Author Topic: Fermentation Temp Control  (Read 25184 times)

Offline tom_hampton

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Fermentation Temp Control
« on: December 20, 2013, 06:14:57 PM »
KernelCrush requested that I put together a description of how I manage my fermentation room, and (by extension) my fermentation temperatures.  So here goes.

Attached is a schematic of the controllers, AC unit, and one fermentation vessel. 

Ok, the fermentation room is a 46x46x9' closet.  I filled the walls with spray foam insulation.  The walls are then lined with 1" foam board insulation and sealed with aluminum tape. There is a double layer of foam board on the ceiling.  I have a ~150 bottle wine rack in the center, and each side of the closet has wire shelving from home depot.  The bottom shelves are high enough to store 4 kegs underneath on each side.  My primary fermenters (plastic buckets) sit on the first shelf.  Bottles, hops, wine, aging commercial beer, and various other stuff are stored on the remaining shelves. 

I use a home Depot 6000 btu ac window unit to cool the room. This unit has a mechanical thermostat.  This makes it a bit easier to bypass it. Normally the fan only comes on when the compressor is on.  But, when the ac is run so close to freezing it helps to run the fan continuously.  When the compressor isn't running the fan helps to warm the coils back up to room temperature faster. This helps to prevent ice from forming on the coils or melt any that may have formed. It also helps keep the temperature more uniform from floor to ceiling.  So, I rewired the fan to be powered directly from wall power. I added a second ac chord to power the fan.

I use two stc1000 controllers to manage the ac compressor. These controllers are connected in series.

The primary controller temp sensor measures the air temp in the room.   It is mounted in a yeast vial that is filled with ice pack gel, and the vial is suspended in the air about 4 feet off the ground.  The controller is configured for a 1c delta, 1 minute delay. The setpoint is set at 9c.   The COOL output is used to drive the secondary controller.

The secondary controller is powered by the primary controller, so it only comes on when the primary controller is on. It's temperature sensor is embedded in the evaporator coils of the ac unit.  The purpose of this controller is to keep the coils from freezing up.  The setpoint is set at - 3c. The delta is set at 8c. The delay is set for 3 minutes.   The COOL output is used to drive the compressor.

So, here is how this works:

1.   The room warms up to 10c, so the primary controller output goes active. This applies power to the secondary controller.

2.  The secondary controller measures the evaporator coil temp at 10c (same as the room).   This starts the delay timer. After 3 minutes, the controller activates it's output and turns on the compressor.

3.  The coils will then get cold.  Most ac units are designed so the coils run about 12c below the room temp.  So, after the system stabilizes, the coils will drop to between 0 and -1 degrees c.  As the room cools the coils will continue to cool also.

4.  Eventually, the coils will get down to the setpoint of - 3c.  When that happens, the secondary controller turns off the compressor until the coils warm back up to 5c.

5.  Once the coils reach 5c, the controller will turn the compressor back on (assuming the 3minute delay has expired).   This temperature and time ensures that any small amount of frost/ice that forms on the coils has a chance to melt, before the compressor kicks back on.

6.  Steps 4 and 5 repeat until the room air temp reaches 9c and the primary controller shuts off.

7.  The whole sequence then starts over.



So, what's the point?  When the coils drop below freezing the condensation that naturally forms will start to freeze on the coils.  Without the secondary controller, the ice will decrease the airflow through the coils, which will cause them to get even colder. Thus more ice forms. This process quickly runs away and the coils get caked in ice. The risk of this is much higher in the summer when the dew point is much higher (more total water in the air).

The secondary controller limits the coil temperature to a manageable level. -3c is what works for me here in Texas in my worst case summer conditions.  I started at - 5c and every time the system froze up I raised the threshold by 1c. It's been running this way for two years.

The ac unit itself is mounted on the wall above the doorway. I built a shelf out of plywood and built a duct, also out of plywood, to redirect the air intake to draw from below instead of in front. The point to to reduce short cycling of the cold exhaust air back into the intake.  I also have a secondary fan to blow the cold air down to the bottom of the room.

The air used to cool the condenser coils is drawn from the house through a vent. The hot exhaust from the condenser coils is vented into the wall above the doorway and then up into the attic.

So, all this gives me a room at 9c (48f).   I can go colder in the winter;  my main limitation is risk of forming ice on the evaporator coils. But, I can hold 9c in the most humid parts of the year.  I suppose if I got it down another degree or two in the winter, I could ferment a lager.  But, I don't have a lagering fridge.

In order to ferment my beer I use more stc1000 controllers with cheap heating pads and reflectix insulation.   As I said above, I tape the probe to the fermenter and cover that with a 1 inch thick layer of insulation.   I have several pads of reflectix insulation that I have folded over to make a 1" thick pad.  I simply tape these over the probe.  I  tape the heating blanket to the fermenter on the opposite side from where the probe is mounted.  I then wrap the fermenter in a layer of reflectix.  This setup is good for fermentation temperatures up to 20c. If I want to go higher I need a second layer of insulation.  I keep saying that I'm going to make something more permanent (sewn pockets with velcro straps or something), but I just use cheap masking tape.  It does the job fine, but it doesn't look very "cool". 

The heating pads need to be the most basic type.  Many (most) heating pads today have an autoshutoff feature, that automatically shuts off the heating after about 2 hours.  These are BAD, BAD, BAD for homebrew.  I use these:

http://www.amazon.com/gp/product/B000F54AOW/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1

Another option is flex watt heat tape:

http://www.amazon.com/Flex-Watt-Heat-Tape-Watts/dp/B00AHEZF6S/ref=sr_1_1?ie=UTF8&qid=1387586995&sr=8-1&keywords=flex+watt

This is what I will use when I rebuild my fermenters out of stainless.

I have room for 4 primary fermenters in the closet.  When things are really hopping, I generally have 2 long term ales (funky beers, sour beer, barely wine, etc), and two short term beers (your standard ales from USA, England, Belgium, and Germany).  This approach allows me to ferment each of the 4 primary fermenters at a different temperature, and on its own schedule.  When fermentation is complete I unplug the heating pad, and allow the beer to cool to storage temp.  After it clears, I drain it into a keg for bulk aging. 

I also store my kegs in the closet: I have 4 serving kegs, and 4 storage kegs.   

Also attached is a picture of one side of the closet, showing two fermenters.  The other side is the same.  I tried to take some pictures of the AC unit.  But, its just too tight in there.  I can't get more than about 2 feet away from it, so its hard to see anything. 

One final note: I don't like lifting full buckets of wort, or full kegs of beer.    So, this fermentation room is located in what was the "coat closet", just inside the side door to our house.  I brew on the covered side porch.  I have a small pump that I use to move the wort from the kettle into a fermenter that has been pre-placed on a shelf in the closet. 

Second, I don't like exposing my cooled wort to unsanitary air.  I have a electric stirrer for my wort.  I use it with my immersion chiller to get the wort down to pitching temp.  The stirrer is attached to a "lid".  Once I turn off the flame, the lid is closed and is not opened again.  Once the wort is chilled and has cleared, I use the pump to push the wort into the fermenter.  So, it is never exposed to outside air after flameout.

I sanitize my fermenters by filling them with 5 gallons of star-san at the start of the brewday.  I let everything cold-side soak for the 4-ish hours it takes to brew.  Then I drain the star-san into another container.  Then I clamp on the lid, and feed my pump hose into the airlock opening.  I pump about 1 gallon of star-san through the pump hose back into the fermenter.  I shake the fermenter to distribute.  Then I drain the star-san out of the spigot, and place the fermenter on the shelf in the closet.  Once the wort is ready to transfer, I pull the hose out of the opening until it reaches the pump.  Then I pump the wort.  Voila, wort in place...sanitary...and I haven't thrown my back out for the umpteenth time.
R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

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KernelCrush

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Re: Fermentation Temp Control
« Reply #1 on: December 21, 2013, 04:46:09 AM »
Thank you Tom for your time & effort in putting this together. 

I have been wanting to do something like this.  We are at the beginning of the outdoor brewing season here in FL so it will be about May before I can get serious.  I will try to keep the questions to a minimum.  I like the flexibility of being able to ferment at different temps inside your cold room. 

Offline MikeinRH

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Re: Fermentation Temp Control
« Reply #2 on: December 27, 2013, 09:20:43 AM »
Tom, you need to write a book. I'd buy it!

Offline OzarkBrewer

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Re: Fermentation Temp Control
« Reply #3 on: January 24, 2014, 09:33:48 AM »
I like this a lot!  I'm in the A/C biz so this interests me.  So I hear all kinds of temps to ferment at. Did I read correctly that you like to keep the room at 48 degrees?

You then go on to say:  "In order to ferment my beer I use more stc1000 controllers with cheap heating pads and reflectix insulation.   As I said above, I tape the probe to the fermenter and cover that with a 1 inch thick layer of insulation.   I have several pads of reflectix insulation that I have folded over to make a 1" thick pad.  I simply tape these over the probe.  I  tape the heating blanket to the fermenter on the opposite side from where the probe is mounted.  I then wrap the fermenter in a layer of reflectix.  This setup is good for fermentation temperatures up to 20c. If I want to go higher I need a second layer of insulation.  I keep saying that I'm going to make something more permanent (sewn pockets with velcro straps or something), but I just use cheap masking tape.  It does the job fine, but it doesn't look very "cool". "

What temp. in degrees are you striving to keep the fermentation vessels?  Right now I have two 5 gal. batches fermenting.  (1) I.P.A. and (1) A.P.A. and the surrounding temps around the vessels varies from 62 to 68.  If I'm understanding you correctly you are saying 48 degrees is where you like to be?

Offline tom_hampton

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Re: Fermentation Temp Control
« Reply #4 on: January 24, 2014, 10:52:51 AM »
I use the room to store about 250 bottles of wine,  another 50 bottles of semi-exotic beers, all of my hops, and all of my kegs.  So, I keep the room at reasonable temperature for storing all these things.  Given the Texas humidity during the spring/summer/fall 48F is about as low as I can go...simply because of the heat load to remove that much water from the atmosphere.  I'm currently experimenting to see how low I can go during the winter.  The room was at 3 C (38F) this morning.  It takes a lot of energy to induce a phase change in water.

Don't think about the air temp as having anything to do with my fermentation temperatures.  The temperature is just down at a low enough temperature to act as a heat sink for my fermentations, and to keep my kegs and bottles cold.

However, my fermentation temperatures are much higher than the room temp.  I use heating pads along with the temperature controllers to warm the fermenters up to my desired temperature.  The cold temp of the room cools them back down.  The STC-1000 temp controllers that I use allow me to set a 0.1 C min/max temp delta. 

So, I program the desired minimum temperature (for example 19C/66F ) into the STC-1000.  When the beer temp drops below this set-point, the heating pad is turned on, which begins to warm the beer.  Since I've also programmed in a delta temperature of 0.1 C, the heater turns off at 19.1C/66.2F.  Because the air temp in the room is colder than that the beer begins to cool back down again, and the cycle repeats. 

I wrap the fermenters in insulation to slow down the rate of cooling.  How many layers of insulation I need depends on the how warm I'm trying to keep the beer.  1 layer is good for about 10C/20F temperature difference.  Since I keep the room at 9C/48F....I can ferment up to about 19C/66F with a single layer.  If I want to go higher I need a second layer. 

Basically for Kolsch, Alt, and hefeweizen yeast strains I use one layer of insulation.  For everything else I use two.  As I move to stainless fermenters instead of plastic, I may need to add one layer of insulation (ie, hefe=2, others=3). 

As far as what temps to ferment different beers at, that varies by yeast strain and style. 

American Ales with WLP001....around 68F starting temp for the first two days (or until the SG has dropped by half...just before the fermentation starts to slow down)....ramping up to 72F, 1 degree F per day. 

American Ales with WLP007....around 65-66F starting temp.  Ramping up to 69-70F after the first two days.

English Ales with WLP002....around 69-70F.  Ramping up to 74-75 after the first two days.  This starting temp depends somewhat on how much english character I really want in a particular beer.  Less character = lowering starting temp. 

German Ales (Kolsch/Alt) with WLP029...58-59F starting temp.  Ramping up to 63-64F after the first 3-4 days. 

Hefeweizen with WLP300....64F starting temp.  Ramping up to 68F after the first 2 days.

I always start my temp ramps when the SG has fallen by roughly half.  This is usually where the yeast begins to slow down noticeably.  I keep daily records of each fermentation (SG, temperature, and set-point...sometimes pH), and base my actual ramp point on the SG where fermentation slows down.  That varies (a little) by yeast strain.  So, while I said "after the first 2 days" above, its really dependant on gravity.  For example, if I over pitch the ferment might progress faster than normal...and the ramp might start sooner.  Conversely, if I under-pitch it might be a little sluggish....so, I might hold off on the ramp. 

When I say over/under pitch....I mean intentionally.  I might manipulate the pitch rate on a beer in order to force more or less growth and therefore more or less yeast character.  There are other ways to do this...this is just my current approach.





R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline TAHammerton

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Re: Fermentation Temp Control
« Reply #5 on: April 24, 2014, 04:49:08 PM »
Nice set-up and very nice explanation Tom. I just have an old fridge with the Analog Johnson controller with gas probe just sitting inside. Typically I set it a couple of degrees cooler that I want the fermentation. I did not think of taping probe to fermentor, perhaps I should try. What do you think the best set-up would be using what I have?
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In process: Farmhouse Saison, Supermarine Kentish Ale

Offline Freak

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Re: Fermentation Temp Control
« Reply #6 on: June 27, 2014, 10:33:59 PM »
I think I just pissed myself. That is pretty cool. My buddy just gave me a window AC unit so I could build a walk-in but I have not gotten around to it yet. This will be helpful.
Brewing massive amounts of freakin' good beer since 1991. We had to learn the hard way. No homebrew stores or beer nerds (like me) to talk to back then. Just pure passion and determination. Relax, Don't Worry, Have A Homebrew! -23 Karma! Yee Ha!! It went up! Smite me if you must but, trust me.

Offline Surf Monkey Beer

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Re: Fermentation Temp Control
« Reply #7 on: May 08, 2015, 06:49:05 PM »
Nice work,

How about using a coolbot?

http://storeitcold.com/




Offline Mofo

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Re: Fermentation Temp Control
« Reply #8 on: May 27, 2015, 10:49:07 PM »
I live in an apartment with limited space and sometimes come reread this post just to daydream a little.

@tom_hampton, you mention you take daily records of each fermentation. I'd really like to do the same. I was hoping you might share your method for taking readings during fermentation. You said you don't like to expose your wort to air. Are you pulling samples from the spigot? Do you use a hydrometer or a refractometer with calc adjustment?

I have a clear plastic wine thief with a widget on the tip that allows wort to fill the tube, but holds it in when the thief is pulled from the wort. It's just large enough in diameter to fit a sanitized hydrometer. The idea is you can take a reading and return the wort to the fermentor by pressing the widget against the side of the vessel. But it requires that you uncork the fermentor. I've used this thief to take daily readings on a few batches. I keep it submerged in a tall flower vase filled with StarSan, covered to keep out dust, and change out the sanitizer each week. And of course the thief and hydrometer get cleaned after each use. Hydrometer gets stored in the thief, in the StarSan. I'm obsessive about cleanliness, but the method still feels invasive.
bottled: Wee Heavy, Belgian Wit
fermenting: Imperial IPA, Citra Pale Ale