The Expansion Valve Adjustment Guide

Adjusting expansion valves can optimize system performance, but it requires careful measurement, patience, and adherence to manufacturer recommendations. This is something you can only learn during an HVAC/R program under the strict supervision of an expert instructor. During our program, you will receive hundreds of hours of hands-on training that builds your confidence in all aspects of HVAC including expansion valve adjustment. Plus, The Refrigeration School (RSI) offers an accredited HVAC/R program that focuses on many of the technical aspects of HVAC that you will need to learn to be a successful HVAC technician.

What is an Expansion Valve in HVAC?

An expansion valve, also known as a thermostatic expansion valve (TXV), electronic expansion valve (EXV) or capillary tubes is an essential component in the refrigeration cycle of an HVAC system. The expansion valve regulates the flow of refrigerant into the evaporator coil, allowing the HVAC system to cool and heat your home.

Thermostatic Expansion Valve (TXV): Uses a temperature-sensing bulb to adjust refrigerant flow based on evaporator temperature.

Electronic Expansion Valve (EXV): Controlled by sensors and an electronic controller for precise refrigerant flow.

Capillary Tubes: Fixed opening with no adjustable settings, common in simpler systems.

How Does an Expansion Valve Work?

The expansion valve reduces the pressure and temperature of the refrigerant as it moves from the high-pressure liquid line into the low-pressure evaporator. This pressure drop allows the refrigerant to absorb heat from the air being cooled.

How Do You Safely Adjust an Expansion Valve?

Adjusting an expansion valve requires the right tools and careful attention to detail. Incorrect adjustments can waste energy and damage to the HVAC system. Here are the steps for safely adjusting an expansion valve:

Step #1: Measure System Superheat

Superheat is the difference between the refrigerant’s temperature at the evaporator outlet and its saturation temperature (pressure-temperature relationship). To measure superheat, attach a pressure gauge to the system’s low-pressure side. Use a temperature probe to measure the refrigerant temperature at the evaporator outlet. To Calculate superheat:

Superheat = Measured Temperature – Saturation Temperature

The ideal superheat range is typically 8–12°F, but this can vary depending on your HVAC/R system.

Step #2: Locate the Adjustment Mechanism

Most expansion valves have an adjustment screw, so consult the system’s service manual for the exact location and direction for adjustments (e.g., clockwise to reduce refrigerant flow, counterclockwise to increase).

Step #3: Make Small Adjustments

Start by adjusting the screw in small increments (typically ¼ or ½ turn at a time). Then, allow the system to stabilize for 10–15 minutes after each adjustment before taking additional measurements.

Step #4: Recheck Superheat

After the HVAC system stabilizes, re-measure the superheat. Continue adjusting until you reach the desired superheat range.

Step #5: Monitor System Performance

After adjusting the expansion valve, keep an eye on the HVAC system to make sure it is working properly and that no unusual noises or pressure fluctuations happen.

When to Consider an Expansion Valve Adjustment

Expansion valve adjustments are not always necessary and should only be completed by a fully trained HVAC/R technician. Some of the things you will need to look for when you think an adjustment is needed include:

Insufficient Cooling or Heating

If the HVAC system is having a hard time maintaining the desired temperature, you may need to  adjust the expansion valve to increase refrigerant flow.

High or Low Superheat Levels

• High Superheat: Indicates not enough refrigerant entering the evaporator.
• Low Superheat: Suggests too much refrigerant, which can lead to flooding and potential compressor damage.

Compressor Short Cycling

The compressor may turn off and on regularly because of uneven refrigerant flow or an incorrect expansion valve setting.

Frost Formation on the Evaporator Coil

Frost buildup is often a sign of excessive refrigerant flow or poor heat exchange.

System Retrofit or Refrigerant Change

When replacing refrigerant, the expansion valve settings may need adjustment to match the new refrigerant’s properties.

Routine Maintenance and Performance Optimization

It is important to check superheat levels and expansion valve performance as part of your routine HVAC maintenance.

Final Thoughts

By understanding when and how to adjust an expansion valve, you can ensure that the HVAC system runs efficiently, maintains the right temperature, and prevents unnecessary wear and tear on components. Regular maintenance, combined with accurate adjustments, keeps HVAC systems running efficiently. This and many other technical aspects of HVAC are discussed in the HVAC/R program at RSI. 

To learn more about our HVAC program offered at the Phoenix, AZ campus, contact us at The Refrigeration School or call 1-888-671-5803.