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HeyZeus

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I’m after some advice on temperature control. My fermenter sits on a heat pad in a fridge which is controlled by a digital temperature controller thermostat. The fridge kicks in when the temperature is getting too hot and the heat pad kicks in when too cool. I have the thermostat sensor submerged inside the fermenter. Going by the recommended or ideal temperature of the yeast what should I set the fluctuation difference to on my thermostat? Should I set it so it’s bang on the recommended temperature without any fluctuation or is there room for a certain amount of fluctuation before the yeast starts producing unwanted flavors? If I have it set so there’s no fluctuation, I’m presuming there will be a lot of switching on and off between the heat pad and fridge which probably isn’t ideal for the life of the appliance.
 

McKnuckle

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I use a +1ºF delta from the controller's set point. This means if the controller is set to 63º, the beer will warm up to 64º before the cooling kicks in. It can over-shoot a bit and drop to, say, 62.5º. I may have that inadvertently set now that I think about it, but it's hardly a problem. I consider 64º the target fermentation temp, so in essence I'm setting the controller one degree below that.

Unwanted flavors are more likely at the extremes of whatever range the yeast strain prefers, and then only in the first 72 hours of fermentation.

I have never tried to heat beer that's in the fridge. It seems counter-intuitive. The natural tendency of the fermentation is to generate heat, and my fermentation fridge is in a room that's warm. So allowing the beer to slowly drift back up to the set point of the controller is the way I choose to let things roll.

I also have a second fermentation area that gets the reverse treatment - it's an insulated chamber in my cold garage. I only use a heating pad in there, and use it for fermenting lager. Same rule applies: -1ºF delta from the set point, so if I set the controller to 50º, the beer drops to 49º before the heat kicks in.
 
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HeyZeus

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I use a +1ºF delta from the controller's set point. This means if the controller is set to 63º, the beer will warm up to 64º before the cooling kicks in. It can over-shoot a bit and drop to, say, 62.5º. I may have that inadvertently set now that I think about it, but it's hardly a problem. I consider 64º the target fermentation temp, so in essence I'm setting the controller one degree below that.

Unwanted flavors are more likely at the extremes of whatever range the yeast strain prefers, and then only in the first 72 hours of fermentation.

I have never tried to heat beer that's in the fridge. It seems counter-intuitive. The natural tendency of the fermentation is to generate heat, and my fermentation fridge is in a room that's warm. So allowing the beer to slowly drift back up to the set point of the controller is the way I choose to let things roll.
Thanks for your advice, it was helpful. 👍

I assumed that keeping the fermentation temperature close to your desired temperature was the safest bet. I have read that the activity of the yeast can raise the temperature of the brew within the first 72 hours so I guess that's the most critical time to keep temperature regulation tight.
 

McKnuckle

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There is nothing wrong with keeping a tighter tolerance on the control, other than - as you mentioned - wear on the electronics. You can definitely relax, though, about a degree or two of drift. In fact, even in the fermenter itself there's likely to be some temperature heterogeneity.

I also keep temp probes on the outside wall of the fermenter, under a layer of thick insulation, held on by a bungee cord. I run a tight ship when it comes to cold side O2, and don't want anything in the beer at that point, or any unnecessary seal compromises.
 

eric19312

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My fermentor is in a stand up freezer in my garage. Depending on time of year I may need cooling or heat or both. For example this last week has been a little unseasonably warm in my area and some cooling has been needed. But fermentation activity has slowed and this morning was about 20F outside I am pretty sure heat was called for during the night to keep temp from falling out of target range.

My controller requires minimum of 1 degree F difference between cooling set point (CSP) and heating set point (HSP). I use that most of the time. It also lets me control maximum and minimum temperature of the air in the freezer which prevents overshoot. I set those to about 10F on either side of the CSP. I've also got an always on fan in the freezer to keep the air mixed and to improve heat transfer between the air and the fermentor.

I don't set the difference between CSP and HSP to 1F is when I am looking for the temperature to free rise. Then I will leave HSP at current temperature and increase CSP to target....might be 5-10F higher than current depending on beer. Once the temp reaches the target I will then increase HSP to 1F below that to keep beer from cooling down on its own as yeast activity slows but before I am ready.

Agree with @McKnuckle that your dangling the probe in the beer sounds not ideal. Either a thermowell or taped to the wall of the fermentor with insulation over is going to work better. Having done both, taping to the side is probably every bit as good as thermowell and easier.
 
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