[hopfenundmalz]

My temp probe for the conical goes into a thermowell that is in the beer.

For lagering in the chest freezer, the temp probe is taped to the cornie, under some insulation.

[bluesman]

My temp probe for the conical goes into a thermowell that is in the beer.

For lagering in the chest freezer, the temp probe is taped to the cornie, under some insulation.

.

+1

Thermowell in conical and bubblewrap over probe around bucket.

[micsager]

My probe is taped to the side of one bucket with some insulation.

Why are you taping and insulating the probe to the bucket?

The idea would be to get a more accurate reading of the temperature of the wort in the bucket instead of just the air temperature in the fermentation chamber.  They can be quite different.

Bingo, that's it.  I heard it on an episode of Brewstrong. 

[micsager]

My probe is taped to the side of one bucket with some insulation.

Why are you taping and insulating the probe to the bucket?

The idea would be to get a more accurate reading of the temperature of the wort in the bucket instead of just the air temperature in the fermentation chamber.  They can be quite different.

I can understand if it's just a temperature probe to display the temperature, but I would not connect the fridge temperature probe to the bucket or immerse it in liquid.

Why not, i've done it since day one.

[Tim McManus]

My probe is taped to the side of one bucket with some insulation.

Why are you taping and insulating the probe to the bucket?

The idea would be to get a more accurate reading of the temperature of the wort in the bucket instead of just the air temperature in the fermentation chamber.  They can be quite different.

I can understand if it's just a temperature probe to display the temperature, but I would not connect the fridge temperature probe to the bucket or immerse it in liquid.

Why not, i've done it since day one.

Fridges and their compressors aren't designed to cool liquids or solids.  They are designed to maintain the ambient temperature of the air in the fridge.  The reasoning behind this is that it takes less energy to cool the air instead of the objects in the fridge.  As long as the fridge maintains the temperature of the air, the objects in the fridge will maintain their temperature.

If you put the probe in the liquid, the air temperature will continue to rise and the compressor won't turn on until the temperature of the liquid triggers it.  Then it will take more energy to cool the liquid by using the air.  The compressor will run longer.  Additionally, the fridge isn't directly cooling the liquid.  If you were using something like a glycol wrap around the bucket or fermenter, then you'd want to measure the temperature of the liquid (and you'd want to measure the temperature of the glycol to determine when the thermal transfer was complete).

So by using the temperature of the liquid to control the fridge compressor, you're running the compressor longer and using more energy to cool the fermenting beer.

[micsager]

As long as the fridge maintains the temperature of the air, the objects in the fridge will maintain their temperature.

Not sure I agree with that statement.  Remember, yeast creates heat. 

[Joe Sr.]

So by using the temperature of the liquid to control the fridge compressor, you're running the compressor longer and using more energy to cool the fermenting beer.

You may be running the compressor longer, but you should be cycling less often since the mass of the liquid does not change temperature as quickly as the air.

So perhaps it's six of one, half a dozen of the other as far as the compressor is concerned.

More to the point, since you're trying to control the fermentation temperature of the beer, not the ambient air temperature, is not the temperature of the beer what you would want to be measuring?

[Hokerer]

Fridges and their compressors aren't designed to cool liquids or solids.  They are designed to maintain the ambient temperature of the air in the fridge.  The reasoning behind this is that it takes less energy to cool the air instead of the objects in the fridge.  As long as the fridge maintains the temperature of the air, the objects in the fridge will maintain their temperature.

In the short term, that is an untrue statement.  Yes, objects in the fridge might eventually reach equilibrium with the air temperature in the fridge, but the timescale is too long to do us any good.

Say you start with your wort and the air in the fridge both at 65F.  As fermentation gets going, since it's an exothermic process, the wort can get 5 to sometimes even 10 degrees warmer than ambient.  If your temp controller is measuring the air temp, it'll turn the fridge on just long enough to cool the air back down to 65F and then cut back off.  NO way does that get the temp of five gallons of wort down to 65F also.  That warm wort will warm the fridge air, the controller will turn the fridge on again, cool the air, and then shut off.  Lather, rinse, repeat.

Eventually the wort temp will reach 65F but it'll take days and days for that the happen.  By that time, the damage (due to too high fermentation temps) has already been done.

If instead, you're measuring the temperature of the wort itself, when the controller kicks in, it won't cut off until the wort reaches 65F.  Yes, it'll run the fridge longer, but it'll get the wort to the temp that you actually want it at.  Also, due to it's thermal mass, it'll take much longer for the wort to warm up, thus making it a much longer time before the fridge needs to run again.

So it's not even as good as six of one / half dozen of the other.  Measuring the air temp, your wort probably won't be at the desired temp during the time you most care about.

[ccarlson]

It's very simple. Either chill to your desired temp with an IC or ???and pitch or cool it in a fridge until you get it to you desired temp and pitch. The second option requires perfect sanitation.

[tschmidlin]

It's very simple. Either chill to your desired temp with an IC or ???and pitch or cool it in a fridge until you get it to you desired temp and pitch. The second option requires perfect sanitation.

"Perfect sanitation" would be sterilization, and no one does that.  I cool stuff overnight in my fridge frequently and don't have problems with standard sanitation procedures.

[ccarlson]

It's very simple. Either chill to your desired temp with an IC or ???and pitch or cool it in a fridge until you get it to you desired temp and pitch. The second option requires perfect sanitation.

"Perfect sanitation" would be sterilization, and no one does that.  I cool stuff overnight in my fridge frequently and don't have problems with standard sanitation procedures.

Don't you agree that good sanitation is even more important when you wait to pitch? And perfect sanitation does NOT mean sterilization, it just means you are extremely careful. Sanitation and sterilization are not the same.

[tschmidlin]

It's very simple. Either chill to your desired temp with an IC or ???and pitch or cool it in a fridge until you get it to you desired temp and pitch. The second option requires perfect sanitation.

"Perfect sanitation" would be sterilization, and no one does that.  I cool stuff overnight in my fridge frequently and don't have problems with standard sanitation procedures.

Don't you agree that good sanitation is even more important when you wait to pitch?

No.  I think good sanitation is equally important whether you pitch right away or wait.

[Joe Sr.]

So it's not even as good as six of one / half dozen of the other.  Measuring the air temp, your wort probably won't be at the desired temp during the time you most care about.

You are correct with respect to the wort.

My point was more to the impact/wear and tear on the compressor. Minimizing cycling should extend the life of the compressor even if it runs longer occassionally.

[Tim McManus]

Fridges and their compressors aren't designed to cool liquids or solids.  They are designed to maintain the ambient temperature of the air in the fridge.  The reasoning behind this is that it takes less energy to cool the air instead of the objects in the fridge.  As long as the fridge maintains the temperature of the air, the objects in the fridge will maintain their temperature.

In the short term, that is an untrue statement.  Yes, objects in the fridge might eventually reach equilibrium with the air temperature in the fridge, but the timescale is too long to do us any good.

Say you start with your wort and the air in the fridge both at 65F.  As fermentation gets going, since it's an exothermic process, the wort can get 5 to sometimes even 10 degrees warmer than ambient.  If your temp controller is measuring the air temp, it'll turn the fridge on just long enough to cool the air back down to 65F and then cut back off.  NO way does that get the temp of five gallons of wort down to 65F also.  That warm wort will warm the fridge air, the controller will turn the fridge on again, cool the air, and then shut off.  Lather, rinse, repeat.

Eventually the wort temp will reach 65F but it'll take days and days for that the happen.  By that time, the damage (due to too high fermentation temps) has already been done.

If instead, you're measuring the temperature of the wort itself, when the controller kicks in, it won't cut off until the wort reaches 65F.  Yes, it'll run the fridge longer, but it'll get the wort to the temp that you actually want it at.  Also, due to it's thermal mass, it'll take much longer for the wort to warm up, thus making it a much longer time before the fridge needs to run again.

So it's not even as good as six of one / half dozen of the other.  Measuring the air temp, your wort probably won't be at the desired temp during the time you most care about.

I disagree.  A fridge is designed to cool air, not liquid.  The thermal transfer of heat from the liquid to the gas may keep the compressor running, but it won't take days to reduce the temperature.  It should take hours.  As an example, put a 2-liter bottle of any liquid in a fridge.  It will cool within 8-10  hours, probably less.  Even with yeast at peak fermentation, an efficient fridge will maintain the temperature of the liquid.  The increase of temperature from a yeast thermal reaction isn't enough to outperform a modern efficient fridge.  Used with a proper temperature regulator (the same Johnson Control one that most folks have) and a proper tolerance, it won't happen.

Heat radiates and is not stored.  The fan in a fridge circulates the air to increase thermal transfer and then maintains the air temperature which subsequently maintains the contents temperature.

Putting the probe in a liquid makes the ambient air drop to the lowest level possible to reach the cut-off temperature of the probe.  In most fridges, this is approximately 30°F-34°F.  So the compressor may turn off when the liquid reaches your desired temperature (let's say 52°F), you still have a chamber full of air that is 30°F-34°F that continues to absorb heat from the liquid.  This can cause the liquid to cool down well below where you want it to.  Additionally, when your liquid reaches the turn-on temperature (let's say, 54°F), the ambient air will be well above that due to the absorption of heat from the yeast reaction and the lack of cooling in the chamber.

The critical thing to remember is that you're not directly cooling the liquid.  You are cooling the ambient air to cool the liquid.  The device is designed to do that efficiently.  If you were using something different to cool the liquid, such as a glycol or another cooling coil, then it would be practical to check the temperature of the liquid.

[narvin]

Tim, I'm going to have to disagree as well.  A fridge is designed to cool air, but not to your fermentation temperature target of 68, or even 48 for lagers.  The coils will always be chilling the air well below your desired temperature, and it's the job of a temperature controller to regulate the duty cycle of the compressor to keep it within your desired temperature range.  Measuring your desired temperature -- beer temperature -- is the best way to do this.

I always ferment with my probe in a thermowell, and the wort temperature swing during fermentation is never more than +/- 1 degree from the target. 

If you are measuring the temperature of the air instead and set the threshold to a single degree, it will be more consistent but far worse for your compressor because it's cycling on and off so much.  Increasing the differential when measuring the air means that the air will heat up and cool down more even though the beer won't be affected as quickly due to its thermal mass --  which is exactly what happens when you measure liquid temp, except you don't have to guess what temperature your beer is at.  So I really see no reason, practical or otherwise, not to measure the beer temperature directly.