When it comes to adding refrigerant to a refrigeration system, there are several different methods a technician can use to determine the correct amount needed. The preferred method will typically depend on the type of system; for example, the method selected for a small self-contained reach-in cooler will typically be different than that for a large walk-in cooler. The type of metering device (capillary vs. TXV) and the piping arrangement (remote vs. self-contained) will also be major factors in determining the best method.
When adding refrigerant to a self-contained capillary tube system, generally the best method is to weigh in the charge. It may not be the only method, but it is definitely a very accurate means of adding the right amount of refrigerant into these systems.