VAV valve systems. Air flow regulation. An overview of the technologies used in air valves. Air shut-off valves, gate valves

Imagine that you want to install a ventilation system in your apartment. Calculations show that in order to heat the supply air in the cold season, a 4.5 kW heater will be required (it will allow heating the air from -26°С to +18°С with a ventilation capacity of 300 m³/h). Electricity is supplied to the apartment through a 32A automatic machine, so it is easy to calculate that the power of the heater is about 65% of the total power allocated to the apartment. This means that such a ventilation system will not only significantly increase the amount of electricity bills, but also overload the power grid. Obviously, it is not possible to install a heater of such power and its power will have to be reduced. But how to do this without reducing the comfort level of the inhabitants of the apartment?

How to reduce electricity consumption?

Ventilation unit with recuperator.
It needs a network to work.
supply and exhaust ducts.

The first thing that usually comes to mind in such cases is to use ventilation system with recuperator. However, such systems are well suited for large cottages, while in apartments there is simply not enough space for them: in addition to the supply air supply network, an exhaust network must be connected to the heat exchanger, doubling the total length of the air ducts. Another disadvantage of recuperation systems is that in order to organize the air overpressure of "dirty" rooms, a significant part of the exhaust flow must be directed to the exhaust ducts of the bathroom and kitchen. And the imbalance of the supply and exhaust flows leads to a significant decrease in the efficiency of recuperation (it is impossible to refuse the air overpressure of "dirty" premises, since in this case unpleasant odors will begin to walk around the apartment). In addition, the cost of a recuperative ventilation system can easily exceed twice the cost of a conventional one. supply system. Is there another inexpensive solution to our problem? Yes, this is a supply VAV system.

VAV system or VAV(Variable Air Volume) system allows you to adjust the air supply in each room independently of each other. With such a system, you can turn off the ventilation in any room in the same way that you used to turn off the lights. Indeed, after all, we do not leave the light on where there is no one - it would be an unreasonable waste of electricity and money. Why let a ventilation system with a powerful heater waste energy in vain? However, traditional ventilation systems do just that: they supply heated air to all rooms where people could be, regardless of whether they actually are there. If we controlled the light in the same way as traditional ventilation, it would burn all over the apartment at once, even at night! Despite the obvious advantage of VAV systems, in Russia, unlike Western Europe, they have not yet become widespread, partly because their creation requires complex automation, which significantly increases the cost of the entire system. However, the rapid reduction in the cost of electronic components, which occurs in recent times, made it possible to develop inexpensive ready-made solutions for building VAV systems. But before proceeding to the description of examples of systems with variable air flow, we will understand how they work.

The illustration shows a VAV system with a maximum capacity of 300 m³/h serving two areas: a living room and a bedroom. In the first figure, air supply is provided to both zones: 200 m³/h to the living room and 100 m³/h to the bedroom. Suppose that in winter the power of the heater will not be enough to heat such an air flow to a comfortable temperature. If we had used a conventional ventilation system, we would have had to reduce the overall performance, but then it would have become stuffy in both rooms. However, we have a VAV system installed, so during the day we can only supply air to the living room, and at night only to the bedroom (as in the second picture). To do this, the valves that regulate the volume of air supplied to the premises are equipped with electric drives that allow you to open and close the valve dampers using conventional switches. Thus, by pressing the switch, the user turns off the ventilation in the living room before going to bed, where there is no one at night. At this point, the differential pressure sensor, which measures the outlet air pressure air handling unit, fixes an increase in the measured parameter (when the valve is closed, the resistance of the air supply network increases, leading to an increase in air pressure in the air duct). This information is transmitted to the air handling unit, which automatically reduces the fan performance just enough to keep the pressure at the measuring point unchanged. If the pressure in the duct remains constant, then the air flow through the valve in the bedroom will not change, and will still be 100 m³ / h. The overall performance of the system will decrease and will also be equal to 100 m³ / h, that is, the energy consumed by the ventilation system at night will decrease by 3 times without sacrificing people's comfort! If you turn on the air supply alternately: during the day in the living room, and at night in the bedroom, then the maximum power of the heater can be reduced by a third, and the average energy consumed by half. The most interesting thing is that the cost of such a VAV system exceeds the cost of a conventional ventilation system by only 10-15%, that is, this overpayment will be quickly compensated by lowering the amount of electricity bills.

A short video presentation will help you better understand the principle of the VAV system:

Now, having dealt with the principle of operation of the VAV system, let's see how you can assemble such a system based on the equipment available on the market. As a basis, we will take the Russian VAV-compatible Breezart air handling units, which allow you to create VAV systems serving from 2 to 20 zones with centralized control from the remote control, timer or CO 2 sensor.

VAV system with 2-position control

This VAV system is based on a Breezart 550 Lux air handling unit with a capacity of 550 m³/h, which is enough to serve an apartment or a small cottage (taking into account the fact that a variable air flow system may have a lower capacity compared to a traditional ventilation system). This model, like all other Breezart units, can be used to create a VAV system. In addition, we need a set VAV-DP, which includes a JL201DPR sensor that measures duct pressure near the branch point.

VAV-system for two zones with 2-position control

The ventilation system is divided into 2 zones, and the zones can consist of either one room (zone 1) or several (zone 2). This allows the use of such 2-zone systems not only in apartments, but also in cottages or offices. The valves of each zone are controlled independently of each other using conventional switches. Most often, this configuration is used to switch night (air supply to zone 1 only) and day (air supply to zone 2 only) modes with the possibility of supplying air to all rooms, if, for example, guests have come to you.

Compared to a conventional system (without VAV control), the increase in the cost of the basic equipment is about 15% , and if we take into account the total cost of all elements of the system, together with installation work, then the increase in value will be almost imperceptible. But even such a simple VAV system allows save about 50% electricity!

In the given example, we used only two controlled zones, but there can be any number of them: the air handling unit simply maintains the set pressure in the air duct, regardless of the configuration of the air supply network and the number of controlled VAV valves. This allows, in case of a lack of funds, to first install the simplest VAV system on two zones, further increasing their number.

So far, we have considered 2-position control systems in which the VAV valve is either 100% open or fully closed. However, in practice, more convenient systems with proportional control, allowing you to smoothly adjust the amount of air supplied. We will now consider an example of such systems.

VAV system with proportional control

VAV system for three zones with proportional control

This system uses a more efficient Breezart 1000 Lux PU at 1000 m³/h, which is used in offices and cottages. The system consists of 3 zones with proportional control. The CB-02 modules are used to control proportional valve actuators. Instead of switches, JLC-100 regulators (outwardly similar to dimmers) are used here. Such a system allows the user to smoothly adjust the air supply in each zone in the range from 0 to 100%.

The composition of the basic equipment of the VAV system (supply unit and automation)

Note that in one VAV system, zones with 2-position and proportional control can be used simultaneously. In addition, control can be made from motion sensors - this will allow air to be supplied to the room only when there is someone in it.

The disadvantage of all the considered options for VAV systems is that the user has to manually adjust the air supply in each zone. If there are many such zones, then it is better to create a system with centralized control.

VAV system with centralized control

Centralized control of the VAV system allows you to enable pre-programmed scenarios by changing the air supply in all zones simultaneously. For example:

• Night mode. Air is supplied only to the bedrooms. In all other rooms, the valves are open at a minimum level to prevent stagnant air.
• day mode. In all rooms, except for bedrooms, the air is supplied in full. In the bedrooms, the valves are closed or open at a minimum level.
• Guests. The air flow in the living room has been increased.
• Cyclic ventilation(used when there is a long absence of people). A small amount of air is supplied to each room in turn - this avoids the appearance of unpleasant odors and closeness, which can create discomfort when people return.

VAV system for three zones with centralized control

For centralized control of valve actuators, JL201 modules are used, which are combined into a single system controlled via the ModBus bus. Programming of scenarios and control of all modules is carried out from the standard remote control of the ventilation unit. The JL201 module can be connected to a carbon dioxide concentration sensor or a JLC-100 controller for local (manual) control of actuators.

The composition of the basic equipment of the VAV system (supply unit and automation)

The video describes how to control a VAV system with centralized control for 7 zones from the Breezart 550 Lux air handling unit:

Conclusion

In these three examples, we have shown general principles building and briefly described the capabilities of modern VAV systems, more information about these systems can be found on the Breezart website.

Air flow control is part of the process of setting up ventilation and air conditioning systems, it is carried out using special air control valves. Regulation of air flow in ventilation systems allows to provide the required supply of fresh air to each of the serviced premises, and in air conditioning systems - cooling of premises in accordance with their heat load.

To control the air flow, air valves, iris valves, systems for maintaining a constant air flow (CAV, Constant Air Volume), as well as systems for maintaining a variable air flow (VAV, Variable Air Volume) are used. Let's take a look at these solutions.

Two ways to change the air flow in the duct

In principle, there are only two ways to change the air flow in the duct - change the fan performance or bring the fan to the maximum mode and create additional resistance to the air flow in the network.

The first option requires the connection of fans through frequency converters or step transformers. In this case, the air flow will change immediately in the entire system. It is impossible to regulate the air supply to one particular room in this way.

The second option is used to control the air flow in directions - by floors and by rooms. To do this, various adjustment devices are built into the corresponding air ducts, which will be discussed below.

Air shut-off valves, gate valves

The most primitive way to control the air flow is to use air shut-off valves and gates. Strictly speaking, shut-off valves and dampers are not regulators and should not be used for air flow control purposes. However, formally they provide regulation at the level of "0-1": either the duct is open and the air moves, or the duct is closed and the air flow is zero.

The difference between air valves and gate valves lies in their design. The valve, as a rule, is a body, inside of which a rotary damper is provided. If the damper is turned across the axis of the duct, it is blocked; if along the axis of the duct - it is open. At the gate, the damper moves progressively, like a closet door. Blocking the section of the duct, it reduces the air flow to zero, and, opening the section, provides air flow.

In valves and dampers, it is possible to install the damper in intermediate positions, which formally allows you to change the air flow. However, this method is the most inefficient, difficult to control and the most noisy. Indeed, it is almost impossible to catch the desired position of the damper when it is scrolling, and since the design of the dampers does not provide for the function of regulating the air flow, the dampers and dampers are quite noisy in intermediate positions.

Iris valves

Iris dampers are one of the most common solutions for air flow control in rooms. They are round valves with petals arranged along the outer diameter. When adjusted, the petals are displaced towards the axis of the valve, blocking part of the section. This creates an aerodynamically well-circumscribed surface, which helps to reduce the noise level during air flow control.

Iris valves are equipped with a scale with risks, which can be used to monitor the degree of overlap of the valve's open area. Next, the pressure drop across the valve is measured using a differential pressure gauge. The pressure drop determines the actual air flow through the valve.

Constant flow regulators

The next stage in the development of air flow control technologies is the emergence of constant flow controllers. The reason for their appearance is simple. Natural changes in the ventilation network, clogging of the filter, clogging of the external grille, replacement of the fan and other factors lead to a change in air pressure in front of the valve. But the valve was set to some standard pressure drop. How will it work in the new conditions?

If the pressure in front of the valve has decreased, the old valve settings will “transfer” the network, and the air flow into the room will decrease. If the pressure in front of the valve has increased, the old valve settings will “underpressure” the network, and the air flow into the room will increase.

However, the main task of the control system is precisely to maintain the design air flow in all rooms throughout the entire life cycle climate system. This is where solutions for maintaining a constant air flow come to the fore.

The principle of their operation is reduced to an automatic change in the flow area of ​​the valve, depending on external conditions. To do this, the valves are provided with a special membrane, which deforms depending on the pressure at the inlet to the valve and closes the cross section when the pressure increases or releases the cross section when the pressure decreases.

Other constant flow valves use a spring instead of a diaphragm. Increasing pressure upstream of the valve compresses the spring. The compressed spring acts on the flow area regulation mechanism, and the flow area decreases. In this case, the resistance of the valve increases, neutralizing high blood pressure to the valve. If, however, the pressure in front of the valve has decreased (for example, due to clogging of the filter), the spring is unclenched, and the orifice control mechanism increases the orifice.

The considered controllers of constant air flow operate on the basis of natural physical principles without the participation of electronics. There are also electronic systems for maintaining a constant air flow. They measure the actual pressure drop or air velocity and change the valve's orifice area accordingly.

Variable Airflow Systems

Variable airflow systems allow you to change the supply airflow depending on the actual situation in the room, for example, depending on the number of people, carbon dioxide concentration, air temperature and other parameters.

Regulators of this type are motorized valves, the operation of which is determined by the controller, which receives information from sensors located in the room. The regulation of air flow in ventilation and air conditioning systems is carried out according to different sensors.

For ventilation, it is important to provide the required amount of fresh air in the room. At the same time, carbon dioxide concentration sensors are activated. The task of the air conditioning system is to maintain the set temperature in the room, therefore, temperature sensors are used.

In both systems, motion sensors or sensors for determining the number of people in the room can also be used. But the meaning of their installation should be discussed separately.

Of course, the more people in the room, the more fresh air should be supplied to it. But still, the primary task of the ventilation system is not to ensure the flow of air "by people", but to create a comfortable environment, which in turn is determined by the concentration of carbon dioxide. With a high concentration of carbon dioxide, ventilation must operate in a more powerful mode, even if there is only one person in the room. Similarly, the main sign of the operation of the air conditioning system is the temperature of the air, and not the number of people.

However, presence sensors make it possible to determine whether a given room needs to be serviced at all at the moment. In addition, the automation system can “understand” that “it’s time for the night”, and it is unlikely that anyone will work in the office in question, which means that it makes no sense to spend resources on its air conditioning. Thus, in systems with variable air flow, different sensors can perform different functions - to form a regulatory influence and to understand the need for the operation of the system as such.

The most advanced systems with variable air flow allow, based on several controllers, to generate a signal to control the fan. For example, in one period of time, almost all regulators are open, the fan is running in high performance mode. At another point in time, some of the regulators lowered the air flow. The fan can operate in a more economical mode. At the third moment of time, people changed their location, moving from one room to another. The regulators have worked out the situation, but the total air flow has not changed much, therefore, the fan will continue to operate in the same economy mode. Finally, it is possible that almost all regulators are closed. In this case, the fan reduces speed to a minimum or turns off.

This approach allows avoiding constant manual reconfiguration of the ventilation system, significantly increasing its energy efficiency, increasing the service life of equipment, accumulating statistics on the building’s climate regime and its changes throughout the year and during the day, depending on various factors– number of people, outside temperature, weather phenomena.

Yury Khomutsky, technical editor of the journal "Climate World">

Systems with variable air consumption (VAV - Variable Air Volume) are energy efficient system ventilation that saves energy without sacrificing comfort. The system enables independent, for each individual room, regulation of ventilation parameters, and also saves capital and operating costs.

The modern base of equipment and automation makes it possible to create such systems at prices that almost do not exceed the prices of conventional ventilation systems, while allowing efficient use of resources. All this is the reason for the growing popularity of the VAV system.

Let's consider what a VAV system is, how it works, what advantages it gives, using the example of a cottage ventilation system with an area of ​​250 sq.m. ().

Benefits of Variable Airflow Systems

Systems with variable air flow (VAV - Variable Air Volume) have been widely used in America and Western Europe for several decades, they have only recently entered the Russian market. Users in Western countries have highly appreciated the advantage of independent room-by-room control of ventilation parameters, as well as the possibility of saving capital and operating costs.

Ventilation "Variable Air Volume" systems operate in the mode of changing the amount of air supplied. Changes in the heat load of the premises are compensated by changing the volumes of supply and extract air at its constant temperature coming from the central supply unit.

The VAV ventilation system responds to changes in the heat load of individual rooms or areas of a building and changes the actual amount of air supplied to the room or area.

Due to this, the ventilation works at a total air flow rate less than necessary for the total maximum heat load of all individual rooms.

This reduces energy consumption while maintaining the desired indoor air quality. The reduction in energy costs can be from 25-50% compared to ventilation systems with a constant air flow.

Consider the efficiency on the example of ventilation country house
250 m², with three bedrooms

With traditional ventilation system, for a dwelling of this size, an air flow of about 1000 m³ / h is required, and in winter it will take about 15 kWh to heat the supply air to a comfortable temperature. In this case, a significant part of the energy will be wasted, because the people for whom the ventilation works cannot be in the whole cottage at once: they spend the night in the bedrooms, and the day in other rooms. However, it is impossible to selectively reduce the performance of a traditional ventilation system in several rooms, since the balancing of air valves, which can be used to control the air supply to rooms, is carried out at the commissioning stage, and the flow ratio cannot be changed during operation. The user can only reduce the total air flow, but then it will become stuffy in the rooms where people are.

If you connect electric actuators to the air valves, which will allow you to remotely control the position of the damper flap and thereby regulate the air flow through it, then it will be possible to turn on and off ventilation separately in each room using conventional switches. The problem is that it is very difficult to manage such a system, because simultaneously with the closing of some of the valves, it will be necessary to reduce the performance of the ventilation system by a strictly defined amount so that the air flow in the remaining rooms remains unchanged and, as a result, the improvement will turn into a headache.

Using a VAV system allows you to carry out all these adjustments in automatic mode. And so we install the simplest VAV system, which allows you to separately turn on and off the air supply to the bedrooms and other rooms. In night mode, air is supplied only to the bedrooms, so the air flow is about 375 m³/h (based on 125 m³/h for each bedroom, area 20 m²), and the energy consumption is about 5 kWh, i.e. 3 times less than in the first version.

Having received the possibility of separate control, in different rooms it is possible to supplement the system with the latest automation of climate control, so the use of valves with proportional electric drives will make the control smooth and even more convenient; and if we turn on / off the air supply according to the presence sensor signal, we get an analogue of the Smart Eye system used in household split systems, but on a completely new level. For further automatization, sensors of temperature, humidity, CO2 concentration, etc. can be integrated into the system, which in the end will not only save energy, but also significantly increase the level of comfort.

If all the automation units that control the electric actuators of the air valves are connected by a single control bus, then it will be possible to centrally control the entire system in scenarios. So, you can create and set individual operating modes for different rooms, in different life situations, So:

at night- air is supplied only to the bedrooms, and in other rooms the valves are open at a minimum level; afternoon- air is supplied to rooms, kitchens, and other premises, except for bedrooms. In the bedrooms, the valves are closed or open at a minimum level.

whole family to gather- increase the air flow in the living room; nobody in the house- cyclic ventilation is configured, which will not allow odors and dampness to occur, but will save resources.

For independent control of not only the volume, but also the temperature of the supply air in each of the rooms, you can install additional heaters (low-power heaters) controlled by individual power controllers. This will make it possible to supply air from the ventilation unit with the minimum allowable temperature (+18°C), individually heating it to the required level in each room. Such technical solution will further reduce energy consumption, and bring us closer to the "Smart Home" system.

The scheme of operation of such a system is rather a question of a specialized specialist, so here we will give only one, the most a simple circuit(working and erroneous options) with an explanation of how it works. But apart from simple systems, there are also more complex options that allow you to create any VAV systems - from household budgetary systems with two valves to multifunctional ventilation systems for office buildings with floor-by-floor air flow control.

Call, the specialists of the company "OVK Engineering" will consult, help you choose the best option, design and install a VAV system that is ideal for you.

Why VAV systems should be installed by professionals

The easiest way to answer this question is with an example. Consider a typical configuration of a variable air flow system and the mistakes that can be made in its design. The illustration shows an example of the correct configuration of the air duct network of a VAV system:

1. Correct scheme of VAV system with variable air flow

In the upper part there is a control valve that serves three rooms (three bedrooms from our example) => These rooms have manually operated throttle valves for balancing during commissioning. The resistance of these valves will not change* during operation, so they do not affect the accuracy of maintaining the air flow.

A valve with manual control is connected to the main air duct, which has a constant air flow P=const. Such a valve may be needed to ensure the normal operation of the ventilation unit when all other valves are closed. => The air duct with this damper is led into the room with a constant air supply.

The scheme is simple, working and efficient.

Now let's look at the mistakes that can be made when designing the air duct network of a VAV system:

2. Scheme of a VAV system with an error

Incorrect duct branches are highlighted in red. Valves #2 and #3 are connected to a duct running from the junction point to VAV valve #1. When the damper position of valve #1 is changed, the pressure in the air duct near valves #2 and 3 will change, so the air flow through them will not be constant. Piloted valve #4 must not be connected to the main duct, because changing the air flow through it will cause the pressure P2 (at the branch point) to not be constant. And valve #5 cannot be connected as shown in the diagram, for the same reason as valves #2 and 3.

*Of course, you can set up controlled airflow for each bedroom, but in this case there will be a more complex scheme, which we will not consider in this article.

IRIS VALVE WITH SERVO

Thanks to the unique damper design, the air flow can be measured and controlled within one unit and one process, delivering a balanced amount of air into the room. The result is a permanently comfortable microclimate.
IRIS butterfly valves allow you to quickly and accurately adjust the air flow. They cope wherever individual comfort control and precise air control are needed.
Flow measurement and regulation for maximum comfort
Balancing the air flow is usually a labor intensive and expensive operation when starting a ventilation system. The linear air flow limitation characteristic of lens butterfly valves makes this operation easier.
Throttle valve design
IRIS throttle dampers can function in both supply and exhaust installations, eliminating the risk associated with incorrect installation errors. IRIS lens throttle dampers consist of a body made of galvanized steel, lens planes that regulate the air flow, a lever for smoothly changing the diameter of the hole. In addition, they are equipped with two tips for connecting a device that measures the strength of the air flow.
Throttle valves are equipped with EPDM rubber seals for a tight connection with the ventilation ducts.
Thanks to the motor mount, it is possible automatic control stream without having to manually change the settings. A special plane is provided for stable mounting of the servo motor, protecting it from movement and damage.
What makes lens throttle valves different from standard throttle valves?
Conventional dampers increase the speed of air flow along the walls of the channels, while generating a lot of noise. Thanks to the IRIS lens closing of the throttle valves, suppression does not cause turbulences and noise in the channels. This allows higher flows or pressures than standard butterfly valves, without noise in the installation. This is a great simplification and savings, because. there is no need to use additional soundproofing elements. Appropriate noise attenuation is possible through the correct installation of dampers in the ventilation system.
For precise measurement and control of air flow, butterfly valves should be placed on straight sections, no closer than:
1. 4 x air duct diameter in front of the throttle valve,
2. 1 x duct diameter behind throttle.
The use of lens dampers is very important for ensuring the hygiene of the ventilation installation. Due to the possibility of full opening, cleaning robots can successfully enter the channels connected to this kind of butterfly valves.
Advantages of IRIS butterfly valves:
1. low noise level in channels
2. easy installation
3. excellent balancing of the air flow, thanks to the measuring and regulating unit
4. simple and quick flow adjustment without the need for additional devices - the use of a handle or a servomotor
5. Accurate flow measurement
6. stepless adjustment - manually using a lever or automatically using the version with a servomotor
7. design allowing easy access for cleaning robots.

Variable air flow controllers KPRK for circular ducts are designed to maintain the set value of air flow in ventilation systems with variable air flow (VAV) or constant air flow (CAV). In VAV mode, the air flow setpoint can be changed using a signal from an external sensor, controller or dispatch system; in CAV mode, the regulators maintain the set air flow

The main components of flow regulators are an air valve, a special pressure receiver (probe) for measuring air flow and an electric actuator with a built-in controller and pressure sensor. The difference between the total and static pressures at the measuring probe depends on the air flow through the regulator. The current differential pressure is measured by a pressure sensor built into the actuator. The electric actuator under the control of the built-in controller opens or closes the air valve, maintaining the air flow through the regulator at a given level.

KRPK regulators can operate in several modes depending on the connection scheme and settings. Air flow rates in m3/h are programmed at the factory. If necessary, the settings can be changed using a smartphone (with NFC support), a programmer, a computer or a supervisory system via MP-bus, Modbus, LonWorks or KNX protocol.

Regulators are available in twelve versions:

• KRPK…B1 – basic model with MP-bus and NFC support;
• KRPK…BM1 – controller with Modbus support;
• KRPK…VL1 – regulator with LonWorks support;
• KPRK…BK1 – controller with KNX support;
• KPRK-I…B1 – controller in a heat/sound insulated housing with MP-bus and NFC support;
• KPRK-I…BM1 – controller in a heat/sound insulated housing with Modbus support;
• KPRK-I…VL1 – controller in a heat/sound insulated housing with LonWorks support;
• KPRK-I…BK1 – controller in heat/sound insulated housing with KNX support;
• KPRK-Sh…B1 – controller in a heat/sound insulated housing and a silencer with MP-bus and NFC support;
• KPRK-Sh…BM1 – controller in a heat/sound insulated housing and a noise suppressor with Modbus support;
• KRPK-Sh…VL1 – regulator in a heat/sound insulated housing and a noise suppressor with LonWorks support;
• KPRK-Sh…BK1 is a controller in a heat/sound insulated housing and a noise suppressor with KNX support.

For the coordinated operation of several variable air flow controllers KPRK and the ventilation unit, it is recommended to use the Optimizer - a controller that provides a change in the fan speed depending on the current demand. Up to eight KPRK controllers can be connected to the Optimizer, and several Optimizers can be combined, if necessary, in Master-Slave mode. Variable air flow controllers remain operational and can be operated regardless of their spatial orientation, except when the measuring probe fittings are directed downwards. The direction of air flow must correspond to the arrow on the body of the product. Regulators are made of galvanized steel. Models KPRK-I and KPRK-Sh are made in a heat/sound insulated housing with an insulation thickness of 50 mm; KPRK-Sh is additionally equipped with a 650 mm silencer on the air outlet side. The body branch pipes are equipped with rubber seals, which ensures the tightness of the connection with the air ducts.