Comparing with floor heating, the fan coil system is essentially a completely watery system. Fan Coil Unit includes a fan and a coil which are used for heating and cooling and these units need a thermostat to be controlled. If there is a single coil in the fan coil used, the system is called 2 pipes fan coil system.  Two pipes circulate in the system making distribution and collection. A distribution pipe and a collection pipe are connected to each fan coil unit. In this case, either cold water or hot water can be circulated throughout the system.   If there are two separate pipes as heating and cooling in the fan coil, the installed system is called a four-pipe fan coil system. Four pipes circulate in the system, making two distributions and two collecting. Two distribution pipes and two collector pipes are connected to each fan coil unit. Cold water circulates independently in one of the pipe pairs and hot water in the other. Therefore, heating and cooling can be done simultaneously in each fan coil unit independently of each other. Compared to the 2 pipes, the 4 pipes are more complex but easier for the water management.Since fan coil systems operate in heating and cooling, it is required to perform heating or cooling in summer or winter periods. In this case, we will normally introduce the  change-over sensor which is used to detect water temperature (to judge winter or summer). In General situation, heating or cooling mode selection can be made manually. When heating mode selected; If the room temperature falls below the set temperature, the fan coil is activated and tries to heat the environment. In cooling mode, if the room temperature rises above the set temperature, the fan coil is activated and tries to cool the environment.Where are the fan coil thermostats installed?Fan coil systems used in commercial buildings such as hospitals, hotels, shopping malls and business centers operate in two types. These systems, called 2-pipe and 4-pipe, directly affect the comfort and energy savings of the users.Based on different applications, Modbus/Bacnet/KNX protocol based fan coil thermostat is needed for different installations.