Last couple days, I've had the chance to work on a reach in cooler, at a restaurant. Under a counter. The old guy who runs the place says it needs freon every six months. The aluminum evaporator gets wet, and probably has a lot of pinhole leaks. I checked all the fittings, and find no leaks at fittings or braze joints. Metering device is TXV, and the system has a receiver.
The system is probably 30 plus years old. The evaporator is above the compressor. About 8 inches higher, and maybe six feet to the side.
Since the evaportator his higher, perhaps oil return isn't an issue. Since it runs off a TXV, maybe it will adjust to the lower heat capacity of 134a. Has anyone else tried such a conversion? I'd much rather be feeding it 134a, compared to some other gas or blend.