Suggestions for diy glycol chiller fluid?

Most threads on here discussing chiller fluids are in the context of hardware being used. Im making my own diy glycol chiller with an old 25k btu window ac. The reservoir is going to be a 55 gallon barrel. Trying to decide the best fluid to use. Found 50/50 green antifreeze but working on getting the actual specs to see if it can handle -20c. Also found barrels of glycol for around 500. So I’m wondering if there’s any suggestions for my application. Needs a to be non corrosive to not destroy the ac condensor. And preferably budget friendly. Any other good options? Sourcing it in southern Oregon would also be a plus. Need a barrel of something. Thanks :slight_smile:

Propylene glycol and water mixture would work fine

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My latest window AC hack hits -20 without a load.

Running 50:50 glycol from Home Despot



LOL that beautiful masterpiece

I bet that thing is a lot more reliable than a Chinese chiller too


American Ingenuity right there baby.

“Lucky” !!

Mine in progress


It went to burningman. Spent a year in gerlach NV, then four years in the back of my shop after being discarded by a buddy who was couch surfing (he left me a school bus too).

Even making it into surgery was amazing…surviving and doing the job well?!?

“Lucky” barely does it justice :shushing_face:

Check the condition of the Alu fins…


That looks way more professional!!


I didn’t see any glycol on Home Depot’s site. Any memory on the price? Filling this huge reservoir is my issue. I found the 50/50 antifreeze for like 300 for a barrel but can’t find the specs on it. Finding locally is also a big plus

@cyclopath damn that AC sure has been through some shit !!! Thats dope it still works

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Any suggestion of mixture or calculation for mixing ratio of the glycol and water? And is there anything I should check for if I end up purchasing glycol? Different types etc

Turns out it wasn’t Home Despot, it was our local equivalent (Jerry’s). I can’t find the empty bottle, but I’m 98% certain it was Prestone Automobile Antifreeze. I was looking for the pink RV winterizing propylene glycol, but it was the middle of summer…


40% PG or 40% EG is good down a little past -20c

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Yes, there are tables out there.

Less glycol/more water = better thermal transfer (heat capacity).

If you’re not using a boiler or risking getting it in your product, you should be fine with any old glycol mix.

The pink stuff is less toxic & dyed with beet juice and is a safer bet if there is a risk of getting in your product.

If you’re HEATing it, you need a mix designed for boilers.

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Found these 3 so far. The splash brand I can get delivered to Walmart and it’s super cheap but I can’t find specs for it. The green coolant is real cheap but can’t get it locally. What would one suggest between then 50/50 green antifreeze and the propylene glycol

There will be no boiling. And it will not be interacting with any consumable or product

Just using it as a cooling resevoir for my ac glycol chiller

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So the Walmart splash brand antifreeze is the cheapest and available local. I found the item on their site, and I noticed the barrel says -50 on it so that should be good. That would be the ideal purchase. Doesn’t say much about its corrosive effects


Then go with the cheap stuff. Remembering to do the math if you’re comparing 50:50 to undiluted :face_with_monocle:

Corrosion is way more of a problem in heated applications.

I’m going to try and find a better spec sheet for that splash antifreeze. But that seems like it might be the choice for me. Just want the best effiency out of this monstrosity of a chiller I’m building.

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