Confused about optimal probe place for thermostat

[Pugilist]

I have purchased the brewers edge digital thermostat for my mini fridge. I have heard the probe should be put in the following places:

1. A small vial of antifreeze
2. a small jar or bottle of water
3. taped to the side of carboy under a damp cloth
4. hanging free about midway down

I have opted for taping it under a damp napkin to the side of my carboy. Are any of these ways better? I have heard that the beer temp in the middle of the carboy can increase about 8+ degrees during active ferment?

 

[Bobby_M]

There is no perfect.

Taping to the side of the carboy and slightly insulating it's exposure to the fridge air is probably the closest you'll get. I'll comment on each option;

1. A small vial of antifreeze. you're not going for freezing temps, no need for antifreeze.
2. a small jar or bottle of water. It will never know how hot the carboy and fermenting beer is. It will only equalize to the average air temp inside, say 67F. Meanwhile, the carboy could be on a runaway 75 degrees.
3. taped to the side of carboy under a damp cloth. I'm not sure about the damp cloth, I'd use a little bubblewrap or something similarly insulative.
4. hanging free about midway down. Bad for a few reasons. It doesn't know the carboy temp at all, and will be immediately exposed to rapid temp fluctuations when you open the door. Could cause too many frequent cycles.

The one you didn't mention, but someone might:

5. Inside a thermoprobe in the middle of the carboy. Also not good. The fridge will run and run to get the probe down to set temp. When finally does, it will really overshoot the temp and maybe even freeze the outter edges of wort.

If I had to really think of the perfect situation, it would be a thermoprobe inside the wort, but only about an inch away from the carboy/fermenter's side wall. Buffered but quite reactive to wort temp at the same time.

 

[Pugilist]

Thanks alot for the informative response. On a side not I really enjoyed your you tube videos, the bottling one with the dishwasher trick really saved me some hassling from the wife!

I also could not believe the one guy who was posting all the nasty comments to you about the videos. I see he didnt have anything posted to the contrary?

 

[peterdulay]

Yeah Bobby that is a great response. I have been torn between the side of the fermenter and mid-air. The side of the fermenter could be the closest to the actual wort temperature without being in it. However, when you're trying to acclimate the wort for the first time it could end up running a while until the fermenter (wort) temp catched up.

I know this to be the consensus for cooling on dual stage controller but what about heating? I bought a Lasko ceramic heater fan and I really don't want it heating up for that long. If the ambient temp is 80 (for my Belgian SA) in the the chest freezer but the fermenter is only at 70, the heater is going to heat the space up quite a bit before the wort catches up. Possibly dangerous but more likely disastrous.

I think I am going to leave the rule: When cooling, strap to side of fermenter. When heating place in ambient air.

If anyone know better for heating, I'm all ears.

 

[damnitbeavis]

I have a ranco dual stage controller, ferment in a sanke with a brewers hardware sanke fermenter kit, and put the thermo-probe inside the thermowell. I think there is no more precise place to read temp for both heating and cooling than to read directly inside the wort. You could just get a stopper thermowell to work in most setups.

I don't buy the argument that taping the probe to your fermenter or putting it in a glass or something like that next to it will even come close to the accuracy of a thermowell. With a metal or glass fermenter, however, I believe attaching your probe to the outside under insulation would be second best. A wet rag would serve to transfer heat from the room( or fridge) to the probe, but fiberglass insulation or a small pillow will insulate the probe from the external temperature and give you a better idea of actual wort temperature.

 

[ChuckO]

I took a different approach. I use one program on a BCS-460 to control the temperature. I have placed the probe under insulation on the outside of the fermenter and have a fairly simple process set up.

First state delays for 15 minutes. Second state monitors temperature between 1 deg. up or down from setpoint. Third state activates on 1 deg. drop and turns on heat for maximum time of 10 minutes or temperature rise of .6 deg. This allows overshoot if necessary without triggering a cooling cycle. Fourth state does the opposite for cooling.

I developed this process by observation from 3 probes, in air, in thermowell and insulated on the side of the fermenter. In free air for controlling the freezer cycled too often and the temperature in the thermowell varied quite a bit. When the controlling probe was in the thermowell there was massive overshoot because of the time delay in temperature change of the center of the wort allowing the freezer or heater to run way too long. Insulated on the side of the fermenter gave the best response with the thermowell probe showing a very consistent temperature although it was above the set point. This was easily compensated for by changing the setpoint.

 

[damnitbeavis]

Chucko- what do you ferment in? I find that with my system, once a set temp is reached, that very little heater or fridge activity is needed to maintain temps unless my uninsulated garage gets very hot. A cold garage seems to pose less of a problem, as the active fermentation inside the fridge produces heat that usually serves to sustain wort temps in ideal range.

In a fermenter, the temperature of the total volume of wort could not be more than a degree off(comparing the center to the side) due to the intense churning currents created by an active fermentation. The only way to know for certain, in my opinion, would be to have thermowells in multiple positions INSIDE your wort, which seems impractical.

Once active fermentation had stopped, it would seem possible for the innermost portion of the wort to have a different temperature than the outer portion, but then you are mostly conditioning, and temperature at that point would seem less critical, to me, at least. Still, every system needs it's own tweaking, and I have no doubt that there is more than one way to skin this cat.

 

[damnitbeavis]

Peterdulay- I would caution you about using a ceramic heater inside an enclosed space. While I think it is unlikely to hurt your beer (because your wort will be happily churning around, stirring itself) your fridge may melt inside due to the extreme amount of heat that ceramic heater puts out. Ceramic heaters are designed to heat a whole room, remember. I use a cheap, low output brew heater that I got from morebeer, and that seems to work well for me.

http://morebeer.com/view_product/16674/102282/The_FermWrap_Heater

 

[peterdulay]

Yeah Beavis, I turned on the heater and that thing does get super hot. I did order those ferm wraps but they aren't supposed to be here for a few days and I'm supposed to be ramping the temps with these yeasts (Belgian and a Saison). I think I'll set the probe in midair and just manually plug the heater in for a minute or 2 until its warm enough inside, then unplug it. The wort should adjust to the air temp eventually. That way I can control how much heat goes into this thing with out melting my freezer.

That should last 2 days until the ferm wraps come. Thanks for the concern and advice; well received. Let me know if you think my strategy will get me by or better yet if you don't.

 

[ChuckO]

Beavis, I'm using a 9cf freezer for 2 or 3 fermenters in a garage with temperature swings from 33 deg. to 80 deg. There is a 60 watt heater and a continuous fan in the freezer.

You're right that the temperature differential between the side of the bucket and the thermowell is lower during active fermentation than later on. Temperature swings are greater after active fermentation with the probe in a thermowell on my system. I've had the freezer turn on when room temperature has been 45 deg. because of heat of fermentation.

The greatest benefit comes from moving the probe from free air to either inside the fermenter or against the wall covered by insulation. Having the probe in air causes the highest swings in wort temperature and the most frequent cycles of the freezer or heater.

I am more concerned with large temperature swings that I am with the actual temperature as long as it is in the correct range during active fermentation. For this reason I keep the probe on the newest batch and let the older batch(s) hold at whatever they will. I might experiment with leaving water in empty fermenters to keep the freezer at capacity for consistency.

 

[damnitbeavis]

Yeah Beavis, I turned on the heater and that thing does get super hot. I did order those ferm wraps but they aren't supposed to be here for a few days and I'm supposed to be ramping the temps with these yeasts (Belgian and a Saison). I think I'll set the probe in midair and just manually plug the heater in for a minute or 2 until its warm enough inside, then unplug it. The wort should adjust to the air temp eventually. That way I can control how much heat goes into this thing with out melting my freezer.

That should last 2 days until the ferm wraps come. Thanks for the concern and advice; well received. Let me know if you think my strategy will get me by or better yet if you don't.

you could just put a small lamp with a 25-40 watt bulb in there, just be sure to protect your wort from the light so you don't get lightstruck beer.