Main faults of air conditioners

When starting and operating the air conditioner compressor, a number of malfunctions may occur, which manifest themselves as follows: the compressor does not turn on (there is no characteristic hum); the compressor does not turn on (characteristic hum); the compressor turns on, but operates in short cycles.

The compressor does not turn on (there is no characteristic hum) for the following reasons:

the compressor has a delay when turning on. It can reach 3... 6 minutes;

the temperature set on the remote control does not correspond to the room temperature. Check the value of the temperature set on the remote control. If it is lower than the room temperature, change the setting;

ambient air temperature discrepancy. Check the ambient air temperature; if it is below 16 °C, the thermistor on the external unit of the air conditioner designed to operate in the "cooling" mode may not allow the refrigeration machine to turn on. If the air conditioner is designed to operate in the "heating-cooling" mode, and the ambient air temperature is below the permissible value (5° ... -25 °C), the external unit thermistor may also be triggered (protection against low evaporator temperature);

the thermistors are faulty: defrosting; discharge; suction and boiling temperature; condenser. A fault in all thermistors may be caused by a break in the circuit: to find such a fault, first determine the presence of resistance in the thermistors, and then the value of its resistance. Also determine the presence of contact between the thermistor and the control board and check the control board itself;

compressor protection is triggered when the voltage in the network deviates more than the set value, there is a phase imbalance and a phase disappears;

compressor protection against incorrect phase connection is activated (for a three-phase compressor);

incorrect setting of the room temperature thermistor or failure of the high and low pressure relays. Adjust the thermistor setting or eliminate the fault in the pressure relay (one or both);

starting capacitor failure;

the defrosting boards of the external unit are faulty; external unit; control.

The compressor does not turn on (there is a characteristic hum) for the following reasons:

malfunction: starting capacitor; working capacitor; starting relay; compressor jamming. Signs: the starting current values exceed the nominal ones, and measurements of the resistance of the compressor electric motor windings show that they are in good condition. In this case, replace the compressor;

the compressor crankcase is filled with liquid refrigerant. If there is no crankcase heater, a non-standard heater is installed. The possibility of formation of refrigerant condensate in the suction manifold at a low ambient temperature is checked;

the compressor's electrical protection is triggered at the moment when the characteristic hum begins. The resistance of the electric motor windings is checked with an ohmmeter, for which the power wires are first disconnected. The possibility of short-circuiting the winding to the housing is checked with a megohmmeter;

remote control malfunction. Symptoms: the system turns on with the emergency switch and does not turn on with the remote control. Test the remote control. Turn on the remote control and check if the liquid crystal display lights up. If it does not light up or the image is unclear, replace the batteries and reset the parameters. Then install a nearby radio receiver in the medium wave range (AM) and turn on the remote control. If there is no interference with the receiver when the remote control is turned on, replace it. Check if there is a source of interference with the remote control (IR emitter, sun rays, powerful consumer of electricity) near the indoor unit. If such a source is found, it is necessary to install a filter on the receiver for IR waves. If no source of interference is detected, replace the IR receiver on the indoor unit.

the working capacitor is faulty;

protection against malfunctions is triggered: condenser fan; drainage system pump;

the protective relay is faulty. Check the values of the operating current of the compressor electric motor with current clamps. If the values of the operating current correspond to the nominal, replace the protective relay; if the values of the operating current of the compressor electric motor are higher than the nominal, there is an interturn short circuit of the compressor electric motor windings. Replace the compressor;

high pressure switch tripping due to excess condensation pressure caused by: a closed valve on the discharge line; a non-operating condenser fan; excess refrigerant in the outdoor unit; non-condensable impurities in the condenser; insufficient suction pressure when starting the refrigeration machine, which can be caused by: insufficient amount of refrigerant; lack of heat flow to the evaporator of the refrigeration machine.

The lack of heat inflow may be caused by:

mechanical obstacles in the air flow path, malfunction of the air cooler fan; failure of the solenoid valve in front of the expansion valve;

clogging of the TRV or its incorrect adjustment (TRV is closed); inverter failure:

if the voltage is balanced, then the compressor windings are checked;

Diagnostics of inverter air conditioners

The operation of the compressor with an inverter is diagnosed by switching on the inverter and measuring the time until the inverter stops due to an increase in current. If the operating time is within 10 s, the fault is a short circuit in the compressor windings. If the inverter switches off after 10... 60 s, the compressor is jammed. If the inverter operates for 1... 5 min, the fault should be looked for in the hydraulic circuit of the refrigeration machine;

failure of all solenoid valves. Signs: the refrigeration machine operates continuously, the set room temperature is not reached in either cooling or heating mode:

excess refrigerant in the system. Signs of excess refrigerant in the system may appear :

when the heat flow to the air cooler is insufficient (mechanical obstructions to the air flow, failure of the indoor unit fan, evaporator freezing, clogging of air filters, build-up of bacterial mucus, insufficient heat flow to the indoor unit). In this case, the superheating value decreases, since the boiling process is hindered. Boiling occurs in the suction pipeline and (or) in the compressor casing. The compressor casing temperature decreases. Dew or frost may appear on the compressor casing due to condensation of moisture from the ambient air. The noise level from the operating compressor decreases, the temperature of the discharge pipeline decreases; when the condenser is excessively cooled. This mainly occurs when the refrigeration machine is turned on at low ambient air temperatures. Under these conditions, the amount of refrigerant in the condenser increases, the amount of supercooling at the condenser outlet increases. A significant portion of the refrigerant remains in the condenser. The condensation pressure decreases. The amount of refrigerant entering the air cooler decreases. The suction pressure decreases. The suction superheat increases, the compressor body temperature rises. The noise from the operating compressor electric motor increases;

when non-condensable gases appear in the refrigeration machine. If there is a small amount of non-condensable gases in the system, part of the condenser is occupied by these gases. The pressure in the condenser increases and the flow through the throttling element increases. The boiling pressure in the evaporator increases. The discharge temperature increases. The temperature of the compressor housing increases. The noise from the operating electric motor increases. The value of the operating current increases.

The supercooling of the liquid refrigerant is reduced. Due to the fact that the amount of condensed refrigerant decreases, the superheating at the suction increases;

If the TRV is not adjusted correctly, when it is too open, the boiling temperature of the refrigerant in the air cooler increases, the suction pressure increases, and the superheating at the suction decreases. Because more refrigerant enters the condenser, the amount of supercooling increases. In order to avoid overfilling the evaporator with liquid refrigerant, proceed as follows. By turning the adjusting screw, increase the superheating until the pressure fluctuations stop. Then turn the screw to the left until the point where the fluctuations begin. After that, turn the screw to the right by 1 turn (V4) turn.

After each operation with the TRV, stop the adjustment work for 20 minutes and then check the consequences;

Lack of refrigerant may be caused by a violation of the technology of filling the refrigeration machine; leakage of refrigerant from the system. External signs of lack of refrigerant in the system may appear in the event of:

the presence of non-condensable impurities in the system. If there are a lot of non-condensable gases in the system, almost the entire condenser is filled with non-condensable gases. During the initial period of compressor operation, the temperature on the discharge line and the condensation pressure increase sharply, but since there is nowhere for the refrigerant to condense, the liquid refrigerant enters the evaporator in an insignificant amount. The evaporator temperature remains high;

presence of moisture in the system. If the system was not drained during installation, moisture remains in the system. Moisture can enter the system with air, as well as due to a violation of the technology for drying the electric motor windings at the compressor manufacturer. Violation of the technology for storing refrigeration oils leads to their humidification and, accordingly, to the appearance of moisture in the refrigeration system. Water is practically insoluble in refrigerants and oils used in air conditioners. During the circulation of moisture in the refrigeration machine, when the temperature in the throttling device decreases, moisture can crystallize and clog the opening of this device (capillary tube, TRV).

Moreover, the crystallization of moisture in the refrigeration machine is caused by the mechanism of formation of gas crystal hydrates. At a pressure of 0.5 MPa (5 atm.), the formation of gas crystal hydrate of water with freon R22 begins at a temperature of 12 °C. Accordingly, the properties of gas crystal hydrates cause the formation of ice plugs in the refrigeration machine not at 0 °C, as one would expect, but already at 12 °C;

presence of mechanical impurities in the refrigeration system. Mechanical impurities are the result of improper installation: cutting pipes with a saw, improper use of a reamer allow copper filings to circulate in the system; rust, scale (free or bound). The use of incompatible refrigerants and oils, mixing mineral and polyester oils leads to coagulation of oils. The resulting clots can also circulate in the system. Mechanical impurities most quickly clog the filters of filter-driers, filters in front of the expansion valve, the expansion valves themselves and capillary tubes, filters at the inlet of the suction pipe to the compressor; lack of refrigerant, which can be caused by improper adjustment of the expansion valve;

failure of the four-way valve. Symptom: the valve switching from cooling to heating mode in case of failure starts to work as a bypass, i.e. it passes the refrigerant from the discharge side to the suction side. To check the four-way valve, disconnect the compressor from the inverter board. Apply power to the indoor and outdoor units of the air conditioner and turn on the emergency start for heating. 3 minutes after applying power, check for voltage between the contacts of the four-way valve and the control board. If there is no 220 V, the control board or noise filter board is faulty. If there is voltage, it is necessary to check the serviceability of the wires of the coil of the four-way valve and the coil itself;

When operating systems with several internal units (multisystems), situations are possible when some internal units do not turn on. If two units are turned on for cooling and heating, only one will work, the one that was turned on first.