Fermentation chamber temp overshoot. What do you do?

[p_p]

Hi,
I just finished assembling an undercounter fridge fermentation chamber using an stc 1000+.
I did a test run using water and noticed that on the cooling cycle the temperature overshoot down by more than 1F (0.7C to be precise). The temperature probe is located in contact with the liquid using a thermowell.

Is this something to worry about? Should I consider insulating the bucket so it is afrected by ambient temperature to a lesser degree?

I guess I could set the set point 0.2C above target and a small 0.1C hysteresis to kind of let the temperature ripple around target?

What are your thoughts? What do you guys do?

Thanks

 

[cilestiok]

You're saying your system has an error of +/- 1 degree? That's as close as it gets my friend.

 

[m00ps]

Im confused. A 1F temperature difference isnt going to hurt anything....

I know theres a setting for how much over/under the set temp before it kicks on. You could try changing that

 

[CUrchin]

Turn it up 1 degree.

 

[TKH]

I believe that's how the temp controller works. It cools it down by one or two degrees more than target and then once temperature gets more than one to two degrees above temp it kicks in again. As m00ps pointed out, this setting should be adjustable. However, you don't want your compressor kicking on and off every minute or two as this will dramatically shorten its life. Sounds like the temp controller is working as it should!

 

[GrogNerd]

not sure about an STC1000, but the BrewPi can keep it within ±¼°

the data logging & web interface are bonuses

 

[p_p]

Thank you all for your replies

 

[p_p]

not sure about an STC1000, but the BrewPi can keep it within ±¼°

the data logging & web interface are bonuses

View attachment 326290

Interesting. Do you have a plot including the on/off state of the compressor?

Does the plot correspond to active fermentation? I think an on/off controller will perform better in its cooling cycle if the wort is being heated by fermentation activity... That should take the edge off the overshoot, I guess.

Thanks

 

[GrogNerd]

It is my currently fermenting IPA

the 2 stages are represented at the bottom of the graph by blue (cooling) and red (heating) bars above the timestamps

 

[p_p]

It is my currently fermenting IPA

the 2 stages are represented at the bottom of the graph by blue (cooling) and red (heating) bars above the timestamps

I see, thanks.
I read the brew pi has a more advanced temperature control algorithm, seems that it predicts overshoots and controls the fridge accordingly.

The stc is a simple on/off controller, I expected overshoots but was hoping the thermal mass of the FV would help damping. I wasn't expecting such a big overshoot.

Cheers for sharing.

 

[Brettomomyces]

You can change the F2 setting to determine the lower and upper limits of the target temp you're shooting for, and F3 to put a lag time on your compressor cycle. I generally leave my F2 at 1C and 10 minutes for F3.

 

[tracyk]

I think if you read the instructions that came with the STC1000 it states something on the line of 1 or 2 degrees. I have mine on a 2 degree differentional, but I also have my fermentor completely full for thermal mass more than anything. If I do not have enough beer to ferment, then I have extra 3 and 5 gallon water bottles that I fill up for thermal mass. Mine comes one about twice an hour and keeps it between 64 and 66 degrees. Initially it will bring it down to 63.8 then go off and does not come back on until 66 degrees.

Yeah that is about as good as you can expect with the STC1000.

 

[p_p]

I think if you read the instructions that came with the STC1000 it states something on the line of 1 or 2 degrees. I have mine on a 2 degree differentional, but I also have my fermentor completely full for thermal mass more than anything. If I do not have enough beer to ferment, then I have extra 3 and 5 gallon water bottles that I fill up for thermal mass. Mine comes one about twice an hour and keeps it between 64 and 66 degrees. Initially it will bring it down to 63.8 then go off and does not come back on until 66 degrees.

Yeah that is about as good as you can expect with the STC1000.

I didn't think of increasing the thermal mass by putting a few bottles of water in, good idea, thanks

 

[cilestiok]

I just read back over your initial post. Are you referring to the chamber temp or the liquid temp?

 

[Gavin C]

Set your hysteresis to the minimum and delay to the maximum.

That's +/- 0.3 C and 10 minutes respectively on my bog standard STC 1000

It appears from unpublished data another HBT user has compiled and fits with basic physics that the use of a thermowell as opposed to placing the probe insulated on the side of the fermentor can and does lead to more over/under shoot of temperature of the fermenting beer.

But this is really splitting hairs.

if you change your settings to what I outline above you will have excellent monitoring and control of fermentation temperatures with a thermowell. All the rest is just brewers' mental handwringing.

 

[alphaomega]

You probably could experiment with:
* insulation on the probe (less of it)
* hysteresis setting (hy)
* cooling delay (cd)
* and of course, if you do use a heater it should be low wattage (as in ~30W) and you should not use it if not needed.

You might be able to get less swing, but as others have said, it could be at the expense of your compressor (short cycling).

 

[RM-MN]

You probably could experiment with:
* insulation on the probe (less of it)
* hysteresis setting (hy)
* cooling delay (cd)
* and of course, if you do use a heater it should be low wattage (as in ~30W) and you should not use it if not needed.

You might be able to get less swing, but as others have said, it could be at the expense of your compressor (short cycling).

You should also experiment with a much larger hysteresis and see if you can detect the difference in flavor if you have a +/- 5 degree swing in the temperature. I think you are tilting at windmills.:rockin: