How to choose an air conditioner?

In summer, the air conditioner performs the function of a lifesaver, creating a pleasant coolness at home, offices, and shops.
And when you have already decided on the type of air conditioner (the previous article "Types of air conditioners - which one to choose?" Will help you with this), it's time to deal with the technical characteristics in order to choose the best option for you.
Power consumed by the air conditioner
Power consumption is often confused with cooling power. In fact, the power consumed by the air conditioner is about 3 times less than the cooling power, that is, a 2.5 kW air conditioner consumes only about 800 W - less than an iron or an electric kettle. Therefore, household air conditioners, as a rule, can be plugged into a regular outlet without fear of "knocked out" plugs. There is no paradox here, since the air conditioner is a refrigeration machine that does not “produce” cold, but transfers it from the street to the room.
The ratio of cooling power to power consumption is the main indicator of the energy efficiency of the air conditioner, which is indicated in the technical catalogs by the ERR coefficient (Energy Efficiency Ratio). Another parameter - COP (Coefficient of Performance - thermal coefficient) is equal to the ratio of heating power to power consumption. The ERR ratio of residential split systems is usually in the range from 2.5 to 3.5, and the COP is from 2.8 to 4.0. You can see that the value of COP is higher than ERR. This is due to the fact that during operation the compressor heats up and transfers additional heat to freon. That is why air conditioners always produce more heat than cold. This fact is often used by unscrupulous manufacturers, indicating in advertising to confirm the high energy efficiency of their air conditioners, the COP coefficient instead of ERR. To indicate the energy efficiency of household appliances, there are seven categories, denoted by letters from A (best) to G (worst). Category A air conditioners have COP > 3.6 and ERR > 3.2, and category G have COP < 2.4 and ERR < 2.2.
It should be noted that power consumption and cooling capacity are usually measured in accordance with ISO 5151 (indoor temperature 27 °C, outdoor temperature 35 °C). If these conditions change, the power and efficiency of the air conditioner will be less (for example, at an outdoor temperature of minus 20 ° C, the air conditioner's power will be only 30% of the nominal value).
"Warm" air conditioning or the possibility of heating the air
There are air conditioners that can only cool the air, called cold only, and air conditioners with the ability to heat air, called hot-cold, heat pump, reversible air conditioner or simply "warm" air conditioner. Models with the possibility of air heating are more expensive, but in the off-season (autumn and spring) they can replace the heater.
The name heat pump is not given by chance. It shows that the air conditioner does not heat the air with an electric coil or heating element, like an electric heater, but with heat taken from the outside air (heat is transferred from the street to the room). Thus, in the heating mode, the same process occurs as in the cooling mode, only the outdoor and indoor units of the air conditioner seem to change places. Accordingly, in the heating mode, as well as in the cooling mode, the power consumption is 3-4 times less than the heating power, that is, for 1 kW of energy consumed, the air conditioner emits 3-4 kW of heat. Please note that all air conditioners with a heat pump can only work effectively at positive outside temperatures, so it is impossible to warm up with an air conditioner in winter!
Air conditioner noise level
If you are going to install an air conditioner in the bedroom, or if there is a neighbor's window next to the outdoor unit, then you should pay attention to the noise level of the air conditioner you are purchasing. The noise level is measured in decibels (dB) - a relative unit that shows how many times one sound is louder than another. The threshold of audibility is taken as 0 dB (note that sounds with a level of less than 25 dB are actually inaudible). The whisper level is 25 - 30 dB, the noise in the office, like the volume of a normal conversation, corresponds to 35 - 45 dB, and the noise of a busy street or a loud conversation is 50 - 70 dB.
For most household air conditioners, the noise level of the indoor unit lies in the range of 26 - 36 dB, the outdoor unit - 38 - 54 dB. It can be seen that the noise of the operating indoor unit does not exceed the noise level of the office space. Therefore, it makes sense to pay attention to the noise level of the air conditioner if you plan to install it in a quiet room (bedroom, private office, etc.).
It would seem that now it is enough to choose an air conditioner with the lowest noise level, and comfort is guaranteed. But not everything is so simple: it may turn out that an air conditioner with a noise level of 26 dB in practice will work louder than an air conditioner with a level of 32 dB. Moreover, there is no deception here, and all measurements were carried out correctly. And here's the thing. Any air conditioner can operate in several dozen modes, and each mode has its own noise level. Since the main noise source of the indoor unit is the air flow through the fan, radiator and distribution louvers, it is logical to measure the noise level at the lowest fan speed and keep this speed as low as possible.
The problem is that in this mode, the air conditioner will not produce the declared power and in hot weather it will either automatically switch to a higher speed (with increased noise) or will not be able to maintain the set temperature. In a complete description of the air conditioner, as a rule, the noise level is given for all fan operation modes, or at least the maximum and minimum values. At the same time, the typical noise level of the indoor unit of an elite air conditioner is 27 - 31 - 34 dB for a three-speed fan. In the advertising booklet, however, only the lowest figure of 27 dB can be given, and not the more correct maximum noise value of 34 dB.
It should be noted that air conditioners can be a source of not only the monotonous noise created by the air flow, but also some other sounds - crackles, hisses, gurgles, clicks. Usually these noises are noticeable only in complete silence, but they can interfere with restful sleep, since sudden sounds are much more annoying than monotonous noise. These sounds are of different nature. Cracks occur when parts of a plastic case expand and contract due to temperature changes. Freon can gurgle and hiss when the compressor is turned on and off. And clicks occur when switching relays that control the operation of the fan, compressor and other components of the air conditioner. Of all these noises, the most annoying is the crackling of the case - such sounds can even wake you up in the middle of the night. You can recognize a “crackling” indoor unit by cheap plastic, which in appearance and feel is significantly different from the plastic from which elite group air conditioners are made.
If you really need a "quiet" air conditioner, before buying, you can be advised to go around several companies that have showrooms with working samples of air conditioners, touch the indoor units, listen to how they work in various modes. In general, as a rule, the most “advanced” and expensive air conditioners are also the quietest.
A few words about the outdoor unit. With the windows closed, otherwise it is not allowed to operate the air conditioner, the noise of the outdoor unit is practically inaudible. But this noise is clearly audible to your neighbors if they themselves do not have air conditioning installed and all windows are open. Although the noise of the outdoor unit of a serviceable household air conditioner never exceeds the level allowed for a residential area, this noise can still greatly disturb residents, especially at night. Note that the difference in the noise level of the outdoor units of air conditioners of the upper and lower price groups is significantly higher than the difference in the noise level of the indoor units.
Air conditioner protection systems
If the consumer functions of all air conditioners are the same, then the functions of protection against improper operation or adverse external conditions, on the contrary, differ significantly. A complete system for monitoring the condition of the air conditioner increases its cost by 20 - 30%. At the same time, it is unlikely that it will be possible to effectively advertise, say, the presence of a low pressure switch and, accordingly, it will not be possible to quickly get a return on investment. Therefore, in "budget" air conditioners, protection systems are virtually absent. Even in the first group, many air conditioners have only partial protection against misuse.
Main control and protection systems:
Restart. This function allows the air conditioner to turn on after a power failure. Moreover, the air conditioner will turn on in the same mode in which it worked before the failure. This simplest function is implemented at the firmware level and therefore is present in almost all air conditioners.
Monitoring the status of filters. If the filters of the indoor unit of the air conditioner are not cleaned, then in a few months such a layer of dust will grow on them that the performance of the air conditioner will decrease several times. As a result, the normal operation of the refrigeration system will be disrupted and liquid freon will enter the compressor inlet instead of gaseous freon, which will most likely lead to compressor jamming. But even if the compressor does not fail, then over time the dust will stick to the radiator plates of the indoor unit, get into the drainage system and the indoor unit will have to be taken to a service center. That is, the consequences of operating an air conditioner with dirty filters can be the most serious. To protect against these consequences, a filter cleanliness monitoring system is built into the air conditioner - when the filters are dirty, the corresponding indicator lights up.
Freon leakage control. In any split system, the amount of freon decreases over time due to normalized leakage. This is not dangerous for a person, since freon is an inert gas, but an air conditioner can only “live” for 2-3 years without refueling. The fact is that the air conditioning compressor is cooled by freon and, if it is lacking, it can overheat and fail. Previously, a low pressure switch was used to turn off the compressor with a lack of freon - when the pressure in the system dropped, this switch turned off the compressor. Now, most manufacturers are switching to electronic control systems that measure the temperature at key points in the system and / or the compressor current, and based on these data, all operating parameters of the refrigeration system, including freon pressure, are calculated.
Current protection. Compressor current can be used to determine a number of refrigeration system faults. A low current indicates that the compressor is running without load, which means freon has leaked out. An increased current indicates that not gaseous, but liquid freon is supplied to the compressor inlet, which can be caused either by too low outdoor temperature or dirty filters of the indoor unit. Thus, the compressor current sensor can significantly improve the reliability of the air conditioner.
Automatic defrosting. When the outside air temperature is below +5°C, the outdoor unit of the air conditioner may become covered with a layer of frost or ice, which will lead to a deterioration in heat transfer, and sometimes even to breakage of the fan from hitting the blades on the ice. To prevent this from happening, the air conditioner control system monitors the conditions of its operation and, if there is a risk of icing, periodically turns on the auto-defrost system (the air conditioner operates for 5-10 minutes in cooling mode without turning on the indoor unit fan, while the outdoor unit heat exchanger heats up and thaws) .
Low temperature protection. It is strongly not recommended to turn on an unadapted air conditioner at negative outdoor temperatures. To prevent breakdowns, some models of air conditioners automatically turn off if the outside temperature drops below a certain level (usually minus 5 - 10 ° C).
Of course, the protection of the air conditioner is not limited to the listed systems, but we have considered those systems, the presence of which is very desirable so that the air conditioner takes care of you, and not you about the air conditioner.
Distance between the outdoor and indoor units of the air conditioner
The distance between units is of great importance, both for the cost of installing an air conditioner and for its service life. This distance is determined by the length of interconnections - copper pipes and cable. The standard installation usually includes a 5-meter track - in most cases this is quite enough. In principle, the maximum length of a route for household air conditioners is 15–20 meters, however, it is not recommended to use a route of this length for a number of reasons. Firstly, the cost of installing an air conditioner increases significantly - by 15 - 20 dollars for each additional meter of communications, and if wall chasing is required, then the total cost of each additional meter can increase to 40 - 50 dollars. Secondly, with an increase in the length of the route, the power of the air conditioner drops and the load on the compressor increases.
If it is necessary to use a route longer than 15 - 20 meters, for example, when placing an outdoor unit on the roof of a building, then you will have to use not a household air conditioner, but a semi-industrial system. So, VRV systems allow you to space blocks by 100 meters with a 50-meter height difference, but the cost of such systems is much higher.
The influence of temperature on the operation of the air conditioner
A properly selected air conditioner is able to set and maintain a comfortable air temperature in the room - usually from +18°С to +28°С. Outside temperature is more difficult. For cooling mode: the lower limit is from -5°С to +18°С for various models, the upper limit is about +43°С. For heating mode: the lower limit is from -5°С to +5°С for various models, the upper limit is about +21°С. A significant spread in the lower temperature limit is explained by the fact that to ensure the normal operation of the air conditioner in a wide temperature range, it is necessary to install additional sensors and complicate the air conditioner circuit, and this increases its cost. If you plan to turn on the air conditioner for cooling when the outside air temperature is below +15°C, then we advise you to pay attention to the operating range of the selected model. The operating temperature range is always indicated in the technical catalogs or in the user manual. Operation of the air conditioner at a temperature below the permissible temperature will cause unstable operation and freezing of the radiator of the indoor unit, as a result of which water may drip from the air conditioner.
If the outside temperature drops below -5°C, then it is strongly not recommended to turn on the air conditioner. At low temperatures, the physical properties of freon and compressor oil change. As a result, at start-up, a cold compressor may jam and have to be replaced. But even in the case of a successful start-up, the wear of the compressor will be significantly higher than the permissible one. Therefore, the operation of the air conditioner in the winter will inevitably lead to the failure of the compressor within 2-3 years. In addition, at low temperatures, the drain hole of the drain hose freezes and during cooling operation, all condensate begins to flow into the room.
However, not everything is so bad. Many manufacturers have air conditioners adapted to the conditions of winter work.
As a conclusion - small practical recommendations:
The power of the air conditioner is determined on the basis of the calculation and does not depend on our desires and preferences. An attempt to save money and buy an air conditioner of less power can be justified only with a small (10 - 15%) deviation from the calculated value.
By choosing an air conditioner with the ability to heat the air and spending an additional $ 100 - 150, you can warm up in the fall and spring, while saving 65% of electricity. However, remember that for the same money you can buy a good heater that can also heat in winter. According to statistics, “warm” air conditioners are bought several times more than “cold” ones.
An air conditioner based on ozone-friendly freon has a price 10-15% higher compared to a similar model based on R-22 freon, and the cost of installing such an air conditioner increases by 20-30%. At the same time, the use of ozone-safe freon does not affect the consumer properties of the air conditioner.
The inverter air conditioner saves up to 30% of electricity, maintains the set temperature more accurately and makes less noise. At the same time, it is much more difficult to manufacture. Therefore, we do not recommend buying inverters of "folk" brands. It is better to buy an ordinary air conditioner of the first or second group for the same money - it will be more reliable.
Since household air conditioners do not have the ability to ventilate the air, a supply ventilation system is required to create comfortable conditions in the air-conditioned rooms. Otherwise, you will have to periodically open the window to ventilate the room.
Consumer functions of all air conditioners are approximately the same, therefore, when choosing an air conditioner, it is better to pay attention to its reliability and the presence of protection systems against improper operation and adverse external conditions.
Modern household air conditioners have a sufficiently low noise level to ignore this parameter in most cases.
Restrictions on the temperature range of outdoor air, inherent in all inexpensive air conditioners, do not play a big role in domestic conditions, since the air conditioner is used in cooling mode only if the temperature outside the window exceeds 20 ° C. If you need stable operation of the air conditioner in a wide range of temperatures, then it is better to choose a model specially adapted to winter conditions.
When planning the placement of split system units, try to minimize the length of interunit communications. In a typical installation of an air conditioner (outdoor unit under the window, indoor unit not far from the window), the length of the route does not exceed 5 meters. If the length of the route is more than 7 meters, then it is advisable not to use "budget" air conditioners.

How to choose an air conditioner?
How to choose an air conditioner?
How to choose an air conditioner?
How to choose an air conditioner? How to choose an air conditioner? How to choose an air conditioner?



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January 29, 2023 08:57:39 +0200 GMT
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