Symphy`s 3 stager

[LukeXE]

Yo Luke I was afraid of this, you need to get a higher pressure going on the high side. Something like autocascading it and having propane condense or the like will definitly bring your pressure up.

Yes, I see that now.

that sucks about the very low pressure in the third stage.
How big is that look, maybe ya need a bigger compressor for that stage also. Sometimes low pressure means compressor cant pump enough, also what low side pressure you have?

low side pressure of third stage, -0,9bar or less while HX temps is around -100. When, for example, I will open oil return valve on stage 2, then Hx temps is going up to about -70, discharge pressure on stage 3 is raising to around 11-12bar (still going up, but at 11-12 gas become condensed I think) and evap temps is going down very, very, very fast to -130. Then I`m closing 2 stage oil return valve, HX temp is going to -95-100C and evap temps is usually -13xC. If I won`t do that, HX will have -100C and at third stage discharge will be around 3-4bar...all the time, evap temp around ambient.

I was afraid about first stage when I was building that unit, that it won`t hold load etc. I think around -55*C with 3 stages ON is pretty good ! autocascading power