1. Remove the old filter-drier. (If it is silver-brazed, use a tubing cutter and cut about one-fourth inch from the drier. If it is a flared connection, unscrew the nuts.) Do not use the same flare again as it can become weak from tightening and loosening the nut. Cut the old flared end off and make a new one.
2. Install the new drier paying heed to the flow-direction arrow on the body of the new drier. When using a flared connection, wrap the male threads of the connector (on each end of the drier) with Teflon tape to get a good, leakproof seal.
Residential units do not use flared connections because of their smaller size of tubing on which brazing works easily. Some of the driers used in residential units also come with access valves (see figs. 76e and 76f). Commercial filter-driers are sized according to the tonnage of the unit. Before buying one, take a look at the nameplate on the unit to see what type of refrigerant is used. Filter-driers are made for different types of refrigerant. Whether a flared or a brazed connection is used, determine what size tubing it has to be connected to and buy a filter-drier for that particular tubing size (see figs. 76b and 76c). Some filter-driers are installed on liquid lines and some on suction lines. Suction-line filters are always installed after a compressor burnout as close the compressor as possible. (See fig. 76a for the brazing technique on a commercial type drier.) When installing a filter-drier on a residential unit, be sure to insert the capillary tube about one and a half to two inches into the filter-drier entry tube. The capillary tube should not touch the element inside the drier, but should be in far enough to preclude any possibility of melted solder running in over the end of the capillary tube, plugging it. Before brazing is begun, the filter-drier entry tube has to be crimped along one side to form a snug fit around the capillary tube.