DIY Chiller Sizing Issue

How would one go about sizing the proper sized expansion valve and evaporator coil to this condenser unit:

1129w of cooling capacity @ -40

Thats the same as a julabo A80 Presto which retails for $40K
The above tecumseh condenser unit is $1500 + valve + evaporator




I was thinking about this today. Funny you should bring it up @pangea!! Let’s figure this out… now, what about plumbing what you linked to to a plate exchanger of sort? Like 100 plate one? Isn’t that all one would need?

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Yes rated plate type evaporators would work, I was thinking more of counter current coil or immersion probe style, but the style matters little compared to understanding how to pair and match them with the condenser unit. Along side the evaporator we need the correct expansion valve.

Thats my next stop if we cant gain any traction here.

Found this…

is very useful info as well.


I’ve got two unused appions showing up at my shop next week…they’ve been sitting collecting dust for several years. I might have to learn me some more stuff & put one to work as the OEM intended.

like I need more projects.


Yeah lol, I’ve been humming and hawing about buying a compressor or modifying one appropriate for refrigeration gases, and then just using a brazed plate as the expansion chamber. Take out some middle men (one of my favourite hobbies) in process.


Im currently working on a diy chiller using an old window ac unit… Looking at the condenser you posted, May i ask how you actually use it, and what will you be using it to chill? Or is it to chill an area/room. Seems interesting. Im new to this stuff so its hard to picture the end goal sometimes

@pangea from Icmag?

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I want to use it as a chiller as well. Mainly chilling solvents and cooling injection/recovery coils, cold traps etc. Once I get this basic setup figured out I want to try to get the advanced tek down for a cascade or autocascade type setup to get into the -80 range. One could also hook it up to a walk in freezer or reg ac air type evaporator as well. This is basically one part of a refrigeration unit, the condenser/compressor. The other side being the evaporator.

@Dabatronicus Dats me


Weedahlic721 here. Long time since those first crystals. Good to see you kicking around


Old Gold here :beers:


MEMED right here…


I remember ya’ll too, Im sure theres more of us here as well, good times.

Heres one of my inspirations for a recirculating chiller:

and cheapish pump:

I think I might just trial and error for the right evaporator size, and start with a 1/2ton expansion valve.(edit: not sure if the half ton is correct,)

also a good thread from a cpu modding forum on how to covert a window banger into a autocascade low temp chiller, which goes over the autocascade principals and such in a somewhat digestible manner.(note: my browser gave me a security warning for this site for some reason:


Yo, you guys inspire me. This bitch has been in storage for years! Messed with her a bit tonight and got her working pretty good.


so the flat-plate goes on the second loop…

thanks @pangea!!

probably the feds :wink: The certificate is only valid for XtremesysServer.XTREMESYSTEMS.local

nah just a config error…


You nailed the dx plater exchanger call, @The_Lone_Stiller

I chickened out last year on this project, again. Hoping to get it going for this year.

Check out the CHN series Plate Exchangers.

Main hold up is still not knowing how to size the expansion valve and evaporator properly and other minor things like the oil charging loading if it doesnt come so already.

Heres a link to the initially posted tecumseh unit for $1300.

CHN half ton plate exchanger - $435(they also have larger sizes)

Capilary tube would cost under $50 or higher end expansion valves for more money.

  • Filter
  • Feed / suction lines
  • Fittings
  • Mounting and the like
  • Refrigerant(and stuff needed to evacuate and charge the system)

= Inexpensive compared to commercial offerings

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I’ve uploaded a great resource for TXV sizing from sporlan. You can also just call them up , ask for an applications engineer, and they’ll size one for you (although honestly i’ve had them undersize me twice now lol so maybe go one side larger).

For very low temp, you face big issues with hunting if you use a mechanical TXV. The off-the-shelf superheat controllers only function down to -60C so that’s a problem as well. You can either mess with getting a mechanical valve to work or write your own logic on something like a Siemens Logo (which is pretty easy honestly).

For ye DIY’ers looking at big compressors for cheap, go get 'em but beware of compression ratios that are too high. Multi-stage will almost certainly be required but it’s not as difficult as it is daunting.

As you mentioned, oil management is a concern for sure, especially with compressors in series. Read up on discharge side oil separators. If you’re building your own skid, you can afford $400 for a spiral separator and a solenoid for oil return.

Overall, great thread everyone!

10-10.pdf (3.2 MB)

Also, there’s a big write up on this thread that would be relevant to picking a random compressor and finding out how much cold you can get out of it:


Northern Lab/Breakover from icmag here… Hey guys!!!

I messed around with an ice machine and a immersed coil tank way back when:

We were lucky to have a txv to rob off existing equipment. I wish I knew more about refrigeration, I’d be elbow deep in this.

Why use refrigerant to chill a fluid that you’d need to pump around when you could just use the refrigerant directly?

Seems like chillers could be made much smaller and more efficient that way.