Fermentation Chamber - separate from but powered by a chest freezer

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BobTheFourth

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First of all, this is my first post in this forum, so Hello Everyone!

I'm about to make the switch to kegging my homebrew instead of bottling, because bottling is a pain in the butt. My plan is to use a chest freezer to hold the kegs - I've picked out one big enough to hold four, plus a carboy on the hump. But that's just the background - it occurred to me that I may be able to use this machine to power an external ale fermentation chamber as well, and was wondering if anyone had tried this and what the results were. Searches on this forum and the internet didn't really turn anything up that sounded similar to my idea.

What I was thinking of doing is adding a collar to the chest freezer and hooking up some 3-4" diameter insulated ducts - one for an inlet and one for an outlet. These would run to an insulated chamber big enough to hold a couple carboys. A temperature controller would turn on a fan mounted in the exhaust duct when the temperature dropped below a typical ale fermentation set point, thus circulating cold air up from the freezer.

Another (more expensive) option I considered was using a system of copper pipes & coils filled with water to move the heat instead. This would require the temperature controller to modulate a small pump, but might be more efficient and responsive. The coil in the freezer could be immersed in a cold water bath to improve heat transfer.

Thoughts? Sound crazy, or doable?
 
The air only sounds good.mount your supply duct low to the bottom, your return duct should be up at the highest point. That is also where you want to mount the thermostat. No such thing as too much insulation for fermentation chamber, all the way around. Just make sure that the thermostat/ temp controller has access to return air. Don't over fill chamber with fermenters you want good air flow or it will not work. Bad side is that all fermenters will be at same temp. Water coils could likely freeze. And you have to factor in viscosity, air elimination in your piping, can the pump handle the cold water? And the air would be a cheaper build. Just my thoughts good luck keep me posted as to how you make out. Cheers
 
Thanks for the votes of confidence. I was pricing out the water-based system a bit and decided it would end up costing as much as just buying another small freezer, so I'll probably go with air just based on cost. I'd like to figure out a way that I could have multiple independent chambers if possible, so that I can have a primary and a secondary going at once with the appropriate cooling - suggestions to that end would be excellent. I'm not sure how the ductwork would have to be arranged - I don't want to have too many holes in the collar and too much ductwork cluttering up the inside of the freezer. Having only one inlet and outlet in the freezer would be best if I could do it that way.
 
A couple more thoughts. I forgot to mention that you are going to need to add dampers in the supply and return ducts to keep cold air from bleeding into fermentation chamber and cooling down too much. Also the more warm air you move you finished beer will also warm. If you want multiple chambers you will need more ducts, especially if you want each one to have its own temp. Difficult but nut impossible. Don't forget to add a t-stat for each chamber. I don't want to be a kill-joy, I want to see you succeed. Good luck keep us posted. Cheers
 
Thanks for the votes of confidence. I was pricing out the water-based system a bit and decided it would end up costing as much as just buying another small freezer, so I'll probably go with air just based on cost. I'd like to figure out a way that I could have multiple independent chambers if possible, so that I can have a primary and a secondary going at once with the appropriate cooling - suggestions to that end would be excellent. I'm not sure how the ductwork would have to be arranged - I don't want to have too many holes in the collar and too much ductwork cluttering up the inside of the freezer. Having only one inlet and outlet in the freezer would be best if I could do it that way.

I think this will work reasonably well, but I'm not an expert in this. I'd build the ferm chamber from insulation, and just put in a foam board divider to separate the two temperatures. You do need a controller with temp sensor in each chamber, but a fan blowing cold air from the freezer can go to the cold side of the ferm chamber, and another fan can blow cool air from the cold side to the warmer side of the ferm chamber. It just requires 2 temp controllers, and 2 computer fans and probably a flap. Easy peasy.
 
A couple more thoughts. I forgot to mention that you are going to need to add dampers in the supply and return ducts to keep cold air from bleeding into fermentation chamber and cooling down too much. Also the more warm air you move you finished beer will also warm. If you want multiple chambers you will need more ducts, especially if you want each one to have its own temp. Difficult but nut impossible. Don't forget to add a t-stat for each chamber. I don't want to be a kill-joy, I want to see you succeed. Good luck keep us posted. Cheers

Yeah, definitely dampers at the inlet and outlets from the chambers and the freezer. Though I'd think if the freezer and the chamber were at the same height, I wouldn't have to worry too much about bleeding since the cold air would naturally settle. Hopefully I won't have to worry too much about the kegs warming up - 10-20 gallons of beer is a lot of thermal mass.

I'm hoping to have only one tube in and one out of the freezer, and having the cold air split up in some sort of manifold. I just need to figure out a way to keep the chambers from drawing air from each other instead of the freezer. Maybe some dampers functioning as check valves could help with that.

Cromwell said:
I think this will work reasonably well, but I'm not an expert in this. I'd build the ferm chamber from insulation, and just put in a foam board divider to separate the two temperatures. You do need a controller with temp sensor in each chamber, but a fan blowing cold air from the freezer can go to the cold side of the ferm chamber, and another fan can blow cool air from the cold side to the warmer side of the ferm chamber. It just requires 2 temp controllers, and 2 computer fans and probably a flap. Easy peasy.

I'm thinking about this as well. I'm just not sure how well it would actually work with them being separately controlled. There may be situations where I have stuff in the "hot" chamber but not the "cold" chamber (or vice-versa) and it would be more efficient to be able to deliver the air there directly. And if only one side was "running", it might have trouble pushing enough air through the other chamber to keep circulation going (and if it could, it might upset the temperature in the other chamber, especially if the cold chamber is running and the hot chamber isn't). But this option does potentially solve the ductwork issue, and having only one chamber with a divider is easier to build and manage, so its worth exploring this option some more. I may be over-thinking the disadvantages.
 
Sounds like a cool idea. The only thing I can think of that may cause a problem is the BTU rating of the freezer. With multiple fermentation chambers and kegs comming in and out you should make sure that the freezer can handle the load and keep up without stressing. I would also try and put this somewhere where ambient temps won't fluctuate much. Good luck with the build, let us know how it turns out.
 
Great idea, but seems a bit unnecessary.

The problems I see

Cost and effort vs the alternative, which is a CL chest freezer(with or without a collar)with a 65-75 dollar temp controller(my 2 carboy holding unit cost me 135 out the door). I can lager, you will not be able to with your set up.

The biggest issue with this is logistics. This would force you to serve and ferment in the same place. For me serving is in my bar room and fermenting is in another room all together.

Also, the possibility of over taxing your compressor is also possible.

I would say if you love to tinker, have a logistical set up for serving and fermenting that makes sense, and are open to the possibility of this not working out...full steam ahead.
 
Sounds like a cool idea. The only thing I can think of that may cause a problem is the BTU rating of the freezer. With multiple fermentation chambers and kegs comming in and out you should make sure that the freezer can handle the load and keep up without stressing. I would also try and put this somewhere where ambient temps won't fluctuate much. Good luck with the build, let us know how it turns out.

It'll be in the back room of the basement, which stays pretty consistent temperature-wise (no windows, several concrete walls). If I do go ahead with this, I think I'll do a trial run with a single chamber and try to get an idea of how much extra stress its putting on the freezer before deciding whether to expand it.

Xpertskir said:
Great idea, but seems a bit unnecessary.

The problems I see

Cost and effort vs the alternative, which is a CL chest freezer(with or without a collar)with a 65-75 dollar temp controller(my 2 carboy holding unit cost me 135 out the door). I can lager, you will not be able to with your set up.

The biggest issue with this is logistics. This would force you to serve and ferment in the same place. For me serving is in my bar room and fermenting is in another room all together.

Also, the possibility of over taxing your compressor is also possible.

I would say if you love to tinker, have a logistical set up for serving and fermenting that makes sense, and are open to the possibility of this not working out...full steam ahead.

Good points. Space is an issue for me, so I'm not sure I can realistically fit more than one freezer in my brewing area. Otherwise, several chest freezers kept at different temperatures would definitely be the easiest and most reliable way to go. I'm not sure I wouldn't be able to lager with my ducted system though - it might work better than I anticipate.

I've got nowhere else in the house where I can put the serving keezer, so its going to be in my brew room no matter what. I wouldn't mind putting it in the dining room, but I think I know what my wife would have to say about that...
 
I was planning a very similar build but got to thinking about how taxing it would be to the freezer. I have a new plan.

I'm going to build a 8 unit fermentation chamber all independently controlled. Each unit will use a heat belt for the fermenter and for cooling I'm going to pump cold glycol through copper coils with fans helping to circulate the air. The chambers will be sized for a 6 gallon better bottle on top and the 4 bottom will be sized for Ale pales or 15 gallon fermenters. The cabinet that holds everything will be free standing and have double pane tinted glass doors with built in led strips for lighting.

The hard part is I want to keep 10-15 gallons of glycol in the base or stand at 0F. I have not yet found an appropriate cooling unit. So I have decieded to build my own using the AC compresser from a car or truck. That way I can have the hot side of the coils outside of my house.

Sorry if i hijacked your thread, I wasn't planning on posting all that when i started typing.

I'm very interested to see how your build goes and works. Hopfully I can steal some ideas.
 
I just tried this recently and continue to run into the issue of air flow from the chest freezer (keezer) to the fermentation chamber. I have a computer fan (jet powered almost) that is 252 cfm. It definitely flows the air into the fermentation chamber but i quickly get suction from all the air being pulled out of the chest freezer. Still haven't figured out how to put more "cold" air back into the keezer so that i can continue providing cold air to the fermentation chamber. If I return the air from the fermentation chamber back to the keezer, I don't think it will cool quick enough before it gets recirculated. Any ideas?
 
The air going into the keezer has to come from somewhere or you'll get the suction, as you discovered. You probably want to run a return line, possibly with its own fan, to return air from the fermentation chamber. Your only other choice would be to suck it in from the room, and that's probably warmer than the chamber...

Don't worry about the time it takes to cool it before recirculating. Think of it this way: when the fans are running and air is circulating, the keezer is attempting to cool the whole volume: both the keezer side and the fermenter side. The fermenter return air will raise the temperature in the keezer a bit, so it'll turn on to accommodate this. Once the fermenter reaches the target temperature, you shut off the circulation and disconnect that side from it. The keezer will need to have enough cooling power to pull this off, but if it does, it shouldn't be a problem.
 
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