Aircon boosted glycol system

[bergerrings]

Afternoon all,

I finished my glycol chilling system a few months ago and have been less than impressed with the results. The original plan was to have it circulate though a few fermenters and then also have it able to circulate though a second heat exchanger to aid in cooling down the wort after boiling. The system is pretty basic with a storage container sitting inside a freezer and pumps and solenoids.
The system can maintain fermentation temperatures well enough but the freezer just can't cool the glycol back down quick enough to have any real impact when used to cool wort.

What I am now thinking of doing is acquiring an old air conditioner and sitting the evaporator coils inside the glycol bath inside the freezer and have the compressor, expansion valve and electronics sitting on top of the freezer. Then having it programmed to turn on when the glycol bath rises above say 0C.

Has anyone seen this or done this or have any potentially helpful ideas? The couple issues I potentially see are:

The evaporator continually sitting in a glycol bath
-I’m using inhibited propylene glycol so this shouldn't* rust...?

I will most likely have to cut the piping and extend it which will then entail re-gassing the air conditioner. I have seen on the net that you can by a simple recharging kit from 'your local hardware store' but these have all been in the US. Any Australians come across anything like this?

If I can get this to work then it should solve all my refrigeration needs. I will then be able to condidently purchase a 100L bright tank for carbonation purposes!

[Backyard Brewer]

I did this several years ago and outlined the whole build. Unfortunately the whole thing was lost when our club forum crashed. Suffice to say a window AC unit works very well. With a minimal output of 5K BTUH they have a lot of power, a typical dorm fridge is only around 400-700 BTUH.

There are two very important points to get it to work long term: 1) make sure you either seal or remove all the pot metal from the evaporator. The metal is super cheap and rusts bad. It will foul your pumps and anything else. It creates a weird electrolysis or something. either take the time to paint it with several layers of paint or remove it. 2) Take the time to pull out all the aluminum fins. They will freeze the liquid between them and create a 32* block, reducing efficiency. Which I guess means I had three points... Add a small recirc pump to the glycol bath to keep it moving.

Here are some images of inital testing and a prototype.

[phillc]

I, also, have done this. Very similar system. All points above are valid. My particular air unit did not have any "pot metal issues". It is a random older used one. It is very efficient. It will bring about 8 gallons of glycol from room temperature to about -10 Fahrenheit in like 12 minutes. It has no problem cooling the two 15 gallon fermenters, even in the heat of summer at lager temps. The fermenters are converted sanke kegs each with 50' of stainless tubing wrapped around them, and then a layer of insulation wrapped around that.