4500-902

The Ranco® Sight Glasses are installed after the filter drier in the liquid line of refrigerating systems. Typically, in a system with an expansion valve, a sight glass is usually fitted in the liquid line immediately after the filter drier. Sight glasses are typically used in refrigeration systems in order to observe the property changes of the refrigerant (liquid/vapor) itself, but also to indicate whether the moisture content of the refrigerant is within an acceptable range. The sight glass also indicates whether liquid refrigerant is present at the expansion component. If the moisture content is within the acceptable range, the indicator color is green and no further action is necessary. If the indicator is yellow, there is a problem with the moisture content of the refrigerant. Excessive moisture content can cause icing of the expansion valve if the evaporating temperature is below freezing. In addition, excessive moisture in the system reacts with the oil normally used in modern refrigeration systems (polyester oil) to form acids. Another phenomenon of Frothing in the sight glass indicates either a shortage of refrigerant or that the refrigerant in the liquid line is not entirely in the liquid state.