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Old 13-12-2011, 18:50   #1
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Fridge Fan??

We have a 7 Cubic foot top loading freezer / fridge in our Boat. The freezer side is evenly separated from the fridge side by a solid 3" thick dividing wall that has a 4" hole cut through in the middle. The freezer side freezes quite well, it has two evaporator plates in the freezer side and none on the fridge side. The 4" hole in the divider is next to one of the evaporators. The evaporator plates are spaced almost 1" away from the walls on the freezer side, We are not satisified with temps in the fridge area. It keeps items cold but not quite cold enough.
Would a small 12v fan mounted in the hole in the dividing wall help to draw colder air from the freezer side into the fridge side? Someone told me this was common, I tried to research it but no luck.
Advice as always is welcome and appreciated.
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Old 13-12-2011, 18:57   #2
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Re: Fridge Fan??

Quote:
Originally Posted by Dulcesuenos View Post
Would a small 12v fan mounted in the hole in the dividing wall help to draw colder air from the freezer side into the fridge side? Someone told me this was common, I tried to research it but no luck.
Advice as always is welcome and appreciated.
This is common, yes, for spillover systems. For best results, rig the fan to a thermostat so that the fridge side is only borrowing cold from the freezer when it needs it.
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Old 13-12-2011, 19:01   #3
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Re: Fridge Fan??

It is very difficult to get satisfactory performance from these devices. If you add a fan then you will also need to add a return port so the air will circulate. This will mean you will be pulling warm air back into the freezer section. The fan will have to be thermostatically controlled in order to prevent the device from freezing the items in the fridge. You may need (almost certainly) something in front of the fan in order not to freeze items directly in the air flow.
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Old 13-12-2011, 19:17   #4
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Why not try increasing the diameter or number of holes connecting the two sides?
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Old 13-12-2011, 19:22   #5
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Re: Fridge Fan??

Don't you wonder at the thinking behind putting 3" of insulation between the fridge and freezer and then cutting a 4" hole in it?
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Old 13-12-2011, 20:00   #6
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Quote:
Originally Posted by DeepFrz
Don't you wonder at the thinking behind putting 3" of insulation between the fridge and freezer and then cutting a 4" hole in it?
And putting a heat source inside the box? Okay the fan motor dont make much heat but...

Hotter air rises - a hole at the top and a hole at the bottom creates natural convection and circulation. One hole may not be enough. Make sure the holes are not blocked with groceries.
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Old 13-12-2011, 20:28   #7
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So if I had a hole at. The top it would naturally circulate? How about a.small computer style fan or something wi th low cfms?
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Old 13-12-2011, 20:39   #8
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Re: Fridge Fan??

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So if I had a hole at. The top it would naturally circulate? How about a.small computer style fan or something wi th low cfms?
Yeah, that's the way the system worked on my last boat. Two holes, the lower of which is the size of a small muffin fan. A thermostat on the fan. Higher up, a return vent.

These spill-over systems are not optimal, but they can be made to work.
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Old 13-12-2011, 20:48   #9
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Quote:
Originally Posted by Dulcesuenos
So if I had a hole at. The top it would naturally circulate? How about a.small computer style fan or something wi th low cfms?
That's how onshore and off shore breezes work...

Dont lose sight of the temp controller for the fan if you install one. An unregulated fan would keep circulating air and eventually both sides would be a freezer.

That's how Canada and Kansas works - LOL

And if you go with the holes idea make sure the air can circulate. No circulation = no weather. That's now the equator works - LOL

And the bigger the temperature differential the bigger the wind blows. That's how the california desert works.
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Old 13-12-2011, 20:52   #10
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Re: Fridge Fan??

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Originally Posted by SV Demeter View Post
Why not try increasing the diameter or number of holes connecting the two sides?
+1
You can always cover extra holes with adjustable baffles if you make too many.
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Old 13-12-2011, 20:55   #11
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Quote:
Originally Posted by Dulcesuenos
So if I had a hole at. The top it would naturally circulate? How about a.small computer style fan or something wi th low cfms?
We are talking tiny fan! Do a test. Run the fan on a bench. Put your hand on the motor. If it is hot or warm remember, you now have to take that heat out of the box before the food cools. We aren't talking a typical computer mufan fan here.

I personally would try it with no fan. I would try a "big hole" at the bottom with a gate to control square area. Open it max first and you can close it down to reduce circulation if the milk freezes.

Also on my mind is Ttere is also only so much cooling. You trade freezer temp for fridge temp and eventually the frozen food aint frozen. But with sufficient cooling power all that is likely to happen is the duty cycle of the compressor goes up and power consumption on the boat goes up.
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Old 14-12-2011, 06:17   #12
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Re: Fridge Fan??

Quote:
Originally Posted by Ex-Calif View Post
We are talking tiny fan! Do a test. Run the fan on a bench. Put your hand on the motor. If it is hot or warm remember, you now have to take that heat out of the box before the food cools. We aren't talking a typical computer mufan fan here.

I personally would try it with no fan. I would try a "big hole" at the bottom with a gate to control square area. Open it max first and you can close it down to reduce circulation if the milk freezes.

Also on my mind is Ttere is also only so much cooling. You trade freezer temp for fridge temp and eventually the frozen food aint frozen. But with sufficient cooling power all that is likely to happen is the duty cycle of the compressor goes up and power consumption on the boat goes up.
Good advice everyone thanks , I think I will try the hole at the top,. I do have an adjustable vent that fits on the 4" hole at the botom. As for fan types should I still need it what type and who has them? We do have a seperate 63 qt freezer we also use for ice cream, ice and perishables,rum Crown, scotch, etc I have heard they go quite bad when kept too warm.
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Old 14-12-2011, 07:48   #13
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Re: Fridge Fan??

Try the second hole. As mentioned, you can always baffle them to control air flow.

I have a 12v fan that's been running for 10 years. I ended up not installing it in a hole but have it circulating air in the frig for uniform temperatures.

Another thing to watch, heavy frosting if warm air from the frig is being forced onto the evaporator plate.

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Old 14-12-2011, 07:56   #14
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Re: Fridge Fan??

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As for fan types should I still need it what type and who has them?
12VDC Brushless Fan : Computer Fans | RadioShack.com
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Old 14-12-2011, 09:38   #15
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Re: Fridge Fan??

Before you go drilling big hole, I'd think more about a muffin fan. They use very little power (thus very very little heat) and you can control them easily with a thermostat. Unless you are fooling with the vents often, you'll want to have a thermostat automatically maintaining the fridge temperaure.

Yes, household refrigerators don't have a separate thermostat for the fridge, but the inside of a house is a very stable temperature compared with the inside of a sailboat.

Muffin fans are about 1" diamer in size and very inexpensive. Figure out where you want to put it, then drill the small hole for it, leaving room around the edge of the hole to screw the fan into.

Then if you don't like the fan, you can always drill a bigger hole later.

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