My A/C unit glycol chiller

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My A/C unit glycol chiller

Postby Backyard Brewer » Sat Jul 29, 2006 12:31 pm

I've posted bits and pieces of this whole experiment and now I'm about done with the thing so I'll post the whole saga more or less from square one. There are a few minor things I'm going to change here and there, but for the most part, the design is what it will be.

The project started with the need to control the fermentation temperature of two 12.2-gallon B3 conicals. The easiest way by far is to put the whole thing in a fridge with a temperature control, but I just don't have room for another fridge, yet alone two and I'm also thinking a third fermenter may be in the future. The cooling option available from B3 was too expensive in my opinion, so I needed another solution.

My first plan was to create a small cold room with two individual compartments and put the fermenters in there. I really don't have the space for that either, so I needed to come up with a solution to hold temp in each fermenter individually and with a compact source.

A glycol jacket and chiller seemed like the ideal solution, but at $1100 for the smallest one I was obviously going to have to figure out how to make one. I already bought a 6,000BTU window A/C unit to cool the cold room, so I decided to use it. I was inspired by an article I found online about building your own reef aquarium chiller from window A/C parts. I didn't want to compromise the sealed system since I didn't want to vent the refrigerant (illegal) and I couldn't re-charge the system. I decided to carefully bend the evaporator under the unit and set it on top of an ice chest full of coolant and put two pumps in the coolant bath. A temp controller would individually operate each pump and the coolant bath would be controlled by a third.

This worked pretty well but was very difficult to get to the pumps. The other problem was I couldn't be careful enough bending the lines and I kinked the suction line. The unit still worked, but ran warm.

The initial bucket test:

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The kinked line:

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The original design with A/C on top of ice chest

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This unit worked as is for two brewing sessions but the kink failed on the third and sent my vanilla porter up to 85* (it's not drinkable). Now that the refrigerant was gone anyway, I decided to experiment with R134a as it is readily available anywhere including my grocery store. I cut the evaporator off, cut out the cap tube and rearranged everything so that I could sit the A/C unit next to the ice chest to get inside it. I rerouted all the copper lines and brazed new ones in place. I sourced some service fittings and brazed them on:

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I bought a venturi vacuum pump and a set of A/C gauges from Harbor Freight Tools for less than $50 for both. Once I had everything sealed back up, I tried evacuating the system, but it wouldn't hold vacuum at all. I pressurized the system and found that my brazing job of the service ports to the tubing was lousy and I had to fill in some material. All my tube-tube connections were great, but those ports are a b**ch! After three tries, I had a system that would hold vacuum. I added the R134A and within seconds the unit was cooling! I was able to drop the coolant bath to 24* within about 1:45 while charging the system at the same time.

To control the pumps, I didn't want to spend the money on several Ranco controllers, so I decided to use cheap digital thermostats and A/C contactors (24VAC relays) Thanks to John for figuring out which one on the market was easy to convert. I added a 24VAC transformer and a contactor for each pump. They work very well.

The blue connects are the pump load wires and the red ones are the control voltage from the thermostat

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Here is the completed unit

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The whole setup with both fermenters

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The control panel. I happen to be fermenting two ales right now

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How the heat is removed from the fermetner

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Overall this was a very cool project. I can keep ther fermenters at almost any tempature I want and within 2*. I've brought the beer down to 35* just to see if I could.

A few things though:

1) Electricty is very dangerous. If you don't understand it, leave it alone. I will be moving the connections into a waterproof box now that I know it all works.
2) It is illeagal to vent refrigerant into the atmosphere.
3) Refrigerant can cause bad frostbite burns.
4) R22 and R134a are NOT compatible refrigerants. Do not mix any refrigerants.
-Derrin

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Postby BeerPal » Sat Jul 29, 2006 2:14 pm

That is a completely awesome setup. Very impressive. Nice work.
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Postby marketfixr » Sun Jul 30, 2006 8:34 am

have you played around with the temp of the glycol to see if running it colder or warmer affects the temp swing on the beer? I like the setup but wonder if having the pumps in a fridge with a bucket of glycol would would cool it enough. It probably wouldn't work because the a/c unit chills the evaporator down to 30* which is a far better heat transfer system then being in the air. Nice job.

Kevin
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Postby Backyard Brewer » Sun Jul 30, 2006 8:50 am

marketfixr wrote:have you played around with the temp of the glycol to see if running it colder or warmer affects the temp swing on the beer? I like the setup but wonder if having the pumps in a fridge with a bucket of glycol would would cool it enough. It probably wouldn't work because the a/c unit chills the evaporator down to 30* which is a far better heat transfer system then being in the air. Nice job.

Kevin


Yes. The larger the tempature differential, the faster I can affect changes to the beer tempature. This unit will get the coolant bath down to 24*. I tried a buvket of water in a small refrigerator and coulsn't even keep the coolant bath at 50*. It was not effective at all, but that was a dorm fridge, not a chest freezer which would probably be more stable.
-Derrin

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Postby BeerBiker » Sun Jul 30, 2006 9:29 am

That is way cool. Over my head, but way cool. Great job!

Mark
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Postby johnplctech » Sun Jul 30, 2006 10:56 am

Derrin,

Mark is pharting on your chiller :lol:

John
Last edited by johnplctech on Sun Jul 30, 2006 11:03 am, edited 1 time in total.
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Postby johnplctech » Sun Jul 30, 2006 10:58 am

marketfixr wrote:have you played around with the temp of the glycol to see if running it colder or warmer affects the temp swing on the beer? I like the setup but wonder if having the pumps in a fridge with a bucket of glycol would would cool it enough. It probably wouldn't work because the a/c unit chills the evaporator down to 30* which is a far better heat transfer system then being in the air. Nice job.

Kevin


Kevin, Now that Derrin has found a good pump and a source for gylcol I plan on doing a unit with a container of gylcol in my chest freezer. It will freeze a 5 gallon bucket of water in about 4 hours so it should work and the freezer is never full anyway...

John
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Postby TastyBrew » Tue Aug 01, 2006 7:11 pm

Has anyone tried using thermoelectric liquid chillers to cool the glycol solution?
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