HVAC Equipment

Fan Coil Valve: Types, Operating Principle and Selection Criteria

Learn how 2-way and 3-way valves control water flow in fan coil units, which actuators are available and how to select the right valve.

ORFA Technical TeamUpdated: Oct 30, 20264 min read

Fan coil units are common terminal devices that provide heating and cooling in offices, hotels, hospitals and shopping centres. Their comfort and efficiency depend on accurately controlling how much hot or chilled water reaches the coil. The component that does this is the fan coil valve.

This article explains what a fan coil valve does, the difference between 2-way and 3-way valves, the actuator types in use and the criteria to consider when selecting a valve.

What Is a Fan Coil Valve?

A fan coil valve controls the flow of heating or cooling water to the fan coil’s coil. It usually consists of a valve body and an actuator mounted on it. Based on the signal from a room thermostat or building management system, the actuator opens, closes or modulates the valve to keep the room at the set temperature. Manually adjusted valves exist, but automatic control is by far the most common solution in fan coil applications.

Types of Fan Coil Valves

2-Way Valves

A 2-way valve opens, closes or throttles the flow to the coil. When it closes, no water passes through the unit, so the total system flow varies with load (variable flow system). Combined with variable speed pumps, this saves pumping energy. In such systems, differential pressure control or a bypass arrangement should be provided so the pump does not run against closed valves.

3-Way Valves

A 3-way valve sends the water either through the coil or through a bypass. When the coil is shut off, water returns via the bypass, so the circuit flow stays roughly constant (constant flow system). It is preferred in installations with fixed speed pumps or where continuous circulation is required at the end of a circuit.

Feature	2-way valve	3-way valve
Function	Opens/closes or throttles flow to the coil	Diverts flow between coil and bypass
System flow	Varies with load	Remains roughly constant
Suitable pump	Variable speed pump	Fixed or variable speed pump
Additional requirement	Differential pressure control / bypass	Bypass line (on the valve or in the piping)

Actuator Options

Thermoelectric (on-off) actuators: A heated element slowly opens or closes the valve. Normally closed (NC) and normally open (NO) versions are available.
Motorised on-off actuators: Drive the valve fully open or fully closed according to the thermostat’s on/off signal.
Modulating actuators: Hold the valve in intermediate positions using analogue signals such as 0–10 V, giving more precise temperature control.

The supply voltage (for example 24 V or 230 V), the control signal and the valve position on power failure (NC/NO) must match the thermostat or building automation system.

Fan Coil Valve Selection Criteria

Fluid: Water or water-glycol; the glycol ratio affects material compatibility and flow calculations.
Operating pressure and temperature: The valve’s pressure rating and temperature range must cover the system values.
Flow rate and Kv value: Size the valve by the Kv value required for the coil’s design flow; selecting by pipe size alone degrades control quality.
Connection type and size: Must suit the fan coil connection and the pipework.
System type: 2-pipe systems usually need one valve per unit, while 4-pipe systems use separate valves for the heating and cooling coils.
Control type: On-off or modulating control determines the actuator type.
Power consumption and tightness: Low-power actuators and valves with good shut-off tightness reduce operating costs.

Tip: Installing the fan coil valve on the coil return with a strainer and isolation valves upstream prevents clogging and makes servicing easier. Follow the manufacturer’s instructions for mounting orientation.

Frequently Asked Questions

What is the difference between a 2-way and a 3-way fan coil valve?

A 2-way valve opens and closes the flow to the coil, so system flow varies with load. A 3-way valve diverts flow between the coil and a bypass and keeps the circuit flow roughly constant.

What do normally closed (NC) and normally open (NO) actuators mean?

They describe the valve position when the actuator is not powered. With an NC actuator the valve closes on power loss; with an NO actuator it stays open. The choice depends on the thermostat logic and the system’s safety needs.

Why is the Kv value important when selecting a fan coil valve?

The Kv value indicates how much flow the valve passes at a given pressure drop. If it does not match the coil’s design flow, the valve either delivers too little flow or loses control accuracy.

Conclusion

Fan coil valves are control components that directly affect comfort and energy efficiency in heating and cooling systems. With the right 2-way or 3-way valve for the system, a correct Kv value and a compatible actuator, fan coil units run in a balanced and economical way. Explore suitable products on our HVAC valves page or contact the ORFA sales team for technical support.

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