Specification for Cold Storage Refrigerant Filling | Practical Points for Weighing Filling, Checking Liquid Mirrors, and Overheating Temperature Review
HFC refrigerants R404A and R507 belong to mixed refrigerants and must be added by weighing. However, estimating the amount of refrigerant based on pressure and current can result in significant errors, making it easy to add more or less.
Before filling, evacuate and ensure that the liquid refrigerant is qualified. Liquid refrigerant should be added from the reservoir side. It is forbidden to add a large amount of liquid refrigerant from the suction side, as it can easily cause compressor liquid hammer.
The nameplate of the Xiteluoduo unit indicates the standard refrigerant filling amount, including the unit body and standard pipelines. Extending the evaporator pipeline requires additional calculation of refrigerant addition per meter of pipeline volume.
When the sight glass is full of liquid without bubbles, it only means that the refrigerant on the supply side is sufficient, not equal to the standard amount of refrigerant added. Many units also have no bubbles when the refrigerant is excessive, which can easily lead to misjudgment.
After stable operation for 30 minutes after refueling, two indicators must be rechecked: evaporation superheat and condensation pressure. Only when both are matched with the working conditions can the refueling be considered qualified.
R404A is a non azeotropic refrigerant, and its components shift after fluorine leakage. Only refrigerant is added without recovery and refilling, resulting in continuous deviation of the system's operating characteristics from the design values.
Many construction sites are accustomed to adding fluorine while monitoring the temperature of the warehouse. When the temperature drops, the refrigerant supply stops. After the load changes, the refrigerant quantity no longer matches, and high-pressure protection is frequent during high temperature seasons.
For long-distance foreign trade projects, a refrigerant filling calculation table is attached with the goods to clarify to local maintenance personnel the formula for refrigerant supplementation after pipeline extension and evaporator expansion.
The environment for adding refrigerant should avoid high humidity on rainy days, as humid air can easily enter the system during the filling operation, leading to excessive moisture and subsequent ice blockage and oleic acid formation.
Typical characteristics of refrigerant excess: high condensation pressure, heavy frosting on the return pipe, and low superheat; Characteristics of insufficient refrigerant: low evaporation pressure, excessive superheat, slow cooling.
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FAQ
1. Recommended way to add R404A/R507 refrigerant? Prioritize weighing and adding, with the highest accuracy.
Can liquid refrigerant be added from the suction side? Strictly prohibited, it is easy to directly damage the compressor by liquid impact.
Does the absence of bubbles in the sight glass indicate that the refrigerant is just right? No, too much refrigerant can also cause no bubbles.
Can R404A be directly replenished due to a large amount of leakage? Not recommended, component offset, it is best to recycle and re inject.
What is the typical phenomenon of adding more refrigerant? High condensation pressure, low superheat of return gas, and easy liquid return.
6. Typical manifestations of insufficient refrigerant addition? Low evaporation pressure, high superheat, and weak cooling.
7. How long until the refueling is stable before rechecking the parameters? Recheck after stable operation for 30 minutes.
