The low pressure alarm of high-precision constant temperature and humidity air conditioner is a problem we often encounter in daily maintenance. Especially in winter. In summary, there are mainly the following reasons:
1. The low pressure protection setting value of high-precision constant temperature and humidity precision air conditioner is incorrect. The correct low pressure protection setting value should be set at about 2bar. If the setting value is incorrect, a low pressure alarm will be generated.
2. The amount of fluorine in the air conditioner is not enough. Similar situations may occur when the temperature is low in winter. If the cause is indeed the lack of fluorine, the system should be supplemented with Freon refrigerant.
3. The air filter of high-precision constant temperature and humidity precision air conditioner is too dirty. If the filter is too dirty and not replaced in time, it is easy to generate a low pressure alarm. When replacing, pay attention to stacking according to the arrow instructions, and do not install it upside down. 4.
The expansion valve of the high-precision constant temperature and humidity air conditioner dedicated to the computer room is faulty. The thermal expansion valve fails or the opening degree is small, causing insufficient liquid supply; causing a low pressure alarm. The opening degree of the thermal expansion valve should be increased or the expansion valve should be replaced.
5. There is a leak in the high-precision constant temperature and humidity air conditioning system dedicated to the computer room. Use nitrogen to perform pressure test and leak detection. The inflation pressure should be ≥1.4MPa, and nitrogen should be introduced from the high and low pressure parts of the system at the same time until equilibrium is reached. After the system is filled with nitrogen, there should be no leakage within the 24h pressure maintenance time. If the temperature changes greatly within 24h, the pressure will change slightly due to the thermal expansion and contraction characteristics of the gas, which should be normal; if the pressure change value exceeds the standard, then the leak point should be checked, mainly in the following places:
(1) The nut connected to the compressor of the high-precision constant temperature and humidity air conditioner dedicated to the machine room;
(2) The one-way valve connected to the outdoor unit;
(3) The connection between the outdoor unit and the pressure switch;
(4) The one-way valve on the liquid storage tank;
(5) Pipes and coils, etc.
After the pressure test and leak detection of the high-precision constant temperature and humidity air conditioner dedicated to the machine room is completed, release the nitrogen in the system, connect the suction and exhaust valves with a double-connected pressure gauge, open the vacuum pump and the suction and exhaust valves to evacuate the system for no less than 90 minutes, until the system vacuum degree is infinitely close to 760mmHg.
After the vacuuming of the dedicated constant temperature and humidity precision air conditioner for the computer room is completed, the Freon liquid is directly injected from the exhaust valve (high pressure end) statically, and the low pressure gauge is observed to rise to 6-7kg/cra2. The exhaust valve is closed, and the machine is turned on to replenish the Freon gas from the suction valve (low pressure end) until the bubbles in the sight glass are just eliminated and the filling is stopped. At this time, the low pressure indication of the double meter should be 0.4-0.5MPa, and the indication of the high pressure gauge should be 1.5-1.8MPa.
If the high pressure of the dedicated high-precision constant temperature and humidity air conditioner for the computer room is high and the low pressure is low, the pipeline is blocked. There is a significant temperature difference before and after the blocked pipe, and even frost. The places where blockage may occur and the treatment methods are as follows:
1. The place where the blockage occurs is at the solenoid valve above the liquid mirror. First, determine whether 24V electricity is sent to the solenoid valve when the compressor of the dedicated constant temperature and humidity precision air conditioner for the computer room is turned on. The inspection method is: remove the top screw of the solenoid valve, and measure whether the corresponding plug of its terminal has 24V. If not, it is a control circuit fault. Otherwise, the solenoid valve is damaged and needs to be replaced.
2. The blockage of the dedicated constant temperature and humidity precision air conditioner for the computer room is in the filter drier. Turn off the power of the air conditioner (the refrigeration solenoid valve is closed at this time), and turn the three-way valve at the liquid storage tank clockwise to the bottom along the valve stem (the valve stem is screwed in). At this time, the liquid storage tank and the pipeline are blocked. Unscrew the filter drier connection nut and replace the filter drier.
3. The dedicated constant temperature and humidity precision air conditioner for the computer room is blocked in the pipeline, especially the pipeline welding. There is a temperature difference before and after the welding, and the pressure difference before and after the pipeline is very large. At this time, it is necessary to re-weld the pipe, re-vacuum and re-fill with fluorine.
4. Under the premise that the above 3 situations are normal, it can be judged that the dedicated constant temperature and humidity precision air conditioner for the computer room is blocked by the expansion valve. The maintenance method:
1. The dedicated constant temperature and humidity precision air conditioner for the computer room is blocked by ice. Apply a hot towel to it, then the pressure at the low-pressure end will rise. It is necessary to release fluorine, re-vacuum, and then add fluorine. It is better to replace the filter drier.
2. The dedicated constant temperature and humidity precision air conditioner for the computer room is dirty and blocked, and the expansion valve needs to be replaced.
3. The control accuracy is insufficient due to the failure of the protector. Repair or replace the low-pressure pressure controller.
4. The low-voltage delay relay is incorrectly set or the low-voltage start delay is too short. Reset the low-voltage delay time of the dedicated constant temperature and humidity precision air conditioner for the computer room.