Comparison Domovent Solo RA1-35A-9 R vs VENTS TwinFresh R-50

The diameter of the holes intended for connecting air ducts to the ventilation unit. The more performant the air ventilation unit, the more air the ducts must pass and the larger, usually, the mounting holes. For wall-mounted models (see above), this parameter determines the size of the channel that must be drilled into the wall to accommodate the unit.

The noise level produced by the air ventilation unit in normal operation.

This parameter is indicated in decibels, while the decibel is a non-linear unit: for example, a 10 dB increase gives a 100 times increase in sound pressure level. Therefore, it is best to evaluate the actual noise level using special tables.

The quietest modern ventilation units produce about 27–30 dB — this is comparable to the ticking of a wall clock and allows you to use such equipment without restrictions even in residential premises (this noise does not exceed the relevant sanitary standards). 40dB is the daytime noise limit for residential areas, comparable to average speech volume. 55–60 dB — the norm for offices, corresponds to the level of loud speech or sound background on a secondary city street without heavy traffic. And in the loudest, they give out 75–80 dB, which is comparable to a loud scream or the noise of a truck engine. There are also more detailed comparison tables.

When choosing according to the noise level, it should be taken into account that the noise from the air movement through the ducts can be added to the noise of the ventilation unit itself. This is especially true for centralized systems (see "System"), where the length of the ducts can be significant.

The type of heat exchanger used in the heat exchanger of the ventilation unit (see "Features").

— Plate. The simplest and most common type of heat exchanger is based on the use of metal plates that separate the incoming and outgoing air into narrow channels. Such heat exchangers are inexpensive, do not require an electrical connection and are almost silent. However, a classic plastic or metal heat exchanger has a relatively low efficiency (about 45 – 80%), “blows out” moisture from the room (which may require the use of humidifiers), and in frosty weather ice forms on the plates, and it is necessary to turn off the heat exchanger, letting air in bypassing it (for this, an automatic bypass is often provided). The last two shortcomings are devoid of plate heat exchangers made of cellulose — they do not freeze; moreover, they retain not only heat but moisture in the room, and the efficiency can reach 92%. On the other hand, cellulose heat exchangers are not applicable in swimming pools and other areas with high humidity.

— Rotary. Heat exchangers, the operation of which is based on the rotation of a disc of a special design. At the same time, each part of the heat exchanger alternately works to cool the exhaust air and then to heat the supply air. Such a system has a higher efficiency than plate heat exchangers, it is more compact, it returns most of the moisture coming out with the exhau...st air and does not freeze in cold weather. On the other hand, due to the complexity of the design, rotary heat exchangers are more expensive and less reliable, in addition, they require power supply and produce some additional noise (although most often not much).

— Ceramic. Advanced recuperators based on highly efficient ceramic materials used in decentralized air ventilation units (see "System"). A feature of such recuperators is that they transfer to the supply air not only the apparent but also the latent heat of the exhaust air (latent heat is released due to moisture condensation). It made it possible to achieve impressive efficiency indicators — from 90% and above. The main disadvantage of ceramic heat exchangers is the high cost due to the complexity of production.

— Tubular. Heat exchanger based on a bundle of thin metal tubes of great length placed in a casing. Usually, outdoor air is supplied through such tubes to the room, and the air from the room on the way out moves between the tubes, transferring heat to them. In such devices, you can achieve a fairly solid efficiency — 70% and above; even though tubular heat exchangers are relatively simple in design and reliable. They appeared relatively recently and, for the most part, have not yet received significant distribution.

The heat transfer efficiency, energy saving indicators and service life of the unit directly depend on the material of the heat exchanger. Most often, heat exchangers of supply and exhaust units are made of the following materials:

- Aluminum. Aluminum is a lightweight metal with good thermal conductivity for efficient heat transfer between air streams. Aluminum heat exchangers quickly respond to temperature changes due to rapid heating and cooling, but just as quickly condense in a humid environment. In addition, aluminum dust particles, when released into the air, pose a potential threat to the human respiratory system.

— Cellulose. Heat exchangers made of cellulose are lightweight and extremely inexpensive to manufacture. However, in terms of thermal conductivity and wear resistance, cellulose is an ineffective material and is therefore quite rare. On a separate line, it is important to mention that cellulose tends to absorb unpleasant odors, and its cleaning process does not involve washing or other contact with water.

— Ceramics. Ceramics as a material for the manufacture of heat exchangers is valued for its wear resistance and high safety, but the cost of such models is often very high. In terms of heat transfer efficiency, ceramics can be called the “golden mean” - it is capable of quickly accumulating heat, but also retains it well, witho...ut completely releasing it to the supply air. This advantage turns into a disadvantage when recovering cold air during the heating period.

- Copper. Heat exchangers made of copper are characterized by high thermal conductivity - copper accumulates and releases heat best, but also cools down just as quickly. The downside of large temperature changes is the formation of condensation, which at low temperatures leads to freezing and a complete stop of ventilation. To avoid freezing, additional heating is used, and this often leads to increased power consumption. However, copper heat exchangers provide the highest efficiency (over 90%), prevent the formation of viral, fungal and bacteriological air pollutants due to natural antiseptic properties, and withstand many years of use. In terms of their combination of qualities, copper heat exchangers are among the best in their class.

— Polystyrene. Some air handling units may use heat exchangers with plates made of plastic, polystyrene and other polymer-based materials. They are lightweight and corrosion resistant, but often have lower thermal conductivity. Another flaw in such materials is that many viruses and bacteria can remain viable for quite a long time on the plastic surfaces of the heat exchanger.

Efficiency of the heat exchanger used in the heat exchanger of the supply and exhaust system (see "Features").

Efficiency is defined as the ratio of useful work to the energy expended. In this case, this parameter indicates how much heat taken from the exhaust air, the heat exchanger transfers to the supply air. The efficiency is calculated by the ratio between the temperature differences: you need to determine the difference between the outdoor air and the supply air after the heat exchanger, the difference between the outdoor and exhaust air, and divide the first number by the second. For example, if at an outside temperature of 0 °С, the temperature in the room is 25 °С, and the heat exchanger produces air with a temperature of 20 °С, then the efficiency of the heat exchanger will be (25 – 0)/(20 – 0)= 25/20 = 80%. Accordingly, knowing the efficiency, it is possible to estimate the temperature at the outlet of the heat exchanger: the temperature difference between the inside and outside must be multiplied by the efficiency and then the resulting number is added to the outside temperature. For example, for the same 80% at an outdoor temperature of -10 °C and an internal temperature of 20 °C, the inflow temperature after the heat exchanger will be (20 – -10)*0.8 + -10 = 30*0.8– 10 = 24 – 10 = 14 °C.

The higher the efficiency, the more heat will be returned to the room and the more savings on heating will be. At the same time, a highly efficient heat e...xchanger is usually expensive. Also note that the efficiency may vary slightly for certain values of the external and internal temperatures, while manufacturers tend to indicate the maximum value of this parameter — accordingly, in fact, it may turn out to be lower than the claimed one.

The lowest outdoor air temperature at which the ventilation unit can be safely used; more precisely, the minimum inlet air temperature at which the unit can operate normally, without malfunctions, for an indefinitely long time.

It is worth choosing according to this parameter taking into account the climate in which it is planned to use the unit: the device should normally tolerate at least the average winter temperature, and it is best to have some reserve in case of a harsh winter. However, many modern models allow operation at -10 °C and below, and in the most cold-resistant ones, the temperature minimum can reach -35 °C. So choosing a unit for a temperate climate is usually not a problem. Also note that if an installation that is ideally suited for all other parameters cannot cope with low temperatures, the situation can be corrected by using an additional heater at the inlet of the ventilation system.

Note that if the minimum temperature is not indicated in the characteristics, it is best to proceed from the fact that this model requires a temperature not lower than 0 °C. In other words, in cold weather, it is worth using only the equipment for which this possibility is directly stated.

The presence of an EC fan(fans) in the design of the air handling unit.

This term refers to fans with synchronous brushless motors, also known as EC motors. Such motors are more advanced than traditional asynchronous ones: in particular, they provide very uniform rotation, allow precise control of speed, have high efficiency, and generate almost no heat (which is extremely important in the presence of a cooler, see "Features"), and also efficiently operate over a wide temperature range. In addition, the noise level of such motors is noticeably lower, and the service life is longer. The main disadvantage of EC fans is the traditionally high price.

Electrical power consumed by the air handling unit in normal operation (for models with capacity control - at maximum speed). Knowing this power, you can determine the requirements for connecting the unit, as well as estimate how expensive its operation will be in light of electricity bills. It should be taken into account that for models with an electric reheater (see “Type of reheater”), in this case we are talking about the power of only the ventilation system, and the power of the reheater is given separately (see above); thus, the total power consumption when operating in full format will correspond to the sum of these powers.

Also, based on the power consumption, you can to a certain extent evaluate the performance of the installation: “gluttonous” units usually provide an appropriate flow.

The minimum wall thickness on which the air ventilation unit can be hung with the possibility of wall mounting.

This parameter is indicated for models mounted directly into a hole in the wall — see "Mounting" for details. The installation length (the length of the pipe between the trims) can usually be adjusted to suit specific wall thicknesses. However, if this thickness is too small, then even an extremely shortened pipe will stick out of it, preventing the entire structure from being securely fixed. This is the reason for this limitation. Theoretically, the situation can be corrected — for example, by building up a wall at the installation site — however, in fact, such options are unlikely to be considered seriously. Nevertheless, in most models, this limitation does not exceed 300 mm, and it is very rarely necessary to install ventilation units on thinner walls.