Domestic air conditioners cool (heat) the air locally in 1-2 rooms. Chiller-fan coil systems are designed to solve a wider range of tasks, for example, simultaneously maintain the microclimate in dozens of separate rooms. Moreover, the facade of an office building or a shopping center is not disfigured by outdoor units of "splits". A similar conditioning scheme (SLE) can be implemented in a private cottage. We offer to understand what fan coil is, to describe the principle of operation and types of modern climate units.
Fan coil design
The English name of the fan coil unit literally means “fan coil” and indicates a constructive similarity with the long-known ABO air heaters (air heating units). The fan coil units also resemble the internal units of the split system in appearance and device, only water or non-freezing liquid - antifreeze is used instead of freon.
Reference. The working fluid in industrial air conditioning systems is traditionally toxic ethylene glycol antifreeze. A safe analogue - propylene glycol - is 30-50% more expensive, therefore it is used less often.
Fancoil consists of the following elements:
- case equipped with air grilles or nozzles;
- heat exchanger - a coil from a copper tube with numerous plates;
- a fan, usually centrifugal;
- coarse air filter;
- electromagnetic valve - regulator of fluid flow through a heat-exchange radiator;
- manual vent valve;
- electronic control board.
A condensate collection tank is installed under the heat exchanger. The latter is discharged through a pipe to the street or to the sewer receiver. If the unit is installed at a considerable distance from the discharge point, condensate is pumped by the drain pump.
Operating principle
The device works according to the principle of the above-mentioned air heater: antifreeze or water of a certain temperature flows through the coil tubes, the fan blows room air through the fins. Heat exchange occurs, the stream heats or cools. Hence the second name of the device - fan coil.
Features of the fan coil:
- the unit is able to work in heating or cooling mode, depending on the temperature of the incoming water;
- the main function is to transfer heat or cold produced by other plants to air;
- the flow of fluid is provided by an external pump, there is no own;
- the intake air stream is cleaned of dust from the filter;
- usually fan coil processes indoor room air (full recirculation);
- some models integrated into the forced ventilation system can heat / cool the supply air;
- thermal / refrigeration power regulation is carried out in two ways - by changing the fan performance and limiting the water flow by an electromagnetic two-way valve.
Note. The electronic unit of the device is engaged in power control - it opens / closes the valve and changes the impeller speed at the signal of the temperature sensor or room thermostat.
So, fan coil is an integral element of a centralized climate system that maintains air temperature in a particular room or in a specific area of the production workshop. Additional functions:
- drainage;
- ventilation (ventilation mode);
- mixing of fresh air is an option;
- remote control;
- heating the flow with an electric heating element (also an option).
The difference between the fan coil and the split system is the principle of operation - there is no vapor compression cycle in it, the working fluid is water that does not change the state of aggregation.Moreover, thermal energy comes to the radiator from the outside along with the liquid, as provided in the heaters.
- Traditional boilers using various energy sources. It is clear that this equipment provides only heating of water or antifreeze.
- Heat pumps (VT) of two types - geothermal and water. In winter, the installation warms up the coolant; in summer, on the contrary, it cools.
- Chillers are powerful air-cooled or water-cooled chillers.
Reference. Modern chillers operate in winter-summer mode and are equipped with inverters - frequency compressor speed controllers. Due to this, the refrigeration unit can heat the coolant (as well as the heat pump) at minus 15 ... 20 ° C on the street, although performance decreases markedly.
The most common bundle is the chiller-fan coil system. This is the best option for the price of equipment, it will be more expensive to buy and install VTs of similar performance. How circuit aggregates interact, read below.
Types of fan coil units
All existing fan coils are divided into types according to the installation method:
- Wall (aka - console) modules. Like the indoor unit, split, are attached to the wall in the upper zone of the room or are placed above the floors.
- Channel devices are often produced without decorative plastic cladding, all parts are mounted on a metal frame. Unpacked models are built into the duct of supply ventilation or recirculation.
- Ceiling cassette fan coil units are similar in appearance to similar split-system units - they distribute treated air in 2–4 directions and are equipped with rotary shutters on servos. These modules are designed for installation in suspended ceilings, a decorative panel is provided only from the bottom.
- Floor column units, respectively, are placed on the floor. For the sake of saving usable area, the block is made in the form of a rectangular column, that is, it is elongated in height.
Note. In addition to these options, there are universal closers, for example, floor-to-ceiling. The module can be mounted in 2 positions - horizontal (ceiling mount) and vertical (above the floor). Accordingly, 2 baths are provided for collecting condensate.
As standard, fan coils are equipped with 1 heat exchanger; it is connected to the mains by a two-pipe scheme. Cassette, floor and channel versions can be equipped with two separate radiators, the connection is four-pipe.
The two-pipe units involved in a single network receive the coolant from one source - a water heating system or a chiller. This means that all rooms of the building will only be heated or cooled, users only set a comfortable temperature.
Closers with 2 heat exchangers are designed for multi-zone SCR. One radiator receives hot water from a boiler or other heater, the second - cold from a chiller. Users in neighboring rooms can simultaneously turn on their fan coil in various modes - heating or cooling.
Chiller-fan coil operation
First of all, we will consider how a single-zone SCR for 3 blocks + an inverter chiller, shown in the diagram below, works. The system maintains a comfortable temperature in the summer and during the transition period autumn - spring. Winter heating functions effectively at -5 ... -10 degrees below zero.
Clarification. Chiller is a unit that uses the Carnot vapor compression cycle for cooling / heating the coolant. The unit is placed on the street, freon R410a or R407a is the working fluid. The heat exchanger-condenser is blown with air or cooled by a liquid.
The working algorithm looks like this:
- In summer, the air-water chiller cools the coolant to a standard temperature of +7 ° C (if the yard is +35 degrees or less).
- The hydraulic module directs cold water to a network of fan coil units connected by a two-pipe scheme (like radiators in a heating system).
- Using the remote control, the user sets the desired air temperature separately in each room.
- At first, door closers reach the set temperature, operating at maximum power. Then, according to the sensor signal, the controller reduces the cooling rate - it decreases the fan speed in steps (from 3 to 8 steps in total, depending on the model).
- When the air reaches the set parameters, a two-way solenoid valve shuts off the coolant supply at the command of the electronics. Further fan coil maintains temperature.
- Heated to 12 ° C (average), the water is returned to the heat exchanger-evaporator of the chiller, the cycle repeats.
- In autumn, the street temperature decreases, the chiller receives a request for a hot coolant from the fan coil and switches to heating mode. Switching is done manually or automatically - at the command of an additional controller.
Note. Well-known manufacturers of HVAC equipment Gree and Carrier indicate the maximum operating ambient temperature plus 46 ° C. Under such conditions, water can be cooled to +18 degrees.
The hydraulic module that provides the coolant supply consists of a pump, an expansion tank and an executive automation unit. Elements are included in the chiller design or are installed separately. Units of increased power are supplied with hydraulic modules for 2-3 pumps.
In order for the single-zone system to work fully in the winter, a boiler is connected to the fan coil network. In frost below minus 10 ... 15 degrees, the chiller stops. Executive valves switch the coolant to a water heater line with a separate pump.
How does the multi-zone system work:
- The required number of door closers is simultaneously connected to the chiller and boiler. A four-pipe scheme is used, more precisely, two two-pipe dead ends. The power of thermal power equipment is determined by calculation.
- When the first user sets the heating, the fan coil automation opens the duct through the “hot” heat exchanger, the second radiator is inactive. At the exit we get warm air.
- If the second user turns on the cooling, then the closer in the next room starts only the “cold” heat exchanger, and the “hot” one closes.
- Fancoils of the same network operate independently of each other.
If for some reason the valves of all closers are closed, the chiller will "understand" by the return water temperature that it is necessary to stop the cold supply and stop. Similarly, the boiler automation will work.
Pros and cons of hard currency with closers
An obvious advantage of fan coil conditioning is the precise maintenance of the desired temperature in different rooms. Multizone systems allow very wide control of microclimate parameters within the same building. Other advantages compared to conventional air conditioners:
- the cost of equipment for 2-3 rooms will come out clearly less than the price of a multi-split system of identical power;
- heat and cold sources are located in the technical room or on the street, the outdoor units do not clutter the facade;
- fan coils can be set 50 ... 200 meters from the chiller;
- communications between units are made of inexpensive plastic pipes - low-pressure polyethylene or polypropylene (the latter must be soldered);
- in the event of an accident and leakage, it is easier to repair and replenish the system with purified water.
Comment. The distance from the chiller to the fan coil is limited only by reasons of expediency, since on too long lines high heat (cold) losses occur, plus the energy consumption of a powerful pump increases.
Do not think that SCR type chiller-fan coil is applicable only in industrial buildings.Brands Daikin, Carrier and Gree produce small two-fan chillers with a capacity of 3 ... 10 kW, which are quite suitable for private homes.
Disadvantages of fan coils:
- SLE for 2 rooms is still more expensive than two separate split systems;
- decent size and weight of the chiller unit;
- qualified installation and commissioning of equipment is required;
- the equipment will have to be serviced, annually call the masters.
On an industrial scale, Freon VRF systems operating on the principle of “splits” remain the main competitors of aqueous SCR. Up to 50 indoor units are connected only to the external vapor compression module. The cost of equipment is about the same, but fan coil units benefit from the ease of laying highways and the lower cost of plastic pipes compared to copper. Another story is the leak of freon from a huge system, which is not easy to find and eliminate.
Conclusion
The question arises: is fan coil a conditioner or not? The answer is definitely yes. Recall the definition of conditioning - bringing the air of the room to the necessary condition. With the help of chillers, boilers and heat pumps, our units just provide the required air temperature. Therefore, they can safely be called air conditioning closers.