Number of views: 525 Author: AILI Industrial Release time: 2027-04-16 Source: Ai Li Industrial
When the air-conditioning box is drained in the negative pressure section, the pressure inside the box is lower than that of the outside world, which may cause air to be sucked in from the drain port, hindering the discharge of condensed water. Water seals or other designed and confirmed drainage structures are used to isolate this pressure difference and maintain discharge conditions; whether they are used and their size should be determined based on the actual negative pressure and structure.
The negative pressure section is located on the suction side of the fan, and the pressure inside the box is lower than the surrounding environment. One side of the drain outlet of the water tray is the negative pressure in the box, and the other side is the drain pipe and external atmospheric pressure. If the drain pipe is directly open, outside air will be sucked into the box through the drain port, causing air flow resistance. The condensed water may not be discharged smoothly, and there may even be water accumulation or backflow in the drain pipe.
This pressure difference persists when the fan is running and may decrease when it is shut down. Drainage design cannot be judged only based on the shutdown state. The drainage conditions should be checked under the operating pressure difference. What is the difference between the positive pressure section drainage and the negative pressure section drainage of the air conditioning box? Please refer toWhat is the difference between the positive pressure section drainage and the negative pressure section drainage of the air conditioning box?。
The water seal uses a water trap or U-shaped structure to form a section of water column. Both sides of the water column bear the negative pressure in the box and the external atmospheric pressure respectively. When the static pressure and pressure difference generated by the height of the water column are balanced, air will not enter the box through the water seal, and the condensed water can still be discharged along the drain pipe. The height of the water seal needs to be greater than the height of the water column corresponding to the actual negative pressure, and leave a certain margin.
Water seals are not permanent. Prolonged shutdown, evaporation of water or siphoning of drain pipes may cause the water seal to fail and allow outside air to re-enter. Therefore, the water seal needs to be replenishable, inspectable, and clearable. How to combine the slope of the water pan of the air-conditioning box with the layout of the drain outlet, please refer toHow to combine the slope of the water pan of the air-conditioning box with the layout of the drain outlet?。
The height of the water seal is usually converted into the height of the water column based on the negative pressure in the box, and then a safety margin is added. For example, a negative pressure of 500Pa corresponds to approximately a 50mm water column, and the actual water seal height should be greater than this value with a margin. The negative pressure value may be different under different units, different operating modes and different filter section resistances, and the maximum operating negative pressure should be used as the basis for calculation.
When the water seal height is insufficient, air may break through the water seal and enter the box; when the water seal is too high, the resistance of the drainage pipe increases, and the condensate may not be discharged smoothly. The water seal height, drainage pipe diameter, slope, and pipe length need to be checked together. What functional segments should be included in the internal resistance of the air conditioning box? Please refer toWhat functional segments should be included in the internal resistance of the air conditioning box?。
The pressure inside the box in the positive pressure section is higher than the outside world. The drain port usually does not suck in outside air, but the treated air may leak out. Drainage in the positive pressure section needs to prevent air leakage and condensation backflow, while drainage in the negative pressure section needs to prevent air inhalation. Both may require water seals or other drainage structures, but the design purposes and accounting directions are different.
For the difference in drainage between positive pressure section and negative pressure section, please refer toWhat is the difference between the positive pressure section drainage and the negative pressure section drainage of the air conditioning box? . The investigation of water seal failure in the negative pressure section can also be combined withHow to prevent external air leakage when a chemical filter is installed in the negative pressure section?。
Common water seal forms include U-shaped water traps, P-shaped water traps and special water seal boxes. The water-sealed box is easy to inspect and clear, while the U-shaped bend saves space but is difficult to clean. The water sealing material should adapt to the condensate water quality and on-site environment, and the drainage pipe should be easy to disassemble and clean. Antifreeze measures should also be considered in cold areas.
Water seals require regular replenishing, especially after long periods of downtime. If the water seal dries up, the negative pressure will draw air directly through the drain pipe. Maintenance records should include water seal rehydration, clearing and leak inspections. What operating status should be recorded during daily inspection of air-conditioning boxes? Please refer toWhat operating status should be recorded during daily inspection of air-conditioning boxes?。
During installation, confirm that the water seal height, drain pipe slope and access point comply with the design. During debugging, the drainage situation should be observed after the fan is running and normal negative pressure is reached to confirm that the condensate can be continuously discharged and the water seal has not been evacuated. After shutting down, check whether there is still water in the water seal and add water if necessary.
For condition checks before starting the machine for the first time, please refer toWhat conditions need to be checked before the air-conditioning box is turned on for the first time? . How to change the debugging sequence from stand-alone to system linkage, please refer toHow to change the debugging sequence of air conditioning box from stand-alone unit to system linkage? . If drainage is abnormal, you should first check the water seal and pressure difference, and then determine the problem with the water tray or coil.
Aili Industrial can provide drainage interface data corresponding to the equipment configuration. The project party should check the foundation height and on-site drainage conditions at the same time to ensure that the negative pressure drainage structure has actual installation space. Aili's industrial manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. Water trays, drain outlets, water seal reservations and box structures can be matched in the same set of packages; non-standard drainage solutions can be adjusted according to on-site negative pressure and space conditions.
Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific water seal height, drainage plan and delivery scope still need to be verified based on the corresponding configuration data and on-site working conditions. Actual results are subject to on-site drainage inspection and performance test results.
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What will happen if there is no water seal for drainage in the negative pressure section?
Outside air may be sucked into the box through the drain port, preventing the discharge of condensed water. In severe cases, water accumulation or backflow in the drain pipe may occur.
How is the water seal height determined?
Convert the water column height according to the actual operating negative pressure, leave a safety margin, and check the drainage pipe diameter, slope and on-site space.
Can Aili Industrial help check the drain pan and water seal?
The water seal form and interface can be checked based on the negative pressure value, water tray structure and on-site drainage conditions. The specific plan needs to be confirmed according to the project conditions.
Check items |
Confirm key points |
Check items |
Confirm key points |
|---|---|---|---|
Pressure difference accounting |
Maximum operating negative pressure and water column height |
Water seal form |
U-shaped, P-shaped or water-sealed boxes and maintenance conditions |
drain pipe |
Pipe diameter, slope, pipe length and access points |
Hydrating and antifreeze |
Shutdown water replenishment and cold environment measures |
Run verification |
Continuous drainage under normal negative pressure |
Maintain records |
Hydration, clearing and leakage inspection |
