>>508541567They transfer the heat from inside the house to outside the house. Also the refrigerants are supposed to be enclosed, it all depends on resi vs commercial and who the tech is. When I started, in commercial and industrial if a system lost like 5 or 10% of total charge the leak would have to be repaired before charging. Residential doesn't have thtlat requirement. I had one dude spend like 3k to keep his AC going for 2 weeks before actually replacing his evap coil and that's separate from the bill for actually fixing and charging it.