Fermentation Temp Control - On the Cheap

RedBeardedBrewer · Sep 29, 2013

Apilowski, thanks again for posting about this project. I think that this system has a few different advantages over a converted chest freezer. The first is that your system is smaller. Not everybody has space for a keezer. The second thing is that with water around your carboy it is less susceptible to fluctuations in temperature. To me, since I already have a keezer, using this system would allow me to have a fermentation chamber that can run simultaneously to the kegerator function. This is the biggest advantage that I can think of for somebody like me. You cant have 38F and 65F at the same time with one keezer! I hate having to wait till one batch was all drank up before brewing the next one. Anyway I will be implementing your system now and I'm excited to get it going!

NeoBrew · Sep 30, 2013

RedBeardBrewer, I'm glad I could help! Good luck with your build!

It's been going for a couple days now and still working well. I actually have noticed a little bit of temperature bounce. In order to more accurately measure the beer temp I have the temp sensor taped to the side of the carboy above the water line. I covered it with some foam rubber pipe insulation so that it's a little closer to the temp inside the carboy.

I think this leads to a little bit of bouncing in the temp since the water will pump until the temp change makes it all the way into the beer, then must have a little extra chill that evens out between the water and the beer.

It seems to be within a couple of degrees of my target all the time. I found a setting that I think sets the range from 2 degrees to 1, so hopefully that will tighten it up even more.

Wynne-R · Sep 30, 2013

Consider putting the probe in the water, at the bottom. When you run the pump, the cold water goes to the bottom. This will give you shorter more frequent cycles.

In my system the water is at the level of the beer and the probe is near the top between the second and third coils, poking out into the water. The water temperature is constant within ± .1°C. The beer temperature difference would be half that as my water bath is about six gallons.

The STC-1000 differential goes down to .3°C. Im getting much much less than that with creative probe placement. My thermometers read to .1°C and they dont move.

Have fun, glad you got it working.

NeoBrew · Oct 1, 2013

Since active fermentation is almost done it has settled into within about 1°F below my set point of 67°F of my set point. That's not too bad.

I'll try the probe in the water for a few days. Since I don't have other sensitive thermometers I'll probably not know the difference. I've been using the readout on the STC 1000 to determine the fermenter temperature. My only other option without opening it and sticking a mercury thermometer in (which I'm not going to do) is a stick on thermometer on the side of the carboy which is not accurate enough.

NeoBrew · Oct 6, 2013

Necessity is the mother of invention.

Yesterday I took a peek into the water bath to see how things were working. There was a giant dead centipede stewing in the cool water. I'm not a squeamish guy, but I HATE those things!

So I came up with what looks like a way better way to do this. The equipment is all about the same, but I don't have a water bath for the fermenter.

The basic concept:
Wrap about 25' of the 1/4" copper line around the fermenter, wrap that in a blanket for insulation, then put the pump in the reservoir of cold water inside the keezer.

I've only been running it about a half hour, but it seems to be quite responsive and took a degree off of the temp just in the time it took me to get it set up. This is way more compact and less monkey business than the cooler full of water.

I took a few shots to show the setup.

NeoBrew · Oct 6, 2013

I think I have one last improvement to make for next time. I'd like to get the reservoir in the keezer to be sealed up so it doesn't introduce so much humidity. I thought about the idea of using a corny keg, but I'm not sure I want to start contaminating them with non-beer. Something that is about that diameter would be good so it doesn't take up too much space would be nice. I'll have to experiment a little with how much quantity it needs to work. I'll either find a small bucket with a lid, or maybe build a chamber out of a 6" or 8" pvc pipe. Metal would be nice, but it looks like I only need that kind of efficiency when I'm cooling things down. When holding a temp it only seems to run for a minute or two.

Eventually a purpose shaped insulated blanket would be a nice touch too. I suspect my Harbor Freight $6 packing blanket is not a very good insulator.

Phunhog · Oct 7, 2013

I am sure you realize this but a drawback of your fermentation control system is that you are fermenting in glass. Glass is a poor conductor but excellent insulator of heat. In other words when your fermentation is cranking it harder to get the "heat" out of the carboy and the "cool" into it. I ferment using a very similar set up except I use stainless kegs as carboys. My thinking is that the stainless is better conductor so it can react quicker to temperature changes.

NeoBrew · Oct 7, 2013

Phunhog said:
I am sure you realize this but a drawback of your fermentation control system is that you are fermenting in glass. Glass is a poor conductor but excellent insulator of heat. In other words when your fermentation is cranking it harder to get the "heat" out of the carboy and the "cool" into it. I ferment using a very similar set up except I use stainless kegs as carboys. My thinking is that the stainless is better conductor so it can react quicker to temperature changes.

That goes without saying. There are a lot of inefficiencies in this system. The whole exercise has been about getting it good enough to work without spending a lot.

Wynne-R · Oct 7, 2013

Actually the thermal conductivity of glass is about 1.0, greater than water at .6. A bucket is slightly less at about .4. I dont think its a big deal in either case. My pump runs for 15 seconds about three times an hour so obviously the heat transfer is more than adequate.

If glass were a good insulator I wouldnt have to use a koozy on my glass. Styrofoam is an excellent insulator at .04.

Phunhog · Oct 7, 2013

Wynne-R said:
Actually the thermal conductivity of glass is about 1.0, greater than water at .6. A bucket is slightly less at about .4. I dont think its a big deal in either case. My pump runs for 15 seconds about three times an hour so obviously the heat transfer is more than adequate.

If glass were a good insulator I wouldnt have to use a koozy on my glass. Styrofoam is an excellent insulator at .04.

Thanks for the info!! Do you know what the thermal conductivity of a stainless keg would be? One of the reasons why I assumed stainless works so well in this set up is that the water bath temperature would pass through to the keg and vice versa much quicker.

Wynne-R · Oct 7, 2013

Stainless is 16 w/m*k

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

thebrewquest · Feb 10, 2014

I got a mini fridge for free, ripped the door off, and spent about $80 at home depot and built this. The stc-1000 I already had.

Sent from my SPH-L900 using Home Brew mobile app

Konadog · Feb 10, 2014

thebrewquest said:
I got a mini fridge for free, ripped the door off, and spent about $80 at home depot and built this. The stc-1000 I already had.

Sent from my SPH-L900 using Home Brew mobile app

Very nice, what's the inside look like?

djt17 · Feb 11, 2014

Konadog said:
Very nice, what's the inside look like?

Yes; more details & pics.

Fermentation Temp Control - On the Cheap

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