Compact Cascade

[Gray Mole]

I've been pretty quiet for a while, hopefully it's cool if I get back to posting again

I ended up selling my 'mini-box' cascade recently. I didn't really advertise, just sort of happened. So I got the itch to get another one made up.

I had a couple of 5200btu compressors (around 7/16hp) and the parts to match, so here it is.

Specs

2x5200btu rotary compressors (samsung and something else)
12 plate HX
Homemade oilsep with ball valve
10000btu HE condensor/fan
A Duniek stepper evap I had kicking around
One of Ron's flexlines (very nice btw)
375psi HS cutoff

1st stage is 5.2' .031" captube
2nd stage is 7.3' .031 captube

Temps around -100c unloaded, est. -80 to -85c 300w

I've gone in the direction of 'what it needs' instead of all the extra stuff that takes up space or gives a big 'bling factor' Seems like we made these to get cold, so I focus on that.

No hot gas bypass, no guages, really it's just the very least you can use and stay safe.

I'm planning on installing a control for stage 1 just like the minibox had. Cools the 1st stage, then switches the 2nd automatically. Cuts off the second if the HX temp gets too high.

I did some really nifty stuff with the 2nd stage to save space and get a decent load holding capacity. I had no space for SLHX's and stuff, nor desuperheaters (Never had much use for them on a cascade) and no Hot Gas Bypass (why did people start using those on 2 stagers? Edit: I know it's a method for temperature control but I don't much like it as such. For short duration defrost and oil flush with R14, sure, but the added compressor strain from extended use makes it a system I don't like to use), oh and no guages either. I figure they're great for someone that's making it, but a bit useless in actual operation. If it stops working it's going to go to someone with guages to get fixed, and it's one less thing to break.

What I did was the same as my SS stuff. I brazed the captube to the suction returns on both stages with oversize tubing (5/8") to deal with the floodback just a bit, and on the second stage I brazed the end of the return before the compressor's accumulator to the discharge just before it went to the HX.

That gave both an enhanced vaporisation of the return refrigerant, and a nice drop in temp of the discharge gas before going into the HX Acts as a slhx/desuperheat combo in a way. The captube is cooled by the suction return before the discharge is cooled, so it gives the condensing gas a boost first.

The oilsep does act as a bit of a desuperheater with the pipes across the fan area. Gas comes back cooled which is nice.

I may draw it up, but it's basically the same as any drawing by Reggie. All I've done is simplified and greatly downsized the application.

The -98c reading is actually a couple degrees warm (stupid display can't be calibrated) but it's running unloaded around -101c.

It's pretty heavy on charge, which is why it's not a really cold cascade unloaded, though the 3/4hp Minibox was only running -110c unloaded too.

The smaller compressors don't dissapoint though, I was impressed at just under 1/2hp.

I ran the 'torch test' on it, usually give a 300-400w temp 'quick check' and it pulled around -83c at worst, -86c at best. so I'm expecting to see something better than -80c at 350 to 375w when the load tester goes on.

So it's basically a -100c/-80c high load cascade.

The really impressive thing was the size. I have a couple of window AC cases here so I figured I'd use one if I could get it to fit.

The full thing fits inside. Dimensions are 14"x14"x18" wide.

So I'm happy so far, I'll post more pics when I have the case together and the wiring and controller done.

Oh yeah, the images suck. iPhones suck and I suck worse at taking pics. Ask anyone.








Had to sign it

Thanks for looking. Any questions on the specifics feel free to ask I've always been happy to help if I can

Gray

[Gray Mole]

Well I'm a bit disappointed but it wasn't unexpected.

The second stage is working really well but I'm seeing just a bit more temp variation in the base stage than I'd like.

The initial temps are -100c evap / -48HX
At 350w I'm getting -75c / -30c

325w is the target for general use full load.

At 325w it's running well for a shorter duration (10-15min) but the HX temp is creeping up, and it's reaching -32c. That high, the evap temp creeps up with it, and -80c is all I'm getting

So the 1st stage compressor is showing it's weakness a bit.

I have another compressor here, a Rechi 1/2+ hp. LRA is 28 as opposed to the 22 of the one that's on the 1st stage, so I'm going to swap that out and see if it can maintain -35 or better at high load.

A stable temp is more important than a low one but anything under -30c and the Ethylene's condensing pressure is higher than I like. Would prefer it closer to -40c HX full load.


Will see, might get that done today now that I have the load tester on it.

Gray

[Splave]

really nice compact build what is the weight approx?

[badatgames18]

really interesting build gray!

if you could get it to hold load a little colder that would be a nice and compact cascade
What's prevented me always from buying one is that i heard you might need to redo some of the electrical components in your house or it will trip a breaker.. how much does it pull from the wall?

just curious.. thanks!

[Gray Mole]

Hey Splave

It's about 60lb so far. I expect about 5-10 more max with the rest, but the majority of the weight is there now. Still heavy, but once it's on wheels I'd call it as close to portable as a cascade gets.

Mr. Bads

I just checked, and the 1st stage draws just under 3 amps on start, down to 2.5 running. The second stage hits at a total of 6.4 amps both stages, then settles to pretty much an even 5 amps running. Would likely settle fully at 4.5 to 4.8 amps if I left it for a while.

Assuming that RLA is around 3 amps each by the startup, I'd say 6 amps, to a max of 7 with full capacity load.

So this kind of Cascade is totally fine on any wall plug. The smallest US type breaker I've seen is 10 amps.

The last one (the Minibox) was 3/4hp compressors, and it ran at 8-9 amps on average with load, possibly 10amp worst case full load. Only issue was that it could, on startup, draw that little extra and potentially see 11-12 amps if the room temp (ambient) was high or it wasn't fully balanced (not left off long enough)

So that one, if you only had a 10 amp breaker on the wall you were using, could give grief and may need an upgrade to a 15amp breaker. Don't usually need to change wiring though, 10 to 15 amp breaker upgrades rarely need upgraded wiring unless the house is seriously old.

Thanks though Nice to hear comments on 'er.

Oh, and yeah when the HX temps go over -35c the relationship from HX to Evap temps was almost linear. These compressors are great up to around 250psi discharge but over that they tend to get a bit soft. You can go to 325psi safely on most compressors that are rated for the higher pressure gasses (like R22 up to R402a) so it's not like it's any problem with them lasting, but you just don't get their 'best'.

I'm hoping the Rechi will do that though. It's the same size, but it's slightly larger capacity and should manage the extra load well enough. I should have used it in the first place but I wanted to save it for the next small cascade. Now that I have a system for this kind of build, it'll be easy to lay it out and more or less replicate the results of this one. The idea of small but just as powerful has always been something I've liked, and IRO -85 to -90ish usable load temps aren't bad for a portable cascade.

I should know later on today if all goes well. Since it's the same size, same wiring it's only a matter of pulling the gas, swapping, and a vac and charge to where it was. Much easier than putting a larger series of compressor in there.


Gray

[Gray Mole]

Just a short post (for a change)

I replaced the compressor and vacced and charged. I store the compressors with nitrogen (whether used or new) for the most part (unless I'm planning an oil change) so it didn't take that long, just a couple hours vac.

Anyways, the good is that the HX is around 5c colder with full load, and the evap is likely the same 5c colder.

The bad is that the probe on the evap's come loose

I was reading -98c (and these displays always seem to be a couple degrees warm, no biggie)

Now I'm getting -92c. I didn't change the gas charge and the pressure is still reading about 0psig unloaded, so I'm 'guessing' that it's still the same temp unloaded more or less.

I'll have to check the probe and see if it's sitting weird, if I pulled on it and it's come away, whatever.

But the 350w temp is around the same, -75c.

So it's...

350w -75c
300w -82c
0w -92c

I'm not going to say it's definitely wrong, but I'll redo the load testing when I check/redo the probe, check calibration etc. I'm pretty sure it should be...

350w -80
300w -85
0w -100c

Or something close to that.

Compressor sure runs cooler on the 2nd stage now though Both compressors are running around 75c now at full load after an hour or so.

time to sleep though. been hard to sleep the last couple weeks :p Still get a lot of grief from where I sliced through the tendon in my hand. Should have cut it off completely.

Gray

Edit:

It was bugging me. Couldn't sleep.

So I pulled the K wire from the display and put a plug on so I could confirm it was the probe.

Unfortunately it's the calibration of the display that's off. Not really a lot, and not the end of the world (the temps are what they are) but it's reading -98c on the Fluke and -93c on the display best no load temp.

Tells me that the display is exactly 5 degrees warm. Weird, the other 3 I had of these never really gave me grief, every one was 1-2 degrees warm so not really any issue.

They don't have any way to be calibrated though

The unit IS running 2c or so warmer than before, but I guess at no load/coldest temp, the HX is more capable maybe? Better condensing means more condensed refrigerant so more capacity and higher temp?

Who knows. I didn't change anything on the second stage and I like the capacity it has. I don't want to fiddle too much, it's working nice.

So I guess that's about it for tuning.

-80c / 350w
-85c / 300w
-98c / 0w

That's extrapolated since the display shows 5 degrees warmer, but it's not that bad I guess. The temp range is really tight from no load to full load. For small compressors, 20 degrees isn't bad.

I'll be painting the case and cutting/modding it for the cooler, wire it up nice and see how it looks

Gray

[Dualist]

I've been pretty quiet for a while, hopefully it's cool if I get back to posting again

Too quiet mate
Good to see you posting your builds here again.

It's a very compact unit, nice work and awesome load holding temps for those size of compressors.

[Gray Mole]

Thanks D

I guess I couldn't really hope for any more, though more is nice too.

The 3/4hp cascade was -100c to -90c usable range with load. This one is -90c to -80c usable range with load. I guess it's more or less where it belongs and about as good as I'm going to get with the size.

I've been pushing things towards 'small as possible/least amount of extras that don't actually give better results' and this size is kind of my best work as far as that goes. It's close to the same size as a high load SS.

I'm glad I have a few decent WindowAC cases around. Saves me trying to weld up a case for it. I need to reinforce the case a little though. The window cases are a bit light and if I end up shipping it somewhere it may get a bit mangled. No plans to ship it anywhere but you never really know.

What I'd really like to do is move on to a 3 stage project soon, but the cost of gas/inexpensive gas options aren't great here in Canada.

The ideal gas to move to is Krypton for the 3rd stage. I know Cold Ice was talking about using it before and it's ideal but really expensive to 'invest' in.

Here the only size available is a 5 cubic meter bottle, which translates into about 40lbs of liquid. Problem is that it's about 15 thousand for that bottle

Working it out into 'cost per unit, I'd say 1/2 to 3/4lb per cooler, so maybe 500 bucks at most for each one. Not bad I guess since a 3 stage cooler that's -150c or so would likely be popular, but you kind of have to know you're going to make 60 of them to use up the gas and get the cost of the Krypton back.

But a decent base that can maintain -100c condensing temp isn't unreasonable now, so Krypton is definitely an option, just expensive.

I'm going to call around and see if anyone has a small bottle. I mean, I could probably save up 3 grand (over time :p) for a 1 cubic meter bottle but 15k is something a person would need some kind of an 'investor' for , and I'm not looking at making this a business. I'd have to stop enjoying it again

Off on a tangent again.

So yeah, thanks I've enjoyed building it, and maybe over the weekend I'll get the case painted up and have some new pics.

Gray

[MaRtIe]

Nice Gray, good to see you building again

looks like a fairly small unit indeed well done and good temps


btw that condenser is a monster

[Gray Mole]

Nice Gray, good to see you building again

looks like a fairly small unit indeed well done and good temps


btw that condenser is a monster

Thankfully not too big to fit the premade AC case but it's way more than needed, even with the fan speed on it's lower setting.

I'm at ambient halfway through the condensor paths, even at full load.

But it's another of the higher efficiency condensors I like so much. 1/4" rifle bore tubes and relatively high FPI.

If I could get a lower FPI version with the same tubing I could use a silent/low volume fan. Would be nice to cut the noise on the fan, though it's not too bad, less noise than the compressors.

Thanks

Gray

[MaRtIe]

very low impact on the condensor then, nice whats it gonna be strapped to?

[Gray Mole]

hehe

I gave up benching ages ago, after a series of catastrophic and expensive hardware failures. About 3k quid's worth

At that time I was starting to focus on building the coolers and never got back to benching to any great extent. I do miss it at times, and having a cascade with nothing to bench feels silly sometimes.

But I bench and tweak the coolers instead of the hardware. Finding little changes and better methods to get the cooler to give me better results. Not really any different than overclocking cpu's, I'm trying to overclock cooling systems.

When it's totally done, I'm sure someone will want it. Whether I actually 'try' to sell it, well likely not. That last one someone contacted me

I'm doing ok at work as far as making a living goes, though I sliced my Tendon and I've been off work a while now, so mostly I don't need the money.

So I don't really bother trying to sell stuff once it's built.

That get's kind of embarrassing at times though. I had 6 finished coolers sitting there, and 3-4 projects at varying stages sitting around.

So the Garage gets pretty full that way.

My dream job would be doing R+D for something like Polycold or some cooling company. That way I could play with the tech stuff all day and never have to worry about a real 'finished product' to sell. I'm a terrible salesman


Gray

[MaRtIe]

i hear ya gray, i can see where the challenge to build better and improve things comes into play. i myself like to build things, even if it costs me more money to build than to buy. only it's usually
engines and bikes etc.

i come across your quad build while researching for myself, pretty good builds you have done over your time.

[Gray Mole]

Well I've finished up the case, installed the switches and stuff.

Not too shabby, though there are rough spots, I had to make the front area from scratch. The case had an ugly plastic front like window units do, so I had to piece it together.

Not really easy, my thumb's still not there and it hurts like crazy when I use it like this. Wiring especially is a pain.

hard to see the ball valve, just sticks out the top (got a close up) but it's all black. Like a camouflaged nipple.

Otherwise, black flush house type switches. Low side has to be powered to activate high side.

For now, it's a basic -50 little 5v display, but it's really very accurate (go figure) and the big -200c display.

Still reading 5c warm throughout, but it's not enough to scrap the display.

Small. Cold. I put a pic or 2 with my small and larger drill for reference.














Just need to touch up the paint here and there, and do a few coats of clear

Hope you like the pics

Gray

[Gray Mole]

So anyways, that's pretty much the end of it.

I accomplished what I was after I suppose. The idea was to get something like Dry Ice temps and keep the size and power consumption to a minimum.

The cost into this kind isn't that high either, with the case being something I made half of. The oilsep I made, and most of the parts are stuff I had from previous orders so I didn't need to buy a lot specifically for this.

Really shows the limit of gasses. I mean, you can strap a giant compressor onto a SS and get a decent result, but the noise and power consumed by a 1.5hp compressor is brutal, and you'll still only get maybe -60 evap load temp at the very best with the coldest of SS gas. I think when I work out costs, it may be cheaper to go this route. The really large rotary compressors are expensive where these are cheap. Even at full retail they're less than half, making up for the other parts needed.

If you avoid valves and coils, and just stick to captube and handvalves you can do it for less than you'd think.

So for someone wanting more from a cooler but doesn't want the noise/heat/power issues this would be the way to go.

If I were looking at a minor upgrade from SS, I think R23 or Ethane in the second stage would be better. A usable range of -60 to -70 would be likely then. Would be an option of great cooling but without the serious insulating/condensation hassles.

And at around 14"x14"x19" with the case on, it's actually no bigger than the usual big single stage, and a lot smaller than one of the big 1hp+ rotary monster SS units.

Gray

[MaRtIe]

nice gray, that case looks the sh*t. nicely done and great temps!

[piotres]

Gray, it's nice to see You playing again .