Three-stages cascade [ designing ]

[Sk_rmouche]

Thanks

Second stage is fully closed, leak test in process, one bar less in ~ 12h, maybe CO2 dissolved in oil ? Or T° :o

[Sk_rmouche]

Hi guys

Vaccuming almost done, ready to load R23 !

[Sk_rmouche]

It works not bad, filled something like 400 gr ( ~1 lb ) of R23, really good surprise, everything is frost, even without any insulation, and hot winf from condensor blowing on them

T° is a bit under-evaluated, since by touching the probe, it gets 10°C under current value, but good surprise from first launch.



And little video :

http://www.youtube.com/watch?v=7xn15...ature=youtu.be

[n00b 0f l337]

How are the oil seps holding up?

[Sk_rmouche]

By the piece of wood, and a steel collar.

[sdumper]

I think he meant how are they performing? These were home made seps right?

[Sk_rmouche]

Oh okay, I really have to learn english
Yes, totally home made oil sep's, made with two oxygen bottle.

There is a 1/4" piece of copper tube, with a solenoid valve, which goes right into the back pressure line.

Solenoid valve will be controlled by hand ( latching button ), or by a timer.

( Electrical box is ready anyway ) :

[Kamil Grzbiecik]

A beautiful beast.
When the final results?

[Sk_rmouche]

Can't answer yet, it's a three-stages, so it isn't done

[Sk_rmouche]

After some tuning with TXV's, no insulation except for the probe :



The R23 TXV is impressive, quite fast response for a vapor charge, no clogging at all, outstanding !
I've borrowed a leak detector from my work, found only one leak with to second stage, the detector displayed 4 grs per year, fair enough it's fine to me

Next step is massive insulation, and electrical wiring. In the mean time I hope being able to bring home some R14, if not I'll go for R1150 I think.

[Kamil Grzbiecik]

I see that things are improving

[Sk_rmouche]

Definitely, I just have to wait for my new probes ( PT100 and type K thermocouple, since I broke my last one ). I started insulation though, I hope I can reach the -100°C club member ASAP

[Gray Mole]

Looks great and I do like how you wire it up too Looks very sturdy and safe.

Shouldn't have a problem with the -100c club now. R23 needs to be stretched a bit to get -100c but you'll do it at this rate and when the next stage comes together you'll blow that away

Hope you get there soon. Looks like it's all working as it should, and the valves are working right. I never seem to have good results with valves.


Gray

[Sk_rmouche]

Hey gray

When you speak about valves, do you mean TXV ? If yes, yeah it totally works good, don't know why you got so much problems with... Cap tube is such a nightmare with cascade IMO

[Gray Mole]

Funny, just what you get used to I guess. I've found captube to be one less thing to go wrong though you're right, when they work they just work. I do the captube brazing and slhx setup on the cascades and have no issues. But getting the length and size right is always a process.

I just had bad luck with them and when you do, you just tend to use what you know.

Yours is working really well and that's great. Wish I'd brought the collection of TXV's back from the UK when I moved, but you can't bring everything. Had to leave a lot behind. Had one R23 TXV and a bunch of the usual 404/507 22 134 etc.

I do have a R22 valve and one cpev left. If I get another valve I may do the 3 stage with valves, but I don't know. Always hard to decide, but I have time.

Speaking of which, you're looking ready to get the 3rd stage together. How long 'til you'll have that done?

Since Ethylene is cheap you could always use that to start I suppose. Need to find a 'sponsor' to buy us gasses Any local refrigeration places want to get some free advertising?

Gray

[Sk_rmouche]

Well, I'm still thinking about how can I manage the third stage, I don't have so much parts for it, only one CPEV, and electrical stuff you know. Compressor and gas are still missing, but it's okay I'll not rush myself, there is a lot of work on the two first stage, including insulation, electrical improvements, and a little tuning to balance pressures. I want so bad some R14 :o Ethylene is the last choice

I can confess you that at the beginning, I wanted to try some electronical valve

[Gray Mole]

I don't blame you

I've wanted to try some electronic expansion valves for ages but the prices have never been anything but crazy. A combo of that and a coil valve with pwm for bypass would give really precise temp control on all stages, but especially on the final evap stage. Would certainly make a cascade universal. Cold bugs, cold boot issues, would all be easy to deal with

But an extra 2-3k for that seems a bit extravagant

[Sk_rmouche]

Oh no, you can put electronic expansion valve ( proportional valve ) for less than that, at least on last stage, all depend of your needs obviously. You get PID regulator + proportional valve for something like 500 dollars. By my side, I've already the PID regulator ( 300$ ), maybe one day ... But thermostatic is still a much better expansion item than cap tube. Your last cascade is really nice performs for cap tube, my experiences are awful ( I made a water chiller two years ago, didn't run nice, since I put TXV it worked amazingly, first try ! )

[sdumper]

I prefer TXVs as well. It makes tuning a snap or should I say twist

[Sk_rmouche]

I think there's no such comparison to make, electronic expansion is far away better than thermostatic expansion, but price is a buzz-killer, and if it's not correctly programmed you lose all benefits of it's fine regulation abilities

[Gray Mole]

For me even the TXV's are costly. Guess using captube's got me spoiled. 5 bucks for captube vs. 50 bucks for a txv on Ebay, and way more from the supplier.

Makes it worth the hassle of captubing things, though a 3 stage I think it's about the only way to go (other than electronics but I'd say not worth it unless it's for yourself)

I try to build 'em good but cheap. Valves and such make that impossible and on a 2 stage cap's not really that hard to do.

On a water chiller (you mentioned that before) TXV is the only way to go. Load variation on startup is crazy, would take ages to cool down a volume and you'd need serious suction volume to cope with the charge and flood issues.

I haven't had any issues with cpev though. I like them fine (as long as you strip and lube them prior to charging) but again it starts to add costs with the reciever, sightglass and valve. If it were just the valve it wouldn't be quite as bad.

[Sk_rmouche]

Hi Gray,

You know, it's only about the kind of behaviour you actually expect, don't make me wrong, but cap tube is easy to make it works, but hard to make it works "well" => expansion is determined mostly by your gas load, over all others parameters, TXV's avoids that problem, for instance I loaded more than a kg of R404a without meeting any issues. A two stager - for me - has to perform with at least a TXV @ the high stage, and why not CPEV @ low stage

Of course, it costs much more, but this is a real upgrade.
CPEV are working great too

[n00b 0f l337]

CPEV's are wonderful, but overtime they have a failure rate at low temperatures. The seals just don't hold up, which is a risk in many cascades produced using ethylene or other flammables.
I've tried them heavily. 3 stager with 3 CPEV's, first ones working great, since its at room temperature. The one at -35C, held up for 6+ months, hasn't flaked yet. The one at -95C though, after 2 months I found microleakage. Luckily I just had it using r1150 and not r14 or I'd be a sad phaser to lose a full R14 charge.

[Sk_rmouche]

Yes, I'll try hard to put between my CPEV and the evaporator, an captube, -80°C is better than -120°C maybe

[n00b 0f l337]

Captube or not, it's going to be coming out of 2nd stage HX very cold.
Very very very cold. I'd stick to captube personally, or get an EEV or try and go with a solenoid and "loose" captube.