Question about a temp controller

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Decimotox

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Hey everyone. So I just got my freezer and temp controller (Inkbird ITC-308). I plugged it all in to test it out and set it at 40 degrees (gonna do cold crashing soon). It gets to 40, the compressor stops, and then the temp still falls to about 30 degrees, obviously below freezing.

Anyone have any experience with this controller or ones like it and can offer some advice about this temp swing? Total novice with temp controllers myself. Thanks!
 
Chest freezers will exhibit some "over-shoot" because when the compressor stops the evaporator is still filled with dense vapor that continues to suck up thermal energy.

The effect becomes more prominent with less mass inside the chamber, so an empty freezer will show it the worst. Once you stuff it with large volumes of liquid the effect will be attenuated - not completely, but to where it becomes manageable through strategic probe placement.

And to that end, I've always found it most practical to have controller probes monitor what I care about: the beer, whether fermenting, cold-conditioning or dispensing. So I pin my controller probes to carboys and kegs using velcro straps with pads of 1" thick closed cell foam as insulation against the chamber temperature, then set the controllers to whatever temperature I want the beer/wort to be at, and let the systems do the rest...

Cheers!
 
Chest freezers will exhibit some "over-shoot" because when the compressor stops the evaporator is still filled with dense vapor that continues to suck up thermal energy.

The effect becomes more prominent with less mass inside the chamber, so an empty freezer will show it the worst. Once you stuff it with large volumes of liquid the effect will be attenuated - not completely, but to where it becomes manageable through strategic probe placement.

And to that end, I've always found it most practical to have controller probes monitor what I care about: the beer, whether fermenting, cold-conditioning or dispensing. So I pin my controller probes to carboys and kegs using velcro straps with pads of 1" thick closed cell foam as insulation against the chamber temperature, then set the controllers to whatever temperature I want the beer/wort to be at, and let the systems do the rest...

Cheers!

That foam idea is a great idea. Thanks for the input, man! I put my fermentor in there and monitored the temp for the first few cycles of the compressor and it was ranging from about 38-43 degrees, with the set temp at 41, so that's pretty solid. Now that beer is crashing... :D
 
I just picked up a Maytag 15cf freezer and hooked up my johnson controller to it. That had been on a fridge that pretty much stayed nailed to whatever temp I set it to. Really accurate. My freezer has been swinging by 10 degrees today. In fact, my controller was set to 38 and the temp inside was 29! Not cool!! I've only got 3 kegs in there right now and a CO2 tank. Lots of space in there right now. I am planning on storing my empty kegs in there which would take up space, but I don't know if that's enough to regulate. Right now, the probe is just sitting in the air, but it's the same way I had it in the fridge before.

I knocked the freezer to its lowest setting. My thinking was that it wouldn't run as cold, but now I'm thinking that setting doesn't affect how cold the air being pumped in is, but is just a thermostat for turning the compressor on and off. So it shouldn't matter if it's on the coldest or warmest setting because they are all going to be below freezing, right?

I bumped my controller to 42 which will hopefully keep my lager from freezing overnight! I may be rethinking fermenting in here if it has this much temperature swing. What kind of temp swing would you expect if you're taping the probe to a bottle of water or setting it against the keg? Is the foam piece to go between the keg and the probe or between the probe and the air?
 
The insulation goes over the probe to minimize the chamber temperature's effect - you want to measure the vessel temperature, not the air temperature. The better the insulation the tighter the resolution.

This plot is from my keezer this morning, showing the last 24 hours of operation. The traces show the beer temperature versus cabinet temperature measured at the lid and floor, plus the air temp of my tap tower and the room temperature.

The beer temperature swings 2°F max while the air temperature swings a good 10 degrees or more...

keezer_plot_012117.jpg

Cheers!
 
what do you use to track that?

The insulation goes over the probe to minimize the chamber temperature's effect - you want to measure the vessel temperature, not the air temperature. The better the insulation the tighter the resolution.

This plot is from my keezer this morning, showing the last 24 hours of operation. The traces show the beer temperature versus cabinet temperature measured at the lid and floor, plus the air temp of my tap tower and the room temperature.

The beer temperature swings 2°F max while the air temperature swings a good 10 degrees or more...

View attachment 385599



Cheers!
 
I agree with what has been said here. For my fridge/fermentation cabinet I measure what I am trying to control. In the refrigerator portion, I have the temp probe in a 16oz plastic bottle filled with water. When i am fermenting, I attach the probe to the outside of the carboy with tape and insulation.

Here is a 6 hour temp graph of my refrigerator. The "Fridge Temp" probe is the one in the water and the "Beer Temp" probe is in the free air (yeah, it is kind of backwards, but it works.). I have my temp set for 39°F with a max overshoot of 0.9°F. The air temp ranges from 20° to about 44°F but the 16oz of water only ranges from 38.9° to 39.9°F.

Fridge.png
 
The only reason for attaching/insulating the probe to primary is to offset the rising temp during fermentation. There is zero reason to attach the probe to the primary during a cold crash. Even if the temp drops past the setpoint it will balance out long before it affects the temp of 5 liquid gallons. In fact if you attach/insulate the probe at the beginning of a cold crash when the beer is still at ferment temp say 68, the compressor will never shut off trying to cool 5 gallons of beer.

For cold crashing just hang the probe in the air in the fridge set to 30-32 deg the entire cold crash and let the freezer do its thing.
 
The only reason for attaching/insulating the probe to primary is to offset the rising temp during fermentation. There is zero reason to attach the probe to the primary during a cold crash. Even if the temp drops past the setpoint it will balance out long before it affects the temp of 5 liquid gallons. In fact if you attach/insulate the probe at the beginning of a cold crash when the beer is still at ferment temp say 68, the compressor will never shut off trying to cool 5 gallons of beer.

For cold crashing just hang the probe in the air in the fridge set to 30-32 deg the entire cold crash and let the freezer do its thing.

That only holds true for very simple on/off controllers. In my system I can set a max deviation from current temp (or something like that) so that when cold crashing it doesn't run the cooling nonstop. If I set that deviation to 10 degrees and the current temp is 65 degrees, it won't drive the chamber temp lover than 55 degrees. It is a PID controller so that target is always changing until the beer reaches the set point.

In the OP's case where an ITC-308 is being used, when the freezer gets to its internal thermostat setting, the compressor will turn off even if the controller is still calling for cooling. The compressor won't run nonstop. If the OP did what you suggest and just control the air temp, the controller would probably constantly hit the compressor delay setting in the beginning of the cold crash.
 
That only holds true for very simple on/off controllers. In my system I can set a max deviation from current temp (or something like that) so that when cold crashing it doesn't run the cooling nonstop. If I set that deviation to 10 degrees and the current temp is 65 degrees, it won't drive the chamber temp lover than 55 degrees. It is a PID controller so that target is always changing until the beer reaches the set point.

In the OP's case where an ITC-308 is being used, when the freezer gets to its internal thermostat setting, the compressor will turn off even if the controller is still calling for cooling. The compressor won't run nonstop.
What controller do you have? I have 2 different controllers and have a deviation setting on both. Its so the fridge doesn't cycle on/off continuously with small temp changes and burn out the fridge not to keep it from running for extended periods. Even by your logic of 10 degrees,You know how long it takes to drop 5 gallons 10 degrees...a LONG time. The fridge would be running for hours and hours with an insulated probe or thermowell. The air temp would get to low 20's or lower while the beer was still chilling 65. Hanging the probe in the air the fridge will cool to 32 quickly as the fridge was designed and the beer will follow suit
 
If one doesn't bypass a fridge's original thermostat, it will ultimately govern how low the chamber temperature can go, which can provide some protection for the compressor.

For example, if you set an external thermostat for a cold crash to 34°F beer temperature, and set the fridge's thermostat to the same temperature, the fridge will limit compressor run time based on the fridge thermostat setting, as the chamber temperature will get to 34°F faster than the beer temperature. So the compressor will cycle, rather lazily.

You'd anticipate a slight stair-step temperature plot for the beer, while the fridge plot might look like a square wave until the beer reaches the desired temperature.

I'd expect similar behavior using a freezer...except the cycling might actually be problematic...

Cheers!
 
What controller do you have? I have 2 different controllers and have a deviation setting on both. Its so the fridge doesn't cycle on/off continuously with small temp changes and burn out the fridge not to keep it from running for extended periods. Even by your logic of 10 degrees,You know how long it takes to drop 5 gallons 10 degrees...a LONG time. The fridge would be running for hours and hours with an insulated probe or thermowell. The air temp would get to low 20's or lower while the beer was still chilling 55. Hanging the probe in the air the fridge will cool to 32 quickly as the fridge was designed and the beer will follow suit

I am using a Raspberry Pi with Arduinos and running BrewPi. The setting I mentioned isn't setting the deviation of the beer temp, it is telling the controller to not change the air temp of the chamber by more than 10 degrees at a time when it is trying to cold crash.
 
If one doesn't bypass a fridge's original thermostat, it will ultimately govern how low the chamber temperature can go, which can provide some protection for the compressor.

For example, if you set an external thermostat for a cold crash to 34°F beer temperature, and set the fridge's thermostat to the same temperature, the fridge will limit compressor run time based on the fridge thermostat setting, as the chamber temperature will get to 34°F faster than the beer temperature. So the compressor will cycle, rather lazily.

You'd anticipate a slight stair-step temperature plot for the beer, while the fridge plot might look like a square wave until the beer reaches the desired temperature.

I'd expect similar behavior using a freezer...

Cheers!

Exactly
 
I am using a Raspberry Pi with Arduinos and running BrewPi. The setting I mentioned isn't setting the deviation of the beer temp, it is telling the controller to not change the air temp of the chamber by more than 10 degrees at a time when it is trying to cold crash.
Interesting...I'm happy with my controller but would like to find out more about this system....Now I have something to keep me busy this evening :D
 
I am using a Raspberry Pi with Arduinos and running BrewPi. The setting I mentioned isn't setting the deviation of the beer temp, it is telling the controller to not change the air temp of the chamber by more than 10 degrees at a time when it is trying to cold crash.
That's a pretty cool system. I heard about the Brewpi but never looked into it. If I had a real time fermenting graph on my computer I'd be glued to it for a week straight. I guess the real question is does it make better beer than a basic Inkbird that holds temp to 1 deg or is it more of a cool factor with the pre programmed step up/down and charting/saving data?
 
I've been running numerous instances of BrewPi for a couple of years, and the two major attractions are the web-accessibility to both status and control, and being able to use profiles that take a batch from pitch through crash.

If someone grafted a web-enabled gui to an STC-1000+ it'd be about 90% of a BrewPi setup...

Cheers!
 
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