I was watching over the shoulder of my HVAC service tech who was attempting to get the old POE oil out before putting new in. The system is a 3.5 ton Goodman heatpump on 410A. The reason for the new oil is that both the flowrater and the TX have jammed up over a period of about 4 years. The flowrater had a waxy residue on it when it was removed a while back. That just isn't right. So they are completely flushing the system and replacing the oil and 410A.

-Trouble is only about 2 tablespoons of POE oil came out. He was pushing nitrogen into the valve on the large diameter line and venting through the valve on the small diameter. This would require the oil to travel from the compressor all the way through the coils in the outdoor unit to get out? This just seems like the difficult way to get the oil out to me. But IANAHVST. Any comments?