So I have a chest freezer that I am using as a fermentation chamber. I have that plus a ceramic heater with a built in fan plugged into a Keg King MkII controller. Also inside the chest freezer is a computer fan that is constantly on to circulate the air inside of the freezer. I have a Speidel fermenter that I installed a thermowell to measure the temp of the wort while fermenting. I have noticed that when I set my target temp (66 degrees F) it is constantly overshooting that temp which in turn will cause a constant swing in the wort temps. When it goes over the 66 degree set point and the freezer kicks on, by the time it reaches that target temp it will continue to drop to around 65 degrees. Meanwhile the heater will then kick on to warm it back up to the target temp, and by the time that is reached it will overshoot it once again causing the freezer to kick back on. It is a never ending cycle throughout the entire fermentation. Does this seem to be the norm for this type of setup or is the constant cycling of temps causing unwanted stress on the yeast or creating unwanted off flavors? Is there something I could be doing differently to not cause the never ending cycle of heating and cooling of the wort? As a side note I have changed the temperature hysteresis on the controller from the default 1 degree, down to .5 degrees. It can go all the way down to .1 degrees, but I am worried at that point the freezer will cycle so often that I will burn up the compressor on the freezer a lot sooner that I would like to. Any tips or words of wisdom? Thanks!
Fermentation chamber temp fluctuation
- Thread starter drovick
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You need to program the heat and cool delays. Constant cycling of the compressor will kill it.
Also, what is the temp of the freezer when the cold side shuts down?
Also, what is the temp of the freezer when the cold side shuts down?
JONNYROTTEN
Well-Known Member
Disconnect the heater...You don't need it in the summer.
Air temp changes WAY faster than liquid temps. It doesn't need to be that precise. Even if you overshoot the air temp on the down side it will naturally free rise quickly without effecting the liquid temp
Air temp changes WAY faster than liquid temps. It doesn't need to be that precise. Even if you overshoot the air temp on the down side it will naturally free rise quickly without effecting the liquid temp
JONNYROTTEN
Well-Known Member
Set the cycle time for at least 10 minutes to save the fridge from burning out. I think my temp is set to 2 deg. If I'm within 2 deg of desired temp I'm fine with that...yeast have a huge temp allowance 2 deg is no big deal
Thanks for the help. I will go look at the manual and find the setting for the heating and cooling delay. I'm not sure what the ambient air temperature is inside the freezer once the freezer kicks off because I don't have a thermometer reading that. Hopefully that cycle delays will prevent this from happening. Cheers!
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+1 to this. This is the advice I received when I had the same problem and it's worked out great. I find I don't need the heater unless it's the middle of winter with freezing cold temps. The air temp does overshoot a little on the downside but it does rise naturally. With this method I can have several hours of stable air and liquid temps and no need for the freezer to come on.
I'm using 16 gallon spiedel with thermowell in a fridge with a ceramic heating lamp. Previously used 6 gallon carboy with probe taped to outside. Find I'm getting fluctuations driven by the overshoots you mentioned that I don't believe I saw in the carboy. Between the heavy plastic container and larger volume (IVe got 15 gal in there now) it's just not as responsive to change in ambient as the carboy.
I looked into the automation friends but needed an ardinuno raspberry pic for dummies thread and couldn't find it. But I found this:
http://www.auberins.com/index.php?main_page=product_info&cPath=8&products_id=671
I like the idea and am trying it out now.
I looked into the automation friends but needed an ardinuno raspberry pic for dummies thread and couldn't find it. But I found this:
http://www.auberins.com/index.php?main_page=product_info&cPath=8&products_id=671
I like the idea and am trying it out now.
Using a temp probe in a thermowell to drive the temp controller almost guarantees overshoot/undershoot, because of the long time lag between liquid temp response and chamber temp. Instead, tape the controlling temp probe to the outside of the fermenter with a little insulation over the probe (1/2" of foam.) This gives you a weighted average of the wort temp and the chamber temp, heavily weighted towards the wort temp. But the contribution of the chamber temp to the control loop helps to minimize over/under shoots in the wort/beer. As others have mentioned, set your compressor delay to the max possible (10 minutes for many common controllers.) If you really want tight control of the wort/beer temp, use a controller like a BrewPi which looks at both liquid temp and chamber temp, and is extremely good at keeping an even liquid temp.
Brew on
Brew on
Using a temp probe in a thermowell to drive the temp controller almost guarantees overshoot/undershoot, because of the long time lag between liquid temp response and chamber temp. Instead, tape the controlling temp probe to the outside of the fermenter with a little insulation over the probe (1/2" of foam.) This gives you a weighted average of the wort temp and the chamber temp, heavily weighted towards the wort temp. But the contribution of the chamber temp to the control loop helps to minimize over/under shoots in the wort/beer. As others have mentioned, set your compressor delay to the max possible (10 minutes for many common controllers.) If you really want tight control of the wort/beer temp, use a controller like a BrewPi which looks at both liquid temp and chamber temp, and is extremely good at keeping an even liquid temp.
Brew on
Doug check out that auber controller I linked. Isn't that basically a brewPi?
The two temp probe Auber controller attempts to do something similar to the BrewPi, but it does not use any kind of algorithm to learn the kinetics of the chamber vs. liquid temp variation, which I believe the BrewPi does. The BrewPi has been shown to be able to control the liquid temp to +/- a few tenths of a degree. I haven't seen any data yet on the new Auber controller. It may work well, or it may not work any better than an insulated probe on the outside of the fermenter (which has been shown to be able to control to +/- 1 or 2 degrees.) It will be interesting to see user reports on it.
Brew on
Hmmm. Wish I would have researched this a little more before I drilled a hole in my fermenter to install the thermowell. I have looked into building a BrewPi setup but with a little one on the way my money has gotten a little tighter. Maybe this Auber controller will be a better more cost efficient option for me down the road. Thank you for sharing that.
Just because you drilled a hole does not mean you have to use the hole. Take Doug's advice and tape the probe to the outside of the fermenter and cover it with insulation. It will also work fairly well even without insulation.
Also, disconnecting the heater will help a great deal. Why is the heater even connected?
Also, disconnecting the heater will help a great deal. Why is the heater even connected?
Relax a bit. Controlling the fermentation temperature within a tenth of a degree isn't necessary. If you keep the fermenting beer within a 5 degree range it will be good enough.
SlitheryDee
General Manager
I'm not familiar with that controller, but
my inkbird allows you to set a differential for the heating and cooling functions individually. What it does is tell the controller how many degrees past the set temperature it should allow before activating heating or cooling. if you don't want the heat to kick on you can just set the heat differential to some very high number that you know would never occur under normal operating circumstances.
my inkbird allows you to set a differential for the heating and cooling functions individually. What it does is tell the controller how many degrees past the set temperature it should allow before activating heating or cooling. if you don't want the heat to kick on you can just set the heat differential to some very high number that you know would never occur under normal operating circumstances.
LarMoeCur
Well-Known Member
Winner!
Two things will fix this.
One putting your temp probe in the center of the beer. The mass of all that liquid will buffer the cooling and heating cycles to help prevent over/under shooting. If you can't do that. Then tape the probe to the side of the fermenter. I tape a mine to the side and cover with a new dry sponge to insulate if from the ambient air.
And two, setting up your controllers differential values correctly. Heating DV should be 2-3 degrees below your desired temperature. And cooling should be 1 or .5 (if you worried) above your desired temp. In the winter if it get's really cold you may have to swap those settings.
JONNYROTTEN
Well-Known Member
So far you've gotten tape the probe to the bucket for the best results and put the probe in the center for the best results....welcome to the world of homebrew.
I did the taping/strapping way for a while and it was a pain in the neck plus I was always wondering if air was getting under the insulation giving a false liquid reading.
I switched to a thermowell and never looked back. You cant get more accurate than actually being IN the liquid....plus its just so damn easy to stick the probe down the tube. PLUS if your liquid temp isn't exactly the same as your set temp when you first start fermentation and your probe is taped on your REALLY going to get an overshoot as the fridge will never shut off trying to bring down the liquid temp. Also you need to measure AIR temp when cold crashing so you need to remove the probe or again, you'll have a massive overshoot/frozen chest freezer trying to bring 5 gallons of 65 deg liquid to 32 deg. The fridge will run for hours and hours and freeze up.
My point is you need to install and remove the probe a couple times(usually)throughout the entire fermentation process and pulling a wire out of a tube is WAY easier than taping and untaping leaning in a chest freezer....JMHO
I did the taping/strapping way for a while and it was a pain in the neck plus I was always wondering if air was getting under the insulation giving a false liquid reading.
I switched to a thermowell and never looked back. You cant get more accurate than actually being IN the liquid....plus its just so damn easy to stick the probe down the tube. PLUS if your liquid temp isn't exactly the same as your set temp when you first start fermentation and your probe is taped on your REALLY going to get an overshoot as the fridge will never shut off trying to bring down the liquid temp. Also you need to measure AIR temp when cold crashing so you need to remove the probe or again, you'll have a massive overshoot/frozen chest freezer trying to bring 5 gallons of 65 deg liquid to 32 deg. The fridge will run for hours and hours and freeze up.
My point is you need to install and remove the probe a couple times(usually)throughout the entire fermentation process and pulling a wire out of a tube is WAY easier than taping and untaping leaning in a chest freezer....JMHO
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Only a PID that will learn your system will really control overshoot. That's Brewpi or similar. I second @Leezer saying unhook heater in Summer, it must've been a wise person that told her that 
But also i second @RM-MN, don't fret a couple of degrees.
But also i second @RM-MN, don't fret a couple of degrees.Well I hooked the heater up because the controller could control a heating device, and also I was worried about overshooting and getting it too cold. After some more thinking and the wise words here it seems that during active fermentation it will naturally warm it up anyways if I overshooting by a degree or too, plus maybe I should be so worried about a degree or too anyways. After active fermentation I do pull the probe out to read ambient temps to slowly raise the temp for a diacetyl rest, so the overshooting will only be taking place for the first few days. I think I am going to be disconnecting the heater now. Looking at my manual, it doesn't seem that I can set different values for heating and cooling, just the set temp differential, and the time between cycling between the 2, which I set to 20 minutes last night.
JONNYROTTEN
Well-Known Member
Are you brewing an ale or a lager? If ale no need for a diacetyl rest. If lager yes pull it out and let it free rise to set temp or youll overshoot and the freezer will become an oven. They say you should step up the temp a few deg each day for the diacetyl rest. I just let it rise all the way to 70 with no ill effect.....but that's a whole different topic
I had same experience. The thermowell is way more convenient than the taped on probe. Also the point about starting beer a few degrees above set gen leading to big initial swings. Did not appreciate just how big till I stuck a datalogger probe into the thermowell. Yowza. I'm traveling now but will post details eventually. I've got a few theories about what is going on but am now thinking issue is lack of mixing until the yeast starts rocking. Maybe the beer in center of in mixed fermenter is warmer than beer near edge. Am hopeful limiting high and low temp of the air in the fridge will kill the swings. Only concern now is the probe on the Auber is so big I can't fit my datalogger and probe in the thermowell. I suppose best answer is a second thermowell for the datalogger probe haha but might try tape and insulation on it first.
Only a PID that will learn your system will really control overshoot. That's Brewpi or similar. I second @Leezer saying unhook heater in Summer, it must've been a wise person that told her that
I was under impression PID needs variable power element to control. I use a PID on my mash tun to drive a gas solenoid so it has to run in relay mode. Which eliminates the learning ability. Would think the fridge/freezer in a fermentation chamber would be similar issue. What am I not understanding?
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Well, Brewpi does use relays. The variable part is how long it cycled cooling/heating.
I thought Brewpi would learn cycle times, measuring beertemp, but also measuring chambertemp, in order to cycle off and let it thermally slide to set point. That's my understanding of it.
I thought Brewpi would learn cycle times, measuring beertemp, but also measuring chambertemp, in order to cycle off and let it thermally slide to set point. That's my understanding of it.
I'm doing an ale right now. I have been following the brulosophy fermentation schedule for my last few brews and they have all turned out well so I am sticking to it.
JONNYROTTEN
Well-Known Member
I've seen his lager method.. curios what the ale method is...would you mind sharing. Haven't seen that.
I just copied and pasted this from his site, not sure if there was a different way to share this.
| ALE FERMENTATION SCHEDULE |
1. Chill wort to target fermentation temp (66°-68°F/19˚-20˚C)), place in temp controlled environment, attach insulated temp probe to side of fermentor, and pitch yeast starter.
2. After 2-5 days (OG dependent) of active fermentation, remove*probe from side of fermentor so it measures ambient then bump regulator to 75°F/24˚C* (the Black Box*makes this easy).
3. After 2-5 more days, once FG is stable and the sample is free of off-flavors, cold crash the beer to 30-32°F/0˚C.
4. 12-24 hours later, when the beer is below 50°F/10˚C,*fine with gelatin.
5. 24-48 hours later,*package the beer.
Lately, Ive been letting my beers carbonate at 40 psi for a day before dropping the pressure to ~12 psi for serving, theyre usually ready to drink at this point. Ive found higher OG beers may take a tad longer to fully ferment, and in my opinion, maltier big beers benefit from a bit more conditioning (cold in keg), so those are some exceptions. Otherwise, APA, Brown Ale, ESB, IPA, Dry Stout, Ive had great luck going grain to glass with all of these styles in 2 weeks or less!
Doug hit the nail on the head regarding the overswings. I agree that you dont need the heater, but the point that of automation is to... well... make things work automatically without your manual monitoring or intervention. I also agree with setting the your gap between the heat and cool setpoints such that they dont overlap. However, using a PID with a compressor base refrigerator will cause it to cycle more often.
Other suggestions: add more thermal mass to your chamber. Use water jugs or whatever Is dense to accomplish this. The temp swings will take longer and be slower. This damps (slows) cycling and gives more time for liquid masses to have consistent temps.
Another: since you have a thermowell, just dont install the probe the whole way. Maybe 1/3 in but you can experiment. This will blend the probe Center/Edge type swings.
Be dev
Other suggestions: add more thermal mass to your chamber. Use water jugs or whatever Is dense to accomplish this. The temp swings will take longer and be slower. This damps (slows) cycling and gives more time for liquid masses to have consistent temps.
Another: since you have a thermowell, just dont install the probe the whole way. Maybe 1/3 in but you can experiment. This will blend the probe Center/Edge type swings.
Be dev
