Author Topic: Raising the temperature in a chest freezer/fermenter  (Read 1396 times)

Offline nathanw

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Raising the temperature in a chest freezer/fermenter
« on: August 23, 2010, 06:30:17 PM »
I recently acquired a chest freezer and digital temperature controller to free myself from the tyranny of whatever temperature my basement happens to be. I made an ale and it worked fine to hold it steady at 66F. Now I'm making a marzen, and I am following the advice in BCS to chill to do a "modified Narziss fermentation" - 44F, pitch, and slowly raise the temperature to 50F. However, 24 hours after I turned the set point from 44F to 50F, the temperature is still down at 44F. This is great for demonstrating the insulation of the chest freezer, but not really what I wanted for my fermentation schedule.

What are some good ways to warm this up? A second controller and a heating pad would be ideal, but I'm not set up for that. Would putting a pint of just-boiled water in the chamber be reasonable? (6 gallons I want to raise ~3 degrees at a time vs. 1/8 gallon that is ~160 degrees above the ambient temperature).

Offline tschmidlin

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #1 on: August 23, 2010, 06:43:53 PM »
What's ambient?  I usually just leave the lid open and let it warm up, provided it actually is warmer in my garage than in the fermentation chamber.  You can use a fan to speed things up too.

Or you can just put a light in there with an incandescent bulb, it will heat things up slowly.  The compressor will come on when you're above your setpoint, so it won't get too warm.  And once it's warm enough you can take the light out.  Don't use a fluorescent bulb though, too much UV and not enough heat.
Tom Schmidlin

Offline narvin

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #2 on: August 23, 2010, 07:08:38 PM »
I wouldn't worry.  As long as you pitched enough healthy yeast, the fermentation temperature will raise on its own.  It you want to monitor the temperature of the beer instead of ambient, tape the probe to the side of the ferment, or buy a thermowell.
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Offline nathanw

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #3 on: August 23, 2010, 07:12:26 PM »
Ambient is about 75F; I'm afraid of overshoot if I leave it open overnight or while I go to work, and it seems like it would be bad if the freezer starts to run continuously, so I'm looking for a more bounded solution. A light fixture wouldn't be bad; I'll have to see if I have something suitable for dropping in there. And I will steer clear of the CFs.

narvin - the probe is secured to the side of the fermenter with a nice piece of foam and some Velcro(tm), so I think I've got that covered. I know the temperature will rise once fermentation gets going, but I wonder how long it will take for that to happen at that temperature. (the yeast is WLP820, built up into a 2L starter on a stir plate, then crashed to the same 44F and decanted).

Offline stadelman

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #4 on: August 24, 2010, 01:34:43 PM »
I use a reptile heating mat.  These are made to run continuosly.  I think mine is only 9W, so it's no space heater.

When I want to warm up my chest freezer I toss it in.  I haven't measured it, but I would say it raises the temp a degree or two per hour.  For my ambient conditions (basement usually in winter only) this produces enough heat to keep fermentation where I want it, but doesn't produce so much that the freezer needs to kick on a bunch.

Offline bluesman

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #5 on: August 24, 2010, 06:49:38 PM »
Where do you have your thermocouple?

As Narvin has indicated,  it should be attached to the fermenter. 

If it is attached to the fermenter then you'll need to determine if the controller is still calling for power to the compressor.
If the compressor is off the temp should slowly rise to the set point of the controller and call for power to the compressor.
But if the compressor is running,  you have a calibration issue.
Put a lab thermometer in a beaker of water in the freezer next to the fermenter in an effort to check the calibration of the controller.

What kind of controller do you have? 


Ron Price

Offline nathanw

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #6 on: August 24, 2010, 07:17:16 PM »
bluesman - as mentioned above, the probe is secured against the side of the carboy with some insulating foam, as seems to be nigh-universal advice. This setup (the controller is a Johnson A419) has worked fine for chilling the wort to a selected temperature from above and keeping it there (at least, as compared against the LCD "Fermometer" strip attached to my carboys); my issue now is that the "slowly rise to the set point" part, once I raise the set point, is very, very slow.

Offline thcipriani

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #7 on: August 27, 2010, 07:53:42 AM »
I'd say let it go at 44F until fermentation raises the temp; however, if you're concerned about leaving it at that temp then throw a fermwrap into your freezer and monitor the temp until it gets to where you want it and then remove it. I fermented a belgian in a 7 cu. ft. chest freezer and a single fermwrap kept the temp at 85F when the temp of our house was somewhere in the upper 60s. It's weird to open a chest freezer and have it be much hotter than the rest of the house, but it does prove that these fermwraps work like gang busters. This is the stuff that fermwraps are made of if you're a DIY/save a bunch o' money type of guy:
http://www.bigappleherp.com/Flex-Watt-Heat-Tape
Tyler Cipriani
Longmont, CO

Offline troy@uk

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Re: Raising the temperature in a chest freezer/fermenter
« Reply #8 on: August 29, 2010, 02:34:54 AM »
What I do is to prop the lid open a few inches when I am warming to allow it to warm.  I usually don't warm or cool faster that 2-3 degrees in 24 hrs.  This works great if I am still shooting for a temp that is below the ambient temp of my garage.  When it reaches the desired temp I simply close the lid and carry on.  I also install a heat belt before I start when doing an ale because I might want to start below the ambient temp of the garage and finish above it.  Start @ 65 and finish a dyacital rest @ 70 while the garage temp is 68.  
I do love temperature control!  It does what I want, when I want, because I want.  Now I just need to know what the best temp really is!  Practice, Practice, Practice (and enjoy the samples along the way)
« Last Edit: August 29, 2010, 02:41:03 AM by troy@uk »
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