Among all types of home air conditioners, “splits” take first place in the number of installations in apartments and private cottages (80–85% of the total). The trend remains, since these climate units are convenient in operation, do not take up useful area, make little noise. Our task is to explain in detail what a split system is, to consider the principle of operation and varieties of these household appliances.
The device and the difference from other air conditioners
First, let's deal with terminology. By definition, air conditioners are any climate systems that process air and bring it to the desired condition. Units can perform a number of functions:
- cooling, heating;
- draining, moisturizing;
- cleaning, disinfection;
- supply and exhaust ventilation of premises with forced motivation.
Reference. Comprehensive air treatment, such as filtration + heating + humidification, is conditioning. All involved units, controls, ventilation ducts and grilles make up the air conditioning system (abbreviated as SLE).
The classic split system is an air conditioner, divided into 2 blocks - external and internal (the English word split means "to separate"). The outdoor module is a large case, where the main elements of the cooler are located:
- compressor;
- heat exchanger - condenser;
- fan;
- expansion valve (in household models - capillary tube);
- four-way valve switching cooling / heating modes;
- reservoir tank - refrigerant dryer;
- sensors, winter kit controller;
- capacitors and compressor enable relays.
Addition. In the external units of inverter models, an electronic control board is installed, connected to the internal module with a special cable.
The outdoor unit is mounted externally on the wall of the building or is placed on the balcony (loggia) without glazing. The second block of smaller sizes is placed inside the room - usually attached to a wall in the upper zone of the room, connected to the outer 2 freon highways and cable. The internal module includes the following elements:
- heat exchanger-evaporator;
- tangential fan with an impeller in the form of a long turbine;
- electronic control circuit, temperature sensors;
- room air filters;
- blinds rotated by stepper motors;
- condensate bath, drain pipe.
The inclusion and configuration of the split system is provided from the remote control. The number of functions implemented in the air conditioner depends on the type and price of a particular model.
How does a split system work?
We turn to the technical side of the issue. The principle of operation of the “split” does not differ from the work of other refrigerating machines - the transfer of thermal energy from one place to another. In this case, from the apartment to the street. The carrier (in technical language - working heat) is the refrigerant - freon, which evaporates at freezing temperatures.
An important point. Freons - compounds of hydrocarbons with fluorine - transfer a large amount of heat due to a phase transition from a liquid state of aggregation to a gaseous state and vice versa. In domestic air conditioners, 2 brands of freons are used - R22, R410a. The characteristics of the latter correspond to modern environmental requirements, R22 is considered obsolete.
How does “split” work after turning on and setting the set temperature in the room:
- The controller receives a signal from a sensor that records the high temperature in the room.The compressor starts, the fan of the indoor unit starts to drive air through the cells of the heat exchanger-evaporator.
- Freon, located in the radiator tubes, goes into the vapor phase, intensively absorbing heat. Then freon goes through the tube to the outdoor unit and enters the compressor, which raises the gas pressure. Compression is done for one purpose - so that the steam condenses at a higher street temperature.
- On the way, the refrigerant is passed through the receiver - dryer, which protects the compressor from moisture.
- Moving through the tubes of an external heat exchanger, blown by a large axial fan, the compressed freon again takes on a liquid state, while simultaneously absorbing the absorbed heat.
- In the throttle (expansion) valve, the fluid pressure decreases, then the refrigerant returns to the indoor unit through a tube of a smaller diameter. The cycle repeats.
- When the room temperature drops to a predetermined value, the controller stops the compressor by the signal of the sensor. The next launch occurs after heating the room by 2-3 degrees.
- Due to the temperature difference between the air flows and the heat exchange surfaces, condensate is released which flows into a special bath. From there, water flows out through an inclined drainage pipe.
Note. We gave a description of the operation of a conventional split system, operating on the principle of "on / off" (on / off). More modern air conditioners - inverters - operate continuously, as described below. We offer you to watch a video on the phase transitions of freon inside the cooler:
When you need to switch to heating mode, a four-way electric valve switches the movement of the freon in the opposite direction. The external radiator becomes an evaporator, the internal radiator becomes a condenser, heat is taken from the street and moved to the living room.
Similarly, the so-called monoblocks work - window and mobile air conditioners. The difference lies in the length of the freon highways - when all the heat exchangers and fans are installed in a single building, the length of the communications does not exceed 1 m, on split systems - up to 7 m.
In inexpensive "splits", room air passes through a coarse mesh made of polypropylene. More advanced models can be equipped with several filters, a dehumidifier and an air ionizer.
Inverter coolers
A feature of these split systems is the continuous operation of the compressor. The power supply unit - the inverter - changes the performance of the unit, reducing or increasing the frequency of the electric current. What does this mean in practice:
- When the cooler starts, the compressor runs at maximum power.
- When the air temperature approaches the set temperature, at the command of the controller, the inverter gradually reduces the compressor performance.
- Upon reaching the set temperature threshold, the power of the unit is reduced to a minimum.
- The split system goes into temperature maintenance mode - the performance is regulated depending on the heating of the air.
Heating takes place in the same way - first the room temperature rises at maximum power, then the engine speed of the compressor decreases and increases according to the sensor signal. Than the "inverter" is better than the on / off conditioner:
- there are no power surges from electric motor starts;
- reduced total energy consumption;
- temperature differences inside the room are almost invisible, as happens after the compressor stops;
- in winter, a constantly running compressor does not freeze in the cold.
Reference. Some models of "inverters" remain operational up to minus 30 ° C in the yard. True, the intensity of heating decreases significantly. Read more about inverter split systems in a separate material.
Power gradation
Since the first air conditioners appeared in the USA, the cooling capacity of the units was measured in British thermal units - BTU.Manufacturers still produce a line of split systems according to a standard range of capacities - 7000, 9000, 12000 BTU and so on. In the designation of a specific model there was a corresponding figure - 07, 09, 12 ...
Reference. One thousand BTU / hour corresponds to 293.07 W or 0.293 kW.
Now most manufacturers indicate cold performance in kilowatts or in two units - kW and BTU. The table below shows the standard line of capacities of household and semi-industrial split systems.
Varieties of air conditioning units
The device of indoor and outdoor modules of all “splits” is the same, with the exception of some small things. Units are divided into types according to the method of placing the indoor unit:
- The most common are wall type. From the name it is clear that the module is suspended on a wall indoors.
- Duct (open-frame) models are built into rectangular ducts of the air conditioning system of a private house.
- Cassette units are attached to the ceiling, cooled air is supplied in 4 directions from top to bottom. The unit casing is hidden behind a suspended / suspended ceiling, the bottom panel remains in sight.
- The column type module is placed on the floor in a convenient place. The name comes from the shape of the unit - a narrow tall body resembles a column (pictured above in the photo).
- Flattened ceiling blocks are mounted to the ceiling. Do not need additional cladding with false ceilings.
- Floor versions are attached to the wall at a height of 10 ... 30 cm from the floor according to the manufacturer's instructions.
Note. Only wall split systems belong to the household series. The rest - cassette, channel, columned, floor-to-ceiling - are semi-industrial units. They are used in offices, cafes, administrative buildings, although no one bothers to hang ceiling air conditioning in the apartment.
Multi-split systems consisting of one powerful outdoor unit and 2-4 internal ones deserve special mention. Such SCR is able to maintain different temperatures in several rooms and is used in exceptional situations when it is impossible to place 2-3 separate modules on the facade of the building.
Why is it better to choose two or three “split” instead of one multi-system:
- higher price of equipment at the same installation cost;
- the external multiblock does not allow simultaneous cooling and heating of two neighboring rooms; operation in only one mode is allowed;
- the outdoor unit is different in size and decent weight;
- the cost of servicing increases due to the increased volume of freon and the complex device of the unit, in which 2-3 compressors can stand.
Large shopping centers and industrial buildings use industrial split systems - central and roof roof-top air conditioners. The blocks are also divided in them - inside the rooms are fan coil units, supply units, outside - cleaning, heating and cooling modules (chillers).
Affinity with heat pumps
The device of the inverter split system and the air heat pump (VT) is identical. Both units use the principle of a refrigeration machine, take the heat of the outside air and heat the inside. Differences in design - for the sake of increasing efficiency, the area of the outdoor heat exchanger-evaporator VT is significantly increased, so the unit is often placed on the ground, as shown below in the photo.
Geothermal pumps that extract soil heat are also structurally close to split systems. The difference is in the method of heat extraction and transfer to an external evaporator - here instead of street air, non-freezing coolant is used, flowing through the loops of underground circuits. The main working cycle is identical - brine or antifreeze evaporates freon in the heat exchanger, which transfers heat to the air or water heating system.
Finally about the installation
As a rule, installation work is carried out by craftsmen - refrigerators, who have special equipment - a vacuum pump, a manometric manifold and a perforator for drilling walls. But low-power models - "sevens", "nines" - can be mounted independently by renting the listed tool.
Installation Recommendations:
- Place the outdoor module under the window for easy maintenance; place the indoor module closer to the external wall. It is better to keep within 3 meters.
- Obtain copper tubes that are appropriate in diameter to the service ports located on the side of the chassis.
- To prevent the unit from vibrating and buzzing during compressor operation, securely attach it to the wall bracket.
- Thoroughly flare copper tubes - the tightness of the system and the performance of the “split” depend on this.
- Do not place the outdoor unit on a glazed loggia or balcony.
We also advise you to carefully read the factory instructions for the air conditioner and familiarize yourself with our installation instructions for a home air cooler.