This equipment is part of ventilation systems. These units are mounted on roofs, and they are necessary to purify the air in residential or industrial buildings. Ventilation and removal of "bad air" from the premises is carried out using special technological channels. Roof fans and their use are optimal in rooms with fireplaces, poorly ventilated rooms and in other cases.

For residential buildings, ventilation problems have become relevant for the last 2 years. It was during this period of time that "European-style repairs" came into fashion. They are often done poorly. As a result, the room is sealed as tightly as possible with double-glazed windows, which results in a shortage fresh air. This leads to various fungal and other deposits on the walls of bathrooms, toilets and other rooms. This can sometimes lead to very serious consequences and even allergies.

Today, more and more people care about a good microclimate in apartments, houses, and production workshops. Therefore, the demand for climate control equipment and ventilation systems has risen sharply. In addition, there is a consistently good demand today for roof ventilation units for private households, multi-storey buildings, public or industrial facilities.

Applications for roof fans

This ventilation equipment is widely used to organize ventilation air flows in any conditions. Often these systems are purchased for installation in residential buildings with a large number of apartments, industrial facilities, supermarkets, restaurants, office buildings, various warehouses, swimming pools and garage buildings. These devices are installed on rooftops. This allows:

• Significantly save usable volume in various types premises, which can then be successfully used for other purposes;
• Minimize the length or completely get rid of the air ducts.

Ventilation communications using this technique are simple and most convenient. From a huge number existing options various exhaust ventilation devices– fans for installation on the roof are the most economical.

Since these devices perform the functions of ventilation equipment, the tasks they solve are the same as those of typical ventilation systems.

Functional features of a roof fan

These units can completely remove humid air from the premises, as well as unpleasant odors that accumulate in household and living rooms. Also, this type of equipment very successfully copes with odors from sewerage systems, removes various fumes that are formed as a result of work. geysers, stoves, fireplaces. This technique can easily cope with the exhaust air that is generated as a result of work. home appliances such as vacuum cleaners or hoods.

In addition to working with odors, the device performs the prevention of various fungal growths and molds on walls, corners, and in utility rooms. If you need a constant flow of air from the street, then there is simply no better device for this.

In case of fires, in rooms with fireplaces, these devices will easily ventilate the room and remove the smoke. Today there are special modifications of these devices to improve draft in fireplaces.

Roof fan impeller differences

Like other mechanisms, these units are able to create air flows. They do this with the help of impellers. These parts are of the following types:

In the case of radial impellers, it is important that the impeller blades are made of a corrosion-resistant material. So, the aggressive impact of the external environment will not have negative impact for equipment.

Axial devices are characterized by low efficiency. They are used in general ventilation systems. Radial equipment has higher efficiency indicators. These are more powerful roof fans and their use is most relevant in exhaust systems, that is, where aerodynamic drag very high.

Design features of roof fans

If we consider circuit diagram, then these devices consist of an engine, a casing, a base, a confuser.

As an electric motor, asynchronous three-phase motors are used. The casing performs the function of forming outgoing air flows. Wheels are also mounted in the casing. The base is used for mounting the structure and its strong fixation on a concrete or brick site. It is worth noting that before installing this unit, the site must be prepared in advance.

The confuser is a special bell that collects and draws air from the room.

In addition to these main components, the design includes additional details. This is a deflector. Its function is to protect the ventilation ducts from natural precipitation. It is mounted inside the body of the model.

Also in the system case there are thermal sensors. They are designed to monitor the temperature of the electric motor. This prevents the unit from overheating.

Installation rules

Roof fans often have very large overall dimensions. Some models can reach up to 1.5 meters in diameter. That is why the installation of these devices must follow the basic rules.

It is best to install on a hard roof. To do this, you need to prepare in advance special load-bearing structures on air ducts or mines. Usually these load-bearing parts are arranged at the end of the duct channel.

On the soft top installation should be carried out according to individual possibilities and schemes. Here the options differ according to the situation.

If you have to install the system at the junction with concrete or brick buildings, you must first waterproof the wall. In order for the device not to collect growths from snow, special insulated deflectors must be mounted at the exits.

Varieties of roof ventilation systems

Models are distinguished by overall dimensions, performance level, device power, sound pressure strength. Among the most roofing models, the following can be distinguished:

• Axial devices for mounting on industrial or administrative buildings;
• Blood devices. They are used exclusively in residential buildings and in production;
• Equipment series VKRM and VKR. These series are designed to remove air volumes through duct networks or from various rooms;
• You can also highlight the devices that are installed in buildings that use open fire for heating, cooking.

Do not install this equipment on fireplace or stove chimney systems.

How to choose roof fans

The choice of these devices is difficult process. In order to purchase the necessary roof fans and their application was the task, you need to consider the main points.

When choosing, it is important to consider the number of floors. For one-story buildings, axial models can be used. In case the building has more than one floor, then only radial equipment.

Also, when choosing, it is necessary to take into account the amount of heat load, for example, in case of fire. For residential premises, it is about 300 degrees. For offices - up to 400 degrees. For industrial and warehouse buildings– the volume is up to 450 degrees.

The place where the system will be mounted is also important. Smoke removal equipment will perform its functions perfectly and in one-story houses and in multi-storey buildings.

In order not to make mistakes when choosing and not to overpay for unnecessary functions, it is better to check all the points once again before purchasing. It will not be superfluous to get advice from an expert on this equipment. But the information provided is enough to select the required device.

Description:

Rooftop (rooftop) ventilation and heating units are autonomous units, the manufacture and assembly of which, including electrics and automation, are carried out by the manufacturer. Such installations are transported and delivered as a single unit, ready for installation and commissioning. Since its inception, such systems have been designed to perform the basic functions of ventilation with the possibility of complete or partial processing of the supply air: heating, cooling, humidification, dehumidification, cleaning.

Roof ventilation and heating units

Technology and methods of application

Rooftop (rooftop) ventilation and heating units are autonomous units, the manufacture and assembly of which, including electrics and automation, are carried out by the manufacturer. Such installations are transported and delivered as a single unit, ready for installation and commissioning. Since its inception, such systems have been designed to perform the basic functions of ventilation with the possibility of complete or partial processing of the supply air: heating, cooling, humidification, dehumidification, cleaning.

The manufacturing technology of roof ventilation and heating installations, constantly developing, in last years has reached a level where, in terms of application methods, they fully meet the most complex and diverse requirements today. Accordingly, the scope of their application has significantly expanded.

The development of technologies has contributed to a significant expansion of the range of functions performed. Today, they include those that, just a few years ago, were considered the exclusive prerogative of the so-called "applied" installations, assembled directly on site according to individual projects.

In addition to the functions listed above, modern roof ventilation and heating installations, at least in most high-performance systems, can include almost any equipment. For example, drying systems with a rotary heat exchanger, natural gas heating systems equipped with a burner or a heating boiler and an accumulator hot water, heat exchangers of free cooling (free cooling) of outdoor air, units for mixing outdoor air with recirculation air and many others. As a rule, next to models that provide only cooling, versions with heat pumps are installed.

To the same extent, the range of ways to regulate the operation of these units has expanded. Now the installation can be controlled via the interface of "Automatic life support systems for buildings and structures" (Building Automation) or from remote control centers via a telephone line via a modem.

All these functions, at least for medium and high power installations, can be selected and ordered by the customer or designer on a "mix and match" basis (individual selection from a certain number of components) in order to assemble a plant that meets the requirements of a particular project. The cooling capacity of today's rooftop units ranges from 5 to 600 kW per unit. Small capacity systems are in the greatest demand, as the user prefers that not one, but several systems are installed at the facility. Most often, this is done in order to rationally divide the facility into service areas and to ensure reliability, in order to avoid the risk of a complete shutdown of the ventilation and heating system of the facility in the event of a breakdown or accident.

If earlier manufacturers offered a lot of roof ventilation and heating units with a wide coverage radius, now this offer has noticeably narrowed. Most of the units offered are zone type. This was facilitated by the introduction of variable air flow (VAV) systems and, more recently, variable air flow and temperature (VVT) systems, which made it possible to cover all service areas of the facility with zone-type units.

In systems with variable air flow, supply fans can be equipped with variable power motors or, even more simply, with air intake dampers that maintain the air flow at a given level.

Most rooftop ventilation and heating systems are equipped with hermetically sealed steam compression cooling circuits. So far, R22 has been most commonly used as a coolant, although HFC group compositions are also sometimes used.

The system provides priority cooling of the condenser before air.

Most wide application found cooling condensers of an alternative type hermetic and semi-hermetic. Recently, condensers with spiral fins (scroll) are becoming more common.

One or more cooling circuits

The number of cooling circuits, on the basis of which the ventilation and heating unit is built, is determined by the indicator of the output cooling power and, consequently, by the size of the unit itself. Most often, systems with one or two hermetic compressors are used to provide small capacities and with semi-hermetic compressors for large ones.

The structural scheme of the roof ventilation and heating installation of medium-high power is shown in fig. 1. The figure shows that the condenser drive unit is located on the end of the unit, while the evaporator unit, including the supply fan, is located on the opposite side. Between them, a mixer, an outdoor air intake unit, a heat exchanger and a restart fan are installed.

On fig. 2 is a sectional view of a real plant having the characteristics described. It is equipped with two hermetic condensers and as many cooling circuits. The system is equipped with a gas air heater to provide air heating. There is also exhaust fan, allowing you to remove up to 100% of the air flow.

Of course, the system configuration may vary depending on the cooling capacity and design features object, as shown in Fig. 3.

This unit is still on the market today. This unit is medium-low power, equipped with a gas air heater and only one compressor (scroll), has one cooling circuit.

Almost always, when the installation has two cooling circuits, evaporators with two separate sections are used.

The sections can be divided vertically or installed face to face, in order to cover the entire heat exchange surface in any case. As an alternative to this solution, sometimes the pipes of both circuits are arranged so that they cover the entire surface not only in height, but also in depth.

In essence, the choice of solution determines whether the system will be able to control relative humidity levels even at partial load, whether large or small.

Cooling capacity management

The control of the cooling capacity of the system, which, as a rule, includes hermetic compressors (scroll), is carried out by stopping and starting the compressors at the command of the thermostat installed in the served room.

But semi-hermetic compressors allow you to provide a change in power by turning off part of the cylinders. Another measure used in particular to ensure continuous operation at low loads is the hot gas bypass.

The combination of power control and compressor shutdown allows for the required heat load in normal operation.

The need to take into account climatic conditions, when in the serviced premises it is necessary to maintain a low level of relative humidity (about 40%) - for example, in crowded restaurants or departments of supermarkets filled with refrigerated counters - prompted the development of new technologies, which are based on the use of chemical adsorbents, liquid or solids (in particular, the RCI mentioned above).

In addition, cooling loop technologies have also been developed for commercially available units to make direct expansion systems energy competitive at low relative humidity levels. The cooling circuit in fig. 4 represents one of modern solutions system organization.

As can be seen in the figure, a coolant heat exchanger is installed under the evaporator at the outlet of the condenser. Cold air at the outlet of the evaporator cools the liquid which enters the evaporator in a form that is more suitable for removing the "latent" heat load. The cold treatment unit is switched on and off by means of a solenoid valve in the coolant circuit. The valve is controlled by a hygrostat installed in the serviced room.

Thus, dehumidification is switched on at full capacity only when it is really needed. With this configuration, according to the manufacturers, the unit can provide a relative humidity level of up to 40% and remain quite attractive in terms of energy consumption compared to other systems traditionally used for this purpose, in particular, heating pipes (heat pipes).

roof effect

The characteristics of roof ventilation and heating units, as well as all other air-cooled units mounted on the roof of a building, are influenced by the special conditions that form just at the roof level on hot days. On a black tar-covered roof, layers of still air can form, having a temperature of 10 o C or more above the temperature of the outside air. As a result, on hot days, the efficiency of the units can drop by 10% compared to passport indicators. In some cases, the system may stall or not start due to the operation of the high pressure switch.

It should be taken into account that, taking into account the operating characteristics of air-cooled machines, the condensing temperature, as a rule, is 14 - 16 o C higher than the outside dry bulb temperature. At an air temperature of 32 0C, the overheating of the lower layers, due to the effect of a dark roof, can reach 42 o C. Therefore, the condensation temperature of the unit will jump to 56 Є 58 o C, and in this mode, few installations can operate.

For the same reasons, if the units are equipped with electronic fan speed control units, these units must be equipped with an appropriate cooling system, since they are usually not designed for hard temperature regime roof systems.

Some of the steps taken during the construction works, can minimize the manifestations of this phenomenon. To cover the roof areas in the area where rooftop units are installed, materials of light reflective tones should be used.

Large capacities and special requirements

There are various configurations of roof ventilation and heating installations. The variety is determined by the applied conditions and special requirements for the power of the units. The constructive choice in each individual case is determined by the specific requirements for the life support of buildings and structures.

High power units are fully assembled at the factory, where they are tested and pre-sales prepared. Then they are disassembled into separate nodes and delivered to the facility.

The system shown in fig. 5 has been specifically designed to handle 100% outside air. In its composition - refrigerator air-cooled and the air handling unit itself, equipped with filters, heat exchangers and a fan. Both nodes are mounted on the same platform. The unit provides control over the level of humidity in the serviced premises and the extraction of heat from the exhaust air. The manufacture of units with a cooling capacity of 700 to 2000 kW (it may seem incredible, but in America there is one manufacturer of systems of this capacity) takes on a completely different scale, as can be seen in Fig. 6.

In fact, these are already several machine rooms under one roof that need to be installed at the facility. Screw compressors are used in installations of this size. Fan blades are typically winged, which reduces noise levels.

They try to equip such installations with as many life support systems as possible for the building, such as air conditioning, ventilation, heating and hot water supply. Most often, such installations provide access and a certain internal space for service personnel.

Coating and materials

Typically, rooftop units are protected from above with epoxy-coated galvanized steel sheet, which is insensitive to UV rays. Some manufacturers use peralluman for this purpose.

From the inside, the system is equipped heat-insulating mats typically 25 to 50 mm thick around the evaporator and supply fan to control condensation and heat exchange with the outside.

Some manufacturers offer such installations, where in general all the outer walls are made of two panels, between which a heat-insulating material is laid. In these cases, the thickness of the panels also ranges from 25 to 50 mm.

Double-wall units, although more expensive than conventional systems, meet modern requirements for the hygiene of the treated air more fully. Actually thermal insulation material on the inside, it is often impregnated with moisture and dust and, therefore, forms an environment favorable for the growth of mold and fungus.

For all types of installations, air tightness, atmospheric precipitation and melt waters, because due to the location and its rectangular shapes in winter period significant snow masses accumulate on rooftop installations.

Finally, one should keep in mind the aggressive nature of the impact of atmospheric reagents on the materials used in the manufacture of aggregates, especially taking into account the general pollution of the atmosphere.

Access panels are fixed with screws on standard units, quick-release elements are used on upgraded models. In other cases, the panels are mounted on hinges and can be easily opened to form convenient entrance doors.

In installations of medium-low power, air is supplied and extracted from them, as a rule, in a horizontal direction. For systems with higher power, you can most often choose the direction of air supply - horizontally or vertically downwards. In the latter case, the neck of the air ducts is covered by the dimensions of the system and passes through the frame of the unit.

Heat exchangers are usually made of copper (piping) and aluminum (fins). Taking into account the general pollution of the atmosphere, heat exchangers are often painted with special protective compounds based on phenolic or epoxy resins. For operation in coastal regions, all-copper batteries are recommended.

Platform and location

Roof ventilation and heating units of medium and medium-high power are mounted on a special platform. In the case when the intake and air supply are carried out in the vertical direction, the air duct channels do not go beyond the platform perimeter (Fig. 7).

The role of the platform is extremely important. In addition to forming a supporting area, it ensures the sealing of the system, since it has a bituminous base and increases the degree of water tightness of the roof. In all cases, the platform should rise slightly above the roof level so that in case of intense rain or snow, water cannot seep inside in places where the unit is not tightly mounted on the platform.

Obviously, all work on sealing and sealing of fasteners must be carried out at the stage of installation of the system in accordance with the recommendations of the manufacturer of the units.

Recommended at the stage installation work work out a solution to the problem of penetration of noise from operating units into serviced premises. It should be noted that if the unit is located directly above the serviced room, and the air ducts have a minimum length, then with noticeable cost savings, the noise of the units will be very noticeable. In these cases, it is recommended to equip the inlet and outlet pipes of the machines with appropriate silencers. In general, in order to avoid problems of this kind, it is best to locate the units at a distance from service areas, for example, above corridors or office premises. Another important aspect is the location of the system relative to the exhaust openings of kitchens and toilets. It seems necessary to determine the wind rose, after which the installation distances of the system are calculated taking into account the dominant directions of air mass movement. Emissions should not be drawn into the units and re-directed to the premises.

Winds can affect the operation of the condenser fans and therefore the cooling efficiency of the units. When there is wind, the fixed fans begin to rotate. If the mechanism is electrically activated during wind-driven rotation, single-phase fans most often continue to rotate in the wind-driven direction. Therefore, if the direction of such rotation is wrong, the passage of air through the condenser will be blocked or very limited with all the troubles that follow from this.

What happens with three-phase fans is different: they have a fixed side of rotation and if the wind rotates in the opposite direction when the mechanism is not running, then when the engine is started, the force created to overcome the force of the wind can damage the drive or the blades.

In this regard, in places where they blow strong winds, it is recommended to install additional protection for the capacitor assembly.

Air distribution

The distribution of air from roof ventilation and heating units is carried out through low-velocity air ducts with low pressure. Horizontal air ducts are discharged from the vertical supply shaft, which exits through the roof, and are laid at the level of ceilings. The norms and rules of installation work do not differ from the work on laying and equipping conventional ventilation systems. Conventional air ducts made of sheet steel, fiberglass and "sandwich" type are used. As a rule, the removal of air from the room is carried out from the space between the ceiling and false ceiling and therefore does not require laying special air ducts.

Systems with adjustable air flow (VAV) or with controlled flow and temperature (VVT) are widely used abroad, where special attention is paid to the division of an object into service areas and, consequently, the possibility of controlling the air temperature in the room at the request of consumers.

On fig. 8 shows a diagram of a rooftop unit with adjustable airflow. The supply air enters the VAV unit, equipped with mechanically operated dampers, from where the air is in turn fed to the air outlets of the served room. A flow and temperature controlled VVT installation equipped with motorized dampers is shown in fig. nine.

In devices of this type, two operating modes are provided - cold and warm. Switching from one to another is carried out by the system adjustment unit in accordance with the actual operational needs.

As with most free-standing direct expansion air conditioners, the average ratio of airflow to cooling output is about 200 m 3 /h per kW of cooling output, with a tolerance of about ±20%. At the same values, installations with a lower air flow - about 160 m 3 /h - allow for higher moisture absorption and, therefore, are more suitable for loads predominantly in "latent" heat, including quite intense ones.

Conversely, more powerful units - from 240 m 3 /h per kW - provide less dehumidification and can be recommended for operation under conditions of quite noticeable loads.

Application prospects

Roof ventilation and heating units can rightfully claim to be successfully used for the implementation of very complex technological tasks. At civil facilities, such installations work with high quality as part of the life support systems of buildings, while energy consumption does not exceed the performance of traditional systems. The fact that such a statement is true is evidenced by the widespread use of units of this kind in the United States. The appearance on the market of modern systems with adjustable air flow and temperature VVT ​​is another evidence in favor of choosing these units, which give the advantage of independent zone control. It would be logical to expect that in Italy, roof ventilation and heating units will find successful application for a wide range of users.

Reprinted from RCI magazine, December 1997

Translation from Italian by S.N. Bulekov

Rooftop ductless air conditioners LM PRO ORION TOP is an advanced line of supply and exhaust recuperative outdoor units designed for installation on the roofs of buildings.
Rooftop ductless air conditioners are an innovative product in the ventilation equipment market. To create this series, modern technologies, the latest design solutions and many years of experience were used, which made it possible to obtain a whole range of advantages.

The vortex adjustable air diffuser, depending on the operating mode, can change the shape of the air jet.

Heating mode

The supply air temperature is higher than the room air temperature. Consequently, the air, having been distributed, rises. The greater the temperature difference between the supply air and the room air, the less swirling it should be to ensure optimal range and air supply directly to the working area

Isothermal mode

The supply air temperature is equal to the room air temperature.

Cooling mode

The supply air temperature is lower than the room air temperature. The air is distributed horizontally parallel to the ceiling. Having distributed, the air descends down - into the working area, without creating a feeling of drafts.

Designed for operation in large facilities with large open spaces and high ceilings - industrial premises, warehouses, shopping centers, stadiums, etc. The units are mounted in the roof of the building and carry out the preparation of supply air and its distribution directly to the working area, as well as the removal of exhaust air with the possibility of partial or complete recirculation.

• Dual freewheel fans provide minimal power consumption and noise, as well as 50% redundancy by running two fans independently in parallel.
• The built-in plate heat exchanger provides heat recovery from the exhaust air.
• An adjustable swirl diffuser allows for an optimal air flow pattern depending on the supply air temperature and the required design solution.
• Heated air valves(option) allow the unit to be started and operated at an outdoor air temperature of up to -40 oC (without this option, up to -25 oC).

Operating modes:

1. supply and exhaust, without recirculation;
2. independent supply or exhaust;
3. supply and exhaust, with partial recirculation;
4. recycling 100%.

Main technical characteristics

Elements of indoor unit and climatic unit are options. The composition of these blocks must be selected depending on the operating conditions. The composition of the outdoor unit cannot be changed.

• The external module /OAT.E1 includes devices 1 to 8.
• The indoor module without silencer /OAT.I1 includes devices 9, 11.
• The indoor module with silencer /OAT.I2 includes devices 9, 10, 11.

VEZA BOX rooftop air conditioners perform various air processing functions and are designed to create and maintain decentralized general ventilation. Air conditioners from this line are produced in four standard sizes with an air capacity of up to 13 thousand m3/h and can be used at any facilities, both civil and industrial.

A wide range of options for the execution of BOX air conditioners is offered, as well as various configurations, among which you can choose best option easily. The variety of design options makes it possible to use these air conditioners as supply, exhaust, supply and exhaust systems, and as installations providing heating and cooling of air. BOX units are equipped with a high-quality system automatic control, which allows you to maintain the exact parameters of the microclimate at the facility and makes the use of central air conditioners more economical and efficient.

Rooftop BOX air conditioners - features and benefits

All BOX rooftop air conditioners consist of two key elements- external and internal blocks. The outdoor unit is mounted on the roof (supplied with a roof plinth matched to the type of roof) and is a frame structure made of reliable and durable materials. Sheathing basis - galvanized steel panels filled with polyurethane foam. The panels provide good heat insulation and reduce heat loss to the lowest possible number.

Outdoor units are also equipped with convenient service panels that are airtight and can be dismantled for repair and maintenance in the shortest possible time. In outdoor unit usually includes the following elements:

• Air intake, exhaust, recirculation valves;
• Fans;
• Filters of different degree of purification;
• Heat recovery units.

The indoor unit works with air coming directly from the room. He gives it and takes it away, ensuring a constant and high-quality exchange. The indoor unit has a heat exchanger, an air distributor, a mating element for an air duct or an air grille. Since the heat exchanger is mounted inside this unit, you can not be afraid of freezing in winter and operate the air conditioner even in severe frosts. In addition, if desired, air conditioning can be through indoor unit equipped with a separate air cooler.

Smart Trading offers a wide range of BOX rooftop air conditioners, among which you can choose the right size with the required air capacity, and a package that ensures the creation and maintenance of the required air parameters. At the moment, thanks to the design, which assumes the location of the main unit on the roof, and thereby saves space in the room, this is really the best option for most objects. Managers of our company will help you choose and calculate the BOX rooftop air conditioner for specific working conditions in a given room.