CO₂ carbon dioxide sensor
A built-in sensor that determines the content of carbon dioxide in the room.
The CO₂ carbon dioxide sensor controls the operation of ventilation and performs two functions at once: it prevents a critical increase in the level of carbon dioxide in the air and at the same time provides energy savings. Recall that carbon dioxide is emitted by people when they breathe, and its high content in the air leads to a deterioration in well-being and even serious health problems. Thus, if the sensor detects an increased concentration of CO2, it increases the intensity of ventilation, providing an additional supply of fresh air. When the concentration of carbon dioxide drops, the intensity of work decreases (up to a complete shutdown if there are no people in the room and the CO2 content does not change); this avoids unnecessary electricity consumption.
Number of fan speeds
The number of speeds at which the fans of the air ventilation unit can operate.
The presence of
several speeds allows you to choose the actual performance of the installation, adjusting it to the specifics of the current situation: for example, in a production room, you can reduce the ventilation intensity during the night shift, where there are fewer people than in the daytime. And the more speeds provided in the device (with the same performance range) — the more choice the user has, the easier it is to find the mode that best suits current needs.
Note that if the minimum and maximum of the air flow are indicated in the specs, but the number of speeds is not given, this does not necessarily mean smooth adjustment. On the contrary, most often such models are regulated traditionally, in steps, but for some reason, the manufacturer decided not to specify the number of speeds in the characteristics.
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.
Heater power
The power of the main heater used in the air ventilation unit. For models with two heaters (see "heater type"), this item indicates the power of the main heating element; at the same time, in units with water-electric heating, the water heat exchanger is considered the main one, in units with a preheater and afterheater, the afterheater.
Power determines primarily the amount of heat produced by the heater. This parameter is selected by the designers for the performance of the installation so that the power is enough for the volume of air passing through the unit. Thus power is more of a reference parameter than practically significant: most likely, it will be enough one way or another for the effective use of the installation. We note only some of the nuances associated with particular types of heaters. So, in water heaters, the actual power depends on the temperature of the supplied coolant; in the characteristics, indicators are usually given for a temperature of 95 °C, at a lower value and power, respectively, will be lower. With electric heating, the power consumption of the heater and, accordingly, the requirements for its connection directly depend on the power.
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.
EC fan
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.
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.
Power consumption (reheater + ventilation)
The power in watts consumed by the supply and exhaust unit with an electric reheater in normal operating mode can provide an estimate of the unit's overall energy consumption. By knowing the approximate power consumption figures, you can assess the unit's total energy demand, determine the connection requirements, and estimate the operational costs in terms of electricity bills.