Fan in the freezer. Good Idea or Bad?

[Charlie]

Hi All:

My refrigeration consists of two boxes side by side. There are two cold plates on one side and nothing on the other. There is a 3" hole in the wall between the two with a wooden plate that can be used to block the hole. I am considering installing a fan in the freezer to help circulate the cold air. My reason for this is that I think that the air circulating will be more efficent and cut down on the cycling time of the compressor. Then I realized that I really don't know enough about refrigeration to know if this is true or not. Can anyone help me out? Is a fan a good idea or not.

[a64pilot]

Will not cut down on cycle time, may if anything increase it as I believe most cold plate systems thermostat actually measures the cold plate temp, not box temp.
Technically, you will be adding energy (heat) to the air by running a fan, but I'd suspect the amount is insignificant.
Now if you have cold spots and warm spots, then a tiny fan will even those out, and I mean tiny as in .1 amp or so., it doesn't take much at all.

[Charlie]

Originally Posted by a64pilot

Will not cut down on cycle time, may if anything increase it as I believe most cold plate systems thermostat actually measures the cold plate temp, not box temp.
Technically, you will be adding energy (heat) to the air by running a fan, but I'd suspect the amount is insignificant.
Now if you have cold spots and warm spots, then a tiny fan will even those out, and I mean tiny as in .1 amp or so., it doesn't take much at all.

I have thought about your reply and I understand what your saying. I didn't explain myself completely. I have to run the freezer at a colder temperature than I would want it in order to get the refrigerator cold. My theory is that I could run the freezer at a higher temperature because the air circulation will transfer the cold from the freezer to the refer more efficiently. Is that correct/possible? Ir is this not enough information to make that call?

[DeepFrz]

Charlie, have you read this?
Kollmann Marine

[chris95040]

My guess is that even a tiny amount of fan circulation will turn your fridge/freezer combo into an icebox with uniform temperature on both sides.

We are only talking a few cubic feet of air, with probably the same insulation in both sides.

It may be better to just increase the size of the opening to perform the sort of "tuning" you are describing.

If you go with the fan, I suppose you also want to make sure you have a good enough return path that you aren't putting positive pressure in your fridge side and forcing cold air out through the hatches, etc.

[Charlie]

DeepFrz thanks exactly what I needed. Grazie Mille

[lovinlifebda]

Charlie, I put a lot of value into advice from Richard Kollmann. On our boat we have a spillover system, though using an evaporator rather than cold plates. There is a hole about half of the height off the fridfge floor with a fan that is on a mechanical thermostat. Then there is a "return" hole near the top. The fridge is kept at a constant temperature this way, in our case 38F. I belive you need the thermostat or you drive the temp down in the fridge and start freezing your lettuce. Jim

[SV THIRD DAY]

Hi Charlie
Technautics has been selling holding plate spill over systems for years and our standard set-up is to let the laws of thermodynamics work for you and circulate the cold air from the freezer to the refrigerator and then back from the refrigerator to the freezer. These systems do take some balancing with the bottom hole being adjustable and then the top holes or divider air gap on top being fixed. A lot of the success depends on how foods is packed in the box and the ability to keep the bottom hole from being blocked by food.

In your case, it sounds like you need more air movement from the freezer to the refrigerator, so my first approach would be to make a larger hole or open the flap on your current hole more to allow more air flow.

If this doesn't do it for you, then you can add a 12v fan (VERY VERY SMALL CFM or you will overpower the set-up) that's tripped on by a thermostat in your refrigerator box. That way you can boost the natural air flow to make things happen faster and have more control over the refrigerator.

If you are after a warmer freezer, have you tried turning up your thermostat in the freezer box?

Get your freezer box temp set first and then start playing with the divider opening to balance things out.

[ErikFinn]

Question about these fans please:
can you use any normal 12 volt small fan (find in hardware shop for example) or does it have to be something special? Normal computer fans work in freezing temps ok?

[SV THIRD DAY]

Originally Posted by ErikFinn

Question about these fans please:
can you use any normal 12 volt small fan (find in hardware shop for example) or does it have to be something special? Normal computer fans work in freezing temps ok?

G4028 Series DC Axial Fan - Mechatronics, Inc.

Think about your box size and how many cubic feet your volume is...what....maybe 8-10. So you don't want a 50CFM (cubic foot per minute) can that's turning the box volume over 5 times per minute. You don't want or need a blast freezer or refrigerator! All you really need is a fan that can turn your box volume over once per minute nice a gentle, don't waste power, don't blow air out of the box when you open the hatch, just a slow gentle movement to disperse the heat energy.

Most off the the shelf computer fans from Radio Shack are around 75-90CFM which is WAY overkill in amps and air movement.

[NoTies]

A friend of mine had a double wall with a void in between in his fridge/freezer combo. The wall on the freezer side had 2 holes, one of which had a fan mounted in it (contolled by a thermostat in the fridge side) and the other didn't (to allow air flow). The wall on the fridge side was simply a sheet of stainless steel to transfer heat. No direct air flow between the freezer and fridge and it worked a treat which was good because he sure liked his cold beer.

[ErikFinn]

Originally Posted by SV THIRD DAY

G4028 Series DC Axial Fan - Mechatronics, Inc.

Think about your box size and how many cubic feet your volume is...what....maybe 8-10. So you don't want a 50CFM (cubic foot per minute) can that's turning the box volume over 5 times per minute. You don't want or need a blast freezer or refrigerator! All you really need is a fan that can turn your box volume over once per minute nice a gentle, don't waste power, don't blow air out of the box when you open the hatch, just a slow gentle movement to disperse the heat energy.

Most off the the shelf computer fans from Radio Shack are around 75-90CFM which is WAY overkill in amps and air movement.

Thanks rich, so the fan volume should correspond to the size of the box.. But what I still do not know, does the fan have to be of some special model or construction?

[oregoncycle]

I have a small computer cooling fan that pulls the air from the freezer section over into the cooler box. Cooler box dropped 15 degrees and is in the low 40 as it should be. Fan was 3 dollars and took ten minutes to wire.

[SV THIRD DAY]

Originally Posted by ErikFinn

Thanks rich, so the fan volume should correspond to the size of the box.. But what I still do not know, does the fan have to be of some special model or construction?

No real need for any special construction, what matters most is the fans low amp draw and relatively "low" by fan standards CFM rating. All the good quality low amp draw fans these days use brushless motors.

[Valmika]

I have the same set up and I put a small computer fan on the refer side to bring the cold air in from the freezer. I don't know if it cycles more but my refer is now good and cold not just cool like it use to be. The fan I bought was the smallest that would fit over the three inch hole. I have not replace it in over 5 years and I think I paid about 7 dollars for it at Fry's