Systems with variable air flow vehicle valve. Systems VAV.

Imagine that you want to install the ventilation system in the apartment. Calculations show that for heating the supply air during the cold season, the calorifer with a capacity of 4.5 kW will be required (it will heat air from -26 ° C to + 18 ° C with ventilation performance equal to 300 m³ / h). The supply of electricity to the apartment is performed through a 32a machine, so it is easy to calculate that the power of the carrier is about 65% of the total power allocated for the apartment. This means that such a ventilation system will not only significantly increase the amount of electricity bills, but also overloads the power grid. It is obvious that the calorifer of such power is not possible and its power will have to be reduced. But how to do this without reducing the level of comfort of the inhabitants of the apartment?

How to reduce electricity consumption?

Estimation with a recuperator.
It requires a network
Support and exhaust air ducts.

The first thing that usually comes to mind in such cases is the use of a ventilation system with a recuperator. However, such systems are well suited for large cottages, the apartments simply do not have enough space for them: besides the supply aircraft, it is necessary to bring the exhaust network to the recuperator, while having doubled the total length of the air ducts. Another disadvantage of recovery systems is that for the organization of the "dirty" premises, a noticeable part of the exhaust flow should be sent to the exhaust ducts of the bathroom and kitchen. And the unbalancement of the supply and exhaust streams leads to a significant reduction in the efficiency of recovery (it is impossible to abandon the air pad "dirty" premises, since in this case unpleasant odors will start walking around the apartment). In addition, the cost of the recovery ventilation system can easily exceed the two-time cost of an ordinary supply system. Is there any other, inexpensive, the solution of our problem? Yes, this is a supply VAV system.

System with variable air flow or Vav. (Variable Air VOLUME) The 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 as you used to turn off the light. Indeed, because we do not leave to burn the light where there is no one - it would be unreasonable spending electricity and money. Why let it vainly spend the energy of the ventilation system with a powerful calorifer? However, traditional ventilation systems are exactly what they work: they feed the heated air into all the rooms where people could be, regardless of whether they really are there. If we drove the light in the same way as traditional ventilation - it would be burned at once in the entire apartment, even at night! Despite the obvious advantage of VAV systems, in Russia, in contrast to Western Europe, they have not yet become widespread, partly because there is a complex automation to create them, which significantly increases the cost of the entire system. However, the rapid reduction of electronic components, which occurs lately, allowed to develop inexpensive ready-made solutions for the construction of VAV systems. But before switching to the description of examples of systems with variable air flow, we will understand how they work.

The illustration shows the VAV system with a maximum capacity of 300 m³ / h, serving two zones: living room and bedroom. In the first drawing, the air supply is made in both zones: 200 m³ / h in the living room and 100 m³ / h in the bedroom. Suppose that in winter the power of the carrier is not enough to heat this flow of air to a comfortable temperature. If we used a conventional ventilation system, we would have to reduce overall performance, but then in both rooms it would be stuffy. However, we have a VAV system installed, so in the afternoon we can serve air only in the living room, and at night - only in the bedroom (as in the second drawing). For this, the valves that regulate the volume of air supplied to the room are equipped with electric drives that allow us to open and close the valve flaps using conventional switches. Thus, by clicking on the switch, the user before going to sleep turns off the ventilation in the living room, where there is no one at night. At this point, the differential pressure sensor, which measures the air pressure at the output of the supply installation, captures an increase in the measured parameter (when the valve is closed, the resistance of the aircondition network increases, leading to an increase in air pressure in the air duct). This information is transmitted to the supply unit, which automatically reduces the performance of the fan exactly so that the pressure at the measurement point remains unchanged. If the pressure in the air 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 decrease 3 times without prejudice to the comfort of people! If you include the air supply alternately: during the day in the living room, and at night to the bedroom, then the maximum power of the carrier will be reduced by a third, and the average energy consumed is twice. 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 reducing the amount of electricity bills.

It is better to understand the principle of operation of the VAV system will help a small video presentation:

Now, having understood with the principle of work of the VAV system, let's see how you can collect such a system based on the equipment market. As a basis, we will take Russian VAV-compatible Breezart supply units, which allow you to create VAV systems serving from 2 to 20 zones with centralized control from the console, by timer or CO 2 sensor.

VAV system with 2-position control

This VAV system is assembled on the base of the Breezart 550 LUX supply unit with a capacity of 550 m³ / h, which is enough to maintain an apartment or a small cottage (taking into account the fact that the system with variable air flow can have less performance compared to the traditional ventilation system). This model, like all other breezart junctions, can be used to create a VAV system. Additionally, we need a set VAV-DP., which includes a JL201DPR sensor, measuring pressure in the duct channel near the branch point.

VAV system for two zones with 2-position control

The ventilation system is divided into 2 zones, and zones may consist of both one room (zone 1) and from several (zone 2). This allows you to use similar 2 zone systems not only in apartments, but also in cottages or offices. The valve management of each zone is made independently from each other using conventional switches. Most often, this configuration is used to switch the night (air supply only to zone 1) and daytime (air supply only to zone 2) modes with the possibility of supplying air to all rooms, if, for example, guests came to you.

Compared by the usual system (without VAV control), an increase in the cost of base equipment is about 15% And if we take into account the total cost of all the elements of the system together with the installation work, then the increase in cost will be almost inconspicuous. But even such a simple VAV system allows save about 50% of electricity!

In the example above, we used only two controlled zones, but there may be any quantity: the supply unit simply supports the specified pressure in the air duct, regardless of the configuration of the airconduct and the number of managed VAV valves. This allows you to first install the simplest VAV system into two zones first, increasing their quantity in the future.

So far, we have considered systems with 2 positional regulation, in which the VAV valve is either opened by 100% or completely closed. However, in practice, more convenient systems with proportional control are more common, allowing to smoothly adjust the volume of the air supplied. An example of such systems we now consider.

VAV system with proportional control

VAV system for three zones with proportional control

This system uses a more productive PU Breezart 1000 LUX per 1000 m³ / h, which is used in offices and cottages. The system consists of 3 zones with proportional control. CB-02 modules are used to control the drives of valves with proportional control. Instead of switches, JLC-100 regulators are used here (externally similar to dimmers). 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 (inlet installation and automation)

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

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

Centralized Vav-System

The central control of the VAV system allows you to include pre-programmed scenarios, changing the air supply simultaneously in all zones. For example:

Night mode. Air is served only in the bedroom. In all other premises, the valves are open at the minimum level to prevent the stress of air.
Day mode. In all rooms, besides bedrooms, air is served in full. In the bedrooms, the valves are closed or open at a minimum level.
Guests. Air flow in the living room is increased.
Cyclical ventilation (Used with a long lack of people). In each room, a small amount of air is served in turn - it avoids the appearance of unpleasant odors and stools, which can create discomfort when returning people.

VAV system for three zones with centralized control

For centralized valve actuators, the JL201 modules are used, which are combined into a single system controlled by the MODBUS bus. Script programming and management of all modules is made from the regular console. You can connect a carbon dioxide concentration sensor to the JL201 module or the JLC-100 regulator for local (manual) drive control.

The composition of the basic equipment of the VAV system (inlet installation and automation)

The video involves the control of the VAV system with centralized control by 7 zones from the BreeZart 550 LUX supply unit:

Conclusion

At these three examples, we showed general principles for building and briefly described the capabilities of modern VAV systems, more detailed information about these systems can be found on the Breezart website.

VARIABLE AIR VOLUME - Variable air flow

Specialists from the company system groups implemented not one project using VAV systems of ventilation and air conditioning systems SYSTEMAIR both at the design and installation stage and the upgrade of existing systems.

Advantages of VAV - A variable consumption systems in front of CAV systems - permanent air flow:

Individual comfort of each room - The organization of air supply is carried out by the need from a certain external factor or their sum and priority: temperature T, humidity, CO2, movement.
Saving electricity - Maximum energy efficiency, saves up to 70% of electricity consumption.
Increases the resource of the equipment
Low system noise system

Consider three examples, from the objects implemented by us, the layouts of the VAV systems from advanced to simple.

In all three examples used supply and exhaust plants with recovery. The ventilation system control mode is carried out by maintaining the temperature of the exhaust air (maintaining the room temperature). The ventilation system controller itself prescribes the temperature of the supply air (Tmin and Tmax).

1. Example

The task delivered by the customer is an individual maintenance of accurate and continuous control of humidity and temperature T in each of the six residential premises: four bedrooms, a hall, a dining room.

This project was required to regulate six zones, the principle of operation of the system was implemented on the VAV-regulators of the OPTIMA air flow and the optimizer controller.

Air flow in this VAV system does not depend on the pressure in this system.

A variable flow regulators receive control signal (0 / 2-10V) from moisture sensors and temperature T installed indoors - VX M3 / h is required.
The moving stream of air creates a pressure drop, which is measured using Pito tube
The actual value of air flow rate M3 / h, obtained using a pressure drop sensor, enters the controller of the variable flow controller
The controller compares the actual air flow m3 / h. And the desired value, in the presence of deviations, sends a corrective signal to an electric drive that adjusts the valve cross section until the required air flow m3 / h. will not be reached
The optimizer controller receives a signal over the MP-BUS network from all VAV regulators and adjusts the operation of the fans.

TopVex TR_EL - Vertical supply and exhaust installation with a rotary heat recovery and electric heater
Aias Combox Module - Controller VAV Flow Regulator Optimizer
CO2RT WALL MOUNTING 0-2000 PPM - CO2 level transducers, humidity and temperature
Optima-R-Blc1 - A variable flow regulators
Mitsubishi Electric SUZ-KA_ Inverter - Compressor Condenser Block (CKB)
DXRE - freon cooler
PAC-IF012B-E - KKB controller
Carel Compactsteam is an isothermal humidifier.

2. Example

The task is supplied by the customer - maintaining accurate and continuous control of CO2 concentration and temperature T and in two sports halls.

In this project, two zones were required, the principle of operation was implemented according to the scheme - Air flow in this VAV system depends on the static pressure of the PA in this system.

Electric valve electric drives receive control signal (0 / 2-10V) from CO2 concentration sensors and temperatures T installed in sports halls
The air valve, changing the cross section, supplies the required air flow m3 / h.
The moving air flow creates a pressure drop of PA, which is measured by differential pressure drop sensors
Differential pressure sensors send a signal to the controller of the supply and exhaust installation, which in turn corrects the operation of the fans depending on the current requirement of air flow m3 / h.

Equipment installed on the object:

TopVex FR_HWL - Horizontal supply-exhaust installation with a rotary heat recuperator and water heater
VAV DUCT PRESSURE CONTROL - Differential pressure drop sensors
BELIMO LF 24-SR - electric drives 0-10V controlled converters of the CO2 level
DXRE - freon cooler
PAC-IF013B-E is the KKB controller.

3. Example

The task is supplied by the customer - maintaining accurate and continuous control of T temperature in the office space.

This project required to ensure the temperature of a single office space (Call Center). The principle of operation of the system is implemented according to the scheme controlled directly by the controller of the Corrigo ventilation system. The Corrigo controller settings allow you to change the air consumption of M3 / h. Depending on the deviation of the temperature T indoor.

Equipment installed on the object:

TopVex FS_EL - Suspended supply-exhaust installation with a recuperator and electric heater
DXRE - freon cooler
Mitsubishi Electric Puhz-Zrp_yka Inverter - Compressor Condenser Block (CKB)
PAC-IF013B-E - KKB controller

VARIABLE AIR VOLUME - Variable air flow

Specialists from the company system group implemented not one project using VAV ventilation and air conditioning systems as at the design and installation stage and the modernization of existing systems.

Advantages of VAV - A variable consumption systems in front of CAV systems - permanent air flow:

Individual comfort of each room - The organization of air supply is carried out by the need from a certain external factor or their sum and priority: temperature T, humidity, CO2, movement.
Saving electricity - Maximum energy efficiency, saves up to 70% of electricity consumption.
Increases the resource of the equipment
Low system noise system

Consider three examples, from the objects implemented by us, the layouts of the VAV systems from advanced to simple.

1. Example

This project was required to regulate six zones, the principle of operation of the system was implemented on the VAV-regulators of the OPTIMA air flow and the optimizer controller.

Air flow in this VAV system does not depend on the pressure in this system.

A variable flow regulators receive control signal (0 / 2-10V) from moisture sensors and temperature T installed indoors - VX M3 / h is required.
The moving stream of air creates a pressure drop, which is measured using Pito tube
The actual value of air flow rate M3 / h, obtained using a pressure drop sensor, enters the controller of the variable flow controller
The controller compares the actual air flow m3 / h. And the desired value, in the presence of deviations, sends a corrective signal to an electric drive that adjusts the valve cross section until the required air flow m3 / h. will not be reached
The optimizer controller receives a signal over the MP-BUS network from all VAV regulators and adjusts the operation of the fans.

TopVex TR_EL - Vertical supply and exhaust installation with a rotary heat recovery and electric heater
Aias Combox Module - Controller VAV Flow Regulator Optimizer
CO2RT WALL MOUNTING 0-2000 PPM - CO2 level transducers, humidity and temperature
Optima-R-Blc1 - A variable flow regulators
Mitsubishi Electric SUZ-KA_ Inverter - Compressor Condenser Block (CKB)
DXRE - freon cooler
PAC-IF012B-E - KKB controller
Carel Compactsteam is an isothermal humidifier.

2. Example

The task is supplied by the customer - maintaining accurate and continuous control of CO2 concentration and temperature T and in two sports halls.

This project was required to regulate the two zones, the principle of operation was implemented according to the scheme - air flow in this VAV system depends on the static pressure of PA in this system.

Electric valve electric drives receive control signal (0 / 2-10V) from CO2 concentration sensors and temperatures T installed in sports halls
The air valve, changing the cross section, supplies the required air flow m3 / h.
The moving air flow creates a pressure drop of PA, which is measured by differential pressure drop sensors
Differential pressure sensors send a signal to the controller of the supply and exhaust installation, which in turn corrects the operation of the fans depending on the current requirement of air flow m3 / h.

Equipment installed on the object:

TopVex FR_HWL - Horizontal supply-exhaust installation with a rotary heat recuperator and water heater
VAV DUCT PRESSURE CONTROL - Differential pressure drop sensors
BELIMO LF 24-SR - electric drives 0-10V controlled converters of the CO2 level
DXRE - freon cooler
PAC-IF013B-E is the KKB controller.

3. Example

The task is supplied by the customer - maintaining accurate and continuous control of T temperature in the office space.

Equipment installed on the object:

TopVex FS_EL - Suspended supply-exhaust installation with a recuperator and electric heater
DXRE - freon cooler
Mitsubishi Electric Puhz-Zrp_yka Inverter - Compressor Condenser Block (CKB)
PAC-IF013B-E - KKB controller