The Capillary Tube vs. The Thermal Expansion Valve

All refrigeration equipment works the same way, circulating a chemical refrigerant to move heat from inside the cabinet to outside. That process enables it to maintain the cold temperatures that keep your perishable products chilled. That said, the way equipment manufacturers design their systems sometimes varies, and refrigeration experts often have strong opinions over many of the technical details that account for those differences. One such debate is over whether a capillary tube or a thermal expansion valve is the superior component.

Thermal expansion valves and capillary tubes both control how refrigerant circulates through the system in order to chill your products quickly and efficiently. More specifically, these devices throttle the amount of refrigerant that passes into the evaporator to maximize the amount of heat it can absorb.

The evaporator is designed to allow refrigerant to evaporate into a gaseous state as it absorbs heat, thereby cooling the cabinet. If too much refrigerant is allowed in, that transition can't occur and the equipment cannot do its job. That's why an accurate metering device is essential to the operation of a refrigerator.

The Simplicity of a Capillary Tube

The capillary tube is the simpler of the two components, with no moving parts and consisting of little more than thin copper tubing. The relationship between the temperature and the pressure of the refrigerant will determine how much gets drawn into the capillary tube and how much is allowed to pass into the evaporator.

Advantages of a Capillary Tube

Lower Equipment Costs - Because capillary tubes are much simpler than TXVs, they come at a lower cost. Cap tubes are built into entry-level and mid-grade refrigerators to help control the final cost of the equipment.

Lower Repair Costs - The simplicity and lower cost of the component also means that it'll likely be easier and cheaper to replace if it should malfunction.

Disadvantages of a Capillary Tube

Slower Response - The simplicity of a capillary tube's design is also the source of its biggest drawback. A cap tube can't respond as quickly to temperature changes as a TXV. So after your refrigerator's door has been held open or when room-temperature food is added and the compressor kicks on, the capillary tube will take some time to adjust and provide the optimal conditions.

The Sophistication of a Thermal Expansion Valve

A thermal expansion valve brings more moving parts into the picture. It operates by monitoring the temperature of the refrigerant and responding by opening and closing a valve to control the flow of refrigerant to the evaporator.

Thermal expansion valve

Advantages of a Thermal Expansion Valve

Quicker Response - Their increased complexity allows TXVs to respond more quickly to temperature changes than capillary tubes. This benefit translates into quicker temperature recovery when your equipment's door is opened and food is added.

Less Equipment Wear and Tear - The fact that TXVs throttle refrigerant more smoothly than capillary tubes means they take some of the pressure off of the equipment's compressor. That means the compressor in a system with a TXV can potentially last longer than one in a cap tube system, everything else being equal.

Disadvantages of a Thermal Expansion Valve

Higher Equipment Costs - Their complexity makes thermal expansion valves more expensive than capillary tubes. Typically, only premium-quality equipment includes thermal expansion valves.