My 1st cascade R22/CO2

[andre X_X]

after building few single stager i think its about time moving to dual stager ....
my E6600 hunger for more colder temps, 5ghz on single stager was achieved, next gonna try it to make it stable on 5ghz and trying suicide clock >5ghz....

details

1st stage:
3/4hp Matsu$hita R22 Rotary Compressor
some desuperheater
condensor 1 row 20x25cm + fan
filter/drier
captube arround 2.15m 0.031"
Heat Exchanger
Dupont R22 refrigerant

2nd stage:
1/3hp Kulthorn R12 Compressor
coil desuperheater 4m
Danfoss KP-5 cut-off switch
Pressure Relief Valve (hard to find it here)
Alco Oil Separator
filter/drier
captube arround 2.3m 0.031"
My Evaporator and flex suction line
Dupont R22 and CO2

the design:




the Heat Exchanger (HX) = 4m 1/2" pipe, inside = 3x3/16" pipe

[andre X_X]

please let me know if there is something wrong with my design... i would really appreciate it...

btw, I'll add accumulator (taken from dead rotary) on 2nd stage suction line
also, do i need to add Hand valve for oil return? i see some not use it, except those with custom made oil sep...

Regards,
Andre

[LukeXE]

You must use hand valve for oil return. If not compressor will suck oil all the time, you will have high suction pressure.

My advice is to not use that long desuperheater coil, 2m should be really enough :-) I would add a SLHX for second stage, you have small compressor, slhx will help a little bit under load.

Remember to use R290/CO2 or R22/CO2 on second stage, if not you will have dry ice in evap. R290 or R22 will easly flush all dry ice.

Good luck

[Big SturL]

Aren't there oilseps with floaters or something, so that the oil won't flush back all the time?

Good luck with your build, it looks like a foolproof design. Hopefully, I will learn something from it.

Subscribed.

[andre X_X]

i see piotres not using hand valve here. i'll be using same oil sep like him... wonder if its ok to not using it, like piotres did... it means he is using floated type hmm... anyone know if alco's is floated type?

thx for your fast reply luke, i'll add SLHX and shorten the desup on 2nd stage...
anyway, how much CO2 should i static charge?

[Marvin]

Remember to use all safety devices....
good luck.

[andre X_X]

thx marvin, i have bought danfoss KP-5 for cut off switch.... still looking for pressure relief valve, its a rare thing here, really hard to find....

[LukeXE]

woah, sorry, didn`t notice that you gonna use new oil separator. If it has float, no need for hand valve.

About CO2 charge. Without any expansion tanks etc static charge should be around 14-15 bar to hold 160-200W load.

[andre X_X]

wow 15 bar.... my 2nd stage compressor could hold until 250-300psi (based datasheet), what would be the 2nd stage pressure while both stage running no load with 15 bar static? will it be over 250psi? do i charge R22 on 2nd stage while system running?

thx for helping me....

[LukeXE]

It depends on a lot of things (I mean a discharge pressure), but probably it won`t hit 11-12bar idle

Yes, you can charge it with R22 while system is running but I would try to get some propane or propane-butane mix for CO2/R290 mixture. It`s better than R22/CO2.

[andre X_X]

ah thats good to hear... such a nice person you are luke
thx for helping... really appreciate it...

tommorow i'll start build it while waiting for CO2.... i'll update with pics...

[Big SturL]

15 bar (!) static? I might have missed out on a vital point with cascades, but will the pressure on second stage actually drop while running?

[LukeXE]

15 bar (!) static? I might have missed out on a vital point with cascades, but will the pressure on second stage actually drop while running?

It will because gas will be cooled by I stage.

For example, my 3 stager. Second stage is charged with 17bar of R1150 (no expansion tanks). why that much ? To hold load

While running, under load, I`ve got 11bar discharge on that stage :-)

[Big SturL]

Yeah, I thought that it had to be because of that. Thank's for the info though

[Xeon th MG Pony]

Yes; Static should be charged with the whole system at room tempriture.

Charge your first stage as you would any A/C, Now after that and the system is at room temp charge static pressur in second stage. Now run first and second stage, tune first stage, and watch second very closely.

[andre X_X]

some photos update....

[ryba]

Why you don't put your inter stage HX in horizontal position?

[marru]

I see in the cascade diagram in first post that you are placing the filter/dryer of the second stage before interstage HX. Wouldn't it be more efficient to place it after the HX where it would deal with liquid, not gas?

[andre X_X]

@ ryba: ok, i'll put it horizontally, btw is there any bad effects if i put it vertically?
@marru: i planned to put it both before and after HX.... is that ok?

[ryba]

@ ryba: ok, i'll put it horizontally, btw is there any bad effects if i put it vertically?
@marru: i planned to put it both before and after HX.... is that ok?

yes, liquid will hang in down part your HX. In horizontal position liquid CO2 in loosely way droop from inlet to outlet

[andre X_X]

ok, got it... thank you...

[LukeXE]

ryba is right, never try to place HX in vertical position, you`re loosing too much with that position.

[marru]

@marru: i planned to put it both before and after HX.... is that ok?

I know there are special filters built for gas. Our usual filters are built to be used with liquid.

Its ok if you plan using filters both before and after HX but dont take any chances using only one filter before HX. Dirt from bad brazing at HX could block captube especially if you dont purge.

good luck

[ryba]

change your desuperheater on 2nd stage, outlet should by lower than inlet. In my suggest, you must change this poor compresor on 2nd stage.

[andre X_X]

ok, desuperheater changed now.... i dont have enough money to buy new compressor right now, anyway, 2nd stage would only be arround 15bar. do you think its really necessary to changed it?