Ive got an old hussmetic condenser with an old copeland 3 hp semi that locked up. After talking with a refrigeration parts house i discovered that this was an old r-12 low temp system. The customer has been using this as a med temp cooler supposedly for 5yrs no problems(that's how long they have owned bldg. it is not a pumpdown system. It had 409a written in the box so i'm assuming that's the drop in that another company put in there..the powerhead/txv was too rusted to make out numbers. Russel evap on indoor, 3/8" liquid line, 1 1/8" suction. The old lal copressor crossed over to a Lacb-032e-cab-800. They said it was an r-12 comp that could be used for medium temp just needed to change out the poe oil so that's what i did. I also had them build me a med temp r-12 power head. I chanfed comp and txv, drier. Recharged system and turned on.. Few hrs later when box temp was around 45 i looked at superheat subcooling but forgot to check amps. Superheat at evap around 8-10. Superheat at condenser was around 32. Subcooling was a little high like 17. But was cooling fine...5 days layer comp locked up and i couldnt get it to break free(yes i put new starting components on the compressor befor i started it up. So i changed compressor again, new starting components, and converted to a pumpdown system. I charged system differently this time. I found that at the right freon charge im over amping compressor by 5 amps. Fla is 15.5. So i took freon out. Dropped amps to 15.2-15.6 range. My sight glass is bubbling. My super heat at evap is now at 15-20 with superheat at condenser being 40. Still pulling down temp ok. I know this isn't right but i don't want to loose another compressor. I think my problem is my txv. Since im using a low temp compressor with low temp freon i should go back with a low temp valve/powerhead so i can get freon charge right. Are there any other possibilities? Also had the brus checked. 23000 btu valve,compressor at med temp, and evap. So that's right. Maybe going back with a low temp valve and adding a cpr valve is the longterm solution as apposed to replacing condenser with a med temp one which customer won't do now that they have a compressor.