Temperature swings with Inkbird + chest freezer

[Andy Brosius]

I'm currently using a chest freezer attached to an Inkbird device to control my fermentation temperature. The problem is that I'm getting pretty large temperature swings. If I have it set at 68 F, when the freezer kicks on it will cool the ambient air in the freezer all the way down to 60, then slowly heat back up to 69 F before switching on again.

I know that the actual temperature of the wort would be higher, and likely not subject to such massive swings, but I do wonder if I should do something about it (e.g., put some bricks in the freezer to help buffer the temp swings).

Is this something I should be worried about? Thanks!

EDIT: I realized that some people have a heating device attached as well, which could definitely help achieve a better temperature balance. I currently don't have any heating mechanism.

 

[IslandLizard]

Where's your probe placed?

Placement of the probe is critical to the unit's functioning as you envisioned it.
We usually tape the probe to the fermenter side with some insulating foam over it. That way it measures a combination of the beer temp inside, and the outer temp of the fermenter wall.

If you hang the probe in the beer you tend to get those kind of huge swings due to the thermal mass of the beer.

 

[Andy Brosius]

I just have it dangling in the corner, just above the floor. Obviously your method would give a more accurate reading of the beer temp - I'll give it a try.

Thanks!

 

[balrog]

and you need a fan

 

[VikeMan]

If I have it set at 68 F, when the freezer kicks on it will cool the ambient air in the freezer all the way down to 60, then slowly heat back up to 69 F before switching on again.

What do you have the controller's differential set to?

 

[balrog]

definitely measure the beer, it's what you want the inkbird to control anyway
and a friend has had good luck with smaller 3g batches being "overblown" by the freezer, by putting the ferm bucket off the freezer floor and add a bucket or two of water in there to act as thermal mass.

But get a fan, and tape the probe to the fermenter's side, covered so as not to "see" the air temp.

 

[IslandLizard]

with some insulating foam over it.

A 2x2" piece of 1/4"-3/8" thick packing foam works well. Tape down or tie around. You want to shield the probe from direct exposure to the cold air in the freezer as it is totally immaterial for the process. You want to measure the beer temp without overshooting the target too much.

This may also save your freezer from early failure by cycling on/off every 10 minutes.

 

[Andy Brosius]

Thanks, guys. Excellent advice. Adding a couple of buckets of water also sounds like a great way to buffer the temperature swings a bit.

What do you have the controller's differential set to?

I have it set at 1 degree, so I'm not really sure what's going on. I'll try the tips above and hopefully it will fix it.

 

[RM-MN]

Thanks, guys. Excellent advice. Adding a couple of buckets of water also sounds like a great way to buffer the temperature swings a bit.


I have it set at 1 degree, so I'm not really sure what's going on. I'll try the tips above and hopefully it will fix it.

The temperature swings are of no consequence and you don't need the buckets of water. It also is no big deal if the temperature of the beer swings more than one degree. I'd probably set the controller to 2 or 3 degrees as then the freezer would not cycle as often but run longer when it turns on. I think the cycling will damage the freezer compressor motor so limiting that will help your freezer last longer.

 

[VikeMan]

I have it set at 1 degree, so I'm not really sure what's going on. I'll try the tips above and hopefully it will fix it.

Okay. So you had the DIF set to one degree, and the probe was hanging loose in the freezer, and the temp was swinging 9 degrees. When the temp gets down to 68F (69F - 1F) or thereabout, does the controller cut the power to the freezer?

 

[AAAV8R]

Although your ambient air temperature may be swinging several degrees, the temperature of the liquid does not change that fast. I would say it is safe to assume that your actual beer temp is sitting in the middle of your temperature mean. Without taking a direct reading, you will never know. I use one of these:

https://www.ebay.com/itm/Carboy-Sto...621745?hash=item4647f00031:g:hyMAAOSw2fRdKO~1

I use the same set up as you with the freezer. It's a cheap alternative to an expensive glycol set up. With that being said, it's going to have some limitations. Your beer may swing a few degrees in temperature, but are you or your friends really going to notice the effects in the final product?

BTW, that is a good buy on that product above. My local homebrew shop wanted $33.99 for it.

 

[ike8228]

In the inkbird there is another setting you have to consider. Look in the manual, I don’t remember the specific name, but it is the duty cycle that allows the motor to rest. Regardless of your temperature swing, if the motor had been on just a few minutes ago, it won’t turn on. This setting allows you to change the number of minutes between on/off cycles too. It is designed to prevent failure. On/off on/off will kill the motor eventually.

To help prevent this to some degree, make sure the chamber is not in direct sunlight or next to something warm like a furnace. Check your seals. Etc. this will help it maintain its temp longer.

That big of a swing in temp is not good for the yeast health. It could go into shock. If the fridge is kicking on with a 9 degree swing is probably much faster than if you just had it sitting in the closest. Kind of defeats the purpose of temp control. You want the temp as constant as possible.

 

[VikeMan]

Although your ambient air temperature may be swinging several degrees, the temperature of the liquid does not change that fast. I would say it is safe to assume that your actual beer temp is sitting in the middle of your temperature mean.

During fermentation, the wort/beer temp is going to be something higher than the mean ambient temp.

 

[Andy Brosius]

RM-NM: This is what I thought initially, but I've been having some consistency issues and wondered if at least part of it could be attributed to fluctuating temperatures. I plan to buy a tilt in the near future, which should allow me to find out for certain.

AAAV8R: That looks like a very useful piece of equipment - thanks for the suggestion.

Vikeman: If I have it set at 68 F, it switches on at 69 F and off at 68 F. The temperature then continues to drop even though the power is off, which to me indicates a lag in the probe reading. But since the freezer is only on for 1-2 minutes, it's hard to imagine the wort itself being cooled to such an extent.

 

[VikeMan]

Vikeman: If I have it set at 68 F, it switches on at 69 F and off at 68 F. The temperature then continues to drop even though the power is off, which to me indicates a lag in the probe reading.

If the power actually switches off, but the temperature continues to drop, that's not a lag by the probe/controller, that's the freezer continuing to cool down because the coils are still exchanging heat with the freezer compartment.

OTOH, if the power is not actually switching off, that's probably due to the setting @ike8228 mentioned, i.e. the setting that reduces frequent on/off cycling.

If you really want to dial in your system, you'll want to understand which it is.

But since the freezer is only on for 1-2 minutes, it's hard to imagine the wort itself being cooled to such an extent.

The wort will basically follow the average freezer compartment temp, plus a bump due to the heat generated by fermentation. If the freezer continues to get cold (down to 60F), that's part of that average compartment temp, regardless of why it continues to go down.

 

[Andy Brosius]

The freezer is definitely off. It takes quite a long time (hours) for the temperature to increase enough for it to switch back on, so I'm not concerned about the possibility of burning out the motor.

Your explanation of the coils still exchanging heat even after the power switches off makes a lot of sense, so that's likely what's happening.

What matters to me most is that the temperature of the wort remains fairly constant, and it seems like that would be the case, based on what you and others have said. It would be nice to have a more accurate temperature reading, but as others have pointed out that would likely require some different equipment.

Thanks again.

 

[Jim R]

All you need to do is tape the temperature probe on the fermenter with surrounding insulation so it measures the actual wort temperature as suggested. My Inkbird is set for 66 degrees with 1 degree differential and after the first few hours it levels off to only fluctuate 1-2 degrees. I am sure the air temperature in the freezer fluctuates more but it doesn't matter.

 

[A1sportsdad]

I have a thermowell with a temperature probe in the center or the wort. Do not worry about the air temp getting down to 60F. I would let is drop down to 45F-50F if you can. Do you know how much air it would take to cool down 5 gallons of wort. Water has a much higher heat capacity than air. That volume of 60F air is hardly going to make a dent on the wort temperature. You need to be measuring the wort temperature and allow the Inkbird to continue to cycle on whenever the wort temperature is above setpoint. I have a 1 degree F deadband in mine, so it will initially kick on at 69F and continue to run until the wort temp goes down to 67F. Then shuts off until is goes back up to 69F. If I could program in a 0.5 degree F deadband I would. The wort temperature will not change that rapidly, so it would not be doing too much ON and OFF cycling.

 

[eric19312]

As somebody else said get a fan in there. This will avoid stratification of the air in the freezer and will increase heat exchange between the walls of the freezer and the air in the freezer and the fermentor.

Some sort of temperature data logging is a nice way to see how you are doing. A Tilt hydrometer is good way to go and lets you watch the current brew from the web and see how you are actually doing with temperature control. I used one of these Elitech RC-4 LCD Display USB Temperature Data Logger Recorder External Sensor | eBay

when I was looking to diagnose a temperature control issue. Works same as the probe on the inkbird but keeps a data log. You have to connect it to a computer to download the data so I don't use it all the time but it really helped with troubleshooting. I ended up adding a fan and replacing my STC-1000 controller (DIY Inkbird made back before Inkbirds were available) with an Auber TD500 which allows me to control both the temperature in the chamber and the temperature of the fermenting beer. Basically it prevents the chamber itself from getting too hot or cold resulting in overshooting fermentation temperature targets.

 

[Andy Brosius]

Thanks, guys. I'll start taping the probe to the side of the fermenter (with insulation) and will get a fan in there. I'll also order a tilt at some point in the not-so-distant future.

 

[madscientist451]

I don't use an Inkbird, but I place the probe from my Johnson Control A419 in an old ice tea jug filled with water and it works pretty good. I'm a lazy brewer and don't wan't the hassle of taping the probe to the carboy. Also, sometimes I have more than one carboy in there. Getting the carboy off the bottom of the freezer is a good tip.

 

[RM-MN]

I don't use an Inkbird, but I place the probe from my Johnson Control A419 in an old ice tea jug filled with water and it works pretty good. I'm a lazy brewer and don't wan't the hassle of taping the probe to the carboy. Also, sometimes I have more than one carboy in there. Getting the carboy off the bottom of the freezer is a good tip.

With the probe in the jug of water you are only partially controlling the fermentation temperature. Sometimes the ferment goes slow and your water and the beer will be very close to the same temperature but on a very vigorous fermentation they can be quite different. Spend the few seconds and tape the probe where it measures the beer temp.

 

[eric19312]

I don't use an Inkbird, but I place the probe from my Johnson Control A419 in an old ice tea jug filled with water and it works pretty good. I'm a lazy brewer and don't wan't the hassle of taping the probe to the carboy. Also, sometimes I have more than one carboy in there. Getting the carboy off the bottom of the freezer is a good tip.

Control the temperature based on the newest batch. It is the one most susceptible to throwing off flavors from hyoeractive yeast and spiking in temp. Taping the probe is hardly going to add a noticeable amount of time to your brewday.

 

[Stormcrow]

Sounds like you're going to tape the probe to the fermenter, which is good. You had mentioned earlier putting bricks or something in the freezer. The more of anything you put in the freezer, the slower the temp swing of ambient temperature is going to be, so I think it wouldn't hurt to do that as well. Will be more stable and efficient in the long run.

 

[Andy Brosius]

Taping the probe to the side of the fermenter seems to have done the trick.

It probably helps that the rest of the freezer is currently stocked with half-liter bottles of saison (as effective as bricks but far tastier).