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Old 05-03-2013, 02:16 AM   #1
radial67
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Default Has anyone ACTUALLY used a chest freezer as a glycol chiller

So Ive been reading through a number of threads and there is a real healthy and constructive Aircon/chest freezer rivalry going on and I was interested whether anyone has actually used a Chest Freezer as their glycol chiller or whether it always comes back to how little BTU's they actually have.

Im starting up a 2bbl brewery and dont want to have to fork out a ton of money for a proper glycol chiller as its a single point of failure and super expensive for a chiller capable of running 8 zones+cost of plumbing, whereas chest freezers are cheap, readily available and one per fermenter reduces the single point of failure.

I cant do aircons because of increased ambient temps caused by the fans will interfere with the already increased ambient temps (tropics) and a limitation of free airspace ventilation.

So - has anyone actually successfully done a chest freezer glycol chiller?


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Old 05-03-2013, 02:32 AM   #2
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There have been at least a few I've seen written up in the forums. Here is one example thread that appears to have been a success, with a pretty good size fermenter - and located in New Mexico, USA.

At least one key is to actually fill the freezer with the working fluid - be it glycol or brine - so the coils are doing the cooling directly without air working against the thermal transfer (ie: a bucket in a chest freezer is not going to work very well if at all). Another is finding a pump that doesn't put too much heat into the efficiency equation..

Cheers!


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Old 05-03-2013, 04:35 AM   #3
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Wasnt thinking of using coils.... its just another way of losing temp. I was going to pump chilled Poly-glycolUSP directly through the jackets on the fermenters.

Pump would be on the return side of the fermenter so as not to warm up the glycol gg to the fermenter.
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Old 05-03-2013, 12:09 PM   #4
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fwiw, the "coils" I was referring to are the cold side coils buried in the freezer walls, not whatever you would use around/in the fermenter at the other end of the loop. They're usually mounted high up in the chest freezer walls, so the working fluid level would want to be pretty high up as well to maximize thermal transfer...

Cheers!
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Old 05-03-2013, 03:28 PM   #5
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Hold on there tiger. Let's get this straight--no matter which you use, be it an air conditioner or a chest freezer, the same amount of heat is going to need to be removed from the fermenter. There might be slight differences in the efficiency of the airconditioner vs the chest freezer, and the air conditioner is going to have a MUCH higher output capacity (and therefore lower duty cycle) than a chest freezer, but at the end of the day you need to move X amount of Joules over Y amount of time.

Chest freezers tend to have relatively small compressors. This is due to the inherently efficient design--only allowing the top to open keeps a vast majority of the cool air in. As a result, if you're going to be cooling a lot of 2BBL fermenters, I have a hard time suspecting that a chest freezer is going to be sufficiently powerful for the occasion.

A modified air conditioner with the evaporator coils dunked in a coolant reservoir is going to have a LOT more cooling capacity than a chest freezer could. This was, at least at one time, a fairly common way of performing sub-zero CPU cooling for computer overclocking...An older hobby of mine .

I am an electrical engineer also certified as an HVAC tech . I'll try to answer any questions you may have .
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Old 05-03-2013, 07:50 PM   #6
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Everyone’s comments bring up valid reasons to use one method over another. I am working on putting the finishing touches on my 15 gallon system with a 16 gallon induction tank (plastic conical) and my plan is to use my beer cooler for the chiller. Considering that the fermentation unit will only hold 15 gallons I plan on making an insulated jacket with tubing on the inside for cooling and have it go into my restaurant beer cooling with a five gallon bucket of brine for chilling. I will have a PID controller running the pump and hopefully keeping it in the desired range. The nice thing about the two keg beer cooler is that can bring things to temperature very quick. It only took two hours to bring my 7.5 gallon keg to 40 degrees so I don’t think I will have any issues with the other.

The new deep sink is installed and the fermenter stand is off being powder coated so all that is left to do is run the 50 amp circuit for my RIMS unit and install the arduino controller, from there I just have to wait for the stand to come back so I can test

Below is the new 15 gallon RIMS unit I built; currently it has a 4500 watt and 1500 watt heater and a March 809 pump. After I run a couple tests I will finalize my design and build a new stand and change from silicone tubing to rigid lines.
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Old 05-03-2013, 10:29 PM   #7
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Ok, some background - I've built glycol chillers for three are micro-brewery's now (ranging in size from 1.5 bbl to 3 bbl) so I've got a little experience in the area.

The biggest problem you'll run into with a chest freezer is the size of the cooling system. Most of them are going to fall somewhere between 500 and 1500 btu/hr. 3 bbl of very active yeast (such as one that would drop 40 pts in 24 hrs) will put out in the neighborhood of 500 btu/hr. Now granted this isn't normal, but does give you an upper bound for the heat put out by yeast. Add into that heat loss's to the surroundings (assuming times when the room is warmer than the desired ferm temp) and you can quickly overwhelm a chest freezer.

You can offset some of these effects by having a larger resevoir of glycol, and has been mentioned above, you would almost have to to have any sort of performance from the chest freezer. Basically fill it up almost directly, without using a bucket, so you have conduction to the cooling coils to transfer the heat out. If you just put a bucket in, you'll get even slower performance because air is an insulator.

What I've done several times now is take a standard 8-12,000 btu/hr window aircon unit, seperate the evaporator out but cutting part of the frame away, and submersing that into a rectangular cooler. You lose about 20% efficiency from the aircon because you're operating it at lower than design temps, but it's still more than adequate and with the added capacity, you can crash cool effectively.

I have a 10,000 btu/hr unit at a brewery that is running 11 - 3 bbl fermentors with this setup, and is coming up on 2 years of continuous use. they are able to crash cool, and even lager some beers without much trouble.

If you have questions on the setup, feel free to ask. For converting an Aircon, I can't give specific instructions because they're all a bit different, but I can say I've been able to do it for under $500 each time for the glycol chiller portion.
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Old 05-03-2013, 10:30 PM   #8
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As for the single point failure aspect - you can always back it up with a trash can filled with ice in a pinch
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Old 05-03-2013, 10:45 PM   #9
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Shockerenger--Exactly what I was suggesting with the air conditioner .
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Old 05-03-2013, 11:30 PM   #10
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Quote:
Originally Posted by RadicalEd View Post
Shockerenger--Exactly what I was suggesting with the air conditioner .
they work like a champ!

(although my personal one was a dehumidifier in a former life)


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