Cant stablize keezer temps -- driving me CRAZY!!

No matter what I do, I just cant get my temps to stabilize in my keezer.

I have a Johnson A419 controller in a chest freezer. Current settings are>

Setpoint: 45F
Differential: 3F
AsD: 12mins

The probe is taped to the outside of a keg, and has a layer of bubblewrap taped over it.

I dont know why, but the temps are dropping into the mid 30's everytime it turns on. I've not opened the freezer in several hours, so the airtemp should be "uniform" throughout (well, at least no warm air from outside).

I just can figure out why it's dropping so low. The only thing I can figure is maybe the bubble wrap is messing the readings up ie...it's insulating the probe from detecting the real temps so it's cooling much longer than it needs to?

Anyone have any suggestions? I know folks say to put the probe into water...but there's nothing in the manual that says the probe is waterproof. Was thinking of maybe taping the probe to the keg with some insulated tape so that it can ONLY detect the temperature of the keg, and not the ambient air in the freezer. Good idea or not?

Make sure the probe is tape over an area of the keg that contains liquid.

OK. How do you know it is dropping that low? Not the read out on the controller I hope? Also, is the contents of the keg the probe is taped too getting that cold?

What I'm thinking is that your freezer kicks on and starts to cool. Your keg takes time to get to that temp, and at that point the ambient temps in the freezer are much colder. They're meant to keep cold in, and they do.

When I ferment, I tape to the side of my carboy, but when I want my kegs to be cold, I set it for ambient temps and let the probe just hang out in the freezer. Your kegs will equalize to that temp. I don't see why you're so worried about the keg temp and not just the overall temp in there.

Hermit said:

OK. How do you know it is dropping that low? Not the read out on the controller I hope? Also, is the contents of the keg the probe is taped too getting that cold?

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I'm looking at the controller readout.....why is that incorrect?

carnevoodoo said:

I don't see why you're so worried about the keg temp and not just the overall temp in there.

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I figured I would get a more stable temp with it taped to a keg, which shouldn't fluctuate much as compared to floating in free air which will have huge fluctuations evertime the keezer is opened.

carnevoodoo said:

When I ferment, I tape to the side of my carboy, but when I want my kegs to be cold, I set it for ambient temps and let the probe just hang out in the freezer. Your kegs will equalize to that temp. I don't see why you're so worried about the keg temp and not just the overall temp in there.

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I'm having the same problem. It's a concern for me because I use the controller to control the temperature and it's not doing that. If I say 45 with a +/-3 differential then I don't expect to see a 38.

Of all the research I did on kegging this was the last thing I expected to have to debug. It seemed pretty obvious to just set the temp you want and let the device handle it. But now it seems like this isn't science but more of an art - as if there is a method to follow to get the results you want.

I just feel like I'm missing some trick everyone else knows.

Freezers will always under-shoot the set temperature, because there will be coolant in the sides when the compressor shuts down. As it evaporates, you get additional chilling. I let the probe sit in the air near the bottom of the kezzer. This will shut the compressor off sooner and result in less of an under-shoot.

The rules are different for a fridge-based unit.

pretzelb said:

I'm having the same problem. It's a concern for me because I use the controller to control the temperature and it's not doing that. If I say 45 with a +/-3 differential then I don't expect to see a 38.

Of all the research I did on kegging this was the last thing I expected to have to debug. It seemed pretty obvious to just set the temp you want and let the device handle it. But now it seems like this isn't science but more of an art - as if there is a method to follow to get the results you want.

I just feel like I'm missing some trick everyone else knows.

Click to expand...

Well, there seems to be sooooo much conflicting "advice" out there. Some say put the probe in water, others say to never do that. Some say let the probe hang free, others say tape it to a keg. Some say it needs to be insulated, some say it doesnt. Some say you need fans, some say there's no point to putting in fans.

Definitely seems to be some voodoo to this.

david_42 said:

Freezers will always under-shoot the set temperature, because there will be coolant in the sides when the compressor shuts down. As it evaporates, you get additional chilling. I let the probe sit in the air near the bottom of the kezzer. This will shut the compressor off sooner and result in less of an under-shoot.

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So David, if freezers under-shoot, would it be better to use a higher setpoint and smaller differential to compensate for this?

I would add a small fan, too - It helps to make the ambient temperature in the keezer uniform throughout. If the whole volume of air in the keezer is at your chosen temp, the kegs will follow.
I've read about jars of water, or that stuff from gel packs. I've never used any of that. Just a probe in the air, and a fan, with great results.

Naked_Eskimo said:

I'm looking at the controller readout.....why is that incorrect?

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It isn't incorrect. It is saying that the controller doesn't seem to know when to shut off.

SweetSounds said:

Just a probe in the air, and a fan, with great results.

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Sweetsounds...when you say you have the probe in the air...are you literally just letting the probe swing loose (from the lid, I assume?) or do you have it hanging against/taped one of the walls?

Hermit said:

It isn't incorrect. It is saying that the controller doesn't seem to know when to shut off.

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It is turning off at the right moment (e.g. 42F), but even after it has shut the compressor off, the temp continues to drop several degrees...so assume there is enough coolant in the lines to cool things past the desired point.

Even if it shuts off at 42 it shouldn't drop into the mid 30s after that. I did appliance repair for over 30 years and that just doesn't seem right to me. Unless you are changing the load quite often it should stabilize around where you have it set.

I primarily use my freezer for fermenting where I usually tape the probe to the bucket and cover with insulation.

The one time I used the freezer for cold crashing, I noticed the same overshoot although not as drastic. Mine did eventually stabilize though. It will probably just take a little time to get there.

david_42 said:

Freezers will always under-shoot the set temperature, because there will be coolant in the sides when the compressor shuts down. As it evaporates, you get additional chilling. I let the probe sit in the air near the bottom of the kezzer. This will shut the compressor off sooner and result in less of an under-shoot.

The rules are different for a fridge-based unit.

Click to expand...

I think this might be the answer to the 3 threads current at the moment.

I sat with my keezer while it was on and watched it cut out as it hit 42. Then I saw the reading drop all the way to 37 while the power was off.

I assume this must happen for everyone. My only guess is that adding a fan can help.

Naked_Eskimo said:

Sweetsounds...when you say you have the probe in the air...are you literally just letting the probe swing loose (from the lid, I assume?) or do you have it hanging against/taped one of the walls?

It is turning off at the right moment (e.g. 42F), but even after it has shut the compressor off, the temp continues to drop several degrees...so assume there is enough coolant in the lines to cool things past the desired point.

Click to expand...

Yep - Just swingin in the breeze.

It works great, as long as you have a fan circulating the air in there...