What is an Oil trap and its application ?

What is an Oil trap and its application ?

An oil trap is a form of U-shape or a circular-shape  pipe that is used when vertical pipe length between IU and OD unit is more than  6-7 meters. An oil trap helps compressors not to lose their lubricant while discharging refrigerant toward the evaporator  and avoid the evaporator not being stuffed with compressor oil.

The responsibility of an oil trap starts when the compressor gets turned off. In this condition, oil intend to return to evaporator when the OU level is higher than IU. As a result, oil trap keeps the oil in itself and avoid the oil returning to the IU.