controlling temperature with a temp regulator

[jrodie]

I am writing to ask for advice/opinions on using a temperature controlled fermentation chamber. I have an old upright freezer and a Johnson thermostat, that I use to control the temperature. I have noticed that the wort is pretty resistant to changing temp as compared to the air in the chamber. If say I am attempting to maintain 62 degrees F on the thermometer attached to the fermenter, and the beer is currently showing 64 degrees F; I would need to drop the temperature of the chamber to 30 degrees F, in order to get the 2 degree F drop in a timely manner.

Does anyone think that would be bad practice (noticing the temp to be a couple of degrees high and drastically changing temperature to get it to change a couple of degrees, and then resetting the temperature of the chamber)?

Thanks

 

[cap]

Heat transfer is is is significantly improved when there is a larger difference in temperature. So you will be waiting quite while if the difference between the air and your beer is only 2 degrees. That being said I think most people here myself included just tape the probe to the side of the fermentor and insulate the other side against the air. That way you're controlling the actual temperature of the beer.

 

[Gavin C]

It shouldn't matter what the freezer is set to. The purpose of the additional controller is to override the internal thermostat. The compressor is either on or off. Set the temperature you want on your controller. Position the probe to accurately measure the temperature of the fermenting wort and do nothing else.

It's like air conditioning. Setting a lower temperature will not make it work faster

 

[jrodie]

Changing the temperature on the thermostat would cause the compressor to run longer until the air inside the fermentation chamber gets to the temperature it is set for. I think my question was really...Is it a bad idea to change the fermentation temperature of the beer as quickly as possible (by changing the air inside of the fermentation chamber to near freezing)? I thought maybe once the beer was at one temp, cooling it too quickly would stress the yeast.

 

[rgrosholz]

Temp swings will stress yeasts. To overcome this, don't pitch until the wort has stabilize at the desired temp. I like to cool the wort a few degrees below the desired temp, then pitch and allow both to rise to the desired.


Sent from my iPad using Home Brew

 

[Gavin C]

Changing the temperature on the thermostat would cause the compressor to run longer until the air inside the fermentation chamber gets to the temperature it is set for. I think my question was really...Is it a bad idea to change the fermentation temperature of the beer as quickly as possible (by changing the air inside of the fermentation chamber to near freezing)? I thought maybe once the beer was at one temp, cooling it too quickly would stress the yeast.

If your probe is measuring the temperature of the wort the compressor will run until that is reached regardless what the fridge is set to. That is the point of the external thermostat. What are the hysteresis settings on the controller? I guess I'm not understanding your setup. Mine is very much set it and forget it. No calculations of required temperature setting on the freezer are needed.

 

[watermelon83]

Thermowells that reach the center of your fermentor are fairly reasonable. The one I just bought from Midwest came with a dual hole stopper.

 

[jrodie]

Mine adjusts to the ambient air of the fermentation chamber, not the wort itself. Which once you get it set is nice, because the temperature of the air changes, but the wort temp never changes, since wort is more resistant to temp changes than air. It does take more monitoring though to find that sweet spot, and you need to adjust the spot as the fermentation changes the temperature of the wort.

 

[Gavin C]

How do you know what the wort temperature is?

Why do you want to control the ambient air temperature and not the wort temp?

I'm not really understanding the rationale to this approach. With my setup I can control the wort temperature directly to +/-0.3C

I'm sure you know what you are wanting to achieve I'm just not seeing the logic behind this approach.

 

[wdwalter]

I use a digital temp gauge directly into the middle of my carboy which gives me the exact temp of the beer. Then I set my chamber temp about 5 degrees cooler than my fermentation temp which keeps the beer at the proper temp. Since it takes a while for the air temp to change the liquid temp I don't think its wise to put the chamber probe in a thermowell to maintain temp. If your air temp gets to 30 degrees the beer will reach your desired temp quickly, but then quickly drop below it.

Best just to adjust the ambient temp a few degrees and let everything equalize.

 

[cjgenever]

Mine adjusts to the ambient air of the fermentation chamber, not the wort itself. Which once you get it set is nice, because the temperature of the air changes, but the wort temp never changes, since wort is more resistant to temp changes than air. It does take more monitoring though to find that sweet spot, and you need to adjust the spot as the fermentation changes the temperature of the wort.

Fermentation is exothermic. You simply can't keep a constant temp in the fermenting beer by measuring the ambient air temp because the heat input into the system by the yeast (which is variable, not constant).

Edit; unless you check it every few hours and adjust accordingly. In which case why do you even have a temp controller?

And no, you shouldn't drop temp once fermenting unless you want to flock your yeast out.

 

[watermelon83]

I use a digital temp gauge directly into the middle of my carboy which gives me the exact temp of the beer. Then I set my chamber temp about 5 degrees cooler than my fermentation temp which keeps the beer at the proper temp. Since it takes a while for the air temp to change the liquid temp I don't think its wise to put the chamber probe in a thermowell to maintain temp. If your air temp gets to 30 degrees the beer will reach your desired temp quickly, but then quickly drop below it.

Best just to adjust the ambient temp a few degrees and let everything equalize.

The thermowell holds the probe, so there's no direct content. The one listed fits the probe that shipped with my STC perfectly. Same concept as what you have, I just don't think that little plastic probe is designed to be submerged for any length of time.