TXV Explained: Complete Guide On Thermal Expansion Valve

HVAC products are made of several mechanical elements, and their function includes the technical process. However, it is advisable to trust professionals to repair and maintain heating & cooling equipment.

If you want to know about these specialized processes and terms, this guide will help you understand one of your equipment’s crucial elements and functions.

We will explain the TXV and all the important information around it for your quick reference while browsing for the best equipment for the house.

Let’s start with the definition and discuss other details about the thermal expansion valve.

What is TXV (Thermal Expansion Valve)?

A thermal expansion valve, also known as a thermostatic expansion valve, TXV, TEV, or TV valve, is an integral component for air conditioning systems and vapor-compression refrigeration.

It manages the quantity of refrigerant released into the evaporator. It regulates the high pressure of the refrigerant that flows out of the evaporator to low pressure for an enduring value. 

Thermal expansion valves are metering devices that release liquid refrigerant into the low-pressure part. It does not react to the temperature, such as a pressure-controlled valve or capillary tube.

What Does A Thermal Expansion Valve Do?

  • The thermal expansion valve separates the air conditioning unit’s low- and high-pressure parts.
  • The TXV regulates the standard pressure of the refrigerant while it enters the compressor. Usually, liquid refrigerant remains under high pressure when entering the thermostatic expansion valve.
  • The TXV facilitates the consistent and even distribution of liquid refrigerant across the compressor with the required pressure.

What TXV Can’t Do?

People get confused about technical elements and functioning. To have a clear understanding of the work that TXV does, we need to know what it does not do.

  • TXV does not regulate air temperature. It does not control the suction or pressure at the unit’s head.
  • There is no impact on humidity control of the AC.

How does the Thermal Expansion Valve work? 

The thermal expansion valve regulates the liquid coolant from the outside condenser and controls the quantity of the refrigerant that runs into the indoor evaporator coil.

The TXV reduces the pressure to allow the liquid to boil at a lower temperature. If you have any idea about how air conditioners work, you must know the importance of pressure management and liquid boiling for the proper operation of the HVAC equipment. The valve changes the pressure to a required level to ensure an efficient and safe operation.

The boiling coolant absorbs the heat from indoor air. After that, it carries the heat to the condenser coil and is released through the radiator-like fins. Later it flows back to the compressor and repeats the cycle. Boiling the refrigerant is not possible without controlled pressure, and without it, your machine will not function efficiently.

Parts of the TXV

  • Valve Body: The valve body is the outer portion of the TXV. It includes all the other elements and an opening to control the flow of the refrigerant.
  • Diaphragm: Generally made of metal Diaphragm puts pressure on the pin.
  • Pin or Needle: It moves up and down to regulate the flow of the liquid refrigerant.
  • Spring: It functions to counter the pressure or force of the needle
  • Capillary Lines and Sensing Bulb: The quantity of the liquid refrigerant for boiling is crucial. Capillary lines and sensing bulb determines the coolant requirement to flow within the compressor and boil under low pressure.

Checkpoints before HVAC expert arrives

We have explained the TXV, its functioning, and its parts. The next point to consider is ways to troubleshoot the malfunctioning TXV. 

If the air conditioner is not working and you suspect something is wrong with the valve, the next logical step is to call an HVAC expert to diagnose and resolve the problem. Before calling or waiting for a technician, you can ensure that the valve is working or not through the following steps;

  • Firstly, check whether the unit is plugged in and the power is on.
  • Remove unnecessary covers from the TXV.
  • Go through the user manual to find the TXV on the unit. After locating, remove the sensing bulb out of the suction bulb well
  • Place the bulb on your hand or put it into some warm water for a few minutes. It will increase the temperature of the bulb. At the same time, refrigerant should start flowing into the evaporator.
  • If it does not flow, your TXV needs repair or replacement entirely.

Reasons For Dysfunctional Thermal Expansion Valve

The most common and ignored reason for AC problems is dust and debris. We often check for technical aspects, whereas the problem lies with cleanliness.

Accumulated dust and debris could be a reason for the dysfunctional valve. Make it a habit to check regularly and keep it clean for durable and efficient operation.

There might be several other technical reasons involved for malfunctioning TXV functioning. Call for an HVAC expert. They will diagnose and explain the exact reason for the problem. They can also replace the valve if required.

Symptoms to recognize the problem with TXV

  • Short-cycling during the low-pressure control
  • Low compressor amp draw
  • Increased discharge temperature
  • Lower condenser split and condensing (head) pressure
  • Normal to higher subcooling for the condenser

Cost and Process of Replacing a Thermal Expansion Valve

With the arrival of e-commerce companies such as Amazon, buying these components have become convenient and beneficial. According to the technician’s recommendation, you can compare different brands, features, costs, delivery options, etc., and buy a TXV.

The average price of a Thermal Expansion Valve is between $75 to $200, which varies according to brands and models. HVAC professionals can take up to 3 hours to install the new valve in place of the old one.

They test & run the unit and hand over a fully functional air conditioner. Labor charges range from $150 to $300, making total replacement cost on an average of $225 to $500.


We hope this guide will help properly understand the Thermal Expansion Valve, its functions, parts, and replacement procedure with a price range.

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