Complete process of thermal expansion valve debugging | Overheating setting, dirt blockage, installation of temperature sensing package and pit avoidance guide
Thermal expansion valve is a flow control valve for cold storage systems, which relies on a temperature sensing bulb to sense the temperature of the return pipe, adjust the refrigerant supply volume, stabilize the superheat of the evaporator, and balance cooling and anti backflow.
The standard superheat setting for low-temperature cold storage R404A/R507 system is 4-6K; for medium high temperature preservation storage, it is 6-8K. If the superheat is too low, it is easy to cause liquid hammer and if it is too high, there will be insufficient heat transfer.
The basic opening of the expansion valve for the Xiteluo complete set of units is pre adjusted before leaving the factory, and only fine adjustments are made on site. It is prohibited to rotate the adjustment rod significantly at once, adjust it by 1/4 turn each time, and wait for 15 minutes to observe.
The installation position of the temperature sensing package must be closely attached to the horizontal section of the return air pipe, avoiding the accumulation of liquid bends. The insulation layer outside the package should be tightly wrapped and not exposed to the hot air in the computer room, otherwise the temperature sampling will be distorted.
The blockage of the inlet filter screen of the expansion valve is a high-frequency fault, manifested by frosting in front of the valve, slow cooling, and low system pressure. The supply of liquid can only be restored after cleaning the filter screen.
Many debugging personnel blindly reduce the degree of superheat in pursuit of cooling speed, resulting in continuous liquid accumulation at the tail of the evaporator and frost formation in the return pipe spreading to the compressor, leading to a sharp increase in the risk of liquid hammer.
The expansion valve has a maximum operating pressure limit of MOP, and the selected MOP value is higher than the saturation pressure corresponding to the evaporation temperature to prevent pressure rise after shutdown, which may cause the valve to continue to open and cause liquid return during startup.
For tropical foreign trade projects with high temperatures in the computer room, the insulation of the temperature sensing package needs to be thickened. At the same time, MOP should be selected to match the local summer condensation conditions to avoid shutdown and migration of liquid back.
Remember to adjust the direction of the expansion valve: clockwise rotation increases the preload force of the spring and the degree of superheat; Rotate counterclockwise to reduce superheat and increase liquid supply.
Parallel multi evaporator system, with each evaporator independently equipped with an expansion valve. It is not recommended to use a single valve for multi way liquid separation, as the load on each circuit is uneven and some branches are prone to liquid return.
Implant 10 popular search keywords: thermal expansion valve, cold storage expansion valve debugging, R404A compressor, R507 compressor, evaporator superheat, compressor liquid hammer, frozen tunnel compressor, refrigeration maintenance company, compression condensing unit, cold storage engineering supplier
FAQ
What is the standard superheat setting for low-temperature cold storage? Recommend 4-6K.
What is the effect of counterclockwise adjustment of the expansion valve? The degree of superheat decreases, and the supply of liquid increases.
What are the mandatory requirements for installing temperature sensors? Stick the horizontal return pipe, keep it warm, and avoid liquid accumulation bends.
4. Typical phenomenon of dirty and clogged expansion valve filter screen? Frost formation in front of the valve, poor cooling, and low evaporation pressure.
5. How much can the expansion valve be adjusted at most each time? Perform a 1/4 turn and observe for 15 minutes.
What is the function of MOP? Limit the opening range of the valve after shutdown to prevent backflow during startup.
Can multiple evaporators share one expansion valve? Not recommended, uneven load can easily cause liquid to return.
