Symphy`s 3 stager

[LukeXE]

Have you tried brazing or soft soldering the capillary as well for a bit more heat transfer? Might want to consider the autocascade with r290/r14 so you don't need a oil separator as well.

i think maybe a cold trap and 2 oil seps might help.
From reading runmc post and your results it seems around -100c your oil is freezing and there comes a point where you condense all the r14 as Redwolf said hence 0psi. pitty Redwolf wasnt around to help. maybe pm chilly1 and see what he thinks.
Then when you let the 2nd stage warm up it oil melts and things run again. also runmcs static pressure was 220psi like chilly1 said yours is alot lower. When chilly was doing his cascade was having same issues as well with r14.

As noob said i guess autocascades dont have this issue because the first stage returns the oil alot better. you would also maybe change the oil in the 3rd stage compressor to a better oil that doesnt freeze.

I would try that option with autocascading third stage or just buy methane and try with it. I don`t have R14 anymore, only some in thrid stage with some ethylene

Must talk with Symphy about getting methane, it costs 80euro netto for 1,73kg, not bad price I think. Then I could do R290/Methane autocascade on last stage.

For more modifications I must talk with owner of cascade. This unit have really big potential, but need still some more work on it !