Johnson Digital Temperature Controller Keezer Build

Hello,
I finally got around to doing work on my Keezer today. I installed the Johnson controller and noticed something interesting. The deep freezer was getting really hot on the sides. It got to the point where at one point it was almost burning. I set the controller to turn the freezer off when it got to 26 F; however, I noticed that the freezer is dropping to 21 and not turning off. I also set the freezer to its lowest setting. I'm afraid of leaving it on overnight for fear of the compressor exploding, or worse. Are there any settings I'm missing on it?

Thanks!

Also, the temperature alarm is going off saying that the fridge isn't cold enough inside, which is false

Pash91 said:

Hello,
I finally got around to doing work on my Keezer today. I installed the Johnson controller and noticed something interesting. The deep freezer was getting really hot on the sides. It got to the point where at one point it was almost burning. I set the controller to turn the freezer off when it got to 26 F; however, I noticed that the freezer is dropping to 21 and not turning off. I also set the freezer to its lowest setting. I'm afraid of leaving it on overnight for fear of the compressor exploding, or worse. Are there any settings I'm missing on it?

Thanks!

Click to expand...

Do you have it in cooling mode?

I haven't opened it up, but from what I can tell it is. It has the snow flake on the display

Actually, I unplugged the controller and plugged the fridge in directly. The temperature light is still blinking and the sides are heating up again

The condenser coils are located in the outer walls of the freezer. They will radiate heat. This is completely normal. The evaporator coils are also located in the freezer walls, but they are up against the inside walls. The two are separated by foam insulation.

The snow flake on the display indicates that the controller is in the cooling mode, so that's OK. That is normally the default setting. The controller default setting should also start the compressor at the Set Point (Cut IN) and it will stay on until it cools to the Set Point minus the Differential setting. IOW, when you set the controller to 26 it will keep running until its gets to the Setpoint temp minus the Differential setting. What do you have the Differential set to? It can be set anywhere from 1 to 30 deg in either F or C.

No need to fear the compressor exploding. It's designed to run for extended periods without issues. I suspect you have the differential set incorrectly and too large. Typically somewhere between 3 and 5 degrees works well. I use a 5 degree Differential.

The freezer alarm will probably keep going off unless the freezer gets to normal sub zero temps which it never will the way that we use them. You may need to figure out a way to disable the alarm somehow. Mine has no alarm, so I can't help you there. You do want the freezer to be set at it's lowest setting. Essentially, this takes it out of the loop and turns over the control to the Johnson.

I'm pretty sure it's a problem with the Differential setting. Check that first.

I actually didn't change the differential. It's set to 5 right now. Everything else is set to default. Is there a way to tell it to cut off the second it hits the set point, that is, from what I understand, if the set point gets hit and the fridge cuts off, then the temperature rises and dips really quickly, the controller won't catch it. I want it to react immediately no matter what

I'm really worried about the sides heating up. I think they could actually burn skin at some points. That doesn't seem normal to me

Pash91 said:

I'm really worried about the sides heating up. I think they could actually burn skin at some points. That doesn't seem normal to me

Click to expand...

It's completely normal. They will be less warm once you get everything cooled down and the compressor begins to cycle. The heat you feel is what is being removed from the interior of the freezer.

Did you check the Differential setting?

One thing you can do is establish the Set Point relatively high initially, then adjust it downward gradually over the next day or so. This will reassure you that the compressor is cycling properly. Set it at 45 F and see if it shuts off. Then go down from there as desired.

Yes, I checked the differential, it's set to 5.

My problem is that, once it cools, it's fine, when it's working. It was dropping to 21 and not cutting off even though my set point is 26. Should I drop the differential to 2?

Pash91 said:

I actually didn't change the differential. It's set to 5 right now. Everything else is set to default. Is there a way to tell it to cut off the second it hits the set point, that is, from what I understand, if the set point gets hit and the fridge cuts off, then the temperature rises and dips really quickly, the controller won't catch it. I want it to react immediately no matter what

Click to expand...

The compressor will turn on when the Set Point is hit and it will turn off when it hits the Set Point minus the differential. ie, Set Point is 26 F and Diff is 5 it will turn on when the temp rises to 26 and shut off when it hits 21 F (actually I think it shuts off at 20.9 F at these settings).

You can set the Differential much tighter to 1 degree F if desired. This will give you the fastest response, but it will cause the controller to cycle frequently and the result is extra wear and tear on the compressor which will eventually shorten it's life. Not generally a good thing and I think it is less energy efficient too.

Pash91 said:

Yes, I checked the differential, it's set to 5.

My problem is that, once it cools, it's fine, when it's working. It was dropping to 21 and not cutting off even though my set point is 26. Should I drop the differential to 2?

Click to expand...

I think it has to get to 20.9 F before it will shut off. The display doesn't read in decimals of a degree, so it's a problem with display resolution, not the controller itself. Be patient.

You can set the Differential to whatever you want between 1 and 30 F or C. While you are playing with it initially, set it tight to 1 degree and you will be able to watch it cycle. Once you are confident that it's not going to explode, you can set the differential wider. I have mine at 5 degrees.

Catt22 said:

The compressor will turn on when the Set Point is hit and it will turn off when it hits the Set Point minus the differential. ie, Set Point is 26 F and Diff is 5 it will turn on when the temp rises to 26 and shut off when it hits 21 F (actually I think it shuts off at 20.9 F at these settings).

You can set the Differential much tighter to 1 degree F if desired. This will give you the fastest response, but it will cause the controller to cycle frequently and the result is extra wear and tear on the compressor which will eventually shorten it's life. Not generally a good thing and I think it is less energy efficient too.

Click to expand...

That's actually really helpful. I was trying to read through the directions, but they were just slightly over my head. I'll give it a try again a little later. In the mean time, I had it unplugged over night as every time the thing would cycle, the alarm would get reset and start buzzing. I need to figure out where that piezzo buzzer is and desolder it.