Ventilation with heat recovery experience of use. Energy-efficient building ventilation systems with heat recovery

Recovery in ventilation plays an important role, as it allows you to increase the efficiency of the system due to design features. There are different designs of recovery units, each of which has its own pros and cons. The choice of supply and exhaust ventilation system depends on what problems are being solved, as well as on the climatic conditions of the area.

Design features, purpose

Recovery in ventilation is quite new technology. Its action is based on the ability to use the removed heat to heat the room. This happens thanks to separate channels, so the air flows do not mix with each other. The design of recuperative units can be different; some types avoid the formation of condensation during the heat transfer process. The performance level of the system as a whole also depends on this.

Ventilation with heat recovery can produce high efficiency during operation, which depends on the type of heat recovery unit, the speed of air flow through the heat exchanger and how large the difference between the temperature outside and inside the room is. The efficiency value in some cases when ventilation system designed taking into account all factors and has high performance, can reach 96%. But even taking into account the presence of errors in the operation of the system, the minimum efficiency limit is 30%.

The purpose of the recuperative unit is the most efficient use of ventilation resources to further ensure sufficient air exchange in the room, as well as energy savings. Taking into account the fact that the supply exhaust ventilation with recovery operates most of the day, and also, taking into account that ensuring a sufficient frequency of air exchange requires considerable equipment power, the use of a ventilation system with a built-in recovery unit will help save up to 30% of electricity.

The disadvantage of this technique is its rather low efficiency when installed over large areas. In this case, electricity consumption will be high, and the performance of the system aimed at heat exchange between air flows may be noticeably lower than the expected limit. This is explained by the fact that air exchange occurs much faster in small areas than in large objects.

Types of recuperative units

There are several types of equipment used in the ventilation system. Each of the options has advantages and disadvantages, which must be taken into account even when forced ventilation with recovery is just being designed. There are:

Recuperator plate mechanism. It can be made on the basis of metal or plastic plates. Along with fairly high performance (efficiency is 75%), such a device is susceptible to icing due to the formation of condensation. The advantage is the absence of moving structural elements, which increases the service life of the device. There is also a plate type of recuperative unit with moisture-permeable elements, which eliminates the possibility of condensation. A feature of the plate design is that there is no possibility of mixing two air flows.

Ventilation systems with heat recovery can operate based on rotor mechanism. In this case, heat exchange between air flows occurs due to the operation of the rotor. The productivity of this design increases to 85%, but there is a possibility of air mixing, which can bring odors back into the room that are removed outside the room. The advantages include the ability to additionally dry the air, which makes it possible to use equipment of this type indoors special purpose with an increased level of importance, for example in swimming pools.
The chamber mechanism of the recuperator is a chamber that is equipped with a movable damper, which allows odors and contaminants to penetrate back into the room. However this type The design is very productive (efficiency reaches 80%).
Recuperative unit with intermediate coolant. In this case, heat exchange occurs not directly between two air flows, but through a special liquid (water-glycol solution) or plain water. However, a system based on such a node has low performance (efficiency below 50%). A recuperator with an intermediate coolant is almost always used to organize ventilation in production.
Regenerative unit based on heat pipes. This mechanism works using freon, which tends to cool, which leads to the formation of condensation. The performance of such a system is at an average level, but the advantage is that there is no possibility of odors and contaminants penetrating back into the room. Ventilation in an apartment with recuperation will be very effective due to the fact that it is necessary to maintain relatively small area. To be able to operate such equipment without negative consequences for it, it is necessary to select a model based on a recuperative unit, which eliminates the possibility of condensation. In places with a fairly mild climate, where the air temperature outside does not reach critical levels, the use of almost any type of recuperator is allowed.

Many buildings that are currently being built, both industrial and residential, have very complex infrastructure and are designed with maximum emphasis on energy conservation. Therefore, it is impossible to do without installing such systems as general air ventilation systems, smoke protection systems and air conditioning systems. To ensure effective and long-term service of ventilation systems, it is necessary to properly design and install a general air ventilation system, a smoke protection system and an air conditioning system. Installation of such equipment of any type must be carried out in compliance with certain rules. And in terms of technical characteristics, it must correspond to the volume and type of premises in which it will be used (residential building, public, industrial).

The correct operation of ventilation systems is of great importance: compliance with the deadlines and rules for carrying out preventive inspections, scheduled maintenance, as well as the correct and high-quality adjustment of ventilation equipment.

For each ventilation system put into operation, a passport and operational log are drawn up. The passport is drawn up in two copies, one of which is stored at the enterprise, and the other in the technical supervision service. The passport contains all the technical characteristics of the system, information about the repair work, copies of as-built drawings of ventilation equipment are attached to it. In addition, the passport reflects a list of operating conditions for all components and parts of ventilation systems.

All data from routine inspection of ventilation systems, including mandatory indicated in the operation log.

Operation of ventilation systems

Many buildings that are currently being built, both industrial and residential, have very complex infrastructure and are designed with maximum emphasis on energy conservation. Therefore, it is impossible to manage without installing ventilation systems, and in most cases, air conditioning. To ensure long-term and high-quality service of ventilation systems, it is necessary to choose the right ventilation. Installation of such equipment of any type must be carried out in compliance with certain rules. And in terms of technical characteristics, it must correspond to the volume and type of premises in which it will be used (residential building, public, industrial).

For each ventilation system put into operation, a passport and operational log are drawn up. The passport is drawn up in two copies, one of which is stored at the enterprise, and the other in the technical supervision service. The passport contains all the technical characteristics of the system, information about the repair work carried out, and copies of the as-built drawings of the ventilation equipment are attached to it. In addition, the passport reflects a list of operating conditions for all components and parts of ventilation systems.

Routine inspections of ventilation systems are carried out according to the established schedule. During routine inspections:

Defects are identified and corrected current repairs;

The technical condition of ventilation systems is determined;

Partial cleaning and lubrication of individual components and parts are carried out.

All data from a routine inspection of ventilation systems must be indicated in the operation log.

Also, during the work shift, the operating team on duty provides for scheduled overhaul maintenance of the ventilation systems. This service includes:

Start-up, regulation and shutdown of ventilation equipment;
Supervision of the operation of ventilation systems;
Monitoring the compliance of air parameters and supply air temperature;
Elimination of minor defects.

Commissioning of general air ventilation systems, smoke protection systems and air conditioning systems

The commissioning phase is very important stage, because it depends on the commissioning work quality work ventilation and air conditioning.

During commissioning, the work of the installation team is visible, and the parameters specified in the project, the equipment indicators are checked and compared with the indicators specified in the project documentation. During the inspection, a complete check of the technical condition of the installed equipment, the distribution and uninterrupted operation of adjustment devices, the installation of monitoring and diagnostic devices, and identification of errors in the operation of the equipment are carried out. If deviations are detected that are within normal limits, then readjustment does not occur, and the object is prepared for delivery to the customer, with all documents completed.

All masters of our company have specialized education, health and safety certificates, extensive work experience and have everything Required documents and evidence.

At the commissioning stage, we measure the air flow speed in the air ducts, noise level, test the quality of equipment installation, and adjust engineering systems in accordance with the project parameters, certification.

Start-up testing and adjustment of ventilation and air conditioning systems must be carried out by a construction and installation or specialized commissioning organization.

Certification of ventilation systems

A technical document drawn up on the basis of checking the operating condition of ventilation systems and equipment, carried out using aerodynamic tests, is called certification of the ventilation system.

SP 73.13330.2012 “Internal sanitary systems of buildings”, updated version of SNIP 3.05.01-85 “Internal sanitary systems” regulate the form and content of the ventilation system passport.

Obtaining a ventilation system passport, in accordance with the requirements of the above document, is mandatory.

Upon completion of the installation of ventilation systems, the customer receives a ventilation system passport.

A passport must be obtained for each ventilation system.

The passport is indispensable for registering purchased equipment, for correct operation, such equipment, in order to achieve the necessary sanitary and hygienic air parameters.

For the period established by law, this document is provided by the control and supervisory authority. Receipt of this document is indisputable evidence in resolving controversial issues with the relevant authorities.

Obtaining a ventilation system passport can be carried out as follows: separate species work, consisting of a complex of aerodynamic tests. The conduct of such events is regulated by the following regulations:

SP 73.13330.2012;
STO NOSTROY 2.24.2-2011;
R NOSTROY 2.15.3-2011;
GOST 12.3.018-79. “Ventilation systems. Methods of aerodynamic tests";
GOST R 53300-2009;
SP 4425-87."Sanitary and hygienic control of ventilation systems of industrial premises";
SanPiN 2.1.3.2630-10.

Due to the increase in tariffs for primary energy resources, recovery has become more relevant than ever. In air handling units with recovery, they are usually used following types recuperators:

plate or cross-flow recuperator;
rotary recuperator;
recuperators with intermediate coolant;
Heat pump;
chamber type recuperator;
recuperator with heat pipes.

Principle of operation

The operating principle of any recuperator in air handling units is as follows. It provides heat exchange (in some models - both cold exchange and moisture exchange) between the supply and exhaust air. The heat exchange process can occur continuously - through the walls of the heat exchanger, using freon or an intermediate coolant. Heat exchange can also be periodic, as in a rotary and chamber recuperator. As a result, the exhaust air is cooled, thereby heating the fresh supply air. The cold exchange process in certain models of recuperators takes place during the warm season and makes it possible to reduce energy costs for air conditioning systems due to some cooling of the supply air supplied to the room. Moisture exchange occurs between the exhaust and supply air flows, allowing you to maintain comfortable humidity in the room all year round, without the use of any additional devices - humidifiers and others.

Plate or cross-flow recuperator.

Heat-conducting plates of the recuperative surface are made of thin metal (material - aluminum, copper, stainless steel) foil or ultra-thin cardboard, plastic, hygroscopic cellulose. The supply and exhaust air flows move through many small channels formed by these heat-conducting plates in a counterflow pattern. Contact and mixing of flows and their contamination are practically excluded. There are no moving parts in the recuperator design. Efficiency rate 50-80%. In a metal foil recuperator, due to the difference in air flow temperatures, moisture may condense on the surface of the plates. In the warm season, it must be drained into the building's sewerage system through a specially equipped drainage pipeline. In cold weather, there is a danger of this moisture freezing in the recuperator and its mechanical damage(defrosting). In addition, the formed ice greatly reduces the efficiency of the recuperator. Therefore, when operating in the cold season, heat exchangers with metal heat-conducting plates require periodic defrosting with a flow of warm exhaust air or the use of an additional water or electric air heater. In this case, supply air is either not supplied at all, or is supplied to the room bypassing the recuperator through an additional valve (bypass). Defrost time averages from 5 to 25 minutes. A heat exchanger with heat-conducting plates made of ultra-thin cardboard and plastic is not subject to freezing, since moisture exchange occurs through these materials, but it has another drawback - it cannot be used for ventilation of rooms with high humidity for the purpose of drying them. The plate heat exchanger can be installed in the supply and exhaust system in both vertical and horizontal positions, depending on the requirements for the size of the ventilation chamber. Plate recuperators are the most common due to their relative simplicity of design and low cost.

Rotary recuperator.

This type is the second most widespread after the lamellar type. Heat from one air stream to another is transferred through a cylindrical hollow drum, called a rotor, rotating between the exhaust and supply sections. The internal volume of the rotor is filled with tightly packed metal foil or wire, which plays the role of a rotating heat transfer surface. The material of the foil or wire is the same as that of the plate recuperator - copper, aluminum or stainless steel. The rotor has a horizontal axis of rotation of the drive shaft, rotated by an electric motor with stepper or inverter control. The engine can be used to control the recovery process. Efficiency rate 75-90%. The efficiency of the recuperator depends on the flow temperatures, their speed and rotor speed. By changing the rotor speed, you can change the operating efficiency. Freezing of moisture in the rotor is excluded, but mixing of flows, their mutual contamination and transfer of odors cannot be completely excluded, since the flows are in direct contact with each other. Mixing up to 3% is possible. Rotary recuperators do not require high costs electricity, allow you to dry the air in rooms with high humidity. The design of rotary recuperators is more complex than plate recuperators, and their cost and operating costs are higher. However, air handling units with rotary heat exchangers are very popular due to their high efficiency.

Recuperators with intermediate coolant.

The coolant is most often water or aqueous solutions of glycols. Such a recuperator consists of two heat exchangers connected by pipelines with a circulation pump and fittings. One of the heat exchangers is placed in a channel with the exhaust air flow and receives heat from it. The heat is transferred through the coolant using a pump and pipes to another heat exchanger located in the supply air channel. The supply air receives this heat and heats up. Mixing of flows in this case is completely excluded, but due to the presence of an intermediate coolant, the efficiency coefficient of this type of recuperator is relatively low and amounts to 45-55%. Efficiency can be influenced using a pump by influencing the speed of the coolant. The main advantage and difference between a recuperator with an intermediate coolant and a recuperator with a heat pipe is that the heat exchangers in the exhaust and supply units can be located at a distance from each other. The installation position for heat exchangers, pumps and pipelines can be either vertical or horizontal.

Heat pump.

Appeared relatively recently interesting variety recuperator with intermediate coolant - so-called. thermodynamic recuperator, in which the role of liquid heat exchangers, pipes and pump is played by a refrigeration machine operating in heat pump. This is a kind of combination of a recuperator and a heat pump. It consists of two refrigerant heat exchangers - an evaporator-air cooler and a condenser, pipelines, a thermostatic valve, a compressor and a 4-way valve. Heat exchangers are located in the supply and exhaust air ducts, a compressor is necessary to ensure circulation of the refrigerant, and the valve switches the refrigerant flows depending on the season and allows heat to be transferred from the exhaust air to the supply air and vice versa. In this case, the supply and exhaust system can consist of several supply and one exhaust unit of higher capacity, united by one refrigeration circuit. At the same time, the capabilities of the system allow several air handling units to operate in different modes (heating/cooling) simultaneously. The conversion coefficient of the COP heat pump can reach values of 4.5-6.5.

Recuperator with heat pipes.

According to the principle of operation, a recuperator with heat pipes is similar to a recuperator with an intermediate coolant. The only difference is that not heat exchangers are placed in the air flows, but so-called heat pipes or more precisely thermosiphons. Structurally, these are hermetically sealed sections of copper finned pipe, filled inside with a specially selected low-boiling freon. One end of the pipe in the exhaust flow heats up, the freon boils in this place and transfers the heat received from the air to the other end of the pipe, blown by the flow of supply air. Here the freon inside the pipe condenses and transfers heat to the air, which heats up. Mutual mixing of flows, their pollution and transfer of odors are completely excluded. There are no moving elements; pipes are placed in flows only vertically or at a slight slope so that the freon moves inside the pipes from the cold end to the hot end due to gravity. Efficiency rate 50-70%. Important condition to ensure its operation: the air ducts in which the thermosiphons are installed must be located vertically one above the other.

Chamber type recuperator.

The internal volume (chamber) of such a recuperator is divided into two halves by a damper. The damper moves from time to time, thereby changing the direction of movement of the exhaust and supply air flows. The exhaust air heats one half of the chamber, then the damper directs the flow of supply air here and it is heated by the heated walls of the chamber. This process is repeated periodically. The efficiency ratio reaches 70-80%. But the design has moving parts, and therefore there is a high probability of mutual mixing, contamination of flows and transfer of odors.

Calculation of recuperator efficiency.

IN technical specifications For recuperative ventilation units, many manufacturers usually provide two values of the recovery coefficient - based on air temperature and its enthalpy. The efficiency of a recuperator can be calculated based on temperature or air enthalpy. Calculation by temperature takes into account the sensible heat content of the air, and by enthalpy, the moisture content of the air is also taken into account (its relative humidity). Calculation based on enthalpy is considered more accurate. For the calculation, initial data is required. They are obtained by measuring the temperature and humidity of the air in three places: indoors (where the ventilation unit provides air exchange), outdoors, and in the cross section of the supply air distribution grille (from where treated outdoor air enters the room). The formula for calculating the recovery efficiency by temperature is as follows:

Kt = (T4 – T1) / (T2 – T1), Where

Kt– recuperator efficiency coefficient by temperature;
T1– outside air temperature, oC;
T2– temperature of the exhaust air (i.e. indoor air), °C;
T4– supply air temperature, oC.

Enthalpy of air is the heat content of air, i.e. the amount of heat contained in it per 1 kg of dry air. Enthalpy is determined with using i-d diagram of the state of humid air, plotting on it the points corresponding to the measured temperature and humidity in the room, outside and supply air. The formula for calculating the recovery efficiency based on enthalpy is as follows:

Kh = (H4 – H1) / (H2 – H1), Where

Kh– recuperator efficiency coefficient in terms of enthalpy;
H1– enthalpy of outside air, kJ/kg;
H2– enthalpy of exhaust air (i.e. indoor air), kJ/kg;
H4– enthalpy of supply air, kJ/kg.

Economic feasibility of using air handling units with recovery.

As an example, let’s take a feasibility study for the use of ventilation units with recovery in systems supply and exhaust ventilation car showroom premises.

Initial data:

object – car showroom with a total area of 2000 m2;
the average height of the premises is 3-6 m, consists of two exhibition halls, an office area and a station Maintenance(ONE HUNDRED);
For supply and exhaust ventilation of these premises, duct-type ventilation units were selected: 1 unit with an air flow rate of 650 m3/hour and a power consumption of 0.4 kW and 5 units with an air flow rate of 1500 m3/hour and a power consumption of 0.83 kW.
The guaranteed range of external air temperatures for ducted installations is (-15…+40) оС.

To compare energy consumption, we will calculate the power of a duct electric air heater, which is necessary to heat the outside air in the cold season in a traditional type air-handling unit (consisting of check valve, duct filter, fan and electric air heater) with an air flow of 650 and 1500 m3/hour, respectively. At the same time, the cost of electricity is 5 rubles per 1 kW*hour.

The outside air must be heated from -15 to +20°C.

The power of the electric air heater was calculated using the heat balance equation:

Qн = G*Cp*T, W, Where:

Qн– air heater power, W;
G- mass air flow through the air heater, kg/sec;
Wed– specific isobaric heat capacity of air. Ср = 1000kJ/kg*K;
T– difference in air temperature at the outlet of the air heater and the inlet.

T = 20 – (-15) = 35 oC.

1. 650 / 3600 = 0.181 m3/sec

p = 1.2 kg/m3 – air density.

G = 0.181*1.2 = 0.217 kg/sec

Qn = 0.217*1000*35 = 7600 W.

2. 1500 / 3600 = 0.417 m3/sec

G = 0.417*1.2 = 0.5 kg/sec

Qn = 0.5*1000*35 = 17500 W.

Thus, the use of ducted units with heat recovery in the cold season instead of traditional ones using electric air heaters makes it possible to reduce energy costs with the same amount of supplied air by more than 20 times and thereby reduce costs and accordingly increase the profit of a car dealership. In addition, the use of recuperation units makes it possible to reduce financial expenses energy consumption for space heating in the cold season and air conditioning in the warm season by approximately 50%.

For greater clarity, we will make a comparative the financial analysis energy consumption of supply and exhaust ventilation systems for car dealership premises, equipped with duct-type heat recovery units and traditional units with electric air heaters.

Initial data:

System 1.

Installations with heat recovery with a flow rate of 650 m3/hour – 1 unit. and 1500 m3/hour – 5 units.

The total electrical power consumption will be: 0.4 + 5*0.83 = 4.55 kW*hour.

System 2.

Traditional ducted supply and exhaust ventilation units - 1 unit. with a flow rate of 650m3/hour and 5 units. with a flow rate of 1500m3/hour.

Total electric power installation at 650 m3/hour will be:

fans – 2*0.155 = 0.31 kW*hour;
automation and valve drives – 0.1 kW*hour;
electric air heater – 7.6 kW*hour;

Total: 8.01 kW*hour.

The total electrical power of the installation at 1500 m3/hour will be:

fans – 2*0.32 = 0.64 kW*hour;
automation and valve drives – 0.1 kW*hour;
electric air heater – 17.5 kW*hour.

Total: (18.24 kW*hour)*5 = 91.2 kW*hour.

Total: 91.2 + 8.01 = 99.21 kW*hour.

We assume the period of use of heating in ventilation systems is 150 working days per year for 9 hours. We get 150*9 =1350 hours.

Energy consumption of installations with recovery will be: 4.55 * 1350 = 6142.5 kW

Operating costs will be: 5 rubles * 6142.5 kW = 30712.5 rubles. or in relative terms (to total area car showroom 2000 m2) in the expression 30172.5 / 2000 = 15.1 rub./m2.

Energy consumption of traditional systems will be: 99.21 * 1350 = 133933.5 kW Operating costs will be: 5 rubles * 133933.5 kW = 669667.5 rubles. or in relative terms (to the total area of the car dealership of 2000 m2) 669667.5 / 2000 = 334.8 rubles/m2.

Supply and exhaust ventilation with heat recovery is a system that allows you to establish a reliable change of exhaust air in the room. Installation of equipment allows you to heat the air entering the room using the temperature of the outlet flow. The cost of purchasing and installing the system quickly pays off.

It is important to know the main points when selecting and installing equipment.

What is heat recovery?

The air recuperator releases heat from exhaust gases. The two flows are separated by a wall through which heat exchange occurs between moving air flows in a constant direction. Important characteristic equipment is the level of efficiency of the recuperator. This value for different types of equipment is in the range of 30-95%. This value is directly dependent on:

designs and types of recuperator;
the temperature difference between the heated exhaust air and the temperature of the carrier behind the heat exchanger device;
accelerating the flow through the heat exchanger.

Advantages and disadvantages of a ventilation system with a heat exchanger

Such equipment allows:

make a permanent shift air masses in rooms of different sizes;
if the residents need it, a heated flow can be supplied;
the incoming oxygen is constantly purified;
if desired, it is possible to install equipment with the ability to humidify the air in the rooms; such systems have a channel for removing condensate;
By recovering heat and selecting equipment with sufficient power, it is possible to significantly reduce the cost of paying for electricity.

Among the disadvantages of the system, several points can be highlighted:

increased noise level during fan operation;
when installing cheap equipment, there is no way to cool the incoming air during hot periods;
it is necessary to constantly monitor and remove condensate.

The principle of operation of the ventilation system

Such ventilation with heat recovery allows reducing the load on the air conditioning system of buildings during the hot season. Conditioned air from the room, when passing through the heat exchanger, lowers the temperature of the atmospheric flow from the street. IN winter period, the outboard flow is heated according to this scheme.

Installation in buildings with large area and a general air conditioning system. In such places, the level of air exchange can exceed 700-800 m 3 / h. Such installations have impressive dimensions, so you will need to prepare a separate room in the basement, on the ground floor or attic. If installation in the attic is necessary, it will need to be additionally soundproofed to prevent heat loss and condensation in the air ducts.

The ventilation system with recovery is manufactured in several types; we will analyze the advantages and disadvantages of each of them.

Types of air recovery devices

For a better comparison, we present the types of recuperators in a separate table.

type of instalation	Short description	Advantages	Flaws
Lamellar with plastic and metal plates	The outgoing and incoming flow passes on both sides of the plates. The average efficiency level is 50-75%.	The streams do not touch directly. There are no moving parts in the circuit, so this design is reliable and durable.	Not identified
Lamellar, with ribs made of water-conducting materials.	The efficiency of the devices is 50-75%, air flows on both sides.	There are no moving parts. Air mass flows do not contact each other. There is no condensation in the system.	There is no possibility of dehumidifying the air in the serviced room.
Rotary	High level of efficiency 75-85%. The flows pass through separate foil-coated channels.	Significantly saves energy and can reduce air humidity in serviced areas.	Possible mixing of air masses and penetration unpleasant odor. Requires maintenance and repair complex design with rotating parts.
Air recuperator with exposure to intermediate coolant	A solution of water and glycol is used as a coolant or filled with purified water. In such a scheme, the exiting gas gives off heat to the water, which heats the incoming flow. Designed for servicing industrial premises.	There is no contact between the flows, so their mixing and the flow of exhaust gases are excluded.	Low level of efficiency
Chamber recuperators	A damper is installed in the chamber of the device, capable of increasing the magnitude of the passing flow and changing the vector of its direction.	Thanks to design features, this type of equipment has a high level of efficiency, 70-80%.	The flows are in contact, so the incoming air may become contaminated.
Heat pipe	The device is equipped with a system of freon-filled tubes.	There are no moving mechanisms, the service life is increased. The air comes in clean, there is no contact between the flows.	Low level of efficiency, it is 50-70%.

A recovery unit with heat pipes is available for individual small rooms in a buiding. They do not require an air duct system. But in this case, if the distance between the flows is insufficient, incoming flows may be removed and there will be no circulation of air masses.

List of possible problems after installing the system

Critical problems do not arise if recuperative ventilation is installed in the building. The main malfunctions are eliminated by the system manufacturers under warranty, but several “troubles” can overshadow the joy of the owners of buildings and premises after installing the equipment for the supply and exhaust air ventilation system. These include:

Possibility of condensation formation. When passing air mass flows from high temperature heating and contacting them with cold atmospheric air, in a closed chamber, drops of water fall out on the walls of the chamber. At sub-zero temperature outside, the fins of the heat exchanger freeze, and the movement of flows is disrupted, reducing the efficiency of the system. If the channels are completely frozen, the operation of the device may stop.
System energy efficiency level. Supply and exhaust systems equipped with an additional heat exchanger of various types require electricity to operate. Therefore it is necessary to carry out accurate calculations equipment different types specifically for the premises that will be served by the system.

You should not save money when purchasing, and purchase a device in which the level of energy savings will exceed the cost of operating the equipment.

Full payback period for an air ventilation system. The period for a full refund of the funds spent on the purchase and installation of equipment directly depends on the previous point. It is important for the consumer that these costs are recouped within 10 summer period. Otherwise, equipping a room or building with an expensive ventilation system is not cost-effective.

During this period, it will be necessary to carry out repairs and possible replacement of system parts and additional costs for their purchase and payment for their replacement.

Ways to prevent recuperator freezing

Some types of devices are made to prevent severe freezing of the heat exchanger surfaces. At low temperatures outside, ice build-up can completely block the access of fresh air to the room. Some systems begin to become overgrown with a crust of ice when the outside temperature drops below 0 0 .

In this case, the flow leaving the room is cooled to a temperature below the dew point and the surfaces begin to freeze. To resume operation of the device, you will need to raise the temperature of the incoming flow to positive values. The ice crust will collapse, the equipment will be able to continue working.
To avoid such situations, supply and exhaust units with a built-in heat recuperator can be protected from such damage using several methods:

To protect the device, it may be necessary to additionally equip the installation with an electric air heater. It does not allow the outgoing air masses to cool below the dew point and prevents the appearance of water droplets and the formation of ice;
most reliable method, eliminating the possibility of freezing of the recuperator fins is the equipment of the device with an electronic control system for defrosting circuit, the activation of which takes into account several parameters. To do this, it may be necessary to set the date for switching on the electric heaters of the incoming air, at the first sub-zero temperatures.
You can install a sensor that reacts to cold air and turns on air heating elements in the ventilation system. In any case, the operation of air heating devices in ventilation is cyclical, only in the cold season. When the supply ventilation is turned on, the incoming flow and exhaust gases removed from the room are heated.

After a certain period of time, a shutdown occurs supply fan. At this time, the incoming flow in the recuperator is heated due to the temperature of the outlet air, which is displaced using exhaust fan. This operating principle of the heating circuit operates automatically throughout the cold period of the year.

To prevent ice from forming on the device, we recommend purchasing a plate-type heat exchanger with plastic ribs.

A method for independently calculating the power of supply and exhaust ventilation

First of all, it is necessary to determine the volume of all air flows required to create comfortable conditions. This can be done in several ways:

You can make a calculation based on the total area of the building, without taking into account the occupants. The following calculation scheme is used here - within an hour, for each m2 of total area, 3 m3 of air should be supplied.
Based on sanitary standards, for a comfortable stay, at least 60 m3 must be supplied per hour for each person living in the room; for arriving guests, another 20 m3 must be added.
Based on the building standards of 08/2/01-89, standards for the frequency of air replacement in a room of a certain area per hour have been developed. Here the calculation is made taking into account the purpose of the buildings. To do this, it is necessary to determine the frequency product full replacements air masses and volume of the entire room or building.

In conclusion, we note.

Regardless of the pronunciation of the word ventilation, in English or other languages, the main task of the supply and exhaust system with a heat recuperator is to create comfortable conditions for people in the room. Therefore, having decided on the calculation required power and the type of heat exchanger, you can safely start equipping your home reliable system ventilation.

To increase service life, air purification filters can be added to the circuit. But you should remember that it is easier to prevent breakdowns by carrying out timely maintenance and care than to spend money on repairs or purchasing new equipment.