Long story this one.
Over a year and a half ago I decided to find out why my cascade started to fail at holding loads so I had the plan of upgrading the condensor, txv, compressors and have a look at the evap.
Her she is in her original state a year and a half ago at Evocarlos's, as Patrick would say "Tapey"
First thing was to remove the first stage comp, condensor and change the orifice in the txv.
Pressure tested and vac'd down we proceeded to charge..
Hit -50c with no load but struck up the second stage and added a load to that in order to tune the txv. After putting it under load with the original NL11F on the second stage it did ok. With 200watts load the first stage was hitting about -35~40C and second stage was hitting -88C(ish) but was mega stable.
So out came the second stage comp...
Left it under pressure test over night and it didn't budge so spent the rest of the afternoon in deep vacuum.
Well after changing that little lot, it turned out there was far too much oil in the second stage oil seperator so it was constantly open so the stage wouldn't pull down very well at all and also I found out that even though I changed the end-cap on the evap with a pukka refridgeration grade copper piece it leaked like a sieve After this I had other peoples work to do so this got stuffed in a corner until last week.
I found an evap that I threw across my workshop car park a couple of months ago as it was blocked. So I heated the whole thing up with my oxy-acetleyne torch to bright orange and it just fell to bits, scraped all he old silver solder off it and cleaned it up in my lathe. Re-assembled it and it looked pretty good and stuck it on my suction line, added captube and then pressure tested it....
No leaks, yay..!!!
After messing about a bit more trying to find a blockage (in a small condensor no less, brought 2nd hand and I can see why :@ ), I vacced it down and gave it a burst of gas....
So Today I lagged it all up and stuck it to my load tester.
Temps not great but you sacrifice low temps for load holding so wasn't too pissed off but wanted to see the magic -100C, temp probe is on the side of evap (as always with me).
Static pressures on second stage startup is too bad and no shock either, static is 150psi then just goes up to about 178-180psi, rather dull but nice and safe
Here's a pick of temp 6" from accumulator for messing with superheat.
But here's the money shot, took the load up every 20mins or so from 150, 200 then 300. Left it at 300 watts for over half an hour and it didn't budge lower than this, well feckin happy..!!
Temp meter on the left for superheat, temp meter on right for evap (though for working out superheat it should be on the tube exiting the evap). Will add this when I get some more temp probes but I happy as it is.
TXV with 01 orifice.
Plate heat exchanger.
4ft custom suction line
0.9mm captube 2.5-2.6mtrs.
And yes I still have the wiring to tidy up, it's the next job on the list
Well I took the evap off the heatloader and finished the insulation.
Took the low side guage off and found a small amount of oil came out so I know I haven't taken too much out of the oil sep and I'm still getting oil circulating, phew
Then I struck it up just for the hell of it and I got my -103C..!! Yay..!!
Gonna use it just on GPU's I think now when I get a SandyBridge rig and kick out some old gpu scores, enjoy