Ventilation systems with variable air flow. VAV ventilation system. How to reduce energy consumption

IRIS VALVE WITH SERVO MOTOR

Thanks to the unique design of butterfly valves, air flow can be measured and adjusted within a single device and process, delivering a balanced amount of air to the room. The result is a constant comfortable microclimate.
IRIS butterfly valves allow you to quickly and accurately regulate air flow. They cope everywhere where individual comfort control and precision air control are required.
Measuring and adjusting flow to ensure maximum comfort
Balancing the air flow is usually a time-consuming and expensive step when starting up a ventilation system. The linear restriction of air flow found in lens throttle valves simplifies this operation.
Throttle valve design
IRIS butterfly valves can function in both supply and exhaust installations, eliminating the risk associated with incorrect installation errors. IRIS lens butterfly valves consist of a galvanized steel body, lens planes that regulate air flow, and 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 force of air flow.
The butterfly valves are equipped with EPDM rubber seals for a tight connection with the ventilation ducts.
Thanks to the engine mount it is possible automatic control stream without the need to manually change settings. A special plane is provided for stable mounting of the servomotor, protecting it from movement and damage.
What makes lens butterfly valves different from standard butterfly valves?
Conventional throttle valves increase the speed of air flow along the walls of the ducts, generating a lot of noise. Thanks to the lens closure of IRIS throttle valves, suppression does not cause turbulence or noise in the passages. This allows higher flows or pressures than standard butterfly valves without making installation noise. This is a great simplification and saving, because... there is no need to use additional soundproofing elements. Adequate noise suppression is possible through proper installation of throttle valves in the ventilation system.
To accurately measure and control air flow, throttle valves should be placed on straight sections, no closer than:
1. 4 x diameter of the air duct in front of the throttle valve,
2. 1 x diameter of the air duct behind the throttle valve.
The use of lens dampers is very important to ensure the hygiene of the ventilation installation. Thanks to the possibility of full opening, cleaning robots can successfully enter channels connected to this kind of butterfly valves.
Advantages of IRIS throttle valves:
1. low level noise in channels
2. easy installation
3. excellent balancing of the air flow, thanks to the measuring and control unit
4. simple and quick flow adjustment without the need for additional devices - use of a handle or servomotor
5. Accurate flow measurement
6. stepless adjustment - manually using a lever or automatically thanks to the use of a version with a servo motor
7. Design allowing easy access for cleaning robots.

The main purposes of this system are: reducing operating costs and compensating for filter contamination.

Using a differential pressure sensor, which is installed on the controller board, the automation recognizes the pressure in the channel and automatically equalizes it by increasing or decreasing the fan speed. Supply and exhaust fan at the same time they work synchronously.

Compensation for filter contamination

When operating a ventilation system, the filters inevitably become dirty, the resistance of the ventilation network increases and the volume of air supplied to the premises decreases. The VAV system will allow you to maintain a constant air flow throughout the entire life of the filters.

The VAV system is most relevant in systems with high level air purification, where filter contamination leads to a noticeable decrease in the volume of supplied air.

Reduced operating costs

The VAV system can significantly reduce operating costs, this is especially noticeable in supply ventilation systems, which have high energy consumption. They achieve savings by completely or partially turning off ventilation separate rooms.

Example: you can turn off the living room at night.

At calculation of the ventilation system are guided by various standards air consumption per person.

Typically, in an apartment or house, all rooms are ventilated simultaneously; the air flow for each room is calculated based on the area and purpose.
What to do if this moment is there anyone in the room?
You can install valves and close them, but then the entire volume of air will be distributed throughout the remaining rooms, but this will lead to increased noise and waste of air, the precious kilowatts were spent heating it.
You can reduce the power of the ventilation unit, but this will also reduce the volume of air supplied to all rooms, and where users are present there will be “not enough air”.
The best decision, is to supply air only to those rooms where there are users. And the power of the ventilation unit must be regulated itself, according to the required air flow.
This is exactly what a VAV ventilation system allows you to do.

VAV systems pay for themselves quite quickly, especially on air supply units, but most importantly, they can significantly reduce operating costs.

Example: Apartment 100m2 with and without VAV system.

The volume of air supplied to the room is controlled by electric valves.

An important condition for constructing a VAV system is the organization of the minimum supplied air volume. The reason for this condition lies in the inability to control air flow below a certain minimum level.

This can be solved in three ways:

in a single room, ventilation is organized without the possibility of regulation and with an air exchange volume equal to or greater than the required minimum air flow in the VAV system.
A minimum amount of air is supplied to all rooms with the valves turned off or closed. The total of this amount must be equal to or greater than the required minimum air flow in the VAV system.
The first and second options together.

Control from a household switch:

To do this, you will need a household switch and a valve with a return spring. Switching on will lead to the full opening of the valve, and the room will be ventilated in full. When turning off return spring closes the valve.

Damper switch/switch.

Equipment: For each serviced room you will need one valve and one switch.
Exploitation: If necessary, the user turns the room ventilation on and off using a household switch.
pros: The simplest and a budget option VAV systems. Household switches always match the design.
Minuses: User participation in regulation. Low efficiency due to on-off regulation.
Advice: It is recommended to install the switch at the entrance to the serviced room, at +900mm, next to or in the light switch block.

The minimum required volume of air is always supplied to room No. 1; it cannot be turned off; room No. 2 can be turned on and off.

The minimum required volume of air is distributed to all rooms, since the valves are not completely closed and a minimum amount of air passes through them. The entire room can be turned on and off.

Control from a rotary regulator:

This will require a rotary regulator and a proportional valve. This valve can open, regulating the volume of supplied air in the range from 0 to 100%, the required degree of opening is set by the regulator.

Circular regulator 0-10V

Equipment: for each room served, one valve with 0...10V control and one 0...10V regulator will be required.
Exploitation: If necessary, the user selects the required level of room ventilation on the regulator.
pros: More precise regulation of the amount of air supplied.
Minuses: User participation in regulation. Appearance regulators do not always fit the design.
Advice: It is recommended to install the regulator at the entrance to the serviced room, at +1500mm, above the light switch block.

The minimum required volume of air is always supplied to room No. 1; it cannot be turned off; room No. 2 can be turned on and off. In room No. 2 you can smoothly regulate the volume of supplied air.

Small opening (valve 25% open) Medium opening (valve 65% open)

The minimum required volume of air is distributed to all rooms, since the valves are not completely closed and a minimum amount of air passes through them. The entire room can be turned on and off. In each room you can smoothly regulate the volume of supplied air.

Presence sensor control:

This will require a presence sensor and a valve with a return spring. When registering in the user’s room, the presence sensor opens the valve and the room is ventilated in full. When there is no user, the return spring closes the valve.

Motion Sensor

Equipment: For each serviced room you will need one valve and one presence sensor.
Exploitation: The user enters the room - ventilation of the room begins.
pros: The user does not participate in the regulation of ventilation zones. It is impossible to forget to turn the room ventilation on or off. Many occupancy sensor options.
Minuses: Low efficiency due to on-off regulation. The appearance of presence sensors does not always suit the design.
Advice: Use high-quality presence sensors with a built-in time relay for the correct operation of the VAV system.

The minimum required volume of air is always supplied to room No. 1; it cannot be turned off. When the user registers, ventilation of room No. 2 begins

The minimum required volume of air is distributed to all rooms, since the valves are not completely closed and a minimum amount of air passes through them. When a user registers in any of the rooms, ventilation of this room begins.

CO2 sensor control:

This requires a CO2 sensor with a 0...10V signal and a proportional valve with 0...10V control.
When the CO2 level in the room is detected, the sensor begins to open the valve in accordance with the recorded CO2 level.
When the CO2 level decreases, the sensor begins to close the valve, and the valve can close either completely or to a position at which the required minimum flow will be maintained.

Wall or duct CO2 sensor

Example: For each room served, one proportional valve with 0...10V control and one CO2 sensor with a 0...10V signal will be required.
Exploitation: The user enters the room, and if the CO2 level is exceeded, ventilation of the room begins.
pros: The most energy efficient option. The user does not participate in the regulation of ventilation zones. It is impossible to forget to turn the room ventilation on or off. The system starts ventilation of the room only when it is really needed. The system most accurately regulates the volume of air supplied to the room.
Minuses: The appearance of CO2 sensors does not always match the design.
Advice: Use high-quality CO2 sensors for correct operation. Duct CO2 sensor can be used in supply and exhaust systems ventilation, if there is both supply and exhaust in the serviced room.

The main reason why room ventilation is required is if the CO2 level is too high.

In the process of life, a person exhales a significant amount of air with a high level of CO2, and being in an unventilated room, the level of CO2 in the air inevitably increases, this is what determines when they say that there is “little air.”
It is best to supply air into the room when the CO2 level exceeds 600-800 ppm.
Based on this air quality parameter, you can create the most energy efficient ventilation system.

The minimum required volume of air is distributed to all rooms, since the valves are not completely closed and a minimum amount of air passes through them. When an increase in CO2 content is detected in any room, ventilation of that room begins. The degree of opening and the volume of air supplied depends on the level of excess CO2 content.

Management of the Smart Home system:

This will require a system Smart House"and any type of valves. Any type of sensors can be connected to the Smart Home system.
Air distribution can be controlled either through sensors using a control program, or by the user from a central control panel or a phone application.

Smart home panel

Example: The system operates using a CO2 sensor and periodically ventilates the premises, even in the absence of users. The user can forcefully turn on ventilation in any room, as well as set the amount of air supplied.
Exploitation: Any control options supported.
pros: The most energy efficient option. Possibility of precise programming of the weekly timer.
Minuses: Price.
Advice: Install and configure by qualified specialists.

Systems with variable flow air (VAV - Variable Air Volume) is an energy-efficient ventilation system that allows you to save energy without reducing the level of comfort. The system makes it possible to independently regulate ventilation parameters for each individual room, and also saves capital and operating costs.

The modern equipment and automation base makes it possible to create such systems at prices almost no higher than conventional systems ventilation, while allowing for efficient use of resources. All these are the reasons for the growing popularity of the VAV system.

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

Advantages of variable air flow systems

Variable Air Volume (VAV) systems have been widely used for several decades in America and Western Europe, they came to the Russian market quite recently. Users Western countries highly appreciated the advantage of independent, for each individual room, regulation of ventilation parameters, as well as the possibility of saving capital and operating costs.

“Variable Air Volume” ventilation systems operate in the mode of changing the amount of air supplied. Changes in the thermal load of the premises are compensated by changing the volumes of supply and exhaust air when it is constant temperature, coming from the central air supply unit.

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

Due to this, ventilation operates at general meaning air flow less than necessary for the total maximum heat load of all individual rooms.

This ensures reduced energy consumption while maintaining desired indoor air quality. The reduction in energy costs can range from 25-50% compared to ventilation systems with constant flow air.

Let's look at efficiency using ventilation as an example. country house
250 m², with three bedrooms

With a traditional ventilation system, for a living space of this area, an air flow of about 1000 m³/h is required, and in winter for heating supply air before comfortable temperature about 15 kWh will be required. In this case, a significant part of the energy will be wasted, because the people for whom the ventilation is working cannot be in the entire cottage at once: they spend the night in the bedrooms and the day in other rooms. However, selectively reduce performance traditional system ventilation in several rooms is impossible, since balancing of air valves, with which you can regulate the air supply to rooms, is carried out at the commissioning stage, and during operation the flow rate ratio cannot be changed. The user can only reduce total consumption air, but then the rooms where people are located will become stuffy.

If you connect electric drives to the air valves, which will allow you to remotely control the position of the valve damper and thereby regulate the air flow through it, you will be able to turn the ventilation on and off separately in each room using conventional switches. The problem is that managing such a system is very difficult, because simultaneously with closing 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, improvement will turn into a headache.

Using a VAV system will allow all these adjustments to be made automatically. 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, therefore the air flow is about 375 m³/h (based on 125 m³/h for each bedroom, area 20 m²), and energy consumption is about 5 kWh, that is, 3 times less than in the first option.

Having received the possibility of separate control, in different rooms you can supplement the system with the latest climate control automation, so the use of valves with proportional electric drives will make control smooth and even more convenient; and if we connect the air supply on/off based on a signal from the presence sensor, we get an analogue of the “Smart Eye” system used in household split systems, but at a completely new level. For further atomization, sensors for temperature, humidity, CO2 concentration, etc. can be built into the system, which ultimately will not only save energy, but will also significantly increase the level of comfort.

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

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

whole family to gather- we increase the air flow in the living room; no one in the house- cyclic ventilation is set up, which will prevent odors and dampness from occurring, but will save resources.

To independently control not only the volume, but also the temperature of the supply air, additional heaters (low-power air heaters) controlled by individual power regulators can be installed in each room. This will allow air to be supplied from the ventilation unit with minimal permissible temperature(+18°C), individually heating it to the required level in each room. This 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 for a specialized specialist, so here we will present only one, the most simple diagram(working and error options) with an explanation of how it works. But besides simple systems, there are also more complex options that allow you to create any VAV systems - from household budget systems with two valves to multi-function ventilation systems administrative buildings with floor-by-floor air flow control.

Call, specialists from the UWC Engineering company will advise and help you choose best option, will design and install a VAV system that is ideal for you.

Why VAV systems should be installed by specialists

The easiest way to answer this question is with an example. Let's consider typical configuration systems with variable air flow and errors that can be made during its design. The illustration shows an example of the correct configuration of the air supply network of a VAV system:

1. Correct diagram of a VAV system with variable air flow

At the top there is a controlled valve that serves three rooms (three bedrooms in 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 air flow.

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

The scheme is simple, working and effective.

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

2. Diagram of a VAV system with an error

Incorrect duct branches are highlighted in red. Valves #2 and 3 are connected to an air duct running from the branch point to VAV valve #1. When you change the position of the valve flap No. 1, the pressure in the air duct near valves No. 2 and 3 will change, so the air flow through them will not be constant. Controlled valve No. 4 cannot be connected to the main air duct, since changes in the air flow through it will cause the pressure P2 (at the branch point) to not be constant. And valve No. 5 cannot be connected as shown in the diagram, for the same reason as valves No. 2 and 3.

*Of course you can set up a managed one air flow for each bedroom, but in this case there will be more complex circuit, which we do not consider within the scope of this article.

Air flow regulation is part of the process of setting up ventilation and air conditioning systems; it is performed using special control air valves. Regulation of air flow in ventilation systems makes it possible to ensure the required flow of fresh air into each of the serviced rooms, and in air conditioning systems - cooling of rooms in accordance with their thermal load.

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

Two ways to change the air flow in the duct

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

The first option requires connecting fans via frequency converters or step transformers. In this case, the air flow will change immediately throughout the system. It is impossible to regulate the air supply to one specific room in this way.

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

Air shut-off valves, gates

The most primitive way to regulate air flow is to use air shut-off valves and dampers. Strictly speaking, shut-off valves and dampers are not regulators and should not be used to regulate air flow. However, formally they provide regulation at the “0-1” level: 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 dampers lies in their design. The valve is usually a body with a butterfly valve inside. If the damper is turned across the axis of the air duct, it is blocked; if along the axis of the air duct, it is open. At the gate, the damper moves progressively, like a wardrobe door. By blocking the cross-section of the air duct, it reduces air flow to zero, and by opening the cross-section, it ensures 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 ineffective, difficult to control and the most noisy. Indeed, it is almost impossible to catch the desired position of the damper when scrolling it, and since the design of the dampers does not provide for the function of regulating air flow, in intermediate positions The gates and dampers make quite a lot of noise.

Iris valves

Iris valves are one of the most common solutions for regulating indoor air flow. They are round valves with petals located along the outer diameter. When adjusted, the petals move towards the valve axis, blocking part of the cross section. This creates a well-streamlined surface from an aerodynamic point of view, which helps reduce noise levels in the process of regulating air flow.

Iris valves are equipped with a scale with marks on which you can monitor the degree of overlap of the valve's live section. Next, the pressure drop across the valve is measured using a differential pressure gauge. The actual air flow through the valve is determined by the pressure drop.

Constant flow regulators

The next stage in the development of technologies for regulating air flow is the emergence of constant flow regulators. The reason for their appearance is simple. Natural changes in the ventilation network, clogged filter, clogged external grille, fan replacement and other factors lead to a change in air pressure in front of the valve. But the valve was set to a certain 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 “transmit” 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 of the climate system. This is where solutions for maintaining constant air flow come to the fore.

The principle of their operation is to automatically change the flow area of the valve depending on external conditions. For this purpose, the valves are equipped with a special membrane, which deforms depending on the pressure at the valve inlet 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 in front of the valve compresses the spring. The compressed spring acts on the flow area control mechanism, and the flow area decreases. At the same time, the valve resistance increases, neutralizing the increased pressure upstream of the valve. If the pressure in front of the valve decreases (for example, due to a clogged filter), the spring expands and the flow area control mechanism increases the flow hole.

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

Variable Air Flow Systems

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

Regulators of this type are valves with an electric drive, the operation of which is determined by a controller that receives information from sensors located in the room. Regulation of air flow in ventilation and air conditioning systems is carried out using various sensors.

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

Both systems can also use motion sensors or sensors to determine the number of people in the room. 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 air flow “for 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 should operate at a more powerful mode, even if there is only one person in the room. Likewise, the main indicator of the operation of the air conditioning system is the air temperature, not the number of people.

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

The most advanced systems with variable air flow allow the generation of a signal to control the fan based on several regulators. For example, during one period of time, almost all regulators are open, the fan operates in high performance mode. At another point in time, some of the regulators reduced the air flow. The fan can operate at more economy mode. At the third point in time, people changed their location, moving from one room to another. The regulators worked out the situation, but the total air flow remained almost unchanged, therefore, the fan will continue to operate in the same economical mode. Finally, it is possible that almost all regulators are closed. In this case, the fan reduces the speed to a minimum or turns off.

This approach allows you to avoid constant manual reconfiguration of the ventilation system, significantly increase its energy efficiency, increase the service life of the equipment, accumulate statistics on the climate conditions of the building and its changes throughout the year and during the day, depending on various factors– number of people, outside temperature, weather phenomena.

Yuri Khomutsky, technical editor of Climate World magazine>

Variable air flow regulators KPRK for air ducts round section are designed to maintain a given air flow rate 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 from a dispatch system; in CAV mode, the controllers maintain the specified air flow

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

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

The regulators are available in twelve versions:

KPRK…B1 – basic model with support for MP-bus and NFC;
KPRK…BM1 – regulator with Modbus support;
KPRK…BL1 – regulator with LonWorks support;
KPRK…BK1 – regulator with KNX support;
KPRK-I...B1 – regulator in a heat/sound-insulated housing with support for MP-bus and NFC;
KPRK-I...BM1 – regulator in a heat/sound-insulated housing with Modbus support;
KPRK-I...BL1 – regulator in a heat/sound-insulated housing with LonWorks support;
KPRK-I...BK1 – regulator in a heat/sound-insulated housing with KNX support;
KPRK-Sh...B1 – regulator in a heat/sound-insulated housing and a silencer with support for MP-bus and NFC;
KPRK-Sh...BM1 – regulator in a heat/sound-insulated housing and a silencer with Modbus support;
KPRK-SH...BL1 – regulator in a heat/sound-insulated housing and a silencer with LonWorks support;
KPRK-Sh…BK1 – regulator in a heat/sound-insulated housing and a silencer with KNX support.

For coordinated operation of several variable air flow controllers of the KPRK and the ventilation unit, it is recommended to use Optimizer - a controller that provides a change in the fan rotation speed depending on the current need. You can connect up to eight KPRK regulators to the Optimizer, and also combine, if necessary, several Optimizers in the “Master-Slave” mode. Variable air flow regulators 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 product body. 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 are additionally equipped with a 650 mm long silencer on the air outlet side. The housing pipes are equipped with rubber seals, which ensures a tight connection with the air ducts.