Understanding exactly how the refrigerant changes its state of aggregation when passing through the throttling device is the key to diagnosing most air conditioning equipment malfunctions. At the moment of a sharp drop in pressure in the capillary tube or thermostatic valve liquid freon instantly boils, beginning to actively absorb thermal energy from the surrounding air. This physical process underlies principle diagram of the air conditioner and explains why we get a cold stream at the outlet of the indoor unit, and not a magical creation of low temperature.
Any breakdown of the system, be it insufficient cooling or icing of the heat exchanger, often lies precisely in the imbalance of pressure or the amount of working substance in the circuit. If circulation refrigerant is broken, heat exchange does not occur at the required intensity, which leads to emergency operation of the compressor. Knowledge of basic physical principles allows the owner or technician to quickly localize the problem without resorting to the random method when replacing expensive components.
Main components of the refrigeration circuitThe basis of any split system is a closed, sealed circuit through which the working substance circulates. The main heart of this system is compressor, which ensures the movement of freon and creates the necessary pressure to change states of aggregation. Without this unit, circulation is impossible, since it is this unit that compresses the refrigerant gas, increasing its temperature and pressure before sending it to the condenser.
⚠️ Warning: Attempting to start the system without evacuating the circuit or with moisture inside will result in irreversible damage to the compressor and the formation of acids in the oil.
The heat exchangers, known as the evaporator and condenser, are copper tubes with aluminum fins. B indoor unit the evaporator is located where freon boils and air cools, and during external unit There is a condenser where the gas releases heat to the atmosphere. These elements are connected by copper pipelines of different thicknesses, and the high pressure line is always thinner than the low pressure line.
- ❄️ Compressor - creates pressure and circulation.
- 🌡️ Condenser - releases heat to the external environment.
- 💧 Throttle assembly - regulates flow and pressure.
- 💨 Evaporator - absorbs heat from the room.
Physics of the process: cycle of compression and expansionThe operating principle of an air conditioner is based on the ability of substances to absorb heat during evaporation and release it during condensation. When freon gas enters the compressor, it is compressed, and its temperature rises sharply to 60-80 degrees Celsius. In such a heated state, the substance enters the condenser of the external unit, where, under the influence of fans, it cools and turns into liquid, throwing the accumulated energy out.
Next, the liquid refrigerant under high pressure approaches the throttling device. Passing through the narrow opening of a capillary tube or thermostatic valve, the pressure drops sharply. This leads to instantaneous boiling of part of the liquid and strong cooling of the remaining mass. It is this mixture of liquid and gas that enters the evaporator of the indoor unit, where the main process takes place heat exchange with the air of the room.
The efficiency of heat transfer directly depends on the cleanliness of the radiators: dirty condenser fins increase the pressure in the system and reduce cooling capacity.
It is important to understand that freon is not consumed during operation, but only transfers thermal energy from one place to another. If a leak occurs in the system, the amount of working fluid decreases, which upsets the entire hydraulic balance. As a result, there may not be enough liquid in the evaporator to fully boil, which will lead to overheating of the gases at the outlet and possible damage compressor.
The role of the compressor and refrigerant in the systemThe compressor is often called the air conditioner motor, and rightly so, since it consumes the bulk of the electricity. Modern inverter models are equipped with compressors with variable speed, which allows you to smoothly change the system performance. Unlike older On/Off models, where the compressor runs at full power or turns off, the inverter maintains the set temperature by changing the rotor speed.
Compressor types
There are piston, rotary and scroll compressors. Spiral (scroll) are considered the quietest and most efficient for household split systems, ensuring a smooth supply of gas without pulsations.
Compressor types
There are piston, rotary and scroll compressors. Spiral (scroll) are considered the quietest and most efficient for household split systems, ensuring a smooth supply of gas without pulsations.
Gases of the grade are most often used as a working fluid R410A or R32. These refrigerants have excellent thermophysical properties but require high system pressure to operate effectively. R32 is considered more environmentally friendly and efficient, but it is slightly flammable, which requires special attention during installation and compliance with safety rules.
- 🔧 Ensures refrigerant circulation throughout the circuit.
- ⬆️ Creates a high pressure zone for condensation.
- 🔻 Creates a low pressure zone for evaporation.
- ⚙️ Regulates system performance (in inverters).
Operation of indoor and outdoor unitsThe external unit of the air conditioner is installed outdoors and contains the noisiest and largest elements. Here are located capacitor, compressor, fan and four-way valve (heated models). The outdoor module's job is to remove heat efficiently, so ensuring free air flow through its heat exchanger is critical.
The indoor unit is a decorative part of the system that is placed indoors. Inside it are evaporator, fan with electric motor, control board and filtration system. Air from the room is sucked in through the top grille, passes through the cold evaporator, where it releases heat and is dried, and then blown back into the room through the blinds.
⚠️ Attention: Installing the indoor unit above cabinets or in niches may disrupt air circulation, the temperature sensor will read incorrect data.
Communication between the units is carried out not only by copper pipelines, but also by electrical control cables. Signals from the internal unit board are sent to the external unit board, regulating the operation of the fans and compressor. Broken contacts in the interconnect cable often lead to erroneous codes on the display or a complete failure of the system to respond to the remote control.
Operating modes: cooling and heatingThe principle diagram of the operation of an air conditioner in heating mode is not much different from the cooling mode, with the exception of the direction of movement of freon. Switching between modes is carried out using a four-way valve, which changes the direction of refrigerant flow. In heating mode, the external unit becomes an evaporator (takes heat from the street), and the internal unit becomes a condenser (returns heat to the room).
Heating efficiency directly depends on the outside temperature. The colder it is outside, the less thermal energy the air contains, and the more difficult it is freon boil in the external unit. At temperatures below -10...-15°C (for conventional models), efficiency decreases and the risk of icing of the external heat exchanger increases, which can lead to fan or compressor failure.
In Dry mode, the air conditioner operates cyclically: it turns on cooling to condense moisture on the radiator, and then slows down the fan so that the moisture is not blown back, but evaporates into the drain. This allows you to reduce humidity without greatly reducing the temperature in the room.
Diagnostics based on pressure and temperature parametersTo professionally assess the operation of the air conditioner, technicians use a pressure gauge station, connecting it to the service ports. The pressure in the system is not a constant value; it depends on the ambient temperature and the load on the system. For example, for R410A The boiling pressure at +5°C in the evaporator will be significantly different from the pressure at +15°C.
The normal temperature difference between the incoming and outgoing air from the indoor unit should be 10-14 degrees Celsius. If the delta is lower, this may indicate a lack of freon, a dirty evaporator, or low compressor performance. If the delta is too large, there may be a lack of air flowing through the radiator (the filter is clogged or the fan is faulty).
☑️ Fault diagnosis
| Parameter | Normal (cooling) | Possible problem with deviation |
|---|---|---|
| Suction pressure | 3.0 - 4.0 bar (R410A) | Low: Leakage, dirty filter. High: excess freon. |
| Outlet temperature | +6...+12°C | Above normal: lack of refrigerant. Below: risk of icing. |
| Compressor current | According to nameplate ±10% | High: The capacitor is dirty. Low: gas shortage. |
| Steam overheating | 5 - 10°C | High: lack of freon. Low: risk of water hammer. |
Common installation errors and their consequencesThe quality of air conditioner operation depends 80% on correct installation, and not on the brand of equipment. The most critical mistake is the lack of evacuation of the route before starting. The air remaining in the tubes contains moisture and nitrogen, which, when mixed with compressor oil, form aggressive acids that destroy winding insulation and bearings.
Evacuation is a mandatory procedure for systems with R410A and R32 freon, since they operate at high pressures and are sensitive to impurities.
Evacuation is a mandatory procedure for systems with R410A and R32 freon, since they operate at high pressures and are sensitive to impurities.
The length of the copper route also plays a role. If it is too short, liquid freon may not have time to completely evaporate and enter the compressor, causing water hammer. If the route is too long, the compressor will not have enough power to pump oil, which will lead to oil starvation and jamming. The optimal length is usually indicated in the instructions, but does not exceed 5-7 meters without additional refilling.
⚠️ Attention: Using low-quality copper pipe (thin-walled or recycled) will lead to rapid formation of cracks and freon leaks in places of bends and vibration.
Questions and answers (FAQ)
Why does my air conditioner blow warm air in cooling mode?
This can happen for several reasons: the freon has completely run out, the compressor does not start (the starting capacitor or the motor itself has burned out), or the four-way valve has not switched. It is also worth checking that the windows are open and that the external unit is dirty.
How often should you clean the indoor unit of your air conditioner?
It is recommended to wash coarse filters (mesh) under water every 2-3 weeks during active use. Deep cleaning of the evaporator and drainage system using a steam cleaner and chemicals should be carried out at least once a year, before the start of the season.
Is it possible to turn on the air conditioner in winter?
You cannot turn it on for cooling in winter without a winter kit - the oil and condensate will freeze. Only models whose instructions indicate the minimum operating temperature (usually up to -5...-15°C) can be used for heating. Special winter kits allow you to work on cooling even in frosty conditions.
What does the flashing indicator on the case mean?
Flashing lights are an error code that is read by the control unit. The number of flashes or combination of lights indicates a specific fault (leakage, communication error, temperature sensor). The decoding must be found in the service manual of the specific model.