Ale Fermentation Temp

So when I attach the temp probe to the fermentation bucket. Do I want the set temperature to be 62F or around 58F to compensate for the higher fermentation temp? In other words does the wort need to be at 62F or does the outside of the bucket need to be at 62F?

If you atach the probe to the bucket and use something (a blanket, foam insulation board) to insulate it from the ambient temperature in fridge/freezer, you will basically be controlling the wort temps. You shouldn't need to compensate at all. You always could leave it uninsulated and compensate with a lower setting, but why introduce guesswork?

You can even just tape the probe on there and then wrap it all in a good sleeping bag or something.

Fermentation temperature is referred to wort temperature.
As said, you can attach probe on side of bucket and insulate it, you should get pretty accurately temperature of fermentation inside of bucket.

Well, I believe you should only use the probe for the ambient temp (assuming you have a temp controlled chamber), I have a separate thermometer that monitors the wort temps (fermentometer). This way the wort has the least amount of temp swing.


Usually the ambient is 60F and wort temp is 64F

Fermentation temp is the temp of the wort. So if the strain you are using has a range between 66 and 71, the wort itself should be in that range. If you aren't putting the temp probe in the wort, attach it to the bucket and wrap insulation or a blanket around it. This will give you the closest wort temp reading.

Wort temps during the highest fermentation point could be 10* higher than ambient temp which is why it is best to know the wort temp so you can adjust

I tend to think that attaching the probe directly to the fermentor will give you the most constant temperature control. Any time your chamber is opened (assuming it isn't a chest freezer), you are going to let all the cool air out. This will make the controller think it needs to cool the wort down, and then you are going to have to deal with the temp swings this causes (namely, the wort will be chilled lower than you want). Due to it's liquid form, the wort will maintain it's lower temperature much better than the air and you will have less of a swing in the temps of the wort.

i set my temp controller at 63 with a differential of 3, so my ambient temp is always 60-63, which has produced very good beer.

djfriesen said:

I tend to think that attaching the probe directly to the fermentor will give you the most constant temperature control. Any time your chamber is opened (assuming it isn't a chest freezer), you are going to let all the cool air out. This will make the controller think it needs to cool the wort down, and then you are going to have to deal with the temp swings this causes (namely, the wort will be chilled lower than you want). Due to it's liquid form, the wort will maintain it's lower temperature much better than the air and you will have less of a swing in the temps of the wort.

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This method will cause to wort temp to swing the most (think temp differential). Your wrong about the open door theory and cooling the wort too low. That doesn't make sense. It makes much more sense control the ambient temp and monitor the wort separately.

Im starting to think people who tape the probe to the fermenter have no idea how the system works best.

I set mine at 62 with a .5 differential. My chamber barely kicks on since its in the basement. In garages you would probably need to make the differential greater as you dont want your fridge kicking on and off frequently.

I know for a fact that water changes temperature more slowly than air. Maybe I'm not explaining myself well. The opening door "theory" makes sense in my head and you've given me no reason to think otherwise.

It seems like controlling the ambient temperature, and then allowing the wort to lag behind, is at least imprecise, if not less efficient. Set your fermentation temperature on the controller, and the controller will adjust the ambient to be whatever it needs to be to keep the wort at the control setting. If my logic is completely flawed, I hope someone will point in out to me. For the good of my beer.

djfriesen said:

It seems like controlling the ambient temperature, and then allowing the wort to lag behind, is at least imprecise, if not less efficient. Set your fermentation temperature on the controller, and the controller will adjust the ambient to be whatever it needs to be to keep the wort at the control setting. If my logic is completely flawed, I hope someone will point in out to me. For the good of my beer.

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The flaw is that by the time your wort is at the target temperature, the ambient temperature is far below your target fermentation temp and the wort will continue cooling due to the differential.

You've convinced me. Once the temperatures equalize, it is more efficient to control the ambient air temperature because the water will hold its temperature more easily. I want to go mess around with it now, just to prove it to myself. Wish this stuff wasn't so counter-intuitive sometimes. Thanks for the correction.