Mounting diameter
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.
Minimum air flow (ventilation)
The lowest performance with which the supply-exhaust unit can operate.
For performance in general, see "Maximum air flow". Here we note that it makes sense to indicate the minimum flow only in cases where the amount of air passed can be regulated (see "Number of fan speeds"). And even then, for such models, this parameter is not always given.
Maximum air flow (ventilation)
The highest performance of the air ventilation unit; or, if the air flow control is not provided for in the design, the nominal capacity of the unit.
In this case, air flow refers to the amount of air that the unit can pass through itself per hour. The optimal air flow value for each room is calculated by the formula "room volume multiplied by the air exchange rate"; the air flow must not be lower than this indicator; otherwise, we cannot talk about effective ventilation. The volume is easy to calculate by multiplying the area of the room by the height of the ceilings, and the multiplicity indicates how many times per hour the air in the ventilated space should be updated. It depends on the type and purpose of the room: for example, a multiplicity of 1 is enough for a residential apartment, and at least 4 is required for a pool (there are special tables by which you can determine the multiplicity for each type of room). Thus, for example, for an apartment with a living area of 70 m², a ceiling height of 2.5 m and a kitchen of 9 m² (air exchange rate of at least 2), a duct of at least 70*2.5*1+9*2.5*2=220 m³ (excluding bathroom and toilet, they have their requirements for multiplicity).
It should be noted that a certain flow margin (about 10–15%) will not be superfluous, but it hardly makes sense to chase higher rates — after all, performance requires appropriate power, which, in turn, affects the dimensions, price and
...energy consumption of the installation. Maximum noise level
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.
Heat exchanger efficiency
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.
Minimum operating temperature
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.
Power consumption in ventilation mode
The electrical power consumed by the supply and exhaust unit in normal operating mode (for models with adjustable performance — at maximum speed) can help determine the connection requirements for the unit and estimate the cost of operation in terms of electricity bills. It should be noted that for models with an electric reheater (see "Reheater type"), this refers only to the power of the ventilation system, while the power of the reheater is provided separately (see above). Therefore, the total energy consumption during full operation will correspond to the sum of these power values.
The power consumption can also be used to some extent to assess the unit's performance: "power-hungry" units usually provide a corresponding airflow.
Minimum wall thickness
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.
Maximum wall thickness
The maximum thickness of the wall on which the air ventilation unit can be hung with the possibility of wall mounting (see "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 the wall thickness is too large, the pipe simply will not reach the outside, and installation will be impossible. Therefore, you need to pay close attention to this parameter — especially when it comes to buildings with thick walls, for example, old houses.
