Best thermometry method for fermentation?

I just bought a big 15CF chest freezer to pull double duty as a fermentor and then when finished, to lower the temps and use it as a serving/kegerator.

My main question comes to the best temp control method using a Ranco temp controller. Would I be best served by buying a stopper that has a thermowell for the beer being fermented? Or should I just dangle the thermocouple into the chest and have it measure the air temps? I've also thought about dangling the probe into a smaller enclosed water container.

I'm not sure which would be best. My apartment has incredibly stable low temps nearly year around. I've used a thermocouple to trend my ambient air temps and they rarely vary from a 62-71 degree band at most. I don't even have AC in my apartment and never turn on the heat. Not sure if that will make much a difference or if it will just save me electricity in the long run. I just want the best, most ideal fermentation environment for my yeast to do it's job. I've considered getting a carboy wrap to add heat if needed, and perhaps get that duel control heat/cold temp controller I saw listed here in the vendor forum.

But mainly I'm just wondering about ideal thermocouple placement. The rest is just me rambling about what I have and what I hope for.

Thanks for any suggestions!

I wouldn't suggest dangling the probe or the water technique unless you're planning on having several actively fermenting batches going at one time. If you're only going to have one actively fermenting batch and a few batches that are a week or two old and are just waiting in primary, you can measure the temp of the actively fermenting one using a thermowell. I think I've also seen a post on here where the temp in the thermowell and taped to the side of the carboy with an insulating rag was measured and they actually measured pretty closely together, so a thermowell isn't necessarily required. Still, I use a thermowell in a minifridge fermenter with a heat wrap around it to dial in the temps (that's another thing, the heat wrap is pretty useless without a thermowell or careful taping of the probe to the carboy). The other nice thing about measuring the specific carboy is that you can prevent some of the big swings that can happen when you open the door if the probe is just hanging in the air. For my kegerator I use a couple of cold packs to sandwich the probe to keep it from registering temp swings, which might be something to consider if you decide to go that route.

I hate to change the subject, but it seems kind of silly to think you can use a fairly giant 15cf chest freezer for both fermentation and serving. I would highly recommend building something else for fermentation and putting it in the chilliest corner of your apartment. Having something that wonderfully large will be very frustrating on a dual/purpose schedule.

Also, for fermentation I have my probe taped to a fermenter and for serving it is taped to the oldest-added-keg. extra extra, I've been told that ranco thermoprobes aren't waterproof, so be careful with the in-a-cup-of-water-method

I did more mental work before buying it, thinking I'd use wraps to dial in specific temps for fermenting, another for cellaring on a separate carboy while perhaps serving off the corny kegs with the main freezer dialed in for ~40º.

I've only read about it being done, but no first hand experience. I have a small apartment and I kinda wanted everything to be contained in one vessel, to keep it less cluttered. Time will tell if a 3 way temp control environment is possible, but I'm thinking with my mild ambient temps, it shouldn't be too difficult or expensive, energy consumption wise.

The only thing that I think could potentially be a challenge, is if the carboy that is in primary is sitting in a 40 ambient environment, the wrap trying to bring it up to ~68º or so, might have the beer closest to the wrap at several degrees higher.

hillhousesawdustco said:

I hate to change the subject, but it seems kind of silly to think you can use a fairly giant 15cf chest freezer for both fermentation and serving. I would highly recommend building something else for fermentation and putting it in the chilliest corner of your apartment. Having something that wonderfully large will be very frustrating on a dual/purpose schedule.

Also, for fermentation I have my airlock taped to a fermenter and for serving it is taped to the oldest-added-keg. extra extra, I've been told that ranco thermoprobes aren't waterproof, so be careful with the in-a-cup-of-water-method

Click to expand...

Agreed, I only have a 5 cf freezer and rotation is my current conundrum.

You might be able to wall off a section of it (with styrofoam/insulation) for fermenting, and just mostly use a heater to keep temps on that side up. While keeper the freezer set at 40, or even higher depending on what you're serving. Not really energy efficient.... But it might work.

I'd still think a mini fridge that can got a couple of kegs and a smaller 7cf freezer is a better option, unless you plan on having 9 kegs (maybe more in that beast of a freezer) tapped at all times.

I did a temp delta study a few batches back. Placed the temp controller in a block of foam insulation and taped it to the bottom edge of my fermenter, where I always place it. Took another temp probe, waterproofed it and placed it in the hole with the airlock. The internal temp was consistently 2 degrees higher than the exterior probe. Now if I want precise temp control, I just set my ferm chamber 2 degrees lower than my desired temp.

william_shakes_beer said:

I did a temp delta study a few batches back. Placed the temp controller in a block of foam insulation and taped it to the bottom edge of my fermenter, where I always place it. Took another temp probe, waterproofed it and placed it in the hole with the airlock. The internal temp was consistently 2 degrees higher than the exterior probe. Now if I want precise temp control, I just set my ferm chamber 2 degrees lower than my desired temp.

Click to expand...

You know, that's really interesting. I've heard the opposite based on some episodes of the Jamil show. He was saying if you tape the probe to the side of your fermentor and put some insulation around it, the temp of the probe is within about .5 degrees of the beer.

I'm just now fermenting my very first lager. My temp controller reads 50 on the dot, but my fermometer reads about 51-52. I figure the johnson controller has to be more accurate, I've heard the fermometers arent the most accurate.

But I'm sticking the probe directly to the fermentor, not inside the insulation, like it sounds you're doing. Seems like the foam would insulate the probe from the fermentor.

Just bought a carboy heater wrap, thermowell and a dual temp controller to go along with the rest. i have at least 6 different thermometers/thermocouples from various manufactures that are calibrated to my altitude and accurate within 0.5ºF I use them primarily in my commercial grade sampler coffee roasting setup. My Thermapen has never let me down yet either. It would be interesting to see what data I gather and how it all dials in. During active fermentation/primary, it would make sense to me that the center of the fermentor will be warmer than the exterior slightly.

tgmartin000 said:

You know, that's really interesting. I've heard the opposite based on some episodes of the Jamil show. He was saying if you tape the probe to the side of your fermentor and put some insulation around it, the temp of the probe is within about .5 degrees of the beer.

I'm just now fermenting my very first lager. My temp controller reads 50 on the dot, but my fermometer reads about 51-52. I figure the johnson controller has to be more accurate, I've heard the fermometers arent the most accurate.

But I'm sticking the probe directly to the fermentor, not inside the insulation, like it sounds you're doing. Seems like the foam would insulate the probe from the fermentor.

Click to expand...

The probe rests in a block of insulation with one edge of the probe in physical contact with the brew bucket. The purpose of the insulation is to minimize the probe reading the ambient air in the ferm chamber. I'm quite sure if I placed the probe at different heights I would get different readings. I place a brew belt at the top of the bucket and wanted to get the sensor as far from it as possible to avoid false readings from the brew belt. I believe the actuals don't matter as long as you can correctly read your setup and account for inaccuracies. I did the test the first time and found the delta 14 degrees. After some head scratching I determined that my internal thermometer was inaccurate. That's when I bought my thermopen.

Keep in mind that the most BAD ASSED freezer will be a crappy wort chiller.

No, but a Thermenator is.