DIY keg cold chamber & fermentation combo

[markag]

I just got my first corny keg for my birthday a week ago, and I'm currently planning out my kegging setup.

I'm on a tight budget for this, but have a plan and wanted to share and document what Im thinking of doing, and get your feedback.

I picked up a bar top mini fridge from a guy I work with (traded him a 6 pack of homebrew for it). He used to do homebrewing, but feel out of the hobby years ago. He told me that he had taken the door of the fridge and used insulation board to build a fermentation chamber with it. I originally picked it up from him to do the same thing. However, I just got the idea today to see if I could come up with a deal chamber kegerator & fermentation chamber combo.

Here is my thought... I essentially want to build an oversized "son of a fermentation chamber" where the side where you put the iced bottles is the kegerator with the mini fridge, and there would be a temperature controlled fan to add cool air from that side into the fermentation chamber side.

I just started on the design of it today. I think I am looking for an overall size of approximately 2'x4', which could get me about 3 kegs + the CO2 tank on the keg chamber side, and probably a single 5-7.5 gallon carboy on the other side. I've got an inkbird temperature controller, that I could use to drive a fan to pull air from the keg side through some kind of duct or passage way.

Some of the concerns and internal questions...
-Will both chambers just equalize to the same temperature?
-do I need to intentionally put vents into the fermentation side to allow cool air to dissipate? Do I need to add a heat source?
-will the mini fridge be enough to keep up and keep the keg side cold enough?

I guess the only way to answer all of those will be to try it out.

 

[markag]

I put together a 3D model of my concept. Picture is attached below. The mini fridge supplies cold air to the keg side, and then there would be a temperature controller with a PC fan to supply cold air to the fermentation chamber side.

The "son of a fermentation chamber" design uses a baffle to separate the return air side from the supply side with the fan. Because I don't want to put a divider on the keg side and take up space, I'm thinking that I could run a PVC pipe down to the bottom of the chamber to take the place of the baffle from the original design.

In this setup, the mini fridge replaces the ice bottles, but functionally it is all the the same.

I still need to plan out how I would actually get items in & out of this design. I'm thinking about possibly just using pegs to make the top of it removable, but I'm also thinking about making the panels hinge open on the front (the panels that are currently hidden from view).

I also haven't figured out how many 4x8 sheets of foam this will take to make. I need to lay out my panels, and see if I can figure that out. I may need to tweak it so I can reduce the number of sheets that I need.

 

[bigdawg86]

I have seen others do "chambers" with freezers similar to yours and I think there was alot of trouble keeping the larger volume of stuff at the desired temperature for kegging / cold crashing.

 

[ancientmariner52]

I put together a 3D model of my concept. Picture is attached below. The mini fridge supplies cold air to the keg side, and then there would be a temperature controller with a PC fan to supply cold air to the fermentation chamber side.

The "son of a fermentation chamber" design uses a baffle to separate the return air side from the supply side with the fan. Because I don't want to put a divider on the keg side and take up space, I'm thinking that I could run a PVC pipe down to the bottom of the chamber to take the place of the baffle from the original design.

In this setup, the mini fridge replaces the ice bottles, but functionally it is all the the same.

I still need to plan out how I would actually get items in & out of this design. I'm thinking about possibly just using pegs to make the top of it removable, but I'm also thinking about making the panels hinge open on the front (the panels that are currently hidden from view).

I also haven't figured out how many 4x8 sheets of foam this will take to make. I need to lay out my panels, and see if I can figure that out. I may need to tweak it so I can reduce the number of sheets that I need.

Interesting idea. Take a look at a side by side refrigerator-freezer, note how the air circulates from freezer side to refrigerator side. I think the fan needs to be at the bottom blowing toward the fermenter, or at top blowing toward keg side.

The biggest question is whether the minifridge has the capacity to cool that volume. Looks to be about 6 to 8 times more than the minifridge is designed to cool. If it works at all, I'd expect pretty short life. Maybe, with enough insulation.... Please keep us posted if you go on with this.

 

[Blazinlow86]

My guess is it won't have the BTU required for what your planning. Most people that build those coffins attached are only using them to maintain a consistent ferm temp. I don't think you'd be able to cold crash or keep your serving kegs cold enough. That being said I have zero experience and could be completely incorrect

 

[bleme]

You might be able to do something like this with a window AC unit, but like Blazin and Mariner said, the compressor in that mini fridge will never be able to cool that volume.

 

[markag]

I share the same concerns about the ability to keep both chambers cold with that counter-top mini fridge. I received the fridge from a former home brewer who said they used it to cool a single fermentation chamber, and it previously did it without issues. Not sure how it will hold up under these conditions with approximately double the volume from what he said they were using before.

I've been brewing Belgian beers where I'm not getting down to a true lager temperature. My fermentation setup is really targeted at getting down to about 50 degrees for a secondary fermentation. Having the ability to get down to true lager temperatures, and possibly be able to cold crash would be a desired future state, but I don't know if I have expectations that this system could do that. I'm not sure if the "son of a fermentation chamber design really has that capability or not. I would be targeting similar types of performance from this system.

Maybe I could even incorporate some Arduino components that open and close a baffle so the two chambers are completely isolated from each other when air circulation is not needed. I don't think this will work well if all of the cold air is free to leak into the fermentation chamber. I would think based on the feedback from my friend that this fridge could sustain the keg temps on a single chamber, but essentially keeping a chest freezer sized volume cold will probably push it pretty hard.

 

[markag]

I started simple with the build. I'm focusing on the keg side to make sure that will work before I add any more into it.

Total investment in this box is about $17 for a single sheet of 1-1/2 foam board. It can hold 2 corny kegs, or one keg + CO2 cylinder. The fridge was free, & I still need to attach it into the system to test it all out.

 

[balrog]

My 1.5cuft dorm fridge would keep 60F using STC+ in foam board chamber just lg enough for ferm bucket. It would not get to 50, running constantly. YMMV