Filter driers are usually installed in the liquid line of a dry-expansion refrigeration system, where they have a dual function.First, they trap coarse particulate contamination and copper shavings, and second, they capture any moisture present in the system. For this purpose, modern filter driers are equipped with a drier core consisting of a 100% molecular sieve for optimal drying performance and filtering.The filter drier should be replaced each time the refrigeration system is opened.

Drying capacity 

If you look at a filter drier data sheet, you will always see the term ''drying capacity''. This specifies the amount of refrigerant that can be dried by the filter drier with a specific type of refrigerant at a specific temperature, based on a certain moisture concentration in the refrigerant before and after the drying process. 

If the refrigerant charge of the planned system is not yet specified, a suitable filter drier can be chosen based on the liquid capacity. The liquid capacity refers to the cooling capacity in kilowatts when the drier is installed in the liquid line.