Miny Cascade : Budget Dual 1/2hp

So recently I had a few asks for a low budget cascade. Now normally those two terms can't be fit in the same sentence. Inherently, they are not low budget.
But sometimes exceptions can be made. And normally that requires a bit of sacrifice. But sometimes, just sometimes, you luck out :p

So, a miny cascade project. Dual 1/2hp 39R131F's from Rechi Precision.
Short toppers, and they run a bit hot, but they've never shown me less than there full 1/2hp :p
Condenser comes from a Copeland condensing unit (have about 20 of these things laying about, so time to use them).
Desuperheater is my new miny condensers, just under the dimensions of a 120mm fan, they're absolutely midgetish! Fitting a 120mm Panaflo 12G12L fan for good air flow with mid range noise.
Foam stack is the preinsulation first cuts for the 10 Plate HX. Which will be "bound" and insulated.

3ft flex line, Evaporator to be determined, and HPCO on the way.

The entire unit will most likely be cased in aluminum extrusion and acrylic/sheet metal to give it a solid indestructible approach. And of course I have a few other upgrades that can be fitted if the budget opens up a bit.

As for refrigerant,

R507a, R23 will be used.
Although not many builders can get their hands on R23 due to cost, I have a 10lb cylinder to be used, and it is much more ideal than trying to muscle R1150 to condense.
The goal will be about -70C, a solid dry ice range temperature, at the flick of a switch :) Of course unloaded will go lower for Spi etc giving that mid range bencher many are looking for to replace clumsy pots.

Hope you all enjoy this build as much as I do, I expect to be done with construction when the final parts arrive by next week (tuesdayish) and tune in the week after.

No owner on this one, so it might just go up for sale or just become a light weight show case.

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Good luck mate :toast:

Quote:

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Originally Posted by n00b 0f l337

So recently I had a few asks for a low budget cascade. Now normally those two terms can't be fit in the same sentence. Inherently, they are not low budget.

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Well said. :)

Quite interesting build especially concerning I'm going to try my best at building smth similar soon -)
n00b could you please give us some specs of that rotaries? Unfortunately found nothing :/

52xx btuh 1/2hp Rechi. The specs on these might as well not exist. Finding the right run cap will be hard since I've found 3 conflicting numbers, will try them all after tuning and see which produces lowest power draw.

Progressing well, made the HX "box" from my favorite pink substance, and slot fitted the brazed and pressure tested plate HX. Using the mill I traced the ports and backside ridge into the foam. Snaps together, 3" thick, 10" tall, 5" wide. What a format.

Enjoy. Evap ordered from Ron. And searching up the HPCO now. I have some valve mount ones, but I raelly have grown to dislike them. Getting a stable long term seal can be a pain or just a general fight. Tho I could rip one off the 3 stager...

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Looks good!

You should get weird with it if this has no purpose... one day im going make a overpowered inefficient beverage chiller..
a co2 cascade drink chiller would be cheap and score some big points with friends on those muggy nj summer days

Subcribed, i have two exact Rechi´s, now find where i can get R23, or im tihinking on blend of 410/CO2 402a/CO2, with Captube instead of txv for lowering the cost.

Next one will be QA075's most likely. Similar size, bit taller, but I've heard they're a tiny bit quieter.
This will be running captube, put 6' 6" of .031 on stage one (which is about to come out of vacuum with 10 psi of r290 and then a full charge of r507a), then I guess she'll sit for the week as I'll plumb the second stage as far as I can go and order up some of the aluminum extrusion.

Could be done with TXV, but it's unnecessary if your goal is for a single load.
Over a large range of loads, sure it can be useful, but it's more of a way to get perfect tuning without having to know how to tune ;)

I'd recommend against R410a or R402a with these, they already run way to hot. I'm using r290 for oil, r507a primary, and already considering swapping to r134a if it'll do the r23.
As to some updates, first stage done, just need to tune when second stage is finished and ready for it. But we have frost! Amazingly she's quite quiet. Certainly can here it, but if you push down lightly on the HX box to muffle the vibration, there's not much but air flow noise. And speaking of that, this condenser setup's quite nice. I'm glad I went with the 13W motor on the fan.

I purchased a Supco vac gauge on ebay a while back, an old style one when my digital crapper out. It was sold as is, but at $25 it was hard to pass up. Even had a bidding war for it. But, I called Supco when I got it, told them I had purchased it second hand and wasn't sure if it was in Calibration.

They said send it over, so I did. They even paid return shipping. Recalibrated, all good now. Talk about great service, it's an old model, nothing close to there new stuff even.

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Quote:

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Originally Posted by -cyclone-

Quite interesting build especially concerning I'm going to try my best at building smth similar soon -)
n00b could you please give us some specs of that rotaries? Unfortunately found nothing :/

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http://www.rechi.com/en/web_en_produ...efrigerantId=1


What wattage are you aiming for.?

Hey Dualist, your a good reminder, I'll pop over to Benchtec as well see what you all are up to ;)

I want 250-300W load. Temperature won't bother me. It'll beat a single stage anyway I charge it.
But, it should show me -65 to -70C.

What a good day, even found a HPCO lurking around while I cleaned.

Nice,
Whats the small radiator for?

RussC

Desuperheater, it's important when you aren't sure if you have room to spare. Also, no oil separator. I've replaced the oil with Zerol 150, and don't think I'll be operating below -80C.

Who likes updates, I like updates!

http://img705.imageshack.us/img705/1153/img10h.jpg

Most of the second stage brazed in, such a tight fit. And could barely braze it up without heat on the first stage, but wet paper towels work out great. Slight amount of heat got to the insulation of box, but it just deflected and melted away a quarter of an inch, now I can slot the pipe insulation in better! (Yay ;) )

We also have a date and trial time for this thing, Dumo would like a crack at it, but OCF is having there forum party and I think this will debut there.

So three weeks. Enough time? Damn right.

Enjoy the shot, I'll add in the HPCO later today when I finish pondering where I'll fit it, and then at this point we are just waiting on that evaporator to show up from Runmc.

Nice clean work Adam :up: Keep it up. I really hope this works for you. :clap:

Very nice on these. What's the cost to build?

Decently high for "budget". Can't cheap out though, and I'm putting in a Yellow jacket 4ft stainless steel flex, Kayl evaporator and mount, full electric and auto starting setup.

Big thanks to Runmc. Purchased an evaporator/mount on Monday, hear on Wednesday in the afternoon.
Could not be better :) And if he was, he'd have to fend off the women more then I'm sure he has to.

250-300W is not enough nowadays. Aim for 350+ albeit with higher temperatures. This cascade should pull 350W @ -75°C w/o issues on R-1150 and TEV on 1st stage.

While I can agree that I will have to push for more than 300W.
I cannot agree that a TEV and r1150 will get you anywhere near that.
We are talking about 5200 btuh rotarys here. There is no chance of holding a heavy load at the evaporator and keeping a HX below -30C.

I'm running 2x MP14FB (1/2hp pistons) and using Piotres' 54mm evap with 2.5m 0.9mm. Cascade holds leaky GTX470 @ ~1100MHz through Heaven benchmark, which is equivalent to about ~ 350W @ -79°C (-81°C after it recovers). Probe stuck to filter/drier on the 2nd stage right after HX shows around -26°C (19-20bar loaded). The key is not to use too much restriction on ethylene stage, otherwise you'll have to charge too much of this high pressure gas which will eventually bring your first stage to it's knees.

With low restriction and smaller amount of R-1150 on 2nd you'll be able to hold 350W on first at decent temperatures. Yes, your idle temps will not be super duper low (perhaps not even sub -100°C - like mine, idles around -98°C w/o anything attached to it), but you'll be able to hold high load.

There's the big difference though. You have 14cc. I have 7cc. These are quite small compressors, and I just don't think it will be possible. I have r23 and that'll be a bit easier, but I also don't find 19-20 bars of pressure acceptable. If this goes to a customer, I want my HPCO set at 300 and normal load between 2 and 250 psi on the high side. These rotarys would cook otherwise.

Maybe on the next one I'll see what r170/r1150 can do, but I just don't see it being viable here.

Extrusion case in the making, baseplate is .09" white painted aluminum plate, and panels are .04" white painted. Bought a bunch of black oxide screw caps for the outside, should look purdy.
Tomorrow the last bits for the case should show up.

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Nice, 80/20, we use that stuff for frames for our etchers.

RussC

Actually not 8020, I found a better provider who would do custom cuts for free at slightly better than 8020 prices. Also, 1010 channels are normally just slightly too tight for the square of a carriage bolt (1/4-20), but he was willing to run a reeming tool down each channel on each piece as well to widen em up just a hair for me. No charge on that as well. So what can I say, had to go with him.

8020 makes good stuff though, and their brackets are nice and premade. But you are always better off cutting your own if you can ;)

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Update! Evap brazed, pick before cleaning, now cleaned up and ready to go. Then brazed on in, piped up, ready to do evvvilll. No, but ready to freeze stuff. Pressure testing, then vacuum and tuning. Let's have some fun.

So give us the specs on cap tube please. :) Loookin goood!!:up:

Shooting close to the hip on this one, 6.5' of .031 on first stage, wrapped VERY tight (and will get a ton of ASC smeared on and wrapped in tightly with electrical tape before insulatino), and 2nd stage is 9ft of .036.

Case building time.
My angle stock showed up so it was time to pump out 3 brackets for every corner, plus four for the bracer, so... 28! Fun!
Setup the mill/drill and made my drills for the first four, then to the band saw to cut perfectly square cuts (or as close as plausible).

Success!
Cost of angle stock? $7. Cost of a bracket, $2.55. Amount saved? About $60 for a few hours labor.

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And a day of labor later....

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Nice going so far :up:

I like that case idea, seems like a little bit of work to get it all setup. But should be nice and strong.

Do you plan on putting anything in for the walls ?
Like plastic panels of some sort ?

Full aluming siding, .040" white painted

Let's get back to the ice..:D

Hahaha well I've got life things to do too Ron ;)
Ice won't be for another few days.

nice mini cascade :)

Hey NOL, lets set up some testing with a decent 2600K:D

Are you coming to the Philly event Dumo?

Wow! Your angle brackets look identical to the manufacturer's ones that I used on my AC-3 unit. great machining job.

Can't wait to see it fully skinned.

Oh yeah, and 1/10th the cost! Just have to take the time to production line them out.

looking good noob love the metal work mate, think think straight r23 or would be the go and r404a stage one

So the base, nicely assembled, squared out, and then filed some edges. Beautiful. Even mounted some epic 1" thick rubber feet. This won't shake any tables. Then time for the tense moment, the transfer. The big shibang. Now I wish I had Richard still around, but this was going to be an "on your own attempt". And two rotarys made it a bit of a lift.

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It survives!


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MMmmmmm pretty.

Your doing an A++++ job on this one Adam. :) Keep it up

Looking good. I like the use of the extruded aluminum.

It's hard to get used to though, cutting things to perfect square is tough too. In general it's just rough to work with up to what the extrusion requires. But once you get it going. Boy does it look beautiful with that white aluminum. My best looking unit in quite some time.

Quote:

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Originally Posted by n00b 0f l337

Then time for the tense moment, the transfer. The big shibang. Now I wish I had Richard still around, but this was going to be an "on your own attempt". And two rotarys made it a bit of a lift.

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Next time build the base first and assemble the cascade on top :)
Just pulling your leg adam ;)

I like the looks of that and I bet it's a nice solid base.

Actually I dislike doing base first. You end up pissed that you didn't pipe it all up first. And I can't hold myself to pipe without brazing. ;)

It's very solid. Overly so, but thats what I want, so that's what it gets.

EDIT: Just had a yelling match with the unit and won.
I noticed while prepping to charge the second stage that, well, the second stage low side didn't drop when the unit was on. So after feeling puzzled, I pumped gas into the high side and noticed the low didn't stage. After cursing at a blocked captube I realized that that diagnosis made no damn sense. On a hunch I swapped my high and low gauges, booted up her, low side (on high gauge) dropped on out, and high (on low gauge) was stuck at static. So I have a valve stem that doesn't want to play nicely with the quick disconnect on the low, but is totally okay with the wierd fitting I have and love on my high side. Fun stuff.

We have ice. High side of 65 psi with r23 straight... interesting.
Will test load before going to r1150. Also need to heavily increase charge in first stage. But boy do these roto's run hot.


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Quote:

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Originally Posted by n00b 0f l337

It's very solid. Overly so, but thats what I want, so that's what it gets.

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Is it as strong as plywood?

Ron I hope you are joking ;)
This stuff makes plywood look like tissue paper.

Quote:

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Originally Posted by n00b 0f l337

Ron I hope you are joking ;)
This stuff makes plywood look like tissue paper.

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hehehehehe ;)

Just a thought Adam: Maybe time to change the layout of your cascades? Putting the HX parallel to the fan/condensor assembly would most likely widen the footprint of the cascade but you would avoid the airflow over the HX (even though it's insulated - every plastic is porous). Maybe cut the last bend on the condensor and splitting it into a 1st stage condensor & 2nd stage discharge gas/oil cooler? You would gain quite a lot in term of footprint.

Also - as you know - these rotaries aren't meant to run in vacuum (they're MBP), they need sufficient back pressure in order to cool them down. The 9600btu/h compressor on the auto-cascade I've built doesn't even get hot even after extended overclocking session, it's just fairly warm. High pressure ratios also put stress on the compressor. You should check the power draw of your compressors if you think they're running too hot. Maybe your start/run capacitors is not correct for this compressor?

All in all - waiting on the subzero digits! :D

Little issue with airflow, moving up to a 13W motor on the fan almost makes the unit want to take flight. The airflow gets well directed, but once you see the outside of the case on you'll see its got 2" of clearance all the way around.
I wouldn't want to split the condenser though, these small ones help quite a bit. We're not pulling much in terms of power actually, sub 300-400W at most according to the kill-a-watt. So 25uf is right for these. Right now I'm definitely undercharged though, and being in vacuum doesn't help their temperatures.

Just saw -95C unloaded. The more I charge the lower my unloaded, total reversal, but I think the first stage is just too cold.. At 200W it was starting to crash though (150W @ -84C) so need to add more to first stage, which I am waiting for it all to cool/warm up depending on what it needs to do ;).

Current temperatures across the board at 150W so far.

Stage 1 Discharge: 66C
Stage 1 Suction: -55C
Stage 2 Discharge: 54C
Stage 2 Desuperheater bottom: 28C
Stage 2 HX outlet: -51C
Stage 2 Evaporator: -84C

Rotarys are hot to the touch obviously, but with 90-110C being their upper range I am really not worried. Many get spooked when it's hot enough to burn your hand, but you get a burning sensation at about 45C on metal, after all 110F(+-) is quite hot. But rotarys will run well into the "I just cooked an egg on the .......... " territory.
Since I think I am out of R290 I will stop by airgas tomorrow to pickup my order.

Guess I'll get on the electrical side of things then.

Quote:

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Originally Posted by n00b 0f l337

Guess I'll get on the electrical side of things then.

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Don't forget to ground that metal case & verify a ground path with a ohm meter.

Will do, both sets of plugs will have their ground wire wired to the case at separate screws or a grounding bar, and compressors to that.
Will verify as well, good point.

How did this one turn out Adam? It was going so well!!

Currently enjoying its home at Columbia University's Laser lab after a retune for there load specs.

She did 250W@ -81C, but they ultimately needed to only hold 40W, so she got R1150 and runs -105C ~ -110C @ 50W with extended captube to 12' of .031".

Just has an 8020 frame since they passed on needing any casing, and last time I saw it they got some acrylic panels for it on their laser cutter.

Too bad it didn't get skinned with aluminum. Based on what you were doing with the framing and base pan, I bet it would've looked real sweet.

Can you get any pictures of what it looks like now with the plastic panels?

I'll drop them an email :)

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Originally Posted by tiborrr

250-300W is not enough nowadays. Aim for 350+ albeit with higher temperatures. This cascade should pull 350W @ -75°C w/o issues on R-1150 and TEV on 1st stage.

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Is 350 really the norm these days? Seems like a lot of heat.