Glycol chiller for Grainfather

[Sadu]

I recently acquired a used Grainfather and a fermenting fridge-freezer.

The fridge is one of those ones where you can hack the electronics to control the temp of the fridge but leave the freezer running at full strength..

I was thinking it might be cool to put a large bucket of glycol in the freezer and connect it up permanently to the grainfather counterflow chiller. The chiller seems pretty good anyway but it would be diabolically good with glycol.

Question is, how much glycol is needed to chill a 6G batch? I'm not sure what temperature the glycol starts at in a freezer. It's an all-or-nothing thing, glycol is mega expensive so if I'm investing in this idea it needs to be awesome. Plus I don't want to be swapping hoses between water and glycol mid way through.

I do have a 1.5G system plus a gallon of glycol from another project, I could definitely run a test and see if it's able to chill adequately. Just wondering if anyone knows the math to get an estimate before I start playing?

 

[Blazinlow86]

I've never looked into it much but as far as I know it would very quickly turn hot if that's your sole Source of cooling. If you did a precool using ground water then switched to the glycol it may be enough to get it abit cooler than your ground water

 

[beermanpete]

You will likely need at least three times, if not five times, as much coolant as you have wort to ensure the coolant temperature stays lower than your target temperature for the wort.

 

[day_trippr]

fwiw, it takes roughly 6700 btus to drop 5.5 gallons from boiling down to a 68°F pitching temperature.
That's a small-ish window A.C. unit rating - per hour.
I'm not certain about the math from there but I expect if the goal was to achieve that drop in 20 minutes the btu extraction rate would at least triple...

Cheers!