If bubbles are seen in the liquid-line sight glass, what does this suggest about the refrigerant charge?

Seeing bubbles in the liquid-line sight glass indicates that the refrigerant charge is low. In a properly charged refrigeration system, the sight glass should show a clear, liquid refrigerant without bubbles. The presence of bubbles suggests that there is insufficient refrigerant to absorb the heat, which leads to the mixing of liquid refrigerant and vapor in the sight glass. This can cause inadequate cooling performance and can be indicative of potential issues such as refrigerant leakage or insufficient charging.

Although other conditions might lead to visible issues in the sight glass, such as contamination or overcharging, these conditions typically manifest differently. Contamination would generally present as discoloration or unusual particulates in the refrigerant. Overcharging would more likely cause a completely full sight glass without bubbles as the liquid refrigerant is compressed too much, rather than showing a mix of liquid and gas. Therefore, the correct interpretation of bubbles in the sight glass consistently points to a low refrigerant charge.