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Old 24-09-2020, 06:22   #1
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Adding Circulation Fan to Refrigerator Box

With my recent installation of a separate system for my refrigerator to get rid of my spillover system I have the return of a problem I haven't seen in 8 years. That is stuff in the bottom of the refrigerator box freezing because there is not good circulation in the box. I have one of those battery powered recirc fans in there, but that isn't enough air flow.

So I am going to install a 12V powered fan in there and am interested in hearing stories from those that have done it as to lessons learned.
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Old 24-09-2020, 06:27   #2
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Re: Adding Circulation Fan to Refrigerator Box

The biggest thing will be making sure the fan is placed so that food doesn't block the air movement. And it will most likely work best if it's circulating cold air upwards from the bottom of the box.

Out of curiosity, what temperatures are you seeing (food temperature) at the top and bottom of the box?
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Old 24-09-2020, 06:42   #3
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Re: Adding Circulation Fan to Refrigerator Box

I was thinking to place so it blows the warmer air down into the section that freezes.Thinking maybe mounting the fan on a pvc tube so it doesn't get blocked.

controlling the air temp in the top 37-39 now to try to keep things from freezing, while staying below 40.
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Old 24-09-2020, 06:45   #4
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Re: Adding Circulation Fan to Refrigerator Box

PVC tube to guide the air is definitely a good idea. With the bottom-up flow, I was thinking of cold falling, so the fan should be assisting natural circulation rather than fighting it. By lifting the cold air to the top, it will then naturally fall over the food, back to the bottom, assisting the circulation from the fan.
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Old 24-09-2020, 06:57   #5
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Re: Adding Circulation Fan to Refrigerator Box

The problem I feel with the fan blowing the cold air up it that due to where I can mount stuff it would blow right on the thermostat and short circuit the system. My system has an evaporator with a fan in it that blows down, but I think that flow is pretty low. I think blowing that warmer air into the bottom would be better at preventing the bottom from freezing, while at same time cooling the warm air.

I of course don't know which is why I asked for lessons learned.
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Old 24-09-2020, 07:06   #6
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Re: Adding Circulation Fan to Refrigerator Box

Is the thermostat sensing box temp or plate temp? If it's box temp, the fan blowing on it shouldn't matter, provided there's enough air circulation to keep the whole box close to the same temperature.
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Old 24-09-2020, 07:14   #7
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Re: Adding Circulation Fan to Refrigerator Box

I've done this in both my fridge and freezer, it has made a huge difference. The only issue you might have is making sure you're not drawing more than 1/2 amp on the fan circuit or you will get short cycles and the fault you will see with an LED is 2 flashes. I went with a centrifugal fan so I could put it right up against the side and still direct my airflow. To prevent the short cycles I am using a 12v relay on the fan circuit to operate this fan and the condenser fan.


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Hope this helps.
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Old 24-09-2020, 07:16   #8
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Re: Adding Circulation Fan to Refrigerator Box

Personally, I wouldn't worry about the power draw concern for the controller. In my mind, a condenser fan (and probably an evaporator fan) only needs to run during compressor cycles. But a fan to circulate air in the fridge will be more effective if it runs all the time regardless of compressor cycles.
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Old 24-09-2020, 07:20   #9
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Re: Adding Circulation Fan to Refrigerator Box

I am considering this as well and am curious what people have done to route the wiring into the box. Have you just drilled through the side and then sealed the penetration with silicone?

On the pushing cold air up and the cold air falling down I don't see how that is different than pushing warm air down. Warm air rises after all.
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Old 24-09-2020, 07:31   #10
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Re: Adding Circulation Fan to Refrigerator Box

Quote:
Originally Posted by rslifkin View Post
Personally, I wouldn't worry about the power draw concern for the controller. In my mind, a condenser fan (and probably an evaporator fan) only needs to run during compressor cycles. But a fan to circulate air in the fridge will be more effective if it runs all the time regardless of compressor cycles.

This would work too, I thought about this and going with a much smaller fan, but then I saw the VD-15 which is basically an evaporator with a circulating fan built onto it. Doing something similar (cycling with the compressor) made sense to me. It's worked out really well so far, I am getting less frost build up and my fridge and freezer are cycling less. Now that I've done the hard part of running the wires and installing the fans, switching them over to run all the time and switching to smaller fans is pretty simple if I want to go that route.


I'll be interested in hearing what you choose and how it works out for you.
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Old 24-09-2020, 08:14   #11
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Re: Adding Circulation Fan to Refrigerator Box

I just finished installing a new refrigeration system. I have holding plates, and I installed the holding plates about 1 inch from the side of the box, and then wired up a computer 12V fan to blow warm air (from near the lid of the box) down along the back of the holding plate, figuring that would give me good air circulation. I am also lining the bottom of the box with the equivalent of Dri-tec tiles. I figure the fans will eventually fail, so I made them easy to get at and replace. They are wired so they come on whenever the compressor comes on and do not run 24/7.
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Old 24-09-2020, 08:26   #12
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Re: Adding Circulation Fan to Refrigerator Box

Fridge fans used to be for sold as a battery operated fan. As a live aboard for 20 + years used to use them often and C batteries lasted fairly long. I cant remember where I bought but will see if I can find them and post.
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Old 24-09-2020, 08:42   #13
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Re: Adding Circulation Fan to Refrigerator Box

When I was young we had a big diesel heater/fireplace in our farm shop. We used large ceiling fans drawing air upward in the summer to keep us cooler working on equipment. When winter came we reversed the fan direction to blow the hot air that had risen to the ceiling the from the heater down towards the floor to keep us warm. You can probably visualize how this works in you fridge.
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Old 24-09-2020, 09:05   #14
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Re: Adding Circulation Fan to Refrigerator Box

I am planning to just use the old 2" spillover fan and power it from the same line it was getting powered from in the past. If it had enough air flow to keep the refrig cold in the past it should have enough to just keep the air moving in the box. Plus I think the screws for it will line up with the edge of a pvc pipe that I can use a "duct"
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Old 24-09-2020, 09:11   #15
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Re: Adding Circulation Fan to Refrigerator Box

I put in a large 3.5 inch blade dia pc fan in the bottom of the box opposite end of holding plate. Runs 24/7 because compressor only runs twice a day. Not too worried about air getting blocked because fan is large. Helped a lot with keeping even box temp.
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