How do you avoid temp swings in a fermentation chamber??

[jbb3]

I'm starting a fermentation chamber build tomorrow. I already have an STC-1000 controller and I'll be fermenting in a Fastferment which has a thermowell in it. I plan to use the temp probe of the STC-1000 in the thermowell of the Fastferment for sensing the temp of the wort.

Trying to think through this; when the controller senses the temp of the wort goes above the set value, the controller will turn on the frig which starts to cool the air in the chamber. But the thermal mass of the wort will be slow to react to the cool air. So when the wort finally does cool and the controller senses the wort is below the set value, it turns off the frig.

But the air in the chamber will be so cool that it continues to cool the wort well below the set value. Then the wort will warm up and the cycle will start over again.

Given the slow reaction to temp changes of the wort compared to the air temp in the chamber, how do you avoid having the controller cause the temp swings in the wort due to this differential?? :smack:

 

[La_Moustachio]

I use a stc-1000 to control a chest freezer as my fermentation chamber and I have a brew belt wired in as a heating element. I've got it set so that it doesn't deviate more than .3 deg C from my set temperature. It works quite well.


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[cannman]

I had the same concern. If you're using the stock programming on the STC-1000, setting the the swing temp to 0.5c and incorporating a heat mat taped to the side fixed things for me. The heat mat will only curb the drop and the STC will shut it off. After about an hour into the initial go, a happy equilibrium will hit and you'll cruise a vast majority of the time between the 1c range (-0.5c/0.5c)

 

[riderkb]

I'm starting a fermentation chamber build tomorrow. I already have an STC-1000 controller and I'll be fermenting in a Fastferment which has a thermowell in it. I plan to use the temp probe of the STC-1000 in the thermowell of the Fastferment for sensing the temp of the wort.

Trying to think through this; when the controller senses the temp of the wort goes above the set value, the controller will turn on the frig which starts to cool the air in the chamber. But the thermal mass of the wort will be slow to react to the cool air. So when the wort finally does cool and the controller senses the wort is below the set value, it turns off the frig.

But the air in the chamber will be so cool that it continues to cool the wort well below the set value. Then the wort will warm up and the cycle will start over again.

Given the slow reaction to temp changes of the wort compared to the air temp in the chamber, how do you avoid having the controller cause the temp swings in the wort due to this differential?? :smack:

If it becomes a problem you can change your set point to just a little below the current temp. That should cut down on the overshoot. As it cools off you can keep adjusting the set point lower. The fastest way is to put the set point half way between the current temp and the target. It will overshoot the set point and coast to a stop near the target. After playing with it you will get a feel for how big a set point change you can make without starting an oscillation.

 

[ChelisHubby]

Does the yeast yeast suffer or the beer taste suffer if the temp varies one degree?

 

[Owly055]

Does the yeast yeast suffer or the beer taste suffer if the temp varies one degree?

This is a bit extreme I think...... There is no question that temp control is going to give better and more consistent results than fermenting on the kitchen table at my house where temps vary significantly, but worrying about a couple of degrees seems a bit extreme.


HW

 

[cannman]

This is a bit extreme I think...... There is no question that temp control is going to give better and more consistent results than fermenting on the kitchen table at my house where temps vary significantly, but worrying about a couple of degrees seems a bit extreme.





HW

It's an easy fix with equipment that may be hanging around anyway.

 

[The_Bishop]

If the sensor is strapped to the side of the fermenter and semi-insulated, it gets a combination of fermenter temps and air temps. This prevents the wild swings up and down you'd get with a thermowell that only gets the temps in the center of the wort/beer/whatever. When the sensor is so isolated from the air in the chamber, it's going to keep the cold or heat on until the center of the fermenter is at the cutoff temperature, which means the liquid near the side of the fermenter is over cooled/heated. The temps will eventually equalize in the fermenter, which will cause the temperature to overshoot (or undershoot, if cooling.)

 

[Peyope]

I keep my ambient temp in the freezer at a specific temperature and understand the carboy will be a few degrees warmer. I should probably put something down so that the carboy is not touching the cooling element but haven't had issues yet.

 

[Beernik]

A fan.

The fan circulates the heat away from the fermenter and mixes it with the cold air of the freezer.

The probe attached to the thermowell will read the temperature of the wort. It will tell the freezer to run at a temperature that creates air cold enough for the heat to be disapated by the fan.

 

[The_Bishop]

A fan is necessary to avoid temperature stratification in the chamber, but I'm not convinced about the thermowell. I tried both ways, thermowell and sensor strapped to the side of the carboy and had a much more stable temperature. The thermowell resulted in large temperature swings up and down and excessive cycling.

 

[zach976]

I tape my temperature controller probe to the side of my fermenter with bubble wrap. I run a different temperature probe to my thermowell, so I can see actual liquid temperature.


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[jbb3]

Got to love this forum and the folks on it!

Some great answers on how to deal with temperature swings! I plan to add a small fan in the chamber and use some of the other techniques mentioned to mitigate the oscillating temp swings of the wort.

The build is going well. Here is a sneak preview. I'll post all my adventures once done. Stay tuned...

 

[riderkb]

I used a piece of Masonite with a white plastic top layer for the bottom of my chamber. It was sold at lowes as DIY whiteboard surface. The foam insulation needs some sort of easy-clean, protective cover on it, at least on the bottom.

Good luck with your project.

 

[emyers]

A PID would remedy this for 3x the cost of the stc if your really that concerned. I ferment in two pails and a keggle so a thermowell isn't the best option with different volumes and vessels. I monitor air temps and set 1-2c below target temps factoring in heat generated by fermentation.

 

[jleiii]

The thermal mass of the beer is very likely much higher than the thermal mass of the chamber, so your beer overshoot is unlikely to be more than slight.

In my purpose built 4 section chamber I use only fans for heating as I quickly learned that they provide enough heat to maintain 15F over ambient, no problem. The chamber temp never gets warm enough to cause any overshoot.
I don't have enough experience on the cooling side yet to gauge the undershoot, but it was not obvious on the first batch. The ambient temp dropped 10F in a weeks time so I had to switch to heating! I have a glycol chiller and use the same fan with a mini radiator for cooling. It is capable of 25 or 30F below ambient, so overshoot could be an issue. I'll have to wait till next year to see for sure.

 

[The542]

Along with the recommendations above, keep your ferm chamber as full as possible. I put as much bottled water, or as many things that can ferment at the same temperature. This adds thermal mass. Your freezer will cycle less often and everything will stay more consistent.

 

[cgrivois]

I tape my temperature controller probe to the side of my fermenter with bubble wrap. I run a different temperature probe to my thermowell, so I can see actual liquid temperature.


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Do you see a big difference between the two?

 

[Weezy]

Set the temp knob in the fridge to half way, max. Keeps the temp differential lower and will help keep the wort from getting over chilled.

Also, let the thermistor dangle in the air until the wort reaches target temp before you pitch. After you pitch, then put the thermistor in the well. This keeps the wort from being over chilled at the beginning, which is the biggest temp differential time during fermentation typically.

 

[beernutz]

Do you see a big difference between the two?

I'm not zach and this may not be what you were asking but on my last brew I wrapped my temp probe in bubble wrap and secured it to the side of the primary bucket with a bungee cord. I set the freezer temp to 65 and the liquid temp was 76 in the bucket as measured with an infrared temperature gun.

I use a remote indoor/outdoor thermometer to measure the air temp in the freezer and was pretty surprised when it showed the freezer had dropped down into the mid 40s an hour or so after the primary went into the fermentation chamber.

On previous batches where I just hung the temp probe near the bottom of the freezer but didn't attach it to the primary bucket the air temp would drop a few degrees, maybe 4 or 5, below the set temp. I had never before seen anything like the 20 degree drop in the air temp that happened this time.

At the time I thought my indoor/outdoor thermometer might have been malfunctioning so I replaced all the batteries but after doing that it showed the same temp as before. A few hours later the temp was up into the mid fifties and 24 hours later it showed that the temp was the same as the set temp which is some evidence that the thermometer was measuring correctly all along. So I learned the lesson that it does make a big difference where the probe is in the fermentation chamber.

 

[zach976]

Do you see a big difference between the two?

They are within a couple degrees normally. I actually used my trusted thermometer in the thermowell to calibrate my STC controller. It was off a few degrees out of the box.


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[jbb3]

Thanks to everyone for sharing your experiences, comments, suggestions and opinions! I want you to know I did listen and will put much of this great information into practice.

The beast is done! Check it out...

https://www.homebrewtalk.com/f51/my-diy-fermentation-chamber-build-499635/

I hope give it a test run this weekend! Maybe a Sweetwater IPA clone??

 

[jbb3]

My initial test of the new chamber with an empty fermenter was a little concerning.

The temperature has dropped here in the Atlanta area so no need for cooling right now (may change tomorrow). I'm using a small ceramic heater as my heat source.

The for the initial test, I used 65 degrees as my set point. Ambient temp was in the mid 50s. The first run overshot the 65 degree target by 4.9 degrees. Not good. And each time the heat cycle kicked on it was the same thing. Around 4.9 deg overshoot.

I checked the STC and it was on the default of 1 deg in temp swing. I changed that setting to .5 deg. and turned the ceramic heater all the way down as low as it would go.

The next run was better. But the overshoot was still about 1.8 deg. Add that to the .5 deg in swing, still not where I would like it to be.

I took a leap of faith and went ahead with brew day. I thought I would figure something out...

With a full fermenter and the probe in the thermowell, I have been pleasantly surprised at the performance and control-ability of the new chamber. When the heating cycle kicks in, I may get a .1 deg overshoot. At most, I get an occasional .2 deg overshoot. So overall I'm getting less than a degree in temp swing from when the heat cycle kicks on until the cycle turns off and the temp tops out.

I can't beat that with a big stick!

It's pretty cool to walk out and see everything working as hoped...