Temperature controlled fridge and fermentation question

[Shipwreck_Jonny]

Hey, all.

So I recently purchased a chest freezer and a thermo-regulator to go along with it. This last Sunday, I made up a 5 gallon batch of a chocolate pumpkin spice stout with WLP004 (Irish Ale yeast), which was pitched at 70° and the whole shootin' match was put in the reefer, set to 65°…
At 24 hours, I had active fermentation, although I am used to borderline explosive fermentation. I've decided not to worry just yet.
At 48 hours, fermentation significantly slowed bit is still showing activity. However, my temp was set to 65° but my thermo strip on the ol' carboy was reading 70-75 degrees!
I've since dropped the temperature on the thermo regulator to 59 degrees, figuring for a 5° temperature swing in the positive direction, but what I want to know is what I'm missing, here... is the CO2 causing my temperature to rise? Is the thermo strip giving me a bad reading? Did I ruin my beer? How much of a tolerance do I need to compensate for using this set up?
Any and all help is greatly appreciated! If this recipe turns out well, I'll surely post it.

Thanks.

-Jonny

 

[IL1kebeer]

The problem is that the vigorous part of fermentation is exothermic, meaning the yeast give off heat while they are fermenting. If you are only controlling the ambient temperature, then the temperature of your beer will be noticeably higher. This could lead to flavor problems.

My advice is to tape your temperature controller's probe to your fermentation vessel and then insulate the probe with some bubble wrap (also taped to the vessel). This will ensure that your controller kicks in when the beer temperature gets out of range, not your ambient temperature, thus controlling your actual fermentation temps to within one degree Fahrenheit or less.

 

[Shipwreck_Jonny]

My advice is to tape your temperature controller's probe to your fermentation vessel and then insulate the probe with some bubble wrap (also taped to the vessel). This will ensure that your controller kicks in when the beer temperature gets out of range, not your ambient temperature, thus controlling your actual fermentation temps to within one degree Fahrenheit or less.

Thanks for the tip! I appreciate it.

 

[norsk]

Taping the probe to the fermentation vessel works fine, though I usually have it inside the vessel inside the beer...

 

[Shipwreck_Jonny]

Taping the probe to the fermentation vessel works fine, though I usually have it inside the vessel inside the beer...

I would have to modify my carboy or my airlock set up; I will keep it under advisement, though

 

[BigFloyd]

I would have to modify my carboy or my airlock set up; I will keep it under advisement, though

You don't need to do anything other than tape the probe to the side of the fermenter, tape over it and then tape some bubble wrap over that to insulate.

A few of our HBT brewers took simultaneous readings to check this. The measured difference in temps between outside edge of fermentor vs. a thermowell in the middle of the beer is negligible.

 

[vinpaysdoc]

Putting the temp probe on the side of the carboy is good enough.

I hollowed out a block of styrofoam and put the sensor in the block. I secured the sensor to the block with duct tape and then secured the block to an elastic band with duct tape. The whole assembly easily slips on and off my 6 gal carboys with a minimum of hassle.

I set the temp to whatever temp I want to ferment at, the differential (diff) to 1 F, and the ASD (anti-short cycle) to 15 minutes. It has been working very well.