When retrofitting R-22 systems with the newer R-410A systems, the best practice is to replace all components in the system, including the line sets, to assure residuals do not contaminate the new system. However, situations exist where it is uneconomical to remove line sets, such as when they are recessed inside finished walls, or under concrete foundations and/or slabs.
In these cases, it is imperative that you flush the old line sets with Qwik System Flush® to remove the residual oil, acid, and moisture! Otherwise, these contaminants in the old lines will cause problems in the new system. Residual mineral oil and contaminates from the old system can contaminate the polyolester oil in the new R-410A system, forming a viscous sludge. Residual acid will continue to cause problems with a new system and moisture will accelerate the future formation of acid. Qwik System Flush® is the only flushing solution specially formulated to remove acid and water in addition to oil, sludge and contaminants.
In addition, if the oil line sets are located under the slab or in the walls of an air-conditioned house, where they can become cooler than the surrounding outdoor air, those tube runs can condense significant amounts of water, if these lines are left exposed to the air for any significant time during the change out. Never leave the line-sets open to the air and use Qwik System Flush® to get all the contaminates including acid and water out of these lines.