Max. heat output
The highest heating power provided by a air curtain.
The simplest general rule for the selection of heaters is that for 2.5 – 3 m3 of heated space in a room with good thermal insulation, it is necessary to have at least 100 W of thermal power. In other words, for rooms with a standard ceiling of 2.5 m, one can proceed from the formula of 100 W per 1 m2 of area.
At the same time, it must be taken into account that the air curtain's purpose is not so much to heat the premises but to prevent the entry of outside air into them through open openings. Therefore, the main performance specs for such units are airflow rate and range (see below), and it makes sense to pay close attention to the heat output only if it is planned to use the air curtain also as the main heater. At the same time, it must be borne in mind that part of the power (sometimes very significant) can be lost especially when it comes to a frequently opening door without a vestibule. If other sources of heating are used in the room, the power of the air curtain can be quite low.
Anyway, to calculate the optimal values of heat output, it is best to use special formulas (or entrust the calculations to a specialist) — so that, on the one hand, the device successfully handles its tasks, and on the other hand, does not consume excess electricity, because energy consumption is directly related to the intensity of heating. (See "Fan power" for details on
...electricity consumption.)
Also note that for water-type models (see above), the actual heat output depends on several external factors: the type of coolant, its temperature, the temperature difference at the inlet and outlet, etc. Therefore, the heat output given in the official specifications is quite approximate and does not always correspond to practical indicators. Heating modes
The maximum heat output shows the capabilities of the device. At the same time, almost all air curtains can adjust the heating mode, thereby reducing power consumption. The reduced power mode is more gentle on the wear of the device and is appropriate for the continuous operation of the air curtain. Which also favourably affects the power supply to which the device is connected.
Fan power
The highest electrical power consumed by the air curtain when operating in ventilation mode, without air heating.
The performance, speed and range of the airflow depend on this parameter (see below). However, this dependence is not unambiguous — units similar in fan power can differ markedly in other specs. But what this parameter directly affects is energy consumption. For water models (see "Type"), as well as curtains that do
not have a heating function at all (see "Features"), it is the power in fan mode that describes the total electricity consumption. And if an electric heater is provided in the design, then the total energy consumption can be derived by adding the power in fan mode and the maximum heat output (see above).
Airflow
The amount of air that the air curtain can drive through itself in a certain time (usually indicated on an hourly basis).
Performance is one of the main parameters that determine the efficiency of the air curtain. The optimal value of this parameter depends primarily on the size of the door to be blocked. However, when calculating, it is also necessary to take into account several additional issues: the width and general configuration of the door, the presence of a vestibule, etc. Specific recommendations for calculating the required performance can be obtained from special sources or heating engineers.
Max. airflow speed
The highest airflow speed that a air curtain is capable of delivering.
Usually, the speed is measured directly at the outlet because airflow weakens with distance. The practical significance of this parameter is that high speed has a positive effect on performance (see above) and range (see below) because a highspeed air curtain drives a lot of air through itself, and the airflow travels a long distance. At the same time, note that models with the same airflow speed may differ markedly in other performance specs due to differences in design and technology. Therefore, we can say that this parameter is of secondary importance and only complements the range and performance data.
Max. range
The greatest effective range provided by an air curtain, in other words,
the greatest distance that the airflow travels from the device before dissipating and losing effectiveness.
It is worth choosing a device according to this parameter in such a way that it is guaranteed to block the corresponding opening. Of course, one should not forget about other specs, first of all, performance (see above); however, if the range is insufficient, then even the most efficient air curtain will be ineffective.
More features
Additional functions provided in the design of the air curtain.
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Air heating. The ability to use the unit for heating the air. Despite their name, not all over-door heaters have this function — many of them are not heaters, but rather "air" curtains. It is because the main task of any curtain is to cover open openings, and not to heat the room. Nevertheless, air heating not only allows the air curtain to be used as a heater (additional, or even the main one) but also increases the efficiency of its main purpose in cold weather.
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Thermostat. The presence in the design of the thermal curtain of a thermostat — a device for adjusting the outlet air temperature. This function is found only in models with heating mode (see above); it allows you to adjust the temperature in such a way as to ensure efficient and comfortable operation of the curtain and, at the same time, avoid unnecessary consumption of electrical or thermal energy (depending on the type of curtain, see above).
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Overheat protection. The presence of a safety system that protects the thermal curtain from overheating during operation. Overheating can occur for various reasons: clogged or blocked air ducts, electrical circuit failures, etc. However, it is a sign of an emergency and can lead to unpleasant consequences — up to accidents with injuries to people. Special protection avoi
...ds these consequences: it turns off the device when the temperature rises critically.
— Remote control. Presence of the remote control in a set of delivery of an air curtain. The ability to control the unit from a distance is very convenient, and it can be especially useful for thermal curtains installed in hard-to-reach places — for example, at high altitudes, where it is simply impossible to reach without a ladder or other devices.Noise level
The highest level of noise generated by the air curtain during normal operation.
The
lower this figure, the more comfortable the use of the unit, the better it is suitable for cases where noise is undesirable. When choosing according to specific values recorded in the characteristics, it should be taken into account that the decibel used to measure the noise level is not a linear quantity: for example, an increase in sound power by 2 times corresponds to an increase of 3 dB, 10 times — by 10 dB, 100 times — by 20 dB. Therefore, to assess the noise level, it is easiest to refer to comparative tables, where the correspondence of specific values in decibels to various real sound sources is recorded. In most modern air curtains, the noise ranges from 25 to 70 dB, here is the simplest table for this range:
20 – 25 dB — a weak audible sound, comparable to a whisper at a distance of 1 – 2 m;
25 – 30 dB — intelligible whisper at a short distance, ticking of a wall clock;
35 dB — muffled conversation;
40 – 45 dB — normal human speech;
50 – 55 dB — talking in raised tones, noise in the office;
60 dB — loud conversation at a distance of 4 – 5 m.
70 dB — loud conversation nearby.
Dimensions (WxHxD)
General dimensions of the over-door heaters. The amount of space occupied by the unit during installation depends on the dimensions, but also the dimensions of the space it covers — namely the width of the airflow (or height, if the flow is directed not down, but to the side). Most air curtains have characteristic elongated proportions, and the mentioned width/height corresponds to the largest dimension of the device.
Note that the width and height of the air curtain, in this case, are indicated for the standard installation method (see above): for example, devices installed on top will have a large width at a low height, and side ones vice versa. For models with universal mounting, the dimensions can be indicated in different ways, but it is usually not difficult to evaluate the characteristics of the flow in them if we take into account the elongated proportions described above — the largest dimension is usually the same as the width/height of the flow.
Features of choosing an air curtain in terms of dimensions (and, accordingly, the width of the covered space) also depend on the type of its installation. When mounted above the doorway, the width of the unit must be no less than the width of the doorway (and ideally, a little more, with some margin). If the curtain is installed on the side, it is enough that its height is 3/4 of the height of the opening — due to the peculiarities of the movement of heated air, this will completely cover the required space.
