Fan Coil Units and Controllers

Fan Coil Units and Controllers

Fan coil unit (FCU) uses a fan and a coil/s to heat or cool a room. Air fed to the FCU can be from the AHU’s duct work (when used with chillers) or directly from the room (without duct work).

The FCU is usually found in HVAC systems of residential, commercial, and industrial buildings. FCU can either be horizontal (ceiling mounted) or vertical (wall mounted).

FCU controls would include a controller and a room sensor/ thermostat for zone air temperature control.

The main goal of the controller is to keep the zone temperature within the user-defined setpoints by driving valves, allowing hot or cold water to flow through heat exchanger coils as required, and then circulating air past these coils into the zone via a fan.

See below sample example of a FCU Prolon controller.

Prolon C1050 Fan Controllers

Prolon C1050 Fan Coil controller


Since the default communication for the most of these controllers is Modbus or BACnet, see here how to interconnect them wirelessly to a network controller for building management system integration or to other controllers with wireless Modbus or wireless BACnet device.

Compatible Prolon digital communicating sensors that can provide the C1050 with room temperature, room setpoint, and schedule override include T1000, T500, and T200.

Fan coil systems can either be 2 pipe or 4 pipe systems:

2 Pipe Fan Coil

The 2 pipe fan coil system consists of a single water coil connected to two pipes (supply and return) and cannot cool and heat at the same time. Also requires a changeover sensor to determine the mode of the system.

The Honeywell TB8575A1000 thermostat can work for the 2 pipe fan coil system.

4 Pipe Fan Coil

The 4 pipe system consists of two separate cooling and heating water coils each with dedicate pipes (supply and return) and valve. Unlike the 2 pipe system, it does not require changeover sensor since both hot and chill water is available.

 The Honeywell TB8575A1000 thermostat can also work for the 4 pipe fan coil system.

See below sample wirings for different fan coil unit controller thermostats:

TB6575A1000 Wiring to a FCU
4 pipes (Heat and Cool) Manual/Auto changeover wiring diagram for TB6575A1000.

2-pipe fan coil unit wiring diagram for Johnson Control's FCP-PA-701-B.

Contact our HVAC Controls Engineering team for assistance with queries on residential and commercial HVAC systems and controls. 

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