I changed out my R22 unit on the 2nd floor to R410a. The line set ran down an interior wall to the underfloor crawl space and then out to the condenser. The existing line set was flushed out with a solvent made for this purpose. No problems thus far for 5+ years.
If replacing the line set was a big pain in the neck, I would have tried the solvent magic goop. But in my last install the new lineset was easy to put in place, and the cost for the parts was $150.
My line of thinking:
- Will the goo work for me? Like most installations, there are dips in both lines, so some of the old lube and the new solvent/neutralizer, etc is almost surely going to remain in the line. IIRC, there was a rash of Copeland compressor failures a few years ago blamed on these flush kits, and I did not want to get into a blame game if that happened to me.
- The existing copper lines had been in place for decades. I know copper water lines do erode at places when water velocities are high, and the gas/entrained droplets in the refrigerant loop can move very quickly. Also, copper does work harden due to vibration, and the vibration can be readily felt when the old system was running (I think slugs of liquid refrigerant moving about).
Anyway, the new lines weren't expensive, the guy would be there with his nitrogen, vacuum pump, refrigerant, torch, etc and ready to do the connections, so no increased labor cost to use the new copper. The insulation on the suction side was generous and new, not like the insulation on the old set that was brittle and cracked. The cost/hassle factor of a failure of the lines was also a big factor in my decision.
Again--there's nothing absolute about my rationale. If the situation were different, I might have attempted to re-use the line set.
FWIW: I have been known to go a
bit overboard in the quest for increased reliability. For example, when I replace our home AC in a few months, I'll be going with a SEER 14 unit rather than a higher efficiency one. This eliminates the need for the thermal expansion valve (TXV) that is a must-have in the 16+ SEER installlations. We only cool for a few months each year, and the benefit of going to a higher SEER unit is not huge. In my system there will be only one moving part in the refrigerant loop (the compressor). Eliminating the TXV removes a second moving mechanical part/potential failure point in the AC refigerant loop. Since I can't service anything in that refrigerant loop myself, and getting someone else to do it is expensive and a hassle, I'm keen to keep it simple and reliable.