Low-voltage alarm and fault repair methods for precision air conditioners in computer rooms

Low-voltage alarm and fault repair methods for precision air conditioners in computer rooms

The low-pressure alarm for the special air conditioner in the data center computer room is a problem we often encounter in daily maintenance. Especially often encountered in winter.

　　 The main reasons are as follows:

　　 1. The setting value of low pressure protection of constant temperature and humidity precision air conditioner is incorrect. The correct low-voltage protection setting value should be set at about 2bar. If the setting value is incorrect, a low-voltage alarm will be generated.

　　2. The amount of fluorine in the special air conditioner in the computer room is not enough. A similar situation may occur in winter when the temperature is low. If it is found that the cause is indeed a lack of fluorine, the system should be supplemented with Freon refrigerant.

　　 3. The air filter of constant temperature and humidity precision air conditioner is too dirty. If the filter is too dirty to be replaced in time, it is easy to generate a low pressure alarm. When replacing, pay attention to stacking in accordance with the arrow indication, and it cannot be installed backwards.

　 　　4. The expansion valve of the precision air conditioner with constant temperature and humidity in the computer room is faulty. The thermal expansion valve malfunctions or the opening degree is small, causing insufficient liquid supply; causing a low pressure alarm. Increase the opening of the thermal expansion valve or replace the expansion valve.

　　 5. There is a leak in the dedicated constant temperature and humidity precision air conditioning system for the computer room. Use nitrogen for pressure test and leak detection. The charging pressure should be ≥1.4MPa, and nitrogen should be allowed in from the high and low pressure parts of the system until it is balanced. After the system is filled with nitrogen, there should be no leakage within 24 hours of maintaining pressure. If the temperature changes greatly within 24 hours, due to the thermal expansion and contraction characteristics of the gas, the pressure will have a slight change, which should be normal; if the pressure change value exceeds the standard, the leak should be checked, mainly the following points:

　　 (1) The connection nut to the dedicated constant temperature and humidity precision air-conditioning compressor in the computer room;

　 　　 (2) At 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 data center computer room special constant temperature and humidity precision air pressure leak detection 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 vacuum, the time is not less than 90 minutes, Until the system vacuum is infinitely close to 760mmHg.

After vacuuming of the precision air conditioner with constant temperature and humidity for the computer room, statically inject Freon liquid from the exhaust valve (high pressure end) directly, observe the low pressure gauge, and make it rise to 6～7kg/cra2, close the exhaust valve, and start the machine. The gas valve (low pressure end) is filled with freon gas, and the filling is stopped when the bubbles in the sight glass are just eliminated. At this time, the low pressure indication of the double-connected meter should be 0.4～0.5MPa, and the indication of the high pressure meter should be 1.5～1.8MPa.

　　 If the precision air conditioner with constant temperature and humidity in the computer room has high pressure and low pressure, the pipeline is blocked. There is a significant temperature difference before and after the pipeline at the blockage, and even frost. The place where blockage may occur and the treatment method are as follows:

　　 1. The place where the blockage occurs is at the solenoid valve above the liquid mirror. First judge whether there is 24V power to the solenoid valve when the dedicated constant temperature and humidity precision air conditioning compressor in the computer room is turned on. The inspection method is: remove the screw on the top of the solenoid valve and measure whether the corresponding plug of the terminal has 24V. If not, the control circuit is faulty. Otherwise, the solenoid valve is damaged and the solenoid valve needs to be replaced.

　　 2. The filter drier is clogged in the dedicated constant temperature and humidity precision air conditioner for the computer room. Turn off the air conditioner power supply (the cooling solenoid valve is closed at this time), turn the three-way valve at the liquid storage tank clockwise to the end in the direction of the valve stem (the valve stem is screwed in), at this time the liquid storage tank and the pipeline are not connected, turn on the drying filter Connect the nut and replace the filter drier.

　　 Third, the computer room dedicated constant temperature and humidity precision air conditioning pipes are blocked, especially the pipe welding. There is a temperature difference before and after the welding, and the pressure before and after the pipeline is very different. At this time, the pipe needs to be re-welded, vacuumed again, and filled with fluorine.

　　4. Under the premise that all the above 3 conditions are normal, it can be judged that the expansion valve of the precision air conditioner with constant temperature and humidity in the computer room is blocked. Repair method:

　　1. The special constant temperature and humidity precision air conditioner for the computer room is ice-blocked. If it is applied with a hot towel, the pressure on the low pressure side will rise. It is necessary to release fluorine, re-vacuum, and add fluorine. It is best to replace the filter drier.

　 　　 2. The dedicated constant temperature and humidity precision air conditioner for the computer room is dirty and needs to be replaced with the expansion valve.

　　 　　 3. The failure of the protector causes insufficient control accuracy. Repair and replace the low pressure pressure controller.

　 　　 4. The low-voltage delay relay setting is incorrect or the low-voltage start delay is too short. Re-set the low-pressure delay time for the dedicated constant temperature and humidity precision air conditioner in the computer room.