Common Faults of Data Center Air Conditioning

The data center can be said to be the heart of an enterprise. A large number of businesses run on sophisticated IT equipment. The application of blade servers makes the power density in the cabinet higher and higher. These IT equipment have high requirements for the operating environment, especially when servers and storage devices are affected by high temperatures, data loss will occur, causing serious losses that are difficult to compensate. Precision refrigeration and air conditioning is an important refrigeration equipment in the data center. In addition to precisely controlling the temperature, it also has its own humidification device. While adjusting the temperature, it ensures that the room has a constant humidity air conditioner. This paper introduces the common faults and maintenance examples of precision air conditioning in detail.

1. The whole air conditioner cannot work normally, repeatedly burning AC 24V insurance, and poor humidification.

According to on-site inspection, multiple fuses have been replaced, and each fuse has a black open circuit, indicating that there is a short circuit or excessive current in the AC 24V post-stage circuit.

The 24V voltage output by the transformer is divided into two channels through 6A fuse. One channel provides working voltage for AC contactor, the other channel is connected to the main control board through connector CON1, and is divided into two groups on the main control board. One group forms DC 5V voltage after rectification and voltage stabilization to supply power to the electronic circuit part of the main control board. The other group is output to the drainage solenoid valve through SCR D2 under the control of the CPU of the main control board. After checking the AC contactor without obvious damage, the main control board rectifier filter part of the circuit is normal, in the inspection of the humidification part, found that the drainage solenoid valve is damaged, the coil short circuit. Since the power supply of the solenoid valve coil is provided by the main control board, it is easy to damage the main control board after the coil is short-circuited. When checking the main control board, it was found that some electronic components had burst. After replacing the main control board and drainage solenoid valve and cleaning the humidifier part, the whole machine returned to normal.

2. The air conditioner has a fault alarm of "large humidification current.

The humidification working principle of the air conditioner in the computer room is to inject an appropriate amount of water into the humidification tank, insert the charged electrode into the water (because the water is a conductive substance), heat the water to form water vapor, and then diffuse into the computer room by the indoor main fan, so as to achieve the purpose of humidification.

There are three electrodes (P) at the top of the humidification tank, where three-phase 380V alternating current is introduced, and L is the water level detection electrode to detect the water level in the humidification tank.

There are generally two reasons for the large humidification current. One is that the conductive resistance is reduced by too much scale and impurities in the humidification tank; the other is that the contact surface between the power supply electrode and water is increased due to too much water injected into the humidification tank. Both aspects will cause a large humidification current.

In some areas of China, the water quality is hard, and there are many minerals in the water. After the humidification tank works for a period of time, it is easy to scale and block. Therefore, during maintenance, first clean the humidification tank, and after washing, detect the humidification current up to 14A, which is still high. In the operation panel of the computer board, check the setting options of the humidifier: the humidification voltage is set to 400V; The humidification tank model is 93Hz and the humidification output probability is 50%-150, and the settings are correct. Enter the menu for manual drainage, do not hear the sound of the drainage solenoid valve closing, and there is no AC 24V voltage at both ends of the measuring solenoid valve coil. During the inspection, it was found that the connecting lines of the drainage solenoid valve and the water supply solenoid valve were installed reversely. After the connection lines were removed, the humidification current was about 8A, which was within the normal range.

This fault is caused by human beings. When the maintenance personnel disassemble and assemble the humidification tank for cleaning, the drain valve connection line is connected incorrectly, thus such a fault occurs.

3. The air conditioner cannot restart automatically when it comes back to power after power failure.

The air conditioners in the computer room basically have the function of automatically restarting incoming calls to ensure that the air conditioners can operate normally, but some air conditioners cannot be restarted when they are powered off and need to be manually turned on. And some parameters set by the user are lost, and the Chinese operation interface of some models is also restored to English. During the inspection, it was found that the memory battery of the main board was damaged. The battery voltage measured by shutdown was OV (normally 2AV), indicating that it was damaged by open circuit. After replacing the battery, the air conditioner can restart automatically and all functions return to normal.

4. The prompt "I/O transmission failure E" appears irregularly.

The machine with this failure phenomenon is basically caused by the aging of some electronic components after a long working life. After groping for maintenance, it is found that the main control board is not in good contact with the v0 board connected behind. The main control board is connected to the 1/0 board through a 6-pin metal plug-in for data communication, which is easy to oxidize for a long time and cause poor contact, resulting in data transmission failure. At this time, remove the main control board and 1/0 board, polish the contact part with fine sandpaper, and reweld the virtual welding part of 1/0 board to restore the test machine to normal.

5. The air conditioner has "loss of wind alarm" from time to time"

In case of "loss of wind alarm", the indoor main fan should be checked to see if there is any damage to the main fan, loose belt, fracture, etc. However, the on-site observation showed that the indoor main fan was running normally and the belt was not too loose. The air output was the same as that of the normal machine. After replacing the air pressure switch, the fault remained. Later, it was found that a memory battery of the main control board had been replaced during the previous maintenance. Because the same model was not found, two ordinary No.5 batteries were found and welded in series on the main control board. The voltage at both ends of the battery is measured to be 3.0V, and the original battery is a 2.4V nickel pick battery. It is obvious that this voltage has far exceeded the rated value. After power off, install the original type of battery, and then boot no longer alarm.

This battery provides a memory maintenance voltage to the CPU of the main control board when the air conditioner is powered off and shut down. If the voltage is too high, it may cause the internal program of the main control board to be disordered, resulting in various strange faults.

6. Air conditioning button failure

Three air conditioners of the same model are installed in a netcom computer room, all of which have some key failures. This air conditioner uses touch keys, that is, a layer of film keys is added to the display panel. The problem lies in the film keys. The touch keys cannot be repaired separately. After the whole air conditioner is replaced, the three air conditioners return to normal.

7. High voltage alarm in air conditioner

Field measurement of refrigeration system pressure, high pressure, low pressure are higher than the normal value, alarm reset, high pressure is still high. After that, check that the outdoor fan does not rotate. After power failure, measure the resistance of each winding of the fan to be normal. If the fan blade is moved by hand, there will be no jamming. Because the outdoor fan is controlled by the pressure switch, the pressure switch is turned on and the contact is found to be rusted. After replacing the pressure switch (P77), the system pressure returns to normal and the whole machine runs normally.

8. The air conditioning screen displays "electric heating overload" alarm

Check that the three-phase power supply and AC contactor of the electric heating part are not obviously damaged. Under the condition of normal power supply, this fault is mostly caused by the tripper of the overheat protection switch. Open the panel, find the protection switch next to the electric heating tube and reset it, the start-up test machine no longer alarms and works normally.

9. The display screen is black

On-site inspection showed that the air conditioner was newly installed, and all functions of refrigeration, humidification and operation were normal. The display screen also had character display, but the background light was not on. Open the whole set of operating surface shell, found that part of the electronic components of the booster plate burned, after the replacement of the booster plate, the background lamp lit up and returned to normal.

10, air conditioning refrigeration effect is not good

Check in the machine room. The air conditioner is a dual refrigeration system. One of the refrigeration systems is working normally, and the air switch of the refrigeration compressor of the other system has been tripped. After shutting down, reset all power supply components again. When starting up the test machine, the air switch of the compressor tripped again. Inspection found that the power supply end of the compressor was leaking electricity to the floor. Obviously, the compressor was damaged. After replacing the compressor with the same type of compressor, the compressor was tested after vacuumizing and fluorine supplementation. The compressor worked normally and the whole machine was repaired.

11. Low pressure alarm of air conditioner

Air conditioning low pressure alarm, with a pressure gauge to measure high and low pressure, are far below the normal value, generally due to the lack of fluorine in the refrigeration system. Usually like this kind of situation is mostly refrigeration pipeline leakage point. After investigation, the leakage point was found at the elbow of the condenser on the upper left side of the outdoor unit. After re-welding and fluorine supplementation, the pressure of the test machine returned to normal and the whole machine worked normally.