my autocascade

[gkiing]

Just finished the brazing and assembly tonight, its currently pressure testing @ 150PSI (of CO2) and I'm going to let it sit overnight to check for leaks. The condenser is passive for now but i'm going to add a fan eventually, I put a large desuperheater after the compressor and on the separated co2 gas line so I think that I might not need one. The compressor is a 1/4+ hp matsua hbp. My heat exchanger is diy, similar to berkuts but with a few minor changes. In the phase separator there is copper wool in the top half to help with oil separation from the CO2. The evap is just a drill press block, and the suction line is a 3/8" rubber hose, which I'm going to change out for a copper flex hose once I get it because I'm afraid of it cracking under the cold temps. No insulation yet, but I'm going to fix that tomorrow . Ordered some 1" wall armaflex (1/2" id) and I'm going to use a cardboard box + polyeurathane foam to insulate the hx.

overview (the thing to the left of the compressor is an expansion tank, these compressors sometimes have a hard time starting).



Nitrogen purging regulator with cga 580 (n2) to cga 320 (co2) adapter



CO2 tank, 20lb


heat exchanger


phase separator


my vacuum pump, old but pulls a 29" vacuum. I always do a triple evac anyway.


pressure testing 150PSIG co2


my cat by the autocascade


drier position


evap and suction line



heat exchanger installed. I wish I hadnt wrapped it with captube first or I would have brazed the co2 liquid line to it as well.


I still have to wire it, insulate it, add a condenser fan, and install the HP cutout. That's all for now, I'm going to charge it tomorrow and see how it fares

[JSU]

ooooooo looking good gking, why do you have 4 schraders btw? that passive condesnor prolly wont cut it, good luck!

[blinky]

nice whats teh first stage refigerant??

looks good man

[gkiing]

ooooooo looking good gking, why do you have 4 schraders btw? that passive condesnor prolly wont cut it, good luck!

yeah I know I went overboard with the shraders. One is for the high pressure cutout, one is to remove only r290, another is to remove only co2 another just came on the filter drier, and the one on the other side of the compressor is low side access. I know the passive condenser is ghetto and probably wont work well, I have a window air conditioner that I'm going to rip apart and steal the condenser from.

I havent charged it yet but it will be running r290/r744 (co2/propane).

[kayl]

thats some nice building there.
i hope it goes well for ya.

[total_assault]

awsome..i like the pipe work alot.

i cant wait to see if that condencer can handle the co2.it's going to get hot..pressure's are going to be high..the HX is small too..it should be interesting.

won't it explode instead of getting hot from pressure?

[Russell_hq]

Those passive condensers are made of steel and have small diameters. Bursting pressures are quite high!

[jan]

Nice looking system.

It won't burst until there is a weak brazing joint. But even then it won't realy "explode".

[gkiing]

Actually I'm changing out that steel condenser for an a/c (~5000btu) condenser I ripped out today. I don't think it could handle it either. This is really just a test system to try out that hx design, I'm building a larger one with a 1/2hp rotary once I figure this all out.

[berkut]

the hx should work, works for me

[gkiing]

I did some preliminary testing, the desuperheater was getting really hot but the condenser was not even warm. The lowest temp was around -51.5c but it was charged way out of proportion, and the evap was taking at least half of the supply of r290 which should have been going to the hx. High side was around 240psi and low was around 15psi. I'm starting a new autocascade with the rotary because I dont think this compressor is powerful eneough and I think the ac condenser will work better with the rotary, its probably too large for this small compressor.

hx was around -28c
evap was around -51c (the temp shown is recorded minimum by the way)

0.026 x 1m for hx (r290)
0.026 x 2.25m for evap (r290)
0.026 x 1m for evap (co2).
The evap got cold really really fast before I added co2 but the hx took a while. I think most of my r290 is being hogged by the evap, and also the hx captube is too short and the r290 isint condensing properly.

[berkut]

Insulate

add more co2, lenghten the R290 evap supply

do you use the T splitter technique i did ?

[gkiing]

I re-measured the cap tube lengths the r290 to the hx is 0.9m and the co2 to the evap is 0.9m (of 0.026"). I think that the hx captube is too short as It does not reach condensing pressure very quickly, for a little while after startup I hear gas hissing inside it.

The evap has two captubes goign into it, and the one for the r290 is a bit shorter than the co2 inside the evap so it sprays onto the end of the co2 captube. I didn't use the "T" technique but I think its working ok.

How much captube do you think I should add for the r290 going to the evap? Do you think I will gain a lot by insulating? I dont really want to insulate until I get the captube lengths worked out, as the polyeurathane foam is really hard to remove and I wont be able to mod the hx afterwards without a lot of trouble.

[berkut]

you wont finetune it untill you insulate

[berkut]

I do not agree.

The lack of insulation on something as big as a HX is worth about 100-200W static. Remember we have a airflow from the condensers fan.

Lack of insulation on the sucktion line and evaporator is also worth about 100W, and we are talking about a autocascade. 100W extra on the evaporator means 200W for the compressor to push.

If the cap tube is too short (not restrictive enough) adding insulation will make it worse (more flooding). In some designs a cap tube wich is not restrictive enough (most of my systems where i use a cap tu) a proper charge with heavy insulation will cause the system to auto stabilize. At least mine do.

If the cap tube is too restrictive adding insulation (if its not extreme) will probably make the system work properly or very close to what we want to get.

[MaZeR]

you guy's made me want to make a auto cascade too.i have been fine tuning it for the past 3 hr's..

Pic's or it didn't happen!

[gkiing]

I'm adding 0.36m to the CO2 and the R290 hx cap tubes for a total of 1.26m 0.026 (~200W), and also 0.69m more for the r290 to the evap for a total of 2.94m (~75W). Then i'll insulate. I may try a TXV for the r290 going to the hx..

[thesaucier]

Hey sorry about the delay but I just sent the pelt today.

[thesaucier]

I'm a little confused, but I'm going to change my cap tubes now. I'm adding 0.36m to the CO2 and the R290 hx cap tubes for a total of 1.26m 0.026 (~200W), and also 0.69m more for the r290 to the evap for a total of 2.94m (~75W). Then i'll insulate. I may try a TXV for the r290 going to the hx..

That was meant for you I forgot to quote. LOL

[gkiing]

thanks, I'm looking forward to getting it so I can test this thing!

[thesaucier]

Looks like things are coming along good so far!

[gkiing]

I've been having some problems with the phase separator, it need to be taller so the gas/liquid can have a larger distance to separate them. Right now some CO2 is getting caught in the r290 line to the heat exchanger..

[Aphex_Tom_9]

my auto cascade is blazing @ -80c right now with 20 psi lowside and 250 psi high side. no insulation..

wow, blazing indeed...

[gkiing]

Holy sh*t pc ice!! We're getting owned!!!

What's the specs on it.. compressor, condenser, captube lengths, txv?

edit: just read your using r1150.. thats awesome, and looks like your condensing pressures arent too bad either. I think that r290 would have an even harder time separating with r1150, from what i remember it blends well with ethane and ethylene which makes it more difficult to separate.

[JSU]

vapor phase r404a might be a good idea, if you have a bottle that almost done just vapor charge it. youle get some r134a in there.