Heating Pad and Probe Placement

[grampska]

I have a 5 cu ft freezer that I'm using for a fermentation chamber. It's controlled with an Inkbird with the probe in a thermowell in the fermenter and I also am using a Tilt hydrometer. I've only been doing 5 gallon batches in here so far but in preparation for 10 gallon batches with 2 fermenters, once I add a collar, I tried leaving the heating pad loose to see if it was powerful enough to maintain the temperature for this last batch.

The Inkbird was set to 68F with 1F of variation and I've had no issues with it so far. When I first put the fermenter in and plugged everything back in, the temperature measured by the Tilt shot up to 77F before settling down and being consistent for the next few days. I attributed this to a fluke but then we lost power for 48 hours and when the power had kicked back on, it did the same thing. Any ideas why this would happen or what to do to avoid it when I have the 2 fermenters in there? Because of the insanity after the power outage I didn't get to double check the Inkbird's display temperature while it was spiking but since I pulled the fermenter out, it's been steady around 68.

I just went back and edited that when I put this batch in, the freezer and heating pad had been unplugged so this may be as simple as making sure the temperature is stable before putting something in. But I still wanted to get thoughts if there's somewhere else I should be putting the probe vs the heating pad.

 

[3 Dawg Night]

A photo of the inside of your fermentation chamber might help. I'm having trouble picturing what you're describing. What do you mean by "leaving the heating pad loose"?

 

[KeizerBrewr]

Have you taken a calibrated thermometer and calibrated both to be the same temperature? Also, when you say "leaving the heating pad loose", you mean as in it is not wrapped around the fermenter, and just taped to the interior? You might want to have a small fan run inside the chamber to circulate the air inside to help with keeping your ambient temp inside more stable. Like @3 Dawg Night I think pictures of your set up would be beneficial.

 

[eric19312]

That is a surprising level of overshoot you are documenting and I'd want to fix that for sure it it is real. Looks like your freezer got pretty hot before the heat reached the middle of your fermentor. This is more likely to happen at beginning and end of fermentation when the yeast activity is not mixing the beer.

I'd get an always on fan set up inside the freezer. I really like these Amazon.com: AC Infinity AXIAL 9225, Muffin Fan, 120V AC 92mm by 92mm by 25mm High Speed, UL-Certified for DIY Cooling Ventilation Projects : Electronics but you can also use an old computer fan if you have a way to power it.

You might also want to get something to track air temperatures inside the freezer.

You may find you have better luck controlling temperature with probe placed on wall of the fermentor with a piece of insulation over it. Again this is more of an issue at beginning of fermentation when the yeast is not mixing the fermenting beer.