Remember having clean copper lines that connect your air conditioner to the evaporator coil (located inside your house connected to your furnace) is one of the most critical pieces of the installation process.
BEWARE OF COMPANIES THAT USE SCRAP COPPER LINES, OLD COPPER LINES THAT HAVE BEEN CUT OUT FROM OTHER JOBS, AND EXISTING LINES THAT ARE CONTAMINATED WITH DIFFERENT OIL, CARBON OR ACID.
Using your existing copper lines on a new installation is okay to do, but it will cost more money to clean them, and if you don’t clean them, you need to replace them. There is only one way to clean them and it is not with nitrogen alone.
With any company you choose, make certain it is listed on the proposal in detail as to if you are getting the line set cleaned or replaced. Should you ever have a problem, this information will serve as proof to the manufacturer of the installation process that was used. Improper install can void the manufacturer warranty.