Cassette Type Fan Coils

The fan coil system can be defined as a system through which heating or coolant fluid passes and which provides the required temperature by heat transfer between fan assisted serpentine and site.

Fan coil unit is a heating and cooling unit with a finned battery at the top and a radial fan and filter which provide air movement at the bottom. They are used in central systems to air-condition certain rooms or certain volumes. Fan coil units are generally composed of a fan, a battery and connected equipment. Either hot or cold water passes through the battery. When hot water passes through the system, it provides heat and when the water is cold, cooling is provided. Room thermostats are used to control the fan coil units. Fan coil units are used in every space where heating and cooling is needed. Fan coil systems are central systems. They are preferred in various places from houses to big shopping malls, sports halls, residences and public buildings. Fan coil units provide heating or cooling in proportion to hotness or coolness of the water running through them. Capacities of fan coil units vary in respect to the space they will be used.

Silent operation is extremely important for fan coil units and it should be particularly noticed when comparing different units. In addition, medium speed ones should be selected in projects. Project design criteria should be taken into consideration when selecting fan coil units. Hot water is generally supplied to fan coil units from hot-water boilers or steam boilers via heat exchangers or all kinds of heat generators or pumps and cold water comes from chiller groups or heat pumps. Although the installation cost of the fan coil system is high, operating expenses are rather reasonable.

When fan coil units are used with heat pumps or heat pump chillers, they provide heating in winters and cooling in summers like air-conditioners. Fan coil installation partly resembles installation of a central heating system but calculations are different. Heating capacity of fan coil units is higher than their cooling capacity. As engineering calculations are based on the most critical value, cooling values are taken into account in calculations. Climatic values are also effective in this selection. If cooling load is high in the zone, cooling values are taken as critical values. If heating load is high in the zone, heating values are taken into account. Behaviors of conveying liquid are also important in system details for heating and cooling. While the liquid shrinks in cooling position, it dilates in heating position. While heated liquid intends to move upwards, chilled liquid moves downwards. Because of these behaviors selection of pump, pipe diameter and type, and shrinkage-expansion tanks should be made carefully.

Even though it is easy to choose pipe diameters of fan coil basing on heating, diameter of cooling pipe should be chosen by considering many values. If the installation is a four pipe system, cost of the system will be very high. This kind of installation is not preferred in villas or small-medium scale buildings because of its cost. In a two-pipe system, critical pipe diameter should be calculated according to heat gain or heat loss due to opposite behaviors of the fluid during heating and cooling.

While it will operate between 0 C (?), it will operate between 6-12 C in summers. Selected pipes should meet these requirements. All pipes in the fan coil line should be properly heat insulated. Selection of pipe diameters in the fan coil installation bases on the heat load. Diameter selection should be based on the capacity of the fluid, length of the line, resistors on the line, and the velocity of air. One of the most important points in a fan coil system is the drainage system. Slope of drainage lines should allow water to flow easily and they should not be blocked. Maintenance of fan coil units is very important in terms of silent and efficient operation and hygiene. People working in environments where the fan coil units are not maintained properly are faced with health problems. Fan coil units are grouped as wall type, cassette type, floor-ceiling type and ducted type.