Having Trouble Getting my SSB Unitank to Crashing Temps

[philm63]

First time using this system. 7-gallon SSB Unitank with the 3/8 hp glycol chiller, FTSs, short lines with the insulating sleeve installed (short distances at either end are exposed to ambient), 5 gallons of APA with some dry-hops, ambient is 70 F, assuming a crashing temperature of 33 F.

The first time I tried I think I iced the coil, so I shut it down and let everything come back to room temperature for a day and tried again.

This time I set the glycol chiller to 40 F thinking there would be no way, even if it ran continuously for several hours, that it could ice the coil. I brought it down to the upper-40s and then adjusted the chiller down to 35 F. This allowed me to get down to around 42 F so I turned the chiller down to 30 F and got the Unitank down to 39-ish.

Not good enough! No way the coil iced again, or at least I think there is no way...

Checked the thermocouple and realized it was only around half-way in the well (factory 1.5" TC thermowell from SSB) so I shoved it in the well until it bottomed out and it gave me a final reading of 37 and change. A little better, but not the 33 F I expected.

Couple of things I noticed when running this chilling system: There seems to be an air gap in the return line coming out of the top of the Unitank - I can see a large bubble inside the line and the glycol is flowing only at the bottom of that line, not filling it. It is as if there isn't enough pressure in the line to fill it all the way. Glycol is flowing, but I'd expect the return line to be full like the input line. Could this be limiting the chiller system's ability to come down to 33 F? Or is this normal for this system? I checked the pump and it is not blocked.

And another thing is the amount of liquid in the Unitank - is 5 gallons enough to hit the bulk of the coil, or is there a substantial portion of the coil sitting above the liquid level thus the liquid is seeing only a small portion of the cooling coil? Is the fix as easy as increasing the batch size to 6 gallons, or is there an extension kit that would lower the coil into the Unitank a bit to account for lower volumes? Could this be the culprit?

 

[Vale71]

And another thing is the amount of liquid in the Unitank - is 5 gallons enough to hit the bulk of the coil, or is there a substantial portion of the coil sitting above the liquid level thus the liquid is seeing only a small portion of the cooling coil? Is the fix as easy as increasing the batch size to 6 gallons, or is there an extension kit that would lower the coil into the Unitank a bit to account for lower volumes? Could this be the culprit?

I never managed to get my SSB Unitank (14 gal size) colder than 1.5°C or 35°F without the coil starting to ice over. The exchange surface is just too small and if you set the glycol reservoir as cold as you'd need it to be to get the required cooling power it will invariably ice over.
A substantial portion of the coil sits above the liquid level which is possibly making things worse. There is no extension kit for the Unitank. This is my biggest peeve with the Unitank, there's really no point in having the cooling coil start this high in the tank as nobody in his right mind would ever fill the tank to the brim. Looks like this part was defininetly designed by someone who had absolutely no idea what they were doing.

 

[mongoose33]

There are a couple threads on here from when I embarked on a journey to get my Spike conical down to crashing temps. Short version: I never succeeded in getting it below about 38.

Before I tell you what I think about all this, the bubble in the line? Squeeze the line where the bubble is, see if you can get it to go through. I sometimes get a bubble in mine, that's all I do and it's gone. I don't think it makes a difference in how it cools, but it makes me feel better.

The temp at which beer freezes drops about .8 degrees fahrenheit for each percent of ABV in the beer. So if you have, say a 5% ABV beer....it'll start to freeze at around 28 degrees.

I'm generally higher on ABV than that, so, with my 1/2 hp Penguin, I set the temp to 28 degrees. But even at higher temps, I can't chill that fermenter colder than about 10 degrees above what the glycol temp is set at.

Why? Primarily because all the little protuberances and such sticking out of the fermenter act as heat sinks, bringing ambient heat into the fermenter. Think about what you have sticking out of your fermenter: legs, blowoff cane, connections for the glycol, racking valve, handles, maybe a testing valve, thermowell; heck, on mine there's something like 13 different things sticking out, all sucking heat into the fermenter. Even with the neoprene sleeve helping, it can't be overcome.

I've tried a variety of things to ameliorate this heat gain, to relatively minimal effect. I tried wrapping almost everything I could in reflectix; my wife said the fermenter looked like the Tin Man from Wizard of Oz. I wrapped it in a big moving blanket to offer more insulation. Heck, at one point I even bought a window air conditioner and built a little closet around the fermenter and directed the cold air from the air conditioner inside. Nothing mattered much. BTW, the cold air from the air conditioner should have worked, but all that did was direct 52-degree air past the fermenter which, when the fermenter's temp dropped below that, served to heat it up! A sort of reverse wind chill, if you will.

I have one more thing to try--I want to build a "closet" around the fermenter using 2" foamboard insulation. If I can get that cut squarely enough, I should be able to seal it to where the air inside will drop in temp, and I might be able to get that down to 35 or 34 degrees. I hope. It's more a question of whether I can solve this than whether it matters all that much. I kegged a beer two days ago, had it down to 38.9 degrees. I wish I could get it to 32, but it's just not possible. If I had a refrigerator in which the fermenter was housed, yeah, but using glycol? No.

Sorry not to be more optimistic, but that's my experience.

 

[philm63]

Thanks, guys. So in the end I reckon I'll just do the best I can and take what I can get with this thing. Heck, 37 F is where I am now, and that's pretty good - not what I used to get with a glass carboy in a chest freezer with a Johnson A419 but it'll do.

 

[Vale71]

Believe me, the advantages of not having your beer come out of the fermenter already oxidized far outweigh what you would gain by dropping the temperature a couple of degrees more.

 

[Jrl1775]

I have the same issue with the 7 gallon chronical, but I am super happy with the temp control for fermenting. I get it as cold as I can in the fermenter then let it finish in the keg.

 

[jekeane]

I will echo what mongoose said. I have several spike uni's and a 1/2hp peguin 38° is is low as I can go and it makes the glycol unit cycle a lot to accomplish that. I am set up in a florida garage so it's not a battle I can win.

I will say that from what I have read traditionally the germans stored their beer for lagering at 40° so while 32° would be nice 40° is probably fine especially if like me you use gelatin for beers that you want to clear quickly.

 

[Bobby_M]

5 gallons is too low for a lot of reasons. You want to put about 6.25 gallons in the 7 gallon. Run the glycol at about 26F. I can get the beer down to 36.5F but the ambient is only 74F. This is really the one thing I truly hate about internal cooling in warmer ambient areas. It's a constant fight and the condensation is obnoxious. If you have two or less tanks, putting them in their own refrigerators is a much better solution.

 

[Blazinlow86]

As others have said it's just one of the compromises of needing to use a glycol setup over a fridge or freezer. I usually crash at 32 but I haven't noticed any difference at higher temperatures. It may clear abit faster but not by much. I wouldn't sweat it. Cheers

 

[philm63]

Well the ambient in my basement is a constant 70 F all year, and without dressing the unitank up like the Tin Man I am still getting a very respectable 37 F.

I just transferred to the keg this morning and before I did, I cleared the racking arm by letting about a cup or so pour out of the racking port and it poured very clear. It would seem the beer cleared very well in 3 days at 37 F so I am fine with it. I suppose I could make a few tweaks and get another half a degree or so but as you've all said - it's no big deal and I'm more than happy with the results.

 

[Jtvann]

I maintain 35 degree cold crash temps on my 14 gallon Ss unitank. I plan for at least 12 gallon a into the fermenter. Glycol is a DIY 6.5k btu window AC unit. Temp is set to cool to 29 degrees with a 5 degree variance.

My ambient temps can be in the 90s.

Volume inside the fermenter is where it's at. As said before, the coil rides high. If I drain off a few test pints I cant maintain 35 degrees anymore.