I'm hoping you misunderstood what the installers are going to do. They can install a new evaporator coil that is rated for R-410A without changing from R-22 refrigerant while still using the existing condensing unit. I say this with the assumption that your current system is using R-22.
If, as you stated they are going to change refrigerant type, I would assume that they would be changing from R-22 to R-410A, and if that was the case the condensing unit would need to be changed. Systems using R-410A refrigerant must be able withstand much higher pressures than R-22 systems and they also use a different type of oil.
"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright
Last edited by fabrk8r; 08-23-2010 at 10:32 AM.