18/12/2025
What is EXV in a chiller?
EXV = Electronic Expansion Valve
It is the device that controls the flow of refrigerant from the high-pressure side (condenser/liquid line) to the low-pressure side (evaporator) in a chiller or HVAC system.
When the refrigerant passes through the EXV:
Its pressure drops suddenly
Its temperature drops
It enters the evaporator as a low-pressure, low-temperature mixture
The EXV adjusts automatically, depending on:
Load demand
Superheat value
Evaporator & suction temperature/pressure
=>Main Functions of an EXV
1. Controls refrigerant flow accurately
2. Maintains correct superheat
3. Improves system efficiency (COP)
4. Prevents liquid flood-back to compressor
5. Saves energy compared to mechanical valves
=> Types of Expansion Valves (Used in Chilllers/AC)
1. EXV (Electronic Expansion Valve)
Controlled by controller or microprocessor
Uses stepper motor
Very accurate control
2. TXV (Thermostatic Expansion Valve)
Mechanical type
Controlled by sensing bulb
3. AXV (Automatic Expansion Valve)
Maintains constant evaporator pressure
4. Capillary Tube
Fixed opening, simple systems (split AC, fridge)
5. Float Valve
Used in flooded evaporators (industrial chiller)
=>EXV in Chiller – Working (Simple)
1. Liquid refrigerant from condenser enters EXV
2. Controller calculates superheat
3. Valve opens/closes step by step
4. Correct amount enters evaporator
5. Evaporator absorbs heat → cooling happens
=>Common EXV Problems
Valve stuck open/closed
Sensor failure (temperature/pressure)
Wiring problem to controller
Blockage due to dirt/moisture
