Solution: After replacing the indoor pipeline temperature sensor, everything is normal after debugging.
Experience: When air conditioning is used for heating, due to the function of preventing cold air, the indoor fan works with breeze when the indoor heat exchanger of the indoor temperature sensor reaches above 25 degrees Celsius, and works at the set wind speed when the temperature reaches above 38 degrees Celsius. First, it is found that the wind speed is low and the outlet air temperature is high. Check whether the fan is normal. When it is determined that the wind speed is normal, the analysis sensor may check that the temperature may be incorrect, which may cause the indoor fan to fail to operate at the set wind speed, so replace the sensor.
Temperature sensor failures account for a large proportion of air conditioning failures. To judge accurately, we must first understand its function. The air conditioning control part is equipped with three temperature sensors:
1. Room temperature sensor: mainly detects the indoor temperature. When the indoor temperature reaches the set requirements, it controls the operation of internal and external machines. When cooling, the external machine stops, while the internal machine continues to run. When heating, the internal machine blows waste heat and then stops.
2. Indoor pipe temperature sensor: mainly detects the temperature of indoor evaporator coil, and plays the role of preventing cold air, overheating and automatic temperature control during heating. If the newly started coil temperature does not reach 25 degrees, the indoor fan will not run; When it reaches 25 degrees and 38 degrees, the indoor fan will work with a breeze, and when the temperature reaches 38 degrees, it will work with a set wind speed; When the indoor coil temperature reaches 57 degrees Celsius for 10S, the outdoor fan will stop running; When the temperature exceeds 62 degrees Celsius to 10S, the compressor will also stop running; The outdoor unit will only be put into operation when the temperature drops to 52 degrees Celsius; Therefore, when the coil resistance is greater than the normal value, the indoor unit may not be started.
Maintenance of common faults of air conditioner
Section 1 Common Maintenance Tools for Air Conditioning and Their Use
1, pressure gauge
Refrigerant leakage is a common problem of air conditioning. In order to detect whether the refrigerant dose in the system is sufficient, a pressure gauge is usually used. Pressure gauges are usually used in Freon refrigeration systems. Their shell diameters range from 60 mm to 250 mm, and there are many specifications. The range of vacuum pressure gauge suitable for air conditioning and refrigeration system is -0. 1 MPa to 2.5 MPa, as shown in Figure 2-33.
Pressure gauges are usually used with three-way maintenance valves. Turn the knob of the three-way repair valve clockwise to reduce the valve hole. When the knob is turned clockwise to the end, the corresponding pipeline will be cut off from the air path of the outdoor unit. When the knob is turned counterclockwise, the valve hole is enlarged, and the corresponding pipeline is connected with the air path of the outdoor unit. The refrigeration system is always connected to the pressure gauge on the three-way repair valve, regardless of the position of the knob. By cooperating with the switch of the three-way repair valve, the refrigeration system can be vacuumized, filled with refrigerant and tested for pressure.
2. Tube expander
When two copper tubes are butted, one copper tube needs to be inserted into the other copper tube. At this time, it is usually necessary to enlarge the inner diameter of the end of the inserted copper tube so that another copper tube can be inserted in a consistent manner. Only in this way can the two copper pipes be welded firmly and not easily leaked. The function of the pipe expander is to expand pipes of different specifications as required. When expanding the pipe, firstly put the annealed copper pipe into the corresponding aperture of the pipe clamp, and the length of the copper pipe extending out of the pipe clamp varies with the pipe diameter. For copper tubes with large diameter, the expansion length is larger, while for copper tubes with small diameter, the expansion length is smaller. For Ф 8 copper tube, the expansion length is generally about10 mm. Tighten the nuts at both ends of the pipe clamp so that the copper tube can be firmly clamped and inserted into the required diameter.
3. Torch device
Flaring device is used to enlarge the bell mouth of copper tube to connect the indoor unit and outdoor unit of split air conditioner through pipeline. When flaring, first cover the annealed copper tube with the connecting nut, and then put the copper tube into the corresponding aperture of the pipe clamp. The height of the copper tube exposed from the pipe clamp is one fifth of the diameter of the copper tube. Tighten the nuts at both ends of the pipe clamp, press the conical head of the flare injector on the nozzle, and slowly turn the screw clockwise to squeeze the nozzle into a bell mouth, as shown in Figure 2-35.
4. Pipe cutter
When maintaining and installing air conditioners, it is often necessary to cut copper pipes with different lengths and diameters with a pipe cutter. The pipe cutter has different specifications, and its structure is shown in Figure 2-36:
When cutting a copper pipe, you must put the copper pipe between the two rollers of the pipe cutter, rotate the feed button clockwise to clamp the copper pipe between the pipe cutter and the rollers, then rotate the feed button and rotate the pipe cutter around the copper pipe. When rotating the feed button, the force must be even and gentle, otherwise the copper tube may be extruded and deformed. After cutting the copper tube, the burr on the edge of the nozzle should be removed with a reamer to prevent copper chips from entering the refrigeration system.
5. Pipe bender
Pipe bender is a tool used to change the shape of copper pipe and process it into the required shape. There are many sizes of pipe benders, which are suitable for copper pipes with bending radius less than 20 mm When bending a pipe, first put the annealed copper pipe into the wheel groove of the pipe bender, lock the pipe hook, and slowly turn the handle until the required angle, as shown in Figure 2-37:
6, gas welding equipment
Copper pipes are mostly used in air conditioning and refrigeration systems, and maintenance requires gas welding. The traditional gas welding equipment uses oxygen and acetylene gas to mix and ignite to produce high-temperature flame. Now more liquefied petroleum gas is used, and oxygen-assisted liquefied petroleum gas welding machine is used to weld the pipeline of refrigeration system. Gas welding equipment is mainly composed of gas cylinders, connecting hoses and welding guns.
7. Clamping table
Clamp meter is a widely used measuring instrument and the most commonly used tool in electrical troubleshooting of refrigeration equipment. It can measure AC or DC voltage, AC current, resistance and so on. , as shown in figure 2-38.
(1), measure AC and DC voltages.
First, switch the transfer switch to AC voltage (ACV) or DC voltage range (DCV), and select a range larger than the voltage to be measured. Then, insert the red and black probes into the jack of the power socket to be tested. The number displayed on the panel is the measured voltage, and the AC voltage has no fixed polarity, so the probe of the clamp meter can be used regardless of the positive and negative poles. When measuring DC voltage, turn the change-over switch to DC voltage range (DCV), and pay attention to the range larger than the measured voltage. At the same time, you should find out the polarity of the voltage to be measured. When measuring, the red stylus is connected with a positive voltage, and the black stylus is connected with a negative voltage. If the polarity of the stylus is wrong, the clamp meter may be damaged.
(2), measuring AC current
Turn the transfer switch to the appropriate alternating current (ACA) range. When measuring, just clamp the wire to be measured in its jaw, and use the principle of electromagnetic induction, the display screen can display the current intensity in the wire.
③ Measuring resistance
Turn the change-over switch to the appropriate range. Before measurement, directly connect two probes (short circuit). At this time, the display should read 0 Ω and chirp. If the displayed number is not 0 Ω, the clamp meter is damaged or the power is insufficient. When measuring, connect the probe to both ends of the measured resistance, and the number displayed on the screen is the measured resistance.
Section 2 Maintenance Cases of Electrical Control System
Case 1, SCR fault, indoor noise
Fault phenomenon: the indoor fan rotates slowly after being turned off and makes harsh noise after being turned on.
Cause analysis: According to user feedback and phenomenon analysis, the indoor motor power supply failure is preliminarily judged. Check the power supply voltage of indoor fan. When the motor is turned off, there is a voltage of 100V on it. After the motor is turned off, the indoor motor still runs slowly and continuously. The indoor motor is heated, which leads to the deformation of the frame of the plastic-sealed motor, and the position of the plastic-sealed motor is deviated, which leads to the collision between the cross-flow fan and the chassis, giving off unpleasant noise and burning smell. Therefore, it is judged that the fan control thyristor is damaged.
Solution: Change the main control board.
Experience summary: the fan speed of the indoor unit of split hanging machine is controlled by SCR. When the power supply voltage is low or fluctuates greatly, it will cause single-phase breakdown of SCR. When the indoor fan stops, the motor will still rotate slowly. Because the thyristor is single-phase breakdown, the motor power supply is non-sinusoidal, the motor is unstable and noisy.
Situation 2: The indoor fan keeps running when it is off and not on.
Fault symptom: After stopping, the indoor fan is running, and the fan is not stopped or turned on.
Cause analysis: According to the fault phenomenon reflected by users, it is found that the indoor fan is running when it is powered on, and it is still running after the remote control is turned off. Preliminary judgment of indoor motor power failure. Check the power supply voltage of the indoor fan. When the motor is powered on or off, the voltage output is 158V, so the indoor motor runs after being powered on, and it is judged that the silicon controlled by the fan is damaged.
Solution: After replacing the controller of the same model, the debugging is normal.
Experience summary: the fan speed of the indoor unit of split hook-up machine is controlled by SCR. When the power supply voltage is low or fluctuates greatly, it will cause single-phase breakdown of SCR. When the indoor fan is shut down or turned off, there is still voltage, so the indoor fan cannot be turned off.
Case 3: The receiver of the remote control is broken.
Symptoms: Remote control cannot turn on the machine.
Cause analysis: Check the remote control, aim at the ordinary radio, press any key on the remote control, and the radio will respond, indicating that the remote control is normal, and the fault lies in the main control board of the indoor unit or the remote control receiver. Open the cover of the indoor unit, check that the 220v input power supply and the voltages of 12v and 5v are normal, and manually start the air conditioner, showing that there is nothing wrong with the main control board, and the fault lies in the components of the remote control receiver. After inspection, it is found that the reason is that the insulation resistance of the ceramic capacitor (103Z/50v) on the receiving circuit of the controller is small, only a few kω, and the quality of the ceramic chip is good.
Solution: After directly cutting off the capacitor 103 or replacing the display panel, the air conditioner has been running normally.
Experience summary: There are many reasons for not receiving the remote control signal. In addition to the capacitor leakage mentioned above, no virtual welding will also cause non-reception. In addition, the air conditioning environment has a great influence on the reception of the remote controller. When the environmental humidity is high, the condensed water condenses at the solder joints on the back of the remote control display board, and the insulation performance of the circuit board decreases. There is electric leakage between solder joints, which causes the remote controller to fail to open or fail. Clean the circuit board, blow dry it with a hair dryer, and weld a layer of glass glue on the back of the display board of the remote controller, and the remote controller can receive it normally. The AM file of the radio can be used to detect whether the remote controller emits signals. If the air conditioner runs normally after manual startup, the fault of the main control board can be eliminated, so it can be determined that the problem lies in the receiver, and the accessories cannot be simply replaced during maintenance, especially when repeated maintenance is carried out in a short time. The reasons for the damage of accessories should be carefully analyzed.
Situation 4: Temperature sensor failure
Fault phenomenon: the heating effect of air conditioner is poor, and the wind speed is always very low.
Cause analysis: door-to-door inspection, hot start, low wind speed, hot air outlet, switching air conditioning mode and cooling air supply mode can adjust high and low wind speed, which proves that the fan motor is normal, and it is suspected that the characteristics of indoor pipe temperature sensor have changed.
Solution: After replacing the indoor pipeline temperature sensor, everything is normal after debugging.
Experience: When air conditioning is used for heating, due to the function of preventing cold air, the indoor fan works with breeze when the indoor heat exchanger of the indoor temperature sensor reaches above 25 degrees Celsius, and works at the set wind speed when the temperature reaches above 38 degrees Celsius. First, it is found that the wind speed is low and the outlet air temperature is high. Check whether the fan is normal. When it is determined that the wind speed is normal, the analysis sensor may check that the temperature may be incorrect, which may cause the indoor fan to fail to operate at the set wind speed, so replace the sensor.
Temperature sensor failures account for a large proportion of air conditioning failures. To judge accurately, we must first understand its function. The air conditioning control part is equipped with three temperature sensors:
1. Room temperature sensor: mainly detects the indoor temperature. When the indoor temperature reaches the set requirements, it controls the operation of internal and external machines. When cooling, the external machine stops, while the internal machine continues to run. When heating, the internal machine blows waste heat and then stops.
2. Indoor pipe temperature sensor: mainly detects the temperature of indoor evaporator coil, and plays the role of preventing cold air, overheating and automatic temperature control during heating. If the newly started coil temperature does not reach 25 degrees, the indoor fan will not run; When it reaches 25 degrees and 38 degrees, the indoor fan will work with a breeze, and when the temperature reaches 38 degrees, it will work with a set wind speed; When the indoor coil temperature reaches 57 degrees Celsius for 10S, the outdoor fan will stop running; When the temperature exceeds 62 degrees Celsius to 10S, the compressor will also stop running, and the outdoor unit can only be put into operation when the temperature drops to 52 degrees Celsius. Therefore, when the coil resistance is greater than the normal value, the indoor unit may not start or always run at low wind speed; When the coil resistance is small, the outdoor machine will frequently stop the indoor machine to blow cold air. It plays an anti-freezing protection role during refrigeration. When the indoor coil temperature is lower than -2 degrees Celsius for 2 minutes, the outdoor unit stops running. When the indoor pipe temperature rises to 7 degrees Celsius or the compressor stops working for more than 6 minutes, the outdoor unit may stop running because the coil resistance is too high, and the indoor unit will blow natural wind, resulting in no cooling failure.
3. Outdoor defrosting temperature sensor: mainly detects the outdoor condenser coil temperature.
When the outdoor coil temperature is lower than -6℃ for 2 minutes, the indoor unit will turn into defrosting state, and when the outdoor coil sensor resistance is too high, the indoor unit will not work normally.