Modify Chest Freezer to Hold at 32-34 Degrees F

How do you deal with temperature fluctuation in converted chest freezer? I set my thermostat turn on and start freezing at 50F and turn off at 48 (this is not final temperature, just a step in a process of cooling down my potatoes.) I also have external thermometer that has its probe next to thermostat prob. And I see the freezer turns on at 50 and turns off at 48. However, in between temperature is falling to 40, making 2 degrees delta to be 10 degrees. It is because cold freezer walls continue to produce cold. The probes are located between potato bags, that are inside insulated cardboard box. I also found, if I put probes 2-3 inches apart it can make difference in temperature up to 4-5 degrees. Will putting thermostat probe right against the wall help? The target temperature range is 40/42, so i am afraid that fluctuation will make it bellow freezing. How do you deal with uneven temperature?


This year I will be suspending a small electric fan to keep the air circulating to even out the temps.

You still need to develop some “shelving” system to keep the produce from actually touching the walls and floor. I used milk crate type storage containers to hold the fruit.


I did the shelving, and also insulated the box, but still…

galinas, there will be fluctuations. All thermostats are built so as to turn the cooling on at T, and turn it off at T+a. You have to accept the “a” gap. But here is the thing. If your freezer is really full, the air will change temperature by “a” between on and off, but your bulk material has much more thermal mass and will change its temperature by a small fraction of a.


@MES111 , two computer fans I used to create a flow for my tomato starters do miracle! Installed them in the morning, reset min and max on thermometer. Came home from work to 2 degree gap! Thanks a lot - I was actually skeptical if they can help in tight place, but they really do.
@glib , I understand the gap and accept it. Actually thermostat doing it’s job turning on and off with 2 degree gap. The temperature fells AFTER thermostat turned off freezer because cold walls continue to produce cold. But fan solves the issue, thanks to @MES111 brilliant idea.


“Brilliant idea” …Aww… you make me blush.


Not at all) I am glad you solved the problem for me

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Off topic maybe but as soon as I have enough fruit to store I want to build a small walk in fridge and use a cool bot and window AC to cool it

You must be selling it, right?

Hi galinas,

When your freezer is empty/mostly empty I’d really appreciate photos. I’m curious where the fans are inside and which direction they push air. Are you putting a slightly damp paper towel in there to monitor humidity?

Thanks a million,


@Barkslip , I will try to make photos, but not sure about it- freezer is small, view from top wouldn’t show much. But I will try or draw a diagram. I don’t need paper towel there. The humidity is very high in summer here and because of the cables the cover is not exactly hermetic, so walls are always wet. I may need it in winter though.
So this is my attempt to draw it. Red cylinders are quart jars of tomato juice, brown box - cardboard box with potatoes. There is also insulation inside the box. I am planning to add more jars as tomatoes getting ripe to fill side space and put my beets on top of the box in some flat container. The fans are that black things on the top view. I am planning to skip jars where the fans are now.

Freezer with all the wires

Top view opened

Jars on one side and one fan

Jars on other side and another fan, fancy one - i may need to remove the light though, I don’t think the preserves will enjoy it much…

First, thank you for your time.

I have a couple questions:

The fans are blowing air upward I assume. Are they kept in place with something and if yes, what?

Did you put any insulation on the bottom or the sides? I would think reflective insulation would be the first choice. When I blow up your photos I can’t tell whether you insulated the inside or if that’s what the freezer looks like on its own.

Looks pretty simple. I think I’ll understand better after you answer these questions.

Thank you,


The walls them self are not insulated, it is just freezer finish. But the box with potatoes is. I have foam packing material(like the one you can see on photo with cover opened) on the bottom and walls inside the box. The thermostat probe is right in the middle of the box, between paper bags with my seed potatoes. Fans have little frame(they both are old computer fans my husband converted to use as standalone fan) , so they just staying on the frame. They are not very stable, but do not fall when I open the chest. They blow horizontally, I think it doesn’t really matter where they blow, because in such a small space any blow will cover whole volume, as soon as there space for air movement. This is why I decided to put jars there - you can make spaces in between and let the air move. Now I can make much more tomato juice :grin:. I like to store it cold. And the juice really does not care how cold it is - I sometimes store it frozen, so i do not need to care about insulating the bottom.

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I moved thermostat prob out of the insulated box closer to the wall and kept thermometer probe in the box. It improved the gap to 1F, so I think this would be the correct set up.

  1. Have something that needs cold storage but wouldn’t mind around freezing temp on the bottom of the freezer and along the sides (canned juice in my case)
  2. Make sure there is a space at least quarter of inch between the objects in the freezer for air flow. To achieve it do not store your things in bags that can’t hold shape, store them in some kind of hard containers and may be put small raisers in between to allow airflow.
  3. Have you valuable things that required constant temperature in insulated box in the middle of the freezer
  4. Have separate wired thermometer that can register min and max to monitor temperature in the box, place it’s prob inside the box
  5. Have your thermostat probe out of the box , couple inches from the wall.
  6. Leave some space open for two small fans(modified computer fans with own power cord work perfect, use old adapters with correct voltage and current to power the fans). Direction of the blow doesn’t matter as soon as you have free space on intake and outtake side of the fans.
  7. Make sure you set up your thermostat to turn OFF the freezer if its probe fails and set up alarm on your remote thermometer on temperature around freezing.
  8. Check if you need to increase humidity inside the box once in a while. To do so, put piece of brown packing paper inside the freezer. It shows very well if it is humid enough inside the freezer when you touch it. Or have a hydrometer!
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I’m with ya now.

Much appreciated!


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