Modbus digital thermostats are widely used in building automation and hotel HVAC fan coil units by RS485 terminal. The thermostats are designed to on/off control the fans, valves, dampers or electric heaters in fan coil units and heating applications. Models are available for heating/cooling/ventilating control of 2 pipe or 4 pipe fan coil units.   FT-09 is the most feature FCU digital thermostat with modbus protocol. Features · Temperature room controller for heating and coiling by central air conditioning system in commercial and residential building automation · For 2 pipes or 4 pipes HVAC fan coil units system and heat pump · RS485 Modbus/RTU protocol communication with complete baud rate and parity selections · Touch lcd display with backlight · 0-10V valve control or 0-10v fan speed control · 3 fan speeds select and auto fan control · Summer/winter changeover in 2 pipe application ·  Cool/ heat/fan/auto operation mode changeover ·  Programmable and manual temperature heating/cooling changeover ·  External sensor in option. More precise temperature detection when using a external temperature sensor · Keycard contact input. When card is removed, room thermostats stop working. · Door/window contact on/off · Time clock reading and setting in option. · Low temperature protection function. · Full configurable parameters such as  ·  °C or °F reading display · Humidity reading display · Flush mounted 86*86 installation box   Besides modbus RS485 fcu thermostat, Etop also has bacnet fcu thermostat and wifi fcu thermostat in the HVAC air conditioner controller category.