Chest freezer fermenter issues: equipment vs. User Error?

[a_gunslinger]

I realize it might be user error. What some people call the ID10T (idiot) error.

I got a 5.5 cu Galanz chest freezer that was on sale. Combined it with the Inkbird ITC 308 wifi. For heat was using a small personal heater (Honeywell Amazon.com: Honeywell HCE100B Heat Bud Ceramic Heater Black Energy Efficient Space Saving Portable Personal Heater With 2 Heat Settings for Home, School, Office: Home & Kitchen).

Problem Im having is it seems the freezer doesnt actuall stop cooling when its turned off.

I have the setting at:

Target temp = 67 degrees (assumption its actually 68 in fermenter)
Cooling differential = 66 degrees
Heating differential = 68 degrees

When the Inbird shows 69 the freezer comes on. But when it hits 67, the freezer does turn off but keep cooling for 10+ degrees? Temps keep plummeting even though freezer off.

It must be user error (or a homebrew unfriednly chest freezer model):

Galanz 5.0 cu ft Chest Freezer

 

[day_trippr]

I presume this was a starkly empty chest freezer?

If so, there's like almost no thermal mass to smooth out peaks and valleys in the temperature profile, so a dangling probe in an empty chest freezer is going to illustrate the "cold lag" of an freezer evaporator that is full of dense vapor when the compressor shuts down. It's going to keep sucking up heat for awhile.

btw, that heater is roughly 6X what you actually want. It's going to be a pita for the Inkbird to manage.
You'd do better with a 40-50W heat source, like a reptile heat lamp, seedling matt, carboy heater...

Cheers!

 

[a_gunslinger]

Roger that. Thanks for the reply! Behaved the same with probe dangling lose and in a cup of water. But the water probably doesnt change any of the logic in your staement.

 

[a_gunslinger]

I ordered a 40w brewpad. Will try it again with that, and a fermentation vessel in there and report back.

 

[day_trippr]

This is a plot of my keezer temperatures and compressor cycles over the last 24 hours.
There were ~5-1/2 compressor cycles with each on-period lasting 65 minutes, so just under 25% duty cycle.

Here's a closeup of one cycle.

The pertinent thing wrt this thread is the difference between a probe hanging in air and one strapped to a large mass.
The green channel is a sensor positioned just above the floor of my keezer, the yellow channel is a probe positioned just under the lid liner.
It's easy to see how rapidly they respond to the compressor state - a sharp drop when on and a fairly steep rise when off.

When Set Point crossings are considered, those quick changes will cause way more frequent shorter compressor cycles than shown, which are the result of using a sensor strapped to the side of a nearly full keg and heavily insulated (the purple trace). The slopes keg sensor - especially the rise time - are way slower, and reflect that mass - the time it takes to warm up to the Set Point is ~4 hours. Using that to control a compressor is much kinder than using either of the other channels...

Cheers!

 

[NewJersey]

I presume this was a starkly empty chest freezer?

If so, there's like almost no thermal mass to smooth out peaks and valleys in the temperature profile, so a dangling probe in an empty chest freezer is going to illustrate the "cold lag" of an freezer evaporator that is full of dense vapor when the compressor shuts down. It's going to keep sucking up heat for awhile.

btw, that heater is roughly 6X what you actually want. It's going to be a pita for the Inkbird to manage.
You'd do better with a 40-50W heat source, like a reptile heat lamp, seedling matt, carboy heater...

Cheers!

I use a stand-up freezer with a heater just like the one the OP is using only mine is 250w.
I use these with an inkbird and have zero issues with over/undershooting temps. My temp probe is in a thermowell in a spike flex+

 

[a_gunslinger]

My initial test was with a dangling probe, no fermenter in the freezer. Im going to cold crash one here soon and will try again with probe in themrawell of the fermenter. Are my inital settings reasonable?

Target temp = 67 degrees (assumption its actually 68 in fermenter)
Cooling differential = 66 degrees
Heating differential = 68 degree

 

[MikeCo]

I have the setting at:

Target temp = 67 degrees (assumption its actually 68 in fermenter)
Cooling differential = 66 degrees
Heating differential = 68 degrees

Heating and cooling differential should be set at 1 or 2 degrees. Are you sure they are set at 66 and 68?

 

[a_gunslinger]

Pretty sure the differential is set correctly, will double check. Just got my fermentaor wrap. Will try it with a fermenter I have ready to cold crash. Although I its ability to hold cold crash temps might not be as hard as 68 egrees. Will report back.

 

[Holden Caulfield]

First, like has been previously mentioned - the differential should be set to +1 and -1 not 66 and 68. Also, the 1 degree differentials will only work well if the temp probe is attached to your fermenter and insulated. This will ensure that the fermenting beer stays within the range rather than the air temperature that can change quickly with limited relevance to the actual temperature of the wort.

When the Inbird shows 69 the freezer comes on. But when it hits 67, the freezer does turn off but keep cooling for 10+ degrees? Temps keep plummeting even though freezer off.

There is a lag between the cooled walls of the freezer and the air temperature surrounding the probe. The further from the wall the longer the lag. During the lag period the walls become colder than the surrounding air so they continue to cool the air for awhile even after the freezer goes off. In other words, the walls become a "cold energy" battery, that gives up the stored "cold energy" after being turned off.

For heat was using a small personal heater

If attaching the probe to the fermenter, I have found that these heaters provide substantially more wattage than necessary causing a lot of heat to build within the freezer before the beer temperature in the fermenter hits the shutoff point - which results in a lot of carry over (similar to the extra cooling you are experiencing, just the other way). If your fermenter does not let light in then a 20-40 watt light bulb in a lamp works well.

 

[a_gunslinger]

Got it. Will set to +1/-1 differential. I took the digital thermometer out of the SS Brewtech 5 gallon fermenter and put the Inkbird thermometer in the thermawell. Its cooling now to 40 degrees for a cold break. Also swithced the heat source from the small c ermic heater to a fermawrap.

Will report back as it cools to 40.

And thanks for all the replies and assistance!

First, like has been previously mentioned - the differential should be set to +1 and -1 not 66 and 68. Also, the 1 degree differentials will only work well if the temp probe is attached to your fermenter and insulated. This will ensure that the fermenting beer stays within the range rather than the air temperature that can change quickly with limited relevance to the actual temperature of the wort.


There is a lag between the cooled walls of the freezer and the air temperature surrounding the probe. The further from the wall the longer the lag. During the lag period the walls become colder than the surrounding air so they continue to cool the air for awhile even after the freezer goes off. In other words, the walls become a "cold energy" battery, that gives up the stored "cold energy" after being turned off.


If attaching the probe to the fermenter, I have found that these heaters provide substantially more wattage than necessary causing a lot of heat to build within the freezer before the beer temperature in the fermenter hits the shutoff point - which results in a lot of carry over (similar to the extra cooling you are experiencing, just the other way). If your fermenter does not let light in then a 20-40 watt light bulb in a lamp works well.

 

[a_gunslinger]

All better now. Having an actual vessel i there helped. And I did swap to a fermenator pad for heat. It does take this Galanz a while to cool, but once its there it seems stable.