What Is an Expansion Valve? -HUBHVACR (2025)

What Is an Expansion Valve?

Controlling the refrigerant flow in the refrigeration system is very important for cooling effect, capability, and cooling capacity. This is where the expansion valve plays its role.

An expansion valve controls the refrigerant flow in the refrigeration system by reducing the pressure and temperature of the refrigerant before it enters the evaporator coil.

Because its main use is in the HVACR industry, an expansion valve is also called HVAC Expansion Valve, TXV, or EXV.

This guide will help you get an understanding of system efficiency, temperature control, troubleshooting, and installation.

Before reading this guide, you should first read what is thermostatic expansion valve, what is electronic expansion valveand What is capillary tube expansion valve.

What Is the Purpose of an Expansion Valve in HVAC&R?

When you learn about what is refrigeration system and how an air conditioning unit or refrigeration unit provides cool or hot air.

You would know it’s done by the process of changing the refrigerant pressure and temperature from liquid to vapor. An expansion valve is the device that does this exact same task.

The expansion valve is located at the high-low pressure dividing line of the refrigeration or air-conditioning system. It connects the condenser and the evaporator. There is an important component (filter) before the expansion valve, which ensures the reliable operation of the expansion valve.

From that location, it mainly serves two purposes in the cooling process.

Firstly, it controls the refrigerant gas amount that will enter the evaporator;

Secondly, it maintains the difference of pressure between the condenser and evaporator where it is located.

This guide can help you know “how expansion valves work?”.

What Types of Expansion Valves?

All types of expansion valves are developed based on basic working principles but differ in control logic and control methods.

For example, thermostatic expansion valves, automobile air conditioning expansion valves, and automatic expansion valves achieve mechanical control through structural design and optimization, capillary expansion valves use friction control (throttle principle), and electronic expansion valves are controlled through coils and electrical signals.

These blogs will help you better understand the differences between different expansion valves.

Difference Between a Thermostatic Expansion Valve and a Capillary Tube, the Difference Between a Thermostatic Expansion Valve and an Electronic Expansion Valve,What is Internal and External Equalizer Expansion Valve(TXV).

• Thermostatic Expansion Valve (TXV)
• Electronic Expansion Valve (EEV or EXV)
• Capillary Tube Expansion Valve
• Automatic Expansion Valve (AEV)
• Manual Expansion Valve
• Float Expansion Valve
• Car AC Expansion Valve

Which Expansion Valve Should You Use?

The choice of an Expansion Valve is closely related to the type of compressor, the application range of the refrigeration and air conditioning unit, the cooling capacity, the pressure, the type of refrigerant, and so on.

Before understanding the application of Expansion Valve, you need to read .

Whether you are purchasing or designing an expansion valve, you need professional technical support.

HUBHVACR is your neighborhood HVAC expert. If you have any expansion valve purchasing and consulting needs, please contact us directly.

We can provide you with genuine expansion valves, such as Danfoss, Emerson, Sporlan, and Saginomiya. Sanhua, STF, DUNANA,etc.

1.Expansion Valve for HVAC

The HVAC expansion valve is used in several HVAC applications including air conditioning systems, split air conditioners, central air conditioners, and other variable refrigerant volumes and different refrigerant flow applications.

As these application cooling requirements demand frequent changes in temperature and precise control, the expansion valve also needs to be one that can control refrigerant flow with accuracy to ensure maximum comfort.

So, they can use electronic expansion valves that use an electronic controller to send much more accurate signals.

VRV/VRF air conditioners also use electronic expansion valves to control the mass flow rate of each indoor unit.

In some air conditioning systems, you might need to use either a fixed-speed compressor or an inverter-type compressor so that you can use both TXV and EEV according to the project needs.

Other kinds of valves are used in air conditioners, for example, four-way reversing valves, ball valves, check valves, solenoid valves, etc.

2.Expansion Valve for Water Heater Unit & Heat Pump:

In applications like water heater units, heat pumps, heat pump compressors, summing pool heat pumps, heat pump drying machines, inverter heat pumps, heat pumps for water heaters, inverter mini split heat pumps and dehumidifiers can use both TXV or EEV.

Based on their compressor type and required temperature levels, the expansion valve can be different.

For example, heat pump drying machines play very important roles in fruit, vegetable drying, and wood drying in industrial, agricultural, and commercial fields.

From the affordability point of view, a thermostatic expansion valve can be used because of its cost-effectiveness, and also an electronics expansion valve can be used because of its higher precision of temperature for better results.

3. Expansion Valve for Refrigerator Freezer

Refrigerator valve mainly refers to the expansion valve that is used in domestic refrigerators, deep freezers, water coolers, room air conditioners, fridges, etc.

It is mainly the capillary valve expansion valve, which is most commonly used in household refrigerators because of its simplicity, accuracy, and efficiency.

This expansion valve is very easy to manufacture and not that costly.

Related products: walk-in refrigeration units, self-contained refrigeration units, remote condensing units, drop-in refrigeration units, indoor condensing units, commercial refrigeration units, etc.

4. Thermal Expansion Valve for Transportation Refrigeration:

Transport refrigeration units, also called truck refrigeration units, can include vehicle, container, marine & rail applications and are very important in food processing, distribution, and retail that need to maintain the temperature according to the required capacity to maintain the food quality.

So, a transportation refrigeration unit always uses a thermostatic expansion valve that is budget-friendly and can maintain a constant set point temperature.

5. Thermal Expansion Valve for Rail Transportation

High-speed transportation like electric buses, rapid transit, and high-speed railways also uses an air conditioning system where the compressor delivers consistent temperatures。

So it also needs to use a TXV expansion valve.

It operates at the same speed, and it is affordable in maintenance and simple in access to replacing components.