The expansion valve is likened to the most important “metering station”, directly affecting cooling performance and compressor safety. Adjusting it incorrectly not only wastes electricity but also risks liquid flooding that seriously damages the equipment. In this article, the engineering team at Tan Long We will provide detailed instructions. how to adjust cold storage throttle valve based on the most accurate superheat measurement method. With more than 20 years of experience in designing and cold storage installation industrial systems, we will help you master the adjustment procedure so your system always runs stably and durably.
What is a thermal expansion valve?
The thermostatic expansion valve is a key device in the refrigeration cycle, whose main job is to reduce the pressure and temperature of the refrigerant as it passes through. The purpose is to let the refrigerant drop in pressure and boil at the required low temperature, so the system achieves its performance
In the systems industrial cold storage today, the expansion valve is an extremely important component, usually imported from reputable European brands (such as Danfoss) for durability and stability. A firm grasp of this component's construction is the essential foundation for a technician to carry out how to adjust cold storage throttle valve to standard, avoiding common errors such as liquid flooding or low refrigerant charge.
Today, on projects delivered by Tan Long , we usually prefer the two most common types: the internally equalised thermostatic expansion valve and the externally equalised thermostatic expansion valve. Let us look in detail at the construction and operating principle of these two valve types.
Construction and operating principle of the thermostatic expansion valve
To perform how to adjust cold storage throttle valve accurately, the technician first needs a firm grasp of the construction and the difference between the two common types: internally and externally equalised.
Internally equalised thermostatic expansion valve
The internally equalised thermostatic expansion valve is usually used in small-capacity cold storage systems, where the evaporator has little pressure drop. Using this valve type on a large system reduces cooling performance considerably because the pressure difference is not compensated.
Detailed construction: The valve comprises these main parts: the sensing bulb, the capillary tube, the flexible diaphragm, the internal equalising port, the spring, the valve pin and the valve body.
Working principle:
- Refrigerant from the high-pressure receiver enters the valve. After passing through the valve needle, the pressure drops suddenly, the refrigerant absorbs heat from the environment and begins to evaporate in the evaporator.
- The sensing bulb (fitted at the coil outlet) senses the leaving vapour temperature and transmits the pressure to the top of the valve diaphragm.
- Self-adjusting mechanism: If the valve opening is small -> less refrigerant enters the coil -> the leaving vapour temperature rises -> the bulb pressure increases -> pushing the diaphragm down -> opening the valve pin further to admit more refrigerant. Conversely, when the leaving vapour temperature is low, the valve closes down automatically.
This is the technical basis you need to understand before touching the adjusting screw when carrying out how to adjust cold storage throttle valve in the field.
Externally equalised thermostatic expansion valve
For systems refrigeration compressor large-capacity systems, refrigerant passing through a long evaporator suffers considerable pressure loss. An externally equalised valve then becomes mandatory to hold superheat steady.
Why is an externally equalised valve necessary? Consider an example with R22:
- Small coil (internally equalised): Suppose the evaporating temperature is 5°C (6.3 bar) and the spring pressure is 0.5 bar. To open the valve, the bulb pressure must reach 6.8 bar (equivalent to 10°C). Superheat is 5K — perfect for the system.
- Large coil (0.75 bar pressure drop): The coil inlet pressure is 7.05 bar. To open the valve, the bulb pressure must overcome both the inlet pressure (7.05 bar) and the spring pressure (0.5 bar) = 7.55 bar. That pressure corresponds to 13.5°C. Superheat then jumps to 8.5K (too high), reducing the effective heat exchange area and cutting cooling capacity.
Tan Long's technical solution: To eliminate the effect of the pressure drop, we take a vapour line from the sensing bulb position back to the underside of the valve diaphragm. The upward force on the diaphragm is then only the coil outlet pressure (6.3 bar) plus the spring force. The system returns to its original optimal working state.
Understanding these pressure values is extremely important in a professional cold storage design procedure, helping avoid an excessively high end-of-compression temperature that burns the lubricating oil and shortens compressor life.
Common cold store expansion valve types
Identifying the correct equipment type is the first and most important step before learning how to adjust cold storage throttle valve. Each valve type has a different construction and feedback mechanism, so the technician needs a solid foundation of knowledge to make accurate adjustment decisions. On projects designed and installed by Tan Long , expansion valves are usually classified by two main criteria: the operating system and the control function.
By operating system, we can divide them into these two groups of auxiliary equipment:
- Hydraulic throttle valves: usually found in drive systems, regulating oil or water flow. This type has a fairly simple construction, working mainly on the pressure difference between inlet and outlet.
- Pneumatic throttle valves: widely used in automated production lines to regulate compressed air flow through the system. This type is more complex than the hydraulic group and can be operated through an electric controller or by air pressure.
For industrial refrigeration, however, classification by refrigerant control function is what determines cooling performance. Depending on the scale and technical requirements of the cold storage, the user will encounter the following valve types:
- Manual expansion valve: This is the most basic type, requiring the technician to turn the adjusting screw directly as needed. Because it cannot respond automatically to a change in cooling load, how to adjust cold storage throttle valve on this type should be carried out by skilled technicians to avoid overloading the refrigeration compressor.
- Thermostatic expansion valve (TXV): This is the workhorse of the refrigeration industry, working from a temperature sensing bulb to adjust the refrigerant fed to the coil automatically. By holding superheat steady, the thermostatic expansion valve keeps the system running durably and saves considerably more electricity than a manual valve.
- Electronic expansion valve (EEV): Representing the most advanced technology, it uses a microprocessor to drive a stepper motor, allowing absolutely precise control of refrigerant flow. This valve type is usually integrated into smart systems, allowing multi-mode programming to meet the most demanding storage requirements.
Understanding these characteristics not only helps you operate the system better but is also the basis for carrying out scheduled maintenance to technical standard.
A detailed, technically accurate guide to adjusting a cold store expansion valve
To perform how to adjust cold storage throttle valve methodically, the technician first needs a firm grasp of superheat (SH).
As we know, liquid refrigerant from the high-pressure receiver drops to pressure P0 after the expansion valve and begins to evaporate at temperature T0. When the refrigerant industrial refrigeration has absorbed enough heat, its temperature rises to T1 before returning to the compressor. This temperature difference, SH = T1 – T0, is the superheat.
If the superheat figure is too large, the end-of-compression temperature jumps, easily burning the lubricating oil and damaging the refrigeration compressor. By the operating standard at Tan Long, ideal superheat should be between 5 degrees C and 7 degrees C.
The 5-step expansion valve adjustment procedure
Below are the practical steps our engineers apply when installing and maintaining cold storage:
- Step 1: Measure temperature T1: Measure the temperature at the evaporator outlet (the point closest to the sensing bulb). If the system uses a Dixell controller, you can read the coil probe value (marked P2).
- Step 2: Measure pressure P0: Use a pressure gauge to measure the pressure near the sensing bulb. On small-capacity coils, you can measure suction pressure right at the compressor return (the value shown on the low-pressure gauge).
- Step 3: Look up the reference table: From the P0 you have just measured, look up the refrigerant's property table (R22, R404A, R134a, etc.) to find the corresponding evaporating temperature (T0).
- Step 4: Calculate and adjust: Apply the formula Superheat = T1 – T0.
- If SH is below 5 degrees C: superheat is low (risk of liquid flooding the compressor), so you need to close down the expansion valve by turning the adjusting screw clockwise.
- If SH is above 7 degrees C: superheat is high (poor cooling performance), so you need to open up the expansion valve by turning the adjusting screw anticlockwise.
- Step 5: Monitor and fine-tune: After adjusting, let the system run steadily for at least 1 hour, then repeat the steps above to confirm the values are within the correct range.
Important notes on the specifications of each valve type
When carrying out how to adjust cold storage throttle valve, you need to know exactly how much each turn changes, to avoid over-adjusting and losing temperature control. Specifically, on common Danfoss valves:
- Van Danfoss TE2: 1 turn changes it by roughly 4 degrees C.
- Danfoss TE5 or TE12 valve: 1 turn changes it by only around 0.5 degrees C.
Besides the manual method, you can use the Danfoss Ref Tools app to calculate superheat automatically and most accurately. If the system still has problems after adjustment, contact the technical team at Tan Long for a site survey and a definitive fix.
Important notes and practical experience when adjusting an expansion valve
Mastering how to adjust cold storage throttle valve is only part of the operating process; for the system to run stably and protect key components such as the refrigeration compressor, you must follow the technical rules strictly. Incorrect adjustment or a lack of periodic checks not only reduces cooling performance but also risks serious mechanical damage to the whole system.
Below are the core points our technical team has distilled from many real projects:
- Choosing compatible equipment: Always ensure the expansion valve is the correct model and design capacity and is compatible with the refrigerant the system uses.
- Controlling oil and refrigerant quality: The lubricating oil must be clean, free of debris and moisture. Contaminants in the pipework are the leading cause of a blocked valve pin, which makes the result of how to adjust cold storage throttle valve inaccurate.
- Protecting the installation environment: Never place the valve in a damp position or where it contacts water directly, to prevent rust seizing the internal springs and diaphragm.
- Operating and maintenance regime: Avoid running the machine overloaded for long periods. Instead, set a schedule of periodic checks to clean the strainer and check the sensing bulb's responsiveness, so the valve always responds promptly to changes in cooling load.
We hope that this detailed account of the construction, principles and procedure for how to adjust cold storage throttle valve has given you a solid foundation of expertise for running your system effectively. At Tan Long, we not only supply genuine components but also deliver complete solutions for consultancy, design and cold storage installation industrial installation to standard. If your system has any technical problem or needs a performance upgrade survey, contact us now on our hotline: (+84) 933 357 058 – Mr. Thinh for the most professional support.
Frequently asked questions about adjusting cold store expansion valves
When does an expansion valve need adjusting?
When the store fails to reach temperature despite an adequate refrigerant charge, when measured superheat deviates from the design value, after replacing the valve or changing the store's load, and when there are signs of liquid returning to the compressor.
What are you actually adjusting when you adjust an expansion valve?
It means adjusting the superheat of the vapour leaving the evaporator. Turning to increase flow reduces superheat; turning to reduce flow increases it.
Why should the valve not be turned too far at once?
Because the system needs time to settle after each adjustment. Turning it far and assessing immediately gives a false reading, and easily leads to over-adjustment causing liquid return or starving the evaporator of refrigerant.
How dangerous is superheat that is too low?
Refrigerant that has not fully evaporated reaches the compressor, causing liquid return — the leading cause of compressor failure, through dilution of the lubricating oil and hydraulic shock in the cylinder.
How should the expansion valve sensing bulb be fitted correctly?
Clamped firmly on the suction line immediately after the evaporator, in good contact with the pipe surface, positioned as the instructions specify and insulated so it is not affected by the surrounding air temperature.
Who should carry out expansion valve adjustment?
A qualified technician with the right pressure and temperature measuring instruments. Adjusting by feel without measuring superheat is the fastest way to destroy a compressor.
Related pages
- Solenoid Valves in Refrigeration Systems: Classification and How They Work
- What is a thermal expansion valve? Structure, principle, and how to adjust a cold storage expansion valve
- Principles and procedures for standard refrigeration system gas charging
- What is a refrigerated object? Concept, classification, and applications.
- turnkey NH3 refrigeration systems
Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
