chest freezer/fermentation chamber high temp variance

I recently put together a chest freezer (5 cubic feet) with an STC-1000 and I currently do not have a heater in this thing, however its in my Denver, CO basement and aside from the freezer compressor turning on, there shouldnt be any outside forces making it too cold this time of year?

Anyways I have a indoor/outdoor min/max thermometer in the freezer and I am getting readings all over the place. The indoor reading is taken at the top of the freezer in the little basket from ~60*F to ~70*F and the outdoor is a reader on a chord that hangs to the bottom of the freezer reading from ~50*F to ~60*F.

I realize hot air rises so this makes sense, but I am getting ~20*F swings from min/max bottom of freezer to top of freezer, this seems pretty excessive? Its that much swing going to effect my fermentation?

Also I think the outdoor reader on the chord that hangs to the bottom is touching the metal lining? Could the metal (anywhere, top/bottom/sides?) be that much cooler than the air at the top/middle/bottom? If so should I put my fermentors on a towel or something so it isnt sitting on the cold metal?

Will the STC-1000 temp reader on the chord be ok in a glass of water in there to try and emulate what temp the beer actually is?

Glenn,
I would secure the probe to the fermenter if possible. That's the best way to control your process. Huge swings in the freezer's temperature are normal When the compressor kicks on and runs for a few minutes to cool down the fermenter i've watched the temps get down to about 0 degrees F before it shuts off.

I have to prop the door to the freezer up slightly to allow it to equalize a bit faster as i've overshot my temperature by quite a bit due to the efficiency of the freezer's insulation.

Another way you could maintain consistent temp is a little fan. Use a computer fan (5-10VDC) and wire it to an old cell phone charger and have it circulate the air around in there. Real easy to do and lots of information on it here on the forums.

+1 on the above.

My chest freezer and controller are newly set-up, but I think there can be some pretty wild swings in the temperature readings of the air inside the freezer.

When I first set it up, I set the temp control to 70 and had the probe basically in the air. When the unit turned off at 70 degrees, the temperature continued to drop all the way to 55 as a result of the residual cold built up in the walls of the freezer slowly seeping into the air. After taping the probe to the side of the fermenter, when the unit would turn off when the temp hit 70, the temp the probe reported bottomed-out at 68 as opposed to 55. In short, the large volume of liquid in the fermemter heats and cools far more slowly than does the air inside the freezer.

If you don't want to try it with beer, perhaps you could tape the probe to the side of your fermenter or other large bucket filled with just plain water to mimic a beer-filled fermenter. I think you'll be pleasantly surprised by how much more even the temp readings are. Many homebrewers go an extra step of putting some kind of insulating material atop the probe which is taped to the fermentation vessel (bubblewrap, styrofoam, even an old shirt). This will give you a clearer picture of what the temperature of the beer is actually doing as the probe will be less influenced by the wider temperature fluctuations of the air.

In fact, when my probe bottoms out at 68 when set to 70, I'm pretty sure that the beer is above 68 as my probe's reading is still influenced by being exposed to some of the surrounding air which cools more quickly.

Cheers!

Try to fill as much remaining space in the freezer with liquid, so add some water bottles, extra carboy filled with water, etc.
A freezer or any closed refrigeration unit will keep temperatures more constant the fuller they are. Air is not a good insulator so if you only have 5 gallons or so of liquid (beer) in the freezer, there is over 30 gallons of air left. Water is a much better insulator and will hold in heat/cold releasing energy more slowly over time.
You will also find it is more efficient as the unit will not need to cycle on as much, so you say a few cents.

You should be measuring the temperature of the beer in the fermentor, not the ambient temp of the freezer or the temp of a glass of water. Who cares what temp the ambient air is as long as your actual fermentation temps are being regulated.

I would use a temp probe that goes directly into your wort or tape and insulate your probe to the outside of your carboy. I tape and insulate my probe to my carboy in a chest freezer and my fermentation temps stay exactly where I want them. Sometimes ambient temp is colder or hotter than my beer but what do I care as long as the freezer turns on and off as needed to keep my yeast at a my specific fermentation temp

I think a fan is a necessity. It doesn't take much air movement to get rid of temperature layering.

As far as the probe, I think keeping it out of air is important. I have a small plastic water bottle with a thermowell in it affixed to my keezer. It does a good job of stabilizing temps and minimizing compressor cycling.

I set my target temperature about 5 degrees lower than my target fermentation temp. I occasionally check my actual fermentation temp with a laser thermometer. It works pretty well.

Lots of good ideas here, I subscribe to the "Place the probe right on the fermentation vessel" and "place a little fan in the chamber" methods

get a thermowell and get that probe inside your fermenter. worth every penny. mine was about $15

Again... Don't put the probe in water unless you want to ferment your beer at at temps higher than intended.

il1kebeer said:

again... Don't put the probe in water unless you want to ferment your beer at at temps higher than intended.

Click to expand...

+1

I've been following this thread since I now have a fermentation chamber. Question: how do I place the thermowell in the carboy with a blowoff tube or airlock?

http://www.midwestsupplies.com/stopper-thermowell.html

Something like this allows you to put an airlock or blow off in addition to running a thermowell into your carboy or BB.

I've found though personal experience that the temp will overshoot quite a bit with these because you are measuring the inner temps of the liquid which isn't the same temperature as the outer temps.

devils4ever said:

I've been following this thread since I now have a fermentation chamber. Question: how do I place the thermowell in the carboy with a blowoff tube or airlock?

Click to expand...

I made small neoprene belts for my carboys and place the probe between the carboy and the belt, but you could use anything handy to fasten the probe directly to the side of the fermentation vessel

Again, you want to control the temperature of the fermenting wort, not the ambient air temperature. The temperature of the liquid will change far more slowly than the ambient air.

I also feel the churning of the solution caused by the yeast fermenting the wort will move the wort solution enough to prevent temperature stratification.

The fan to circulate the air is a good idea.

I have a thermometer measuring the air temperature in my chamber and see swings of over 15 degrees. The strip thermometers on my fermenters change only a few degrees.

kh54s10 said:

I also feel the churning of the solution caused by the yeast fermenting the wort will move the wort solution enough to prevent temperature stratification.

Click to expand...

Have you observed this? For me even during a vigorous ferment there were huge swings (10* F) in temperature. Even when the compressor shuts off, the beer is still cooling down due to the ambient temps.

worksnorth said:

but you could use anything handy to fasten the probe directly to the side of the fermentation vessel

Click to expand...

In addition to the probe being attached, you also need to make sure that the probe insulated or else your temp readings will be off. Bubble wrap works well.

Thanks for all the response's everyone!!!

I read half of them the other day and thought I posted something and now just realized that I didn't...

I think I am going to go for the thermowell idea seems to be the most accurate option, and does not sound to expensive. Think I'm also going to look into getting a small fan in there, sounds like the little fans inside computers will do the job.

Another question about thermowells, if I only have 1 and have 2 or 3 fermenters going, with different yeast in them, is it safe to assume the others are the same temp, or do some yeast ferment hotter than others?

*I guess either way I only have one temp probe so even with 9 thermowells it might not do much good?

I might just start with having the probe in contact with the carboy and use bubble wrap to insulate it and see how this works.

Not to hijack this thread, but what about this diacetyl rest. Is this only for lagers?

So, I start fermenting around 62F-64F and after a week raise it to around 68F. After fermentation is complete, I cold crash it for a few days at around 36F to clear the beer? I'm doing a stout currently, so is this cold crashing a waste of time? Finally, if I cold crash my beer to clear it, I need to move it into my house to rack into my keg which will stir up everything. So, what's the solution for this?

devils4ever said:

So, I start fermenting around 62F-64F and after a week raise it to around 68F. After fermentation is complete, I cold crash it for a few days at around 36F to clear the beer? I'm doing a stout currently, so is this cold crashing a waste of time? Finally, if I cold crash my beer to clear it, I need to move it into my house to rack into my keg which will stir up everything. So, what's the solution for this?

Click to expand...

Whether or not cold crashing is a waste of time depends on how clear you want your stout to be. It's a matter of opinion in my view.

In terms of moving the vessel, what I've done is to move it as gently as I can, stirring up as little sediment as possible, to the location I plan to rack into my bottling bucket from... the evening before.

This at least, allows some time for whatever I might have inadvertently stirred up to settle once again. Some might think overnight isn't long enough to let it sit, but this is what works for me given my personal circumstances (i.e. I bottle in my kitchen and it minimizes the amount of time I have my fermenting vessel hogging up a good part of our island).

Cheers!

Mozart said:

the evening before.

This at least, allows some time for whatever I might have inadvertently stirred up to settle once again. Some might think overnight isn't long enough to let it sit, but this is what works for me given my personal circumstances (i.e. I bottle in my kitchen and it minimizes the amount of time I have my fermenting vessel hogging up a good part of our island).

Click to expand...

Genius!

Hijack away I got my questions answered, and have actually been curious about this cold crashing, now that I have the ability to do it.

Theoretically can you cold crash any and all beers?
Would there ever be a time that cold crashing would be bad?
What do you do with your other beers that are fermenting while you are cold crashing?

PorterGlenn said:

Another question about thermowells, if I only have 1 and have 2 or 3 fermenters going, with different yeast in them, is it safe to assume the others are the same temp, or do some yeast ferment hotter than others?

*I guess either way I only have one temp probe so even with 9 thermowells it might not do much good?

Click to expand...

When I add a new fermenter to the chamber I move the probe to it. I figure the temperature sensitivity of the previous one is less important after the height of fermentation has passed.

I have also taken fermenters out of my swamp cooler after active fermentation had passed. I needed the space for a new batch. The beers did not seem to suffer being at about 70 degrees for an additional week.

PorterGlenn said:

Genius!

Hijack away I got my questions answered, and have actually been curious about this cold crashing, now that I have the ability to do it.

Theoretically can you cold crash any and all beers?
Would there ever be a time that cold crashing would be bad?
What do you do with your other beers that are fermenting while you are cold crashing?

Click to expand...

I'm really new to the hobby myself but I'm sure someone will correct me if I'm wrong. Based on my understanding, though, you can cold crash any and all beers, but it wouldn't personally make sense to me to cold crash a wheat beer as those, at least according to style guidelines, are supposed to be cloudy. But hey, if someone wanted to cold crash a wheat? It's your beer, go for it! On a side note, I'm going to try adding gelatin (plenty of threads on its use around here) to my next cold crash. I hear it works really well.

As far as what I do with my other beers when cold crashing, I only have space for one fermenter in my chiller, so the answer is 'nothing'. I will, however, have one batch still conditioning (if I have the patience not to drink it!) when my next is cold crashing, however.

Cheers!

WDT said:

Have you observed this? For me even during a vigorous ferment there were huge swings (10* F) in temperature. Even when the compressor shuts off, the beer is still cooling down due to the ambient temps.

Click to expand...

After the compressor turns off and the ambient temperature is quite low, have you watched the wort temperature. It will swing much more slowly. I have seen my ambient temperature as low as 59 degrees, I looked at the strip thermometer on the fermenter and it read 64. The next time I looked the ambient was 75 degrees and the wort was 65.

kh54s10 said:

When I add a new fermenter to the chamber I move the probe to it. I figure the temperature sensitivity of the previous one is less important after the height of fermentation has passed.

I have also taken fermenters out of my swamp cooler after active fermentation had passed. I needed the space for a new batch. The beers did not seem to suffer being at about 70 degrees for an additional week.

Click to expand...

Seems like a pretty logical answer!

WDT said:

I also feel the churning of the solution caused by the yeast fermenting the wort will move the wort solution enough to prevent temperature stratification.

Have you observed this? For me even during a vigorous ferment there were huge swings (10* F) in temperature. Even when the compressor shuts off, the beer is still cooling down due to the ambient temps.

Click to expand...

I get paid to, and get to spend a whole bunch of money, to measure this sort of phenomena. It's essentially impossible to get a stable, stratified temperature condition in a single liquid or gas.

Any temp difference at any two points will produce energy exchange and mixing. The universe attempts to reduce order and increase entropy.

Want to win a Nobel? Build a bucket of a single liquid with stable layers of stable temperatures.

Cheers!

PorterGlenn said:

Thanks for all the response's everyone!!!

I read half of them the other day and thought I posted something and now just realized that I didn't...

I think I am going to go for the thermowell idea seems to be the most accurate option, and does not sound to expensive. Think I'm also going to look into getting a small fan in there, sounds like the little fans inside computers will do the job.

Another question about thermowells, if I only have 1 and have 2 or 3 fermenters going, with different yeast in them, is it safe to assume the others are the same temp, or do some yeast ferment hotter than others?

*I guess either way I only have one temp probe so even with 9 thermowells it might not do much good?

Click to expand...

Your fermenters will be at different temp if your probe is hooked up to one fermenter. This makes it hard to accurately regulate temps for more than one fermenter in the same fridge/freezer.

You really want to control their temps closely for the first 2-3 days during their growth stage. After that you can have them at a slightly higher temp without worrying about off flavors. Colder temps might cause the yeast to flocculate early