My large fermentation chamber on the cheap.

My first (major) DIY in the hobby.

40 dollar fridge from craigslist.
30 dollars in insulation.
30-40ish in wood
50ish in thermostat(s)

I'm really happy with it. Easily fits 2 6.5g carboys and 3 5g carboys. I could squeeze at least one more in. Second thermostat kicks on the 110v fan to cool the middle fermentation chamber. Right now using chamber 1 for primarying a lager, chamber to for primarying an ale, and the third is ambiently around 70 degrees (2 degrees under the basement air) for the secondaries.

Woot!

Pictures?

Kolsch_Meister said:

Pictures?

Click to expand...

Whoops!

Nice looking build!

First off, awesome!

Second, all I can think about is covering the outside with brewing stickers and a mounted brewing log to keep track of beers, transferring, and fermentation gravities.

Nice dude. Very nice.

Just put a fresh batch of my witbier in primary. The lager from the pictures is still in the "fridge" area. The fridge section is sitting up at 17.2-17.3C (according to temp. probe taped to carboy) and the witbier is slowly dropping from 25C down to the target of 18.5C.

I don't like that the lager is up in the 17s during this process, however it's right around time for the diacetyl rest so for now I'll deal with it. I'm hoping that things will come to more of an equilibrium when the witbier gets down to fermentation temperature.

It seems like the fan is pulling air out of the lager chamber faster than the fridge can replace it with cool air. I might have to but a speed controller on it.

Really nice work. What kind of fridge is it? I have a standard top freezer type and I hate that the freezer section goes to waste. Your post gave me an idea. I could build a vertical collar similar to the ones used on keezer builds. This way the fridge AND freezer would share one open airspace regulated by one thermostat. Unless someone out there has figured out how to control the freezer section separately from the fridge section? Any thoughts?

This is one of the fridges with the freezer integrated inside of the fridge.

I'm beginning to wonder if I should have another fan on the opposit corner of the divider blowing back into the fridge. Any other thoughts on improving the design?

I added a small fan to the bottom of the divider separating the fridge from the 2nd chamber, so now there is a fan blowing from the fridge to the chamber on the top of the divider and a fan blowing from the second chamber back into the fridge. This has helped, however I still think the cooling can be more efficient.

I'm wondering if anyone has thoughts on this:

Move the fan that is on the top of the divider to blow FROM the second chamber into the fridge with duct work that directs this return air through the freezer chamber. This air will then fall down the back of the fridge and circulate past the carboy that is IN the fridge and back through a fan from the fridge to the secondary chamber. I feel this will utilize the freezer coils and help efficiency.

Can't get a good visual with the pics you posted; do you have any that show the fridge itself? In general, I think some air circulation from the freezer section to the fridge section should help equalize the temperature thereby reducing the demand on the compressor....

I just gave myself an idea for my standard freezer on top unit. What if I cut 2 large (say 4 inch) holes in the side of both the upper and lower section. I could then use insulated 4" PVC for "ducts", one with a fan and one without. The goal is to have the same temperature on the top and bottom section. Currently the top goes to waste and is much colder than the lower section...
What ya think? I don't have the space for the above setup but at least this would give me some bottle storage above the lower chamber...

What are you using for thermostats? STC-1000?

I like the lights in there so you can see what you're doing. I struggle with lighting in my shed all the time.

Hmmmm.. I was always told those compressors wouldn't work without the fridge being upright because of the oil inside of them. Old wive's tale maybe?

That's a mini fridge, right?

DUDE, I had this same idea like 2 weeks ago!! it is so awesome to see that it works!! I have TWO mini fridges from college that still work great and that no one wants and I have no other use for.

I'll be honest: I would have expected this build to not work at all, considering you've increased the volume that dorm fridge needs to cool by about 4x.

I'm typically a strong proponet of the Craigslist freezer with temp control. I would say with what you spent here you could have easily have gone this route (and maybe saved yourself some $), but the ability to have lager ferm, ale ferm going at the same time is definitely plus.

I'd be interested to hear about about how you have this set up. Is the main fridge unit on a controller? If not, how do you control the lager ferm? If it is on a controller, what happens to the lager ferm chamber temp when the ale ferm chamber kicks on? Have you tested this "fully loaded" with actively fermenting carboys?

broadbill said:

I'll be honest: I would have expected this build to not work at all, considering you've increased the volume that dorm fridge needs to cool by about 4x.

I'm typically a strong proponet of the Craigslist freezer with temp control. I would say with what you spent here you could have easily have gone this route (and maybe saved yourself some $), but the ability to have lager ferm, ale ferm going at the same time is definitely plus.

I'd be interested to hear about about how you have this set up. Is the main fridge unit on a controller? If not, how do you control the lager ferm? If it is on a controller, what happens to the lager ferm chamber temp when the ale ferm chamber kicks on? Have you tested this "fully loaded" with actively fermenting carboys?

Click to expand...

I know you weren't talking to me, but I am thinking about doing something similar with extra dorm fridges I have. However, because I already have a lager fridge, I would just be using this as a way to efficiently keep my ales fermenting between 60-70 degrees. So I thought that if I took one fridge and added enough space to fit 2-3 carboys (with a similar type set up, but no divider), it would not overwork the fridge because although the volume is larger, the temp controller is keeping the temperature around 67 rather than 35. In other words, my thought was that the extra volume would not overwork the fridge because it would not have to work so hard to keep the space at nearly twice the temperature it normally keeps a much smaller space. Does that make sense? I am not a tech guy and have no refrigeration or HVAC experience other than a very basic understanding of how it works.

nolabrew85 said:

I know you weren't talking to me, but I am thinking about doing something similar with extra dorm fridges I have. However, because I already have a lager fridge, I would just be using this as a way to efficiently keep my ales fermenting between 60-70 degrees. So I thought that if I took one fridge and added enough space to fit 2-3 carboys (with a similar type set up, but no divider), it would not overwork the fridge because although the volume is larger, the temp controller is keeping the temperature around 67 rather than 35. In other words, my thought was that the extra volume would not overwork the fridge because it would not have to work so hard to keep the space at nearly twice the temperature it normally keeps a much smaller space. Does that make sense? I am not a tech guy and have no refrigeration or HVAC experience other than a very basic understanding of how it works.

Click to expand...

This is my understanding as well. I would think that you would want to go with the largest refrigerator you can find; and build the smallest fermentation chamber that will fit your needs, resisting the temptation to "future-proof" for larger capacity, just because you can.

As an aside, I'd be curious to see how many of these types of builds are still in use after 1 year. You see a bunch of people around here building them, but not to many with follow up on them. This would indicate to me that these do not work as well as planned and get scrapped along the way. I could be wrong.

broadbill said:

This is my understanding as well. I would think that you would want to go with the largest refrigerator you can find; and build the smallest fermentation chamber that will fit your needs, resisting the temptation to "future-proof" for larger capacity, just because you can.

As an aside, I'd be curious to see how many of these types of builds are still in use after 1 year. You see a bunch of people around here building them, but not to many with follow up on them. This would indicate to me that these do not work as well as planned and get scrapped along the way. I could be wrong.

Click to expand...

Yeah. Will see. I just have 2 fridges laying around and extra foam board, and sealant. So basically have everything to see if I can out this fridge to work. Just seems more efficient than running a/c all day to keep the ale in the fermentation closet at a steady temp

It works perfectly so far. Sorry I have not had a ton of time to follow up with pics and explanation.

The first chamber is inside the fridge itself. The system uses 2 stc-1000 thermostats. One thermostat controls the fridge chamber which is currently set at 12.5C. There is a divider built from foamboard where the fridge door was. On this divider, there is a fan on the top which pulls air from the second chamber into the fridge and blows it directly over the integrated freezer. This air, now cold (hopefully) falls and passes the carboy in this chamber. Another fan in the same divider pulls air from the fridge chamber to the second chamber. These fans are controlled by a second thermostat, so these fans are only circulating air through the second chamber when it needs to be cooled. The second chamber is currently set to 18.5C.

The third camber simply has some secondary fermenting carboys in it. There is no temperature control to this chamber.

At first, I only has one fan in the main divider. This fan was located at the top of the divider and pulled air from the fridge to the second chamber. I was having a really hard time maintains temps. It wasn't Until I switched this fan to blow over the freezer coils and added a return fan that this thing started working flawlessly. I've also added a terrarium infrared heat lamp to the secondary for when fermentation has tapered in the second chamber and passive cooling from the fridge chamber brings it below 18.5C.

I'll post more pics soon.

Some new pics

trbig said:

Hmmmm.. I was always told those compressors wouldn't work without the fridge being upright because of the oil inside of them. Old wive's tale maybe?

Click to expand...

That's very true actually. Compressors should be run upright and not jostled while running either. You also want a 'refrigertaion aware' thermostat, which I think a true STC1000 is. This keeps the thermostat from short-cycling the compressor, which can seize it.

BackDoorBrew said:

That's very true actually. Compressors should be run upright and not jostled while running either. You also want a 'refrigertaion aware' thermostat, which I think a true STC1000 is. This keeps the thermostat from short-cycling the compressor, which can seize it.

Click to expand...

Yes, the stc-1000 has a configurable compressor delay.

As far as the mini fridge goes, once the contents reach the desired temperature, the compressor will turn off. The point being the BTU's of the compressor's output. As long as the doors stay shut on your fermentation chamber, and it is well insulated it will be fine. Initially the compressor will "overrun" and then be fine. When installing fans in your chamber, always send the coldest air from that chamber with the fan on the bottom. Warm air rises, cold air sinks. So the cold air will give up it's cooling before naturally rising and returning to the source chamber. The coils in the back, need air flow too to dispel their heat, otherwise the compressor will overrun to try to give up it's heat in the liquid freon.

subb'd, awesome!

c3hutson said:

My first (major) DIY in the hobby.

Click to expand...

Wow, talking about hitting it out of the park on your first 'at bat'. Major Leagues indeed!

A nice solution to multiple temp control. I can see myself building one, just on a smaller three or four carboy scale.

I can give you some ideas on maintaining the temp if it continues giving you issues.

Look at a side-by-side freezer-fridge for clues. It all in ducting the cold air.

'da Kid

Oh, and keep containers of liquid in there at all times to act as buffers (and heat sinks). An empty chamber will have little reserve cooling compared to one with a 5-gal carboy full of water . . . . . or store lots of beer.

Do you think you need a small hole to the outside to vent excess CO2 from fermentation?

Great project,
'da Kid

BackDoorBrew said:

That's very true actually. Compressors should be run upright and not jostled while running either. You also want a 'refrigertaion aware' thermostat, which I think a true STC1000 is. This keeps the thermostat from short-cycling the compressor, which can seize it.

Click to expand...

I thought the same when i saw this post, but maybe everything is workin fine.

trbig said:

Hmmmm.. I was always told those compressors wouldn't work without the fridge being upright because of the oil inside of them. Old wive's tale maybe?

Click to expand...

The fridge is upright it's a mini fridge on the end providing the cooling to a homemade box.

Subbed. I recently made an ad hoc ferm chamber from a hurricane Katrina window unit and a cardboard box. I am making plans to build something more permanent, but it's working nicely right now.

Great work btw!!!!!

Thanks. It's working very well. I've been able to hold a carboy at lager primary temps in the first chamber and ale primary temps in the second. The third is not thermostatically controlled (yet), but I keep things in secondary in there.

Added a heat lamp to the second chamber cause I was actually running into about a degree lower than set point when there was a big difference between the chambers due to the passive air flow through the fans.

Most of the old top freezer bottom fridge units operate on a "hot air rises" principle. The evaporator (cooling element) is in the upper freezer section with a blower passing freezer air over the cooling coil. There is a simple plastic diverter valve that controls how much of the output of the fan travels to the lower warmer refrigerator section and how much stays in the freezer section. There is minimal insulation between the warm and the cool section. And there is also a set of "hot air returns" at the top of the refrigerator section that feed up into the bottom of the freezer section (probably toward the front of the unit). The built in thermostat maintains the temperature of the refrigerator section by cycling the compressor and the freezer temperature is allowed to "float" based on the compressor cycle time and the setting of the plastic diverter near the cooling coil fan.

I suspect that with some clever manipulation of the airflows and some additional insulation a cheap craigslist top and bottom refrigerator could be converted into a two zone fermentation chamber or a combination cold bottle storage at the top and cool fermentation chamber at the bottom.

Get two temperature control units. The "freezer" unit cycles the compressor to maintain your cold serving temp. The "refrigerator" until controls a pair of small dc fans with weighted vanes (like the dryer vents you see on the side of houses sometimes) that pull cold air from the freezer section into the refrigerator section and push warm air from refrigerator into freezer to maintain the fermentation chamber temp. Seal up any unused vents between the two chambers and add some insulation to help maintain the temp differential and I think it could work.

You just gave me a great idea....

I am going to build another compartment on top of my chest freezer to hold a 15 g conical. I was trying to work out how I could turn it upright, remount the compressor etc. so that it would work, but this way I will have a lot more space for a 15 gallon conical (and eventually 2 of them) and still have room for some carboys underneath.

Much appreciated!

You may have even better luck using insulated PVC off the freezer for a cooling loop to another chamber.