Dual Stage Fermentation Chamber getting too hot

I have a mini fridge hooked up to an STC-1000, and this 25w space heater http://www.williamsbrewing.com/BREWERS-EDGE-SPACE-HEATER-P518.aspx

I insulate the probe with bubble wrap and have it pressed against the glass of the carboy. I keep everything set at 67 F.

I just went in to check on it and noticed the heat light had been on for a while but the temperature was hovering at 63. I opened up the min fridge and double checked the temp with a mercury temp display I have resting on top of the carboy and the temperature was 82!!

The air in the chamber felt very warm, but the glass carboy felt cooler.

I ended up unplugging the space heater. It seems like an air temp of 82 would be detrimental for the beer. Also, my most recent batch had some kind of off flavor, so I am wondering if my ferm chamber isn't dialed in yet?

It seems like the air would have to get really really hot to heat up all of the liquid in the carboy...

Do you have a fermometer?

I bungee my sensor to the carboy with a small towel insulating it. No problems

I bubble wrap my temp probe to the outside also and have noticed the same thing, air significantly hotter than beer. I use a fermometer on my car boys and beer stays where I want. Overly hot surrounding air just gets beer to the set point faster. Get a fermometer, just to double check

So, the consensus is that the air temp doesn't matter one bit, only the wort temp.

After investing so much into getting a controlled fermentation environment, my brain does not want to accept that this means 80+ degree air temps

onthedot said:

So, the consensus is that the air temp doesn't matter one bit, only the wort temp.

After investing so much into getting a controlled fermentation environment, my brain does not want to accept that this means 80+ degree air temps

Click to expand...

The STC-1000 has a 3 degree spread I believe. So if your wort temp drops a couple degrees, that heater will come on and stay on until the wort heats up...that's going to take a long time for 5 gallons which means the ambient air will get very warm during this time.

I use a FermWrap heater, wrapped around the fermentor with bubble insulation over it, that way the heat is spead over the surface of the fermentor and tends to be more effective than heating the air only.

helibrewer said:

I use a FermWrap heater, wrapped around the fermentor with bubble insulation over it, that way the heat is spead over the surface of the fermentor and tends to be more effective than heating the air only.

Click to expand...

Thanks, I'll have to look into that. I'm curious - have you measured the ambient temp while the fermWrap heater is heating?

Here's my take on it, from using multiple temperature controllers (RANCO) for a few years now:

First off, my fermentation area is a sort of half basement that is only half underground. So, the temp swings in the various seasons. It can get really cold in there in winter or pretty warm in the summer.

I have multiple fermentation chambers. The main one is a chest freezer.

I sometimes measure the wort temp with a thermal well. I sometimes measure the air temp. Depends on my needs. The demijohns I use for fermentation sometimes have a heat belt under them. But, in the winter, the chamber can get too cold for that to work well enough to maintain the wort at a warm enough temperature, for Belgians and beers that end higher. I then measure the air temp and use a hair dryer to heat the entire chamber, using a 5 degree differential. The probe is hung so that it doesn't touch the sides of the freezer. It's in the open air about midway up. The air then maintains an average temp. The demijohn has a fermometer on the side so I can monitor the wort temp and raise or lower the temp as needed. It doesn't need to turn the air dryer on very often. With the hair dryer, the temp will go 2-3 degrees about set point, so that's got to be figured in with the differential. If I use 67 with a 5 degree differential, as an example, it will go down to 62 before it turns on and will heat to 69 or so. It turns off at 67,but there's some additional hot air mixing in, so it usually hits 69. So, from there, figure the average temp.

The fermentation generates more heat during the early fermentation, so for me the second and third day are usually trying to warm up more and there's a drop off after that. And the wort is usually higher than the ambient air. So, for an average ale, say I ferment at 67, the air in there might be at 62 or something. Then after the vigorous part of the fermentation ends, the wort will cool, so I will need to raise the temp of the air if I am using that method, sometimes all the way up to 67 so that the wort doesn't drop down in temp.

Right now, I have a split batch lager fermenting in that freezer. Maintaining the air at 50 keeps the fermenter at 50.

When is not winter, I will usually use the thermal well with a 1 degree differential. Set to 67, if we use my previous example, the freezer turns on if the wort hits 68 and turns off once it reaches 67. The heat belt under the demijohn will likewise turn on if the wort goes below 67. This is the ideal, for me, because I can set it and forget it. If your fermentation chamber isn't wildly hot or cold, you should do this, IMHO. Buy a thermal well. Easy to set up, easy to use. I use it with one of those orange carboy caps, then a blowoff or airlock can be put in the second hole. The stopper that comes with it, though, just doesn't fit my demijohns. Maybe it'll fit your carboys.

I have 2 other fermentation chambers set up the same way. One is for bottle conditioning and uses a hair dryer to maintain the air at 70-73 or so. Works great. The 3rd one is just a styrofoam enclosed area that uses the same set up, either thermal well and belt heater, or measuring the air and using a hair dryer.

Anyway, that's my experience.