What is a fan coil and how it works in conjunction with the chiller

Having the appropriate heating and cooling system is crucial for keeping your house cozy during the winter and cool during the summer. A popular option that is frequently used in conjunction with a chiller is the fan coil unit. However, what is a fan coil and how does it function in conjunction with a chiller? Let’s dissect it.

A fan coil unit is a device that uses a coil to circulate hot or cold water to help control the temperature in a space. After that, a fan is attached to this coil, and it blows air over it to heat or cool the air before distributing it throughout the space. It essentially serves as a sort of bridge between the interior environment and the heating or cooling source—in this case, a chiller.

You may be asking yourself, what function does the chiller serve in this arrangement. A chiller is a type of refrigeration unit that generates cold water, which is subsequently pumped through a fan coil unit. In order to cool the water to the appropriate temperature before it enters the coil, it works by taking heat out of the water. Instead, hot water from a boiler or heat pump would be used for heating, and it would be circulated similarly.

Thus, how do the chiller and the fan coil unit function together? It’s an easy to follow but efficient method. Depending on the season and the desired interior temperature, the chiller produces either hot or cold water. After this water is pumped through pipes to the fan coil unit, the air that passes over the coil is heated or cooled, and then vents or ductwork are used to distribute the air throughout the room.

Flexibility is one of the main advantages of combining a fan coil unit with a chiller. The fan coil unit is easily integrated into a variety of heating and cooling systems, including hydronic systems and geothermal heat pumps, because it runs on water. Because of this, it’s a flexible choice for both home and business use.

In understanding how a fan coil works alongside a chiller for heating and cooling your home, it"s like having a dynamic duo on your side. Imagine your chiller as the cool-headed mastermind, responsible for chilling water to the perfect temperature. Then, enter the fan coil, the trusty sidekick, which takes that chilled water and uses it to regulate the temperature in different rooms. Here"s the scoop: the fan coil has a simple job but does it oh-so-well. It blows air over the chilled water coils, either warming or cooling it before distributing it throughout your home via ducts or vents. It"s like having your own personal temperature controller in each room. Together, they make sure your home stays comfy and cozy, no matter the season.

Design of a fan-coil

The device’s English name, fan coil, literally translates to "fan coil," indicating that it shares structural similarities with the well-known AHE (air heating units) air heaters. Fan coils are similar to the internal blocks of split systems, but they use antifreeze in place of Freon water or other non-freezing liquid.

Citation. Traditionally, the active component of industrial air conditioning systems is ethylene glycol, a toxic antifreeze. Propylene glycol, the safe analog, is used less frequently because it costs 30–50% more.

The components of a fan coil are as follows:

• housing equipped with air grilles or spigots;
• The heat exchanger is a coil made of copper tubing with numerous plates;
• fan, usually centrifugal;
• coarse air filter;
• electromagnetic valve – regulator of liquid flow through the heat exchanging radiator;
• manual air release valve;
• electronic control board.

Beneath the heat exchanger is a condensate collection tank. The latter is released into the street or into a sewage receiver via a pipe. A drain pump is used to pump the condensate if the unit is situated far from the discharge point.

operating principle

The device operates using the same principle as the previously described calorifier: room air is blasted through the fins by the fan while antifreeze or water at a specific temperature passes through the coil tubes. There is a heat exchange, and the flow gets heated or cooled. This accounts for the device’s second name, fan coil unit.

Characteristics of fan coil operation:

• 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 units to the air;
• liquid flow is provided by an external pump, there is no pump of its own;
• the intake air stream is cleaned from dust by a filter;
• usually the fan coil treats the internal room air (full recirculation);
• Some models integrated into the forced ventilation system can heat/cool the supply air;
• the heat/cooling capacity is regulated in two ways – by changing the fan capacity and by limiting the water flow rate with an electromagnetic two-way valve.

Note: The device’s electronic unit regulates power by opening and closing the valve and adjusting the impeller speed in response to signals from the room thermoregulator or temperature sensor.

Thus, the fan-coil is a part of the centralized climate system that regulates the temperature of the air in a specific room or area of the production workshop. Extra characteristics

• dehumidification;
• ventilation (ventilation mode);
• Fresh air supply is an option;
• remote control;
• flow heating by electric heating elements (also optional).

The working principle of a fan-coil differs from that of a split system since it does not have a vapor-compression cycle and uses water as its working body, which does not change its aggregate state. As with calorifiers, the heat energy enters the radiator externally along with the liquid.

Sources of heat or cold can include:

1. Traditional boilers using different energy carriers. It is clear that this equipment only provides water or antifreeze heating.
2. Two types of heat pumps (HP) – geothermal and water-cooled. In winter, the unit heats the coolant, in summer, on the contrary, cools it down.
3. Chillers are powerful air-cooled or water-cooled condenser chillers.

Citation. Contemporary chillers are fitted with inverters, which are frequency regulators of compressor speeds, and run in winter-summer mode. As a result, even though performance is noticeably decreased, the refrigeration unit can heat the coolant (like a heat pump) at minus 15 to 20 °C outside.

The most typical combination is a fancoil-chiller system. In terms of equipment cost, this is the greatest choice; a TH with a comparable capacity will cost more to purchase and install. Read on to learn how the scheme’s units communicate.

Types of fan coil units

The types of fan coil units that are currently in use are based on how they are installed.

1. Wall-mounted (otherwise – cantilever) modules. Similar to the split indoor unit, they are fixed to the wall in the upper area of the room or placed above the floors.
2. Duct units are often produced without decorative plastic cladding, all parts are fixed on a metal frame. Enclosure-less models are installed inside the supply or recirculation ductwork.
3. Cassette ceiling fan-coils are similar to similar blocks of split-systems – they distribute treated air in 2-4 directions and are equipped with rotary louvers on servo drives. These modules are designed for installation in suspended ceilings, with a decorative panel only at the bottom.
4. Floor-mounted column units, accordingly, are placed on the floor. To save space, the unit is made in the form of a rectangular column, i.e. it is extended in height.

Note: There are universal door closers available, such as floor-to-ceiling closers, in addition to the options mentioned above. There are two mounting positions for the module: vertical (above the floor) and horizontal (ceiling mounting). As a result, the condensate collection has two tubs.

Fan coils in the standard version have one heat exchanger and are connected to the mains via a two-pipe system. Two independent radiators can be added to cassette, floor, and duct versions; the connection is four-pipe.

The coolant for two-pipe units in a single network comes from either a chiller or a water heater. As a result, users will only be able to adjust the temperature to what they find comfortable in each room of the building.

For multi-zone RACs, chillers with two heat exchangers are intended. A boiler or other heater provides hot water to one radiator, while a chiller provides cold water to the other. Users can simultaneously turn on their fan coils in two different modes—heating and cooling—in adjacent rooms.

Chiller-fancoil circuit operation

Let’s start by looking at the operation of a single-zone ACS for three units plus an inverter chiller, as illustrated in the diagram below. In the summer and in the period between fall and spring, the system keeps the temperature comfortably high. Effective winter heating occurs between -5 and -10 degrees frost.

To be clear. A chiller is a device that heats or cools coolant using the Carnot vapor-compression cycle. The unit is outside, and freon R410a or R407a is used as the working fluid. Air blows into the heat exchanger-condenser, or liquid cools it.

This is how the operational algorithm appears:

1. In summer, the air-to-water chiller cools the heat transfer medium to a standard temperature of +7 °C (if it is +35 degrees Celsius or less).
2. The hydromodule directs cold water to a network of fan-coils connected in a two-pipe scheme (like radiators in a heating system).
3. With the help of remote control the user sets the desired air temperature separately in each room.
4. At first, the closers catch up the set temperature by operating at maximum capacity. Then the controller reduces the cooling intensity according to the sensor signal – it decreases the fan speed in steps (from 3 to 8 steps depending on the model).
5. When the air medium reaches the set parameters, the two-way electro-valve closes the coolant supply at the command of the electronics. The fan coil then maintains the temperature.
6. Water heated to 12 °C (on average) is returned to the evaporator coil of the chiller and the cycle is repeated.
7. In the fall the outdoor temperature drops, the chiller receives a request for hot coolant from the fan coils and switches to the heating mode. Switching is done manually or automatically by command of an additional controller.

Note: The maximum operating ambient temperature specified by renowned air conditioning equipment manufacturers Gree and Carrier is plus 46 °C. Water can be cooled to +18 degrees Celsius under such circumstances.

The executive automation unit, expansion tank, and pump comprise the hydromodule, which supplies coolant. The components are installed individually or as part of the chiller design. Hydromodules for two to three pumps are included with higher capacity units.

Low-cost fan-coil models might not have a solenoid valve. Next, the door closer’s external plumbing is completed, including the installation of shut-off valves, servo drives, and executive three-way valves. The video will explain how it operates to the master:

In order to fully operate the single-zone system during the winter, the fan coil network is connected to a boiler. The chiller is turned off when the temperature drops below minus 10 to 15 degrees. Using a different pump, the actuating valve transfers the heat carrier to the water heater line.

The operation of the multizone system:

1. The right number of door closers can be connected to the chiller and boiler at the same time. A four-pipe scheme is used, or rather 2 two-pipe dead-end branches. The capacity of the heat and power equipment is determined by calculation.
2. When the first user adjusts the heating, the fan coil automation opens the flow through the "hot" heat exchanger, the second radiator is idle. We get warm air at the output.
3. If the second user turns on cooling, the door closer in the neighboring room starts only the "cold" heat exchanger, and the "hot" one is shut off.
4. Fan coils of one network work independently of each other.

The chiller will "realize" by the temperature of the return water that it is necessary to stop the cold supply and will shut off if, for whatever reason, all of the closers’ valves close. The boiler automation will function in a similar manner.

Pros and cons of air handling units with door closers

One clear benefit of fan-coil air conditioning is that it can precisely maintain the desired temperature in various rooms. A single building can have a very broad range of climate control thanks to multi-zone systems. Additional benefits over traditional air conditioners:

• The cost of the equipment for 2-3 rooms will be obviously less than the price of multi-split-system of identical capacity;
• heat and cold sources are located in the technical room or on the street, outdoor units do not clutter the facade;
• Fancoil units can be installed 50…200 meters away from the chiller;
• communications between units are made of inexpensive plastic pipes – low-pressure polyethylene or polypropylene (the latter must be soldered);
• in case of breakdowns and leaks it is easier to make repairs, replenish the system with purified water.

Note: The only factor limiting the distance between the chiller and the fan coil is practicality—longer lines result in higher heat (cold) losses and higher energy usage from the strong pump.

Never assume that an ACS type chiller-fancoil can only be used in an industrial setting. Brands like Daikin, Carrier, and Gree offer compact double-fan chillers that are ideal for residential use, with capacities ranging from 3 to 10 kW.

• ACS for 2 rooms is still more expensive than two separate split systems;
• decent size and weight of the chiller unit;
• qualified installation and start-up of the equipment is required;
• the equipment will have to be serviced, and the technicians will have to be called annually.

Freon VRF systems—which function on the basis of "splits"—remain the primary industrial rivals of water SCVs. Up to 50 interior units are connected solely to the external vapor compression module. Although the equipment costs are roughly equal, fan coils prevail because it is simpler to lay the mains and because plastic pipes are less expensive than copper pipes. A different story: difficult to locate and remove Freon leakage from a large system.

In contemporary HVAC systems, a fan coil unit is an essential part, especially when combined with a chiller. Together, they effectively control interior temperature by distributing heated or cooled air throughout a structure. A fan coil unit basically consists of a coil, fan, and control system that all cooperate to keep the interior comfortable.

Chilled water is produced by the chiller and passes through the coil in the fan coil unit. Depending on the required indoor temperature, heat exchange happens as the fan blows air over this coil, causing the air to either get heated or cooled. This procedure works wonders for quickly regulating the temperature inside a room so that people can stay comfortable no matter what the outside weather does.

A fan coil unit’s versatility and adaptability to different building layouts and requirements is one of its most notable features. These units can be tailored to meet specific needs, whether they are installed in commercial buildings, residential buildings, or industrial facilities. Furthermore, they are frequently small in size, which allows them to be installed in confined areas like utility closets or false ceilings.

Furthermore, there are advantages to energy efficiency when fan coil units and chillers are integrated. Fan coil units effectively cool interior spaces without the need for separate air conditioning units in each room by using chilled water produced by the chiller. This centralized cooling method lowers energy usage while simultaneously lowering maintenance expenses and improving system dependability as a whole.

In summary, the cooperation of chillers and fan coil units is a vital component of contemporary HVAC systems, allowing for efficient temperature control and energy conservation. Homeowners and building managers can create cozy and environmentally friendly indoor spaces by making informed decisions based on their understanding of how these components interact.

Video on the topic

What is a fan coil, working principle

What are fan-coils and the principle of their operation

Chiller-fancoil system. Scheme, limitations, scope of application

What is the difference between air conditioners and fan coil units