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Old 24-01-2015, 10:46   #1
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Computer Fan for Refrigerator Cooling?

Hi all,

I have separate 12v fridge and freezer units that were installed when I bought my boat. They are built into tight-fitting cabinets, with no real provision for air circulation around the coils. I have drilled some ventilation holes on the sides and tops to allow for some natural convection, but I would like to add a small computer fan to each unit to aid in moving the warm air out.

I have seen several discussions about this, and was wondering if anyone has done this, and if so, what fan did they use, and how did they wire it up? If I can find a fan that draws low enough amps, I could just have it run all the time. Also, I guess I could wire it to run every time the unit cycled on.

Suggestions are always welcome.

Thanks and cheers, Bill
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Old 24-01-2015, 11:12   #2
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Re: Computer Fan for Refrigerator Cooling?

I've used one a long time ago. It's simple. I got a pretty big one... I just hooked into the Coldmachine electrical tab that was on the unit for a fan. So it shut off and on when the refridge unit said to..
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Old 24-01-2015, 11:14   #3
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Re: Computer Fan for Refrigerator Cooling?

I use the 1 1/2" fans, set behind a vent cover. I built a tube under the shelf to convey the cold from the cold plate to the high end of the box. The fans are connected to a timer.
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Old 24-01-2015, 16:13   #4
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Re: Computer Fan for Refrigerator Cooling?

I use these: SilenX EFX-12-15 Case Fan - Newegg.com

They draw 0.1A, move 74 CFM and are dead-silent. I use them slightly differently than you propose - I use one to draw air into the compartment and condenser coils - rather than exit, and I replaced the existing compressor fan with the other. The replacement was because these are SO much quieter than the stock fan. I connected the extra one to the auxiliary fan terminal on the Danfoss control board so it turns on whenever the compressor runs.

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Old 24-01-2015, 17:05   #5
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Re: Computer Fan for Refrigerator Cooling?

I use one taken from the case of an old computer - it's about 4" square - to exhaust warm air from the cupboard the condenser is in. Draws 0.13 amps. I fabricated a simple duct and mounting out of fibreglass to mount it on so I could use an off the shelf louvred grill to place it behind. I connected it in parallel with the condenser fan so it's only on when the compressor runs. It's quiet and has a noticeable effect on compressor run time.

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Old 24-01-2015, 18:48   #6
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Re: Computer Fan for Refrigerator Cooling?

What Cheechako says. I bought a 4" 12 volt computer fan for $7 from an electrical junk shop. I wired it to the control box on my Adler Barbour Coldmachine. It turns on and off when the fridge goes on and off. There is a connector on the control box for the optional water pump, which is the one I used for the fan since I don't use the water pump.

I use the fan to blow air INTO the compartment where the Coldmachine is. The fan ON the Coldmachine blows the air OUT of the compartment. Been cruising Florida/Bahamas with this unit for the past ten years and it works great.

If you can, have the fan blow directly on to the control box, as per advice of fridge guru Richard Kollman. It's the most temperature sensitive part of the fridge and one of the costliest parts to replace.
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Old 24-01-2015, 19:15   #7
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Re: Computer Fan for Refrigerator Cooling?

Yeah, been there, done that:
Used 2 small cc fans to ventilate the compressor compartment.
Each pair lasted about 5-6000 hours.
Had to solder in a relay as the start loads would stop the Danfoss compressor.
The fans probably paid for them selfs in increased efficiency.
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Old 24-01-2015, 19:15   #8
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Re: Computer Fan for Refrigerator Cooling?

If you're wanting to cool a specific object, the fan should blow on it. If you want to exchange air in an enclosure, the fan should exhaust it. There are good reasons for this with probably the most valid being the resistance to ingress of dust and moisture. In my installation, cool air draws from the bilge and is exhausted high to allow convection to both contribute and to continue to vent heat even after the compressor has turned off.



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Old 24-01-2015, 20:07   #9
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Re: Computer Fan for Refrigerator Cooling?

On RV fridges, I use 4 120mm fans. 2 on the outside, pushing air over the coils, and 2 inside moving air over the cooling fins and getting the food colder, basically making the entire inside of the fridge an even temp.

I use these on the outside, about $4.75 ea

Amazon.com: Cooler Master Sleeve Bearing 120mm Silent Fan for Computer Cases, CPU Coolers, and Radiators (Value 4-Pack): Electronics


I use these blue LED ones for the inside, the extra light helps a little. They're about $7.50 ea.

Amazon.com: Cooler Master Sleeve Bearing 120mm Blue LED Silent Fan for Computer Cases, CPU Coolers, and Radiators (Value 2-Pack): Electronics
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Old 25-01-2015, 06:13   #10
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Re: Computer Fan for Refrigerator Cooling?

I have done this and would suggest ball bearing fans rather sleeve bearing fans. Also consider, depending on you box's design, placing a fan to push the cold air up from the bottom of the box where it is usually cooler to maximize circulation.
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Old 25-01-2015, 06:15   #11
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Re: Computer Fan for Refrigerator Cooling?

Two things to be aware of about these computer case fans are air flow and noise, because they are inter-related and not all fans are equal.

Many "quiet" fans have low air flow because they run at slower speeds. Higher air flow fans are often very noisy. Some fans are VERY loud. If these will be in, or near, a living space, you will be surprised at the differences between fans.

I would be wary of just pulling fans out of a junk pile, or randomly grabbing a fan without a bit of research.

These fans are pretty cheap regardless (the "expensive" ones I linked to only cost $3 more than the fans out of onestepcsy37's junk pile - and I didn't even shop around).

The fans socaldmax linked to are good ones, but only have 60% of the airflow as others.

I recently did a lot of esoteric research in attempting to get quieter fans than our system shipped with, while still meeting the specs the system required. I was surprised to find whole communities around nothing but case fans! Boy, if you think we all waste a lot of time on CF, you should visit some of these case fan forums! They even have the equivalent of our anchor and gun threads...

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Old 25-01-2015, 07:15   #12
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Re: Computer Fan for Refrigerator Cooling?

I've built a few computers over the years and the "gold standard" case fan is considered to be Noctua. They are exceptionally quiet, efficient, and durable. You want, if it will fit, the 120mm size as that will give you the best balance of flow vs. noise. In addition to adding a couple to ventilate the compressor compartment I also discovered last summer, when the fan on the unit itself failed, that it was a 120mm case fan. While these are pricy at @ $20 a pop, you get what you pay for.

Noctua fan on Amazon

There are several different fans for different applications if you just search on "Noctua fan"

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Old 25-01-2015, 09:01   #13
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Re: Computer Fan for Refrigerator Cooling?

Thanks folks for the great info. I will make good use of it. Unfortunately, it may be a while before I get down to the boat again.

Cheers, Bill
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Old 25-01-2015, 10:31   #14
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Re: Computer Fan for Refrigerator Cooling?

Often if a 12v fan is too loud you can reduce the voltage to slow and quiet it down. You can run fans on USB chargers an internet search shows how to wire it, as others have said it is better to push air in then to pull it out in most cases. Larger diameter fans move more air quietly, then smaller ones. 120mm or larger can be very quiet.
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Old 25-01-2015, 10:51   #15
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Re: Computer Fan for Refrigerator Cooling?

Quote:
Originally Posted by Ostinato View Post
I have done this and would suggest ball bearing fans rather sleeve bearing fans. Also consider, depending on you box's design, placing a fan to push the cold air up from the bottom of the box where it is usually cooler to maximize circulation.
Excellent point! While I've been very lucky with sleeve bearing fans (no failures yet in about 10 yrs) RV fridges are not running near as much as a fridge on a liveaboard.

The ball bearing version of these silent fans is $30/4, or $7.50 ea. Ball bearing fans are definitely the better choice.
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