How to choose an air conditioner?

The device and principle of operation of the air conditioner

Although air conditioners may differ in modification, their internal components are approximately the same:

Outdoor unit — compressor, tubes with liquid and gaseous freon, fan, filter, 4-way valve and condensate outlet.
Indoor unit — control board, filters, fan, evaporator and freon tubes.

The principle of operation of the device (cooling mode) consists in the following steps: the gaseous refrigerant (freon) enters the compressor, where it is heated by increasing the pressure. After that, it moves to the condenser, where the substance passes into a liquid state. The expansion valve, into which liquid freon enters, changes the pressure, causing the substance to boil. Reaching the evaporator, the substance undergoes a change in pressure, which causes it to turn into steam. The steam removes heat from the room and cool air enters.

Unit operation in cooling mode

In heating mode, the 4-way valve changes position and freon begins to flow in the opposite direction. Now the indoor unit takes cold air from the room and releases warm air.

Unit operation in heating mode

Air conditioner installation method

When choosing a suitable model, special attention should be paid to the design features:

Window. This is a monoblock system mounted directly in the window unit. The disadvantage of the device is that it is necessary to separately order the appropriate window for it, and it also creates considerable noise in the room. Window models are more suitable for industrial premises where people are rarely.

window construction

Floor. They consist of two blocks, one of which is placed on the floor in the room, and the other is mounted outside the window on the street. The disadvantage of floor models is that they take up a lot of space in the room. Also, some users complain that during work they strongly “pull” on their legs, which is harmful to health. Of the pluses, one can note a good distribution of cold or hot air throughout the room.
Mobile. Monoblocks usually have one or two pipes for cold air intake and hot air exhaust, which are discharged through the window. They are easily installed by one person, and you do not need to have special skills for this. The advantage of mobile devices is the ability to use them in any room of the house, you can even take them to the country house. But like windows, they make a lot of noise.

floor structure

Cassette (ceiling). They consist of two blocks, one of which is mounted directly into the ceiling, and the other is brought out. Air blowing occurs clearly vertically, due to which the “chill” is evenly distributed throughout the room. This design is convenient for office space, where workplaces are separated by partitions that do not reach the ceiling. Also, cassette units are an excellent solution for large stores and supermarkets. Powerful ceiling-type models are able to serve more than 100 m2.

ceiling structure

Wall. This is the most popular type of air conditioning devices that are used for installation in an apartment. The indoor unit is fixed on the wall in the room, and the outer unit is outside the window. Wall models have low noise level, good cooling of the room and many additional functions controlled by the remote control. For this type, there are multi-systems, which consist of several indoor units and one outdoor unit (as shown in the figure below). They are convenient when you need to install air conditioning in two rooms at the same time.

Wall multi system

Additional functions of air conditioners

The choice of a suitable air conditioner is also determined by a number of useful functions for daily use:

Inverter temperature control. This function allows you to automatically maintain the temperature set in the system by changing the compressor power. Thanks to this compressor, you do not need to constantly turn on / off, which prolongs its service life. The inverter model is convenient when it is necessary for the air conditioner to work for a long time without shutting down (for example, in a cafe from morning until midnight). Also, the inverter allows you to save electricity by working to maintain cooling or heating. When choosing an inverter model, pay attention to the SEER and SCOP coefficients. They show the ratio of heat / cold output to the electrical power of the device. For example, if the SCOP is 5.1, then this means that the air conditioner gives off 5.1 kWh of heat when consuming 1 kWh of electricity. Thus, the higher the SEER and SCOP coefficients, the more economical the air conditioner. It is true to note that in severe frosts, the heat transfer coefficient decreases.
Air ionization. Some models are equipped with an ionizer, which produces negatively charged ions, saturating the air in the room with them. Such air is good for the human respiratory tract. It is worth noting that the air conditioner itself somewhat dries the air, which contributes to the creation of a favorable environment for the development of harmful bacteria. In this case, you should additionally use a humidifier. In this article, you can read about how to choose a humidifier.
Night mode. Units with this function are equipped with a special regulator responsible for maintaining the optimum temperature throughout the night. At the same time, the fan in the indoor unit reduces its speed, reducing noise. Although in most regions of the CIS countries the nights are quite cool in summer and there is no need for air conditioning, but on especially hot days, night mode can be a real salvation.

As well as additional, but no less useful device chips:

Smartphone management. The devices are equipped with a Wi-Fi sensor and an infrared port. Using a special application (downloaded from the Play Market or App Store), you can control the air conditioner with a smartphone based on Android or iOS. Please note that a smartphone with an infrared port is required for correct operation, otherwise nothing will work.
Presence sensor. The sensor starts the unit only when there is a person in the room. A very convenient thing that allows you to significantly save electricity, since in the absence of a person, the device goes into standby mode. However, this function also has a minus: entering the room after a long absence, you have to wait until it cools down.
Fresh air supply. When this function is started, the unit ventilates the air in the room, blowing it outside and taking fresh oxygen from there. Thanks to this, more comfortable conditions for being in the room are created. It also eliminates the need to open windows from time to time to ventilate the room. However, these models are quite expensive and their price starts from $200. It will also be necessary to additionally make a hole for fresh air supply, which complicates the installation of the unit.
Heating. The vast majority of devices are able to work on space heating, which is very convenient in winter. The consumption of some inverter models in this mode is less than that of most convectors (in the absence of gaps and insulated walls).

Air conditioner power calculation

The calculation of the power of the air conditioner (degree of cooling) is made according to the following formula:

X = X1 + X2 + X3, where X1 is the heat gain from the volume of the entire room, X2 is the heat gain from a person and X3 is the heat gain from working household appliances.

X1 \u003d S * H * Q / 1000, where S is the area of \u200b\u200bthe apartment, H is the height, Q is the coefficient for the sunny side, equal to 40.

X2 of one person is 0.1 kW, and the heat gain of a computer is 0.3 kW.

Suppose we need to select a device for a room with an area of 20 m2 and a ceiling height of 2.7 m, with one occupant and one working computer. Then the calculation will be as follows:

X (air conditioner power) \u003d 20 * 2.7 * 40 / 1000 + 0.1 + 0.3 \u003d 2.56 kW. Thus, we need a device with a power of 2.56 kW and above. And although the cultivated area is written on all models, it is important to remember that the number of people and working electrical appliances in the room may increase, which means you need to purchase with a 15% power reserve.

Conclusion

For apartments no larger than 30 m2, split systems up to 2 kW with power are suitable. For office and industrial buildings, it is worth looking at ceiling models with a power corresponding to the area of \u200b\u200bthe room. In other cases, it is worth first making calculations according to the formulas described above, and then purchasing an air conditioner that is suitable in terms of parameters.