Well, the old hands around here will recall quite a while back, I was working on my Lennox heat pump/ Air con unit which was producing inadequate cooling while the gauge pressures didn't seem quite right. That system also had endured repeated shutdown on compressor temp due to the condensor fan motor shutting down. That issue was solved, but who knows what damage occured to the compressor?

Today temperatures were cool enough to risk a tinker on my unit and I finally assembled the recycling gear, vac pump, parts and whatnot to proceed. The issue before was inadequate cooling with low high side pressure and high low side gauge readings. Folks will recall back then I throttled back the blower, adjusted charge and measured system performance numerous time, all to no avail.

I obtained a factory 4 ton R22 expansion valve for this system. So this morning, I vacuumed out a new recovery tank, set up my Promax Minimax and recovered the system charge. I'm a newbie at this recovery biz, we used to open the manifold and walk away 30 years ago. So I don't know why I was surprised, but through the process, I had to stop, put cooling fans across the recovery tank and let pressures and temperatures of the tank drop. Finally, with the charge pumped out, I installed a factory fresh 4 ton expansion valve in place of the 3 ton valve that was configured before in this 3.5 ton system. Next I vacuumed the system for two or three hours, closed the valves, watched gauges and vacuumed some more. When I was happy the vacuum was solid, I recharged the system using as much of the old charge as would return from my recovery tank and then added additional charge from my service tank. This left me with 80 PSIG in my recovery tank. I would like to know how much R22 in pounds remained in this tank which seems to be 1400 cubic inches. How would I calculate this?

Anyway, I continued charging, checking amperage draw, subcooling and whatnot. The low side gauge is too high at 80 PSIG +/- which is worse than before. The high side gauge is only 140 PSIG with outdoor temps today of 85 degrees F. I'm getting around 12 degrees drop across the evaporator which is similar to before. The suction line was around 62F with a suction line pressure between 78 and 82 PSIG. Superheat is still too much.

I attempted charging to subcooling specs for the condensor and as I add more charge, the high side creeps up but the low side stays mostly unchanged. I get a subcooling of 7 degrees while the spec is 12 +/-2. As I add more charge, mostly the low side gauge creeps higher and the high side gauge stays unchanged. I could add more until subcooling is right, but past experience with this unit is it won't make significant difference. It was a few pound charge between bubbles vanishing and finally stopping work tonight with 7 degrees subcooling. I'm having an intermittent lead in my thermometer, so I don't have a full set of system temperature readings tonight.

Am I looking at excessive internal pump leakage in a worn out scroll compressor or should I direct my attention elsewhere?