triple effect

Abnormal heat in part of the territory of our country has caused the interest in split systems to rise sharply. Now it is perhaps the most frequently discussed equipment for houses and apartments. According to sociological research, 57% of the capital’s residents are going to install such equipment at home. Today we will talk about their little-known variety.— channel air conditioners and features of operation of these devices.

In the “Letter of the Law” section, we have already addressed the topic of air conditioners (see the article “On a Hot Midday, or How to Install an Air Conditioner Legally”, “IVD”, 2010, N 5). This article is devoted to ducted air conditioners, which are gaining popularity. Why is this happening?

What is a «duct»?

A split system provides a comfortable temperature and humidity, and also removes odors and dust, but does not maintain an oxygen content sufficient for a living space. In order for the room to feel fresh, atmospheric air must be let in. However, due to the heat and stuffiness, you have to keep the windows closed. You can combine air conditioning with ventilation if you use a channel-type split system. She will first be able to purify the air of poplar fluff and other large particles.

Architects
Y. Filatov, D. Belov, A. Strelkov
Photo by E. Kulibaba A ducted split system consists of two blocks (outdoor and indoor) connected by a pipeline through which the refrigerant moves— carrier of cold or heat. The principle of operation of all split systems is the same. The compressor of the outdoor unit compresses the gaseous refrigerant, which, moving through the radiator blown by the fan, condenses and is sent in liquid form through the copper tube to the indoor unit. Here, the liquefied coolant, passing through the thermostatic valve, evaporates again, passes into a gaseous state, while its temperature drops significantly. The cold gaseous coolant intensively absorbs heat from the air driven by the fan through the heat exchanger. Cooled air through flexible ducts— channels— enters the premises. This is where its name comes from.— «duct».

The indoor unit cools or heats (if the system has a heat pump mode) the air, cleans it from dust and odors using filters and returns it to the room. The cost of such turnkey systems— about 1800-3300rub. for 1m² refrigerated area. Duct pipes are supplied to the Russian market by such manufacturers as Daikin, Fujitsu General, Hitachi, Mitsubishi Electric, Mitsubishi Heavy, Panasonic, Sanyo (all— Japan), Dantex (UK), Carrier, York (both— USA), LG Electronics, Samsung Electronics (both— Korea), Electrolux (Sweden), Ballu, Gree, Midea (all— China) andetc. To understand why ducted air conditioners are good for creating a comfortable microclimate and why they need an additional air distribution system, let’s consider the main differences between a “duct” and other types of indoor units.

Three pluses

First advantage channel split system lies in the fact that it is invisible in the interior and reminds of itself only with narrow slots of decorative exhaust grilles and almost imperceptible disks of supply diffusers in the wall or ceiling. ATIn the simplest version, the indoor unit of a ducted air conditioner is a small metal box, on the edges of which there are branch pipes or holes for connecting air ducts and fittings for refrigerant pipes. Its unpretentious appearance does not affect the interior, because it is closed by structures. Inside it is an air filter, a finned heat exchanger, a fan, a drip tray for collecting condensate formed on the heat exchanger, and controls. Some models can be equipped with various complex filters, air heaters, humidifiers, ionizers and automation units (manufacturers offer all this as additional options). A number of devices are assembled according to a modular principle: each functional additional element is made in the form of a separate «brick», and all of them are combined into a single box-shaped structure. The unit, as a rule, is mounted above the false ceiling or in a specially built semi-cornice (a box adjacent to the ceiling along the walls), and the grilles and diffusers are placed in the plane of the false ceiling or in the wall. The indoor unit can also be placed in a vestibule, corridor, hallway or pantry. However, it does not have to be fixed to the wall.— Can be placed on a shelf or on the floor. An air conditioner of this design is suitable for both a city apartment and a country house. Recall that the second, outdoor unit of a split system is always placed outside the living rooms.— on the street (that is, on the outer wall of the house), a balcony or in a technical room, but in such a way that it is well blown by air, since the device generates a lot of heat.

Second plus «ducts» in that flexible ducts allow you to improve the direction of the air flow by installing supply diffusers anywhere in the ceiling and adjusting them. In addition to cooling or heating, the air conditioner is able to ventilate the room, purify and humidify the air (if the appropriate modules are available). If you install the device for only one room, it is not necessary to install air ducts: the indoor unit of the ducted air conditioner can supply air to the room directly from the front panel. ATsome devices, such as those included in the FS Multi (Panasonic) range, are specifically provided with the ability to switch the air supply method— via air duct or directly.

The presence of air ducts allows you to supply air to different zones of one room or to several rooms. The benefit is obvious: the “duct” works like a multi-split system, but its simplest version is 2 times cheaper, since it uses only two units (outdoor and indoor), there is no need for additional indoor units, because thanks to the optimal air distribution, a comfortable atmosphere is created everywhere .

However, do not fall into euphoria: the longer the air ducts, the greater the fan power should be compared to other types of indoor unit. ToIn addition, the temperature of the air supplied from one unit to different rooms will be the same, and the requirements for a comfortable temperature in them are different: say, 18 FROM— in the bedroom, 20 FROM— in the living room, 25 FROM— in the nursery. Although such temperature zoning is quite “on the shoulder” of a channel split system. But for this you will have to use a complex system of electromechanical valves that will block the access of air to those rooms where a favorable temperature has already been reached.

Architect G. Podobulkin Photo by R. Shelomentsev Due to the presence of air ducts, one more indicator of air conditioning operation has to be taken into account— static pressure of the fan. This is the pressure with which the unit can «push» the conditioned air supplied to the room forward when using ductwork. It is usually measured in pascals (Pa). The volume of processed air must be delivered to the appropriate diffusers and then fed into the room through them. According to this indicator, three groups of devices are distinguished: low-pressure (pressure up to 50 Pa), medium-pressure (up to 150 Pa) and high-pressure (up to 300 Pa). Each of them is designed for a certain length and diameter of the air ducts. So, for a high-pressure unit model PEA-RP500GA (Mitsubishi Electric) at a static pressure of 290 Pa, the maximum length of the air duct with a diameter of 150mm is 50m (given that the air flow rate is not lower than 1.5m/s). You can, of course, install an air duct even longer, but the speed of the air flow will decrease so much that the final effect will be comparable to the movement of a cold wave seeping out of the open door of the refrigerator. ATIn any case, it is necessary to choose the dimensions and capacity of the air duct, and to coordinate the static pressure with its length and cross section. However, it should be noted: the higher the air velocity, the higher the noise level. Therefore, at high speeds (5m / s and above) it is necessary to soundproof the air ducts or even install silencers, as on the exhaust pipe of a car.

Typically, consumers choose household split systems with ducted indoor units with a capacity of up to 12 kW (or up to 25 kW). This is enough to maintain a comfortable temperature in a country house with an area of ​​200-300m² or a three- or four-room city apartment. The air intake at the channel unit can take place both from below and from the side, while the filter for cleaning the air from dust and odors is installed accordingly. When working without air ducts, some models are provided with dampers that swing automatically (Autoswing), changing the direction of the air flow horizontally from left to right or right to left. They can also be locked into one of five angle positions.

Third plus «ducts» is that they allow you to simultaneously air-condition and ventilate the room due to the additional installation of a kit for mixing fresh air. ATIn this case, fresh air from the street is supplied through a heat-insulated duct to a mixing chamber built into the indoor unit or attached to it as an additional unit. There it combines with the air taken from the room (i.e. recirculated). The air mixture is filtered and processed in the indoor unit depending on the specified thermal regime (cooling or heating). The ratio of supply air to recirculated air is usually regulated depending on the season and is a maximum of 25-30%, but most often 8-15%. If you use «ducts» all year round in regions with a cold climate, you will have to provide a duct heater with a thermostat and reduce the volume of supply air in winter so that this heater has time to warm up the volume of cold street air before mixing. ATIn this case, we can talk about creating a climate control unit with a common IR remote control that allows you to change the fan speed. But the air mixing system increases the installation cost by almost 2 times.

Despite all the advantages of «ducts», they have one drawback: with sub-ceiling installation, the ceiling height in the room will decrease by at least 250mm.

How to mix fresh air?

Atmospheric air enters through a protective grille at the end of the air duct, led through the wall to the street. Behind it, a mechanical air filter is installed. After the filter, you can mount a duct heater with a thermostat to periodically heat up too cold outdoor air. The power of the heater fluctuates in the range of 1.5-4 kW, depending on the serviced area and the difference in air temperatures (atmospheric and indoors). To increase the pressure of the supplied atmospheric air, a supply fan is often mounted in front of the heater.

Air mixing is «managed» by a controller installed inside the kit. It gives the command to turn the supply fan on or off. An electronic board and a thermistor located in the air duct behind the filter control the temperature of the supplied atmospheric air, periodically changing the power of the duct heater. ATthe air duct through which fresh air enters is provided with an electrovalve (it does not allow cold air to enter the room when the system is turned off) and a filter for cleaning the supply air.

Some manufacturers offer a ready-made kit for mixing atmospheric air. It is designed for ceiling duct and cassette indoor units.

The percentage of mixed volumes is not regulated and depends on the air temperature in them, as well as on atmospheric pressure. However, using a single channel air conditioner, you can solve the problem of ventilation and air conditioning of the home. The main thing is that the specialist of the company in which you buy this equipment correctly calculates the future air exchange, including the distribution of air supply diffusers to each room and between them; picked up the performance of the split system and static pressure, providing sufficient pressure; foresaw an electric or water heater to heat the atmospheric air in the cold season. Andfinally, it is necessary to correctly mount the «duct» in order to save space and not lose performance.

Air distribution with VAV system

Recently, in the practice of building country houses, automatic systems for zonal air flow control are increasingly used.— the so-called VAV systems (Variable Air Volume). They allow you to create a multi-zone system based on a «duct» with high performance (25 kW or more). In order to synchronize the operation of the indoor unit fan with the system of controlled dampers, two special connectors can be provided on its electronic board (see diagram on page XX). The first of them receives an external analog signal from the controller of the zonal air flow control system, which controls the speed of the “duct” fan. The second connector receives an external digital signal that starts and stops the system, and also switches the operating modes (heating or cooling). The compressor capacity of the outdoor unit of the system will automatically change according to the air flow of the indoor unit.

Since the VAV system controller provides a smooth change of the damper position, the air flow in the indoor unit is regulated by maintaining a constant static pressure at its outlet. The differential pressure transducer generates a control analog signal, which is fed to the first connector of the control board. This signal will maintain a constant static pressure in the duct regardless of the position of the dampers. If all of them are closed at the same time, the interface unit will immediately turn off the air conditioner.

Features of the installation of the «duct»

Flexible air ducts with a diameter of most often 150 are attached to the protruding nozzles of the kit.mm. It is desirable that there is a service hatch near the place of their connection in the ceiling for free access to the air duct. It must be ensured that there are no bends or twists along the entire length of the flexible duct— because of them, the cross-sectional area is significantly reduced and aerodynamic resistance increases. ATthe place where the supply air duct is attached to the wall on the outside of the building, a protective cover is provided.

Architect
N. Eliseeva
A photo
R. Shelomentseva If it is necessary to separately regulate the temperature in different rooms, it will be necessary to install dampers with electric drives in the air ducts, and in all rooms where it is required to independently control the temperature,— thermostats. BUTif the temperature can be the same everywhere, a ducted air conditioner will cost about 50% cheaper than a multi-split system and 3 times cheaper than a multi-zone unit such as VRF or VRV. It will also be possible to save if you install, for example, two channel split systems, one of which serves rooms with windows facing north, northwest and northeast, and the other— with windows to the south.ATIn this case, during the off-season, the first of them will often work in heating mode, and the second— in cooling mode. If you install a high-level group controller, you can individually set different operation modes for several indoor units at once (up to 16).

Some characteristics of channel split systems of various manufacturers

Maintenance

Maintenance of duct indoor units is more difficult than maintenance of other types of air conditioner indoor units. It is better to entrust this to a service center specialist. When the air is cooled, condensate is released, which flows into a tray specially provided for this purpose, located in the duct block. From there, the condensate leaves by gravity or is periodically pumped out by a drainage pump through a pipeline outside the room, but dirt gradually accumulates at the bottom of the pan. Therefore, the pallet will have to be washed periodically. The drainage pump is supplied and mounted separately from the unit, but it can also be built-in (the second option, of course, is more convenient). Through the service hatch provided during the installation of the air conditioner, the owner will be able to independently control the condition of the air filter and the drainage pan, as well as wash them. By the way, installers do not need to be reminded to embed such a hatch when installing an air conditioner,— they themselves will offer this service. ATRecently, equipment has appeared, for example, from the FS Multi (Panasonic) model range, with a filter contamination indicator, which will save you from periodic checks of this device and tell you when it should be replaced.

Maintenance is simplified if the model has a self-diagnostic mode. When it is activated, the correct operation of the air conditioner is automatically checked, and if an error is detected, its code is displayed. Knowing it, you can call the service center, where they will tell you what to do.

The material was prepared based on the results of a survey of readers on the website of the action «Create new ideas»

The editors would like to thank the Rusclimat Group of Companies, as well as the representative offices of Mitsubishi Electric, Panasonic and LG Electronics for their help in preparing the material.

• Source: Ideas for Your Home Magazine#145