Thermowell and swamp cooler

[Scoggin]

Quick question for those of you who use a thermowell and a swamp cooler. how much temperature difference are you experiencing during active fermentation? between the swamp cooler water, and the core of the fermenter? Assuming the frozen water bottle method

I'd assume the temperature difference would be less with a swamp cooler (ambient water temp/core temp of fermenter). And the temperature difference would be greater in open air (ambient air temperature/core temp of fermenter)? is this correct reasoning?

some numbers would be great

 

[Grantman1]

I was just wondering this myself. Does anyone have any input?

 

[NordeastBrewer77]

From what I've seen, and this is using a floating thermo in the swamp bucket and a digital probe in a thermowell in the wort, during active fermentation it's usually around a ~3-5 degrees F, but it can vary. Obviously, the most drastic difference will be when the fermentation is most active and when there's little to no activity, there's little to do difference between the two thermos. YMMV

 

[Grantman1]

Thanks. That's prob about right. I was thinking the wort has to be a few degrees warmer if it's slowly increasing the water temp.

 

[porcupine73]

I have a very makeshift setup with a 6.5 gal carboy sitting in a rubbermaid container, with a towel around it, and the container filled with water, and a fan blowing on it. The most difference I could get was about 5 deg. F. between ambient and the brew after a couple days. I imagine it varies with the relative humidity, maybe working better at low humidity. Then ... well of course ... the indoor/outdoor thermometer I was using just HAD to fall into the rubbermaid container and drown so now I don't know what the temp difference is anymore.

 

[pelipen]

This is a complicated answer.
When the fermentation is active, very little.
When the fermentation is not active, it depends on the water level and where in the carboy you take the readings. Here is a graphic from the last three weeks of my most recent batch. These are the important notes:

Conditions:
The water bath probe is roughly 1 inch in from the container wall.
The Carboy probe is an additional 8 inches further in, so there is a solid 7 inch liquid gap between them.
All my probes were calibrated against a reference between 35 - 80 F. I apply correction factors in-software.
In general, I see less than 1 degree F delta when things are running well.

Data voiceover:
1. Fermentation was most active through the middle of the first Wednesday.
2. Mid Wed, I could not recharge my water bath with ice and the temp elevated. I could not bring this down which was curious.
3. Thursday, the significant drop in temp (green) is due to a large charge of ice, still no carboy temp recovery.
4. Friday, I increased the water level to be above the carboy probe, charged with ice, immediate results. This is how I discovered the temperature stratifies quite a lot when fermentation is not active.
5. Over the next week (sat to sat) you can see I lost control of the temps several times (green spikes), but when it's stable and I charge the bath with ice consistently, the differential is between 0.5 - 1 degree F.
6. Saturday of the second week I had to leave the country on business, so I had to let it go. The result is fluctuation due to ambient room temp. Note the delta is minimal.