of the return air fan and the supply air fan can be reduced, thereby reducing unnecessary energy consumption. In the transitional season, when the full fresh air mode requires a large air pressure, the system can intelligently increase the fan power to ensure the efficient operation of the system. Technical effect: This solution not only improves the stability of the system, but also greatly reduces the energy consumption, enabling the system to achieve the best energy efficiency ratio under different operating conditions. Compared with traditional systems, this dynamic adjustment mechanism can effectively reduce energy waste and improve economic benefits.

[0035] The technical features disclosed above are not limited to the combinations with other disclosed features. Those skilled in the art can also make other combinations among the technical features according to the purpose of the invention, subject to achieving the purpose of the invention.

Claims

1. A building fresh air system, characterized in that: include: An air conditioning unit, the air conditioning unit comprises an air mixing box, the air mixing box comprises an air mixing part, an air processing part and an air supply part which are connected in sequence, an air processing device is installed in the air processing part, and a blower is installed in the air supply part; the air mixing part is provided with a first inlet, and the air supply part is provided with a first outlet; the air mixing part is connected to an air inlet pipe, and a fresh air valve is installed in the air inlet pipe; a mixing box pressure sensor is provided in the mixing box, and the mixing box pressure sensor is arranged at a position close to the air inlet pipe; A return air unit, the return air unit comprises a return air box, the return air box is provided with a second inlet and a second outlet, a return air fan is installed in the return air box; the second outlet is connected to an exhaust duct, an exhaust valve is installed in the exhaust duct; one end of the return air duct is connected to the exhaust duct, the other end of the return air duct is connected to the first inlet of the air mixing box, and a return air valve is installed in the return air duct; a return air pressure sensor is installed in the return air duct, located at the air inlet side of the return air valve; A controller is connected to the air mixing box pressure sensor and the return air pressure sensor; the controller controls the status of the return air valve and the return air fan according to the pressure sensor information.

2. The building fresh air system according to claim 1, characterized in that: An air guide vane is also provided in the air mixing box of the air conditioning unit. The air guide vane is installed at a first inlet position of the air mixing box. The air guide vane guides the return air in a direction away from the pressure sensor of the air mixing box.

3. The building fresh air system according to claim 2, characterized in that: The included angle between the air guide plate and the top plate of the air mixing box is 30 degrees to 59 degrees.

4. The building fresh air system according to claim 1, characterized in that: The return fan of the return air unit is connected to the return fan frequency conversion controller, and the return fan frequency conversion controller is connected to the controller.

5. A fresh air system control method, characterized in that: The fresh air system is the fresh air system described in any one of claims 1 to 4; the fresh air system is in the minimum fresh air operating condition: the exhaust valve is in a closed state, and the return air valve and the fresh air valve are in an open state; the controller controls the return air fan operating state through the first pressure value range of the mixing box pressure sensor to maintain a negative pressure in the mixing box; when the pressure value of the mixing box pressure sensor is higher than the maximum value of the first pressure value range, the controller controls the return air fan to reduce the operating power, thereby reducing the wind pressure at the return air fan outlet; when the pressure value of the mixing box pressure sensor is lower than the minimum value of the first pressure value range, the controller controls the return air fan to increase the operating power, thereby increasing the wind pressure at the return air fan outlet; the pressure value of the return air pressure sensor is set to 0±10Pa, and the return air pressure sensor is in a monitoring state.

6. The fresh air system control method according to claim 5, characterized in that: The first pressure value range is -50±10Pa; the controller monitors whether the pressure value of the return air pressure sensor is within 0±10Pa, and the controller monitors whether the return air system fails according to the pressure value of the return air pressure sensor.

7. The fresh air system control method according to claim 5, characterized in that: The fresh air system is in a fresh air operating condition: the exhaust valve is in an open state, the return air valve is closed, and the fresh air valve is in an open state; the controller controls the return air fan operating state through the second pressure value range of the return air pressure sensor to maintain a positive pressure at the return air fan outlet; when the pressure value of the return air pressure sensor is higher than the maximum value of the second pressure value range, the controller controls the return air fan to reduce the operating power, thereby reducing the wind pressure; when the pressure value of the return air pressure sensor is higher than the minimum value of the second pressure value range, the controller controls the return air fan to reduce or increase the operating power, thereby increasing the wind pressure.

8. The fresh air system control method according to claim 7, characterized in that: The second pressure value range is 50±10Pa; the controller monitors whether the pressure value of the mixing box pressure sensor is within -50±10Pa, and the controller monitors whether the air supply system fails according to the pressure value of the mixing box pressure sensor.

9. The fresh air system control method according to claim 7, characterized in that: The fresh air system is in a variable fresh air operation state: the exhaust valve, the return air valve, and the fresh air valve are all in an adjustment state; The controller controls the operating state of the return fan through the third pressure value range of the return air pressure sensor to keep the return fan outlet at positive pressure; when the pressure value of the return air pressure sensor is higher than the maximum value of the third pressure value range, the controller controls the return fan to reduce the operating power, thereby reducing the wind pressure; when the pressure value of the return air pressure sensor is higher than the minimum value of the third pressure value range, the controller controls the return fan to reduce or increase the operating power, thereby increasing the wind pressure; The controller controls the opening of the return air valve through the fourth pressure value range of the mixing box pressure sensor to maintain a negative pressure in the mixing box; when the pressure value of the mixing box pressure sensor is higher than the maximum value of the fourth pressure value range, the controller controls the opening of the return air valve to become smaller; when the pressure value of the mixing box pressure sensor is lower than the minimum value of the fourth pressure value range, the controller controls the opening of the return air valve to become larger.

10. The fresh air system control method according to claim 9, characterized in that: The third pressure value range is 50±10Pa, and the fourth pressure value range is -50±10Pa.

Images