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Old 01-02-2015, 03:36   #16
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Re: Computer Fan for Refrigerator Cooling?

Proper ventilation of the condenser and compressor is pretty vital to fridge performance. The single best way to increase efficiency is to make sure the condenser is not bathed in recycled heated air that it itself has heated.

The Danfoss compressor controllers have a fan output which can handle 0.5 amps of computer fans.

I have a c51is Vitrifrigo fridge which came with a 72 CFM fan that was located to pull air through the finned condenser. I added extra insulation to the side of the fridge, and this extra thickness allowed me to relocate the fan to the other side of the condenser and so it can PUSH air into the condenser rather than pull it through.

I also used the Noctua Fan shown a few posts above in place of the vitrifrigo provided fan. The VF fan rated at 0.24 amps, actually pulls .12 amps, and is quite loud. The Noctua fan is only rated at 53 CFM, but it has a high static pressure rating, meaning it has good performance when pushing air through a restriction, and it is very quiet too!

When I installed this Noctua NF-f12 fan, which only draws 0.05amps, so that it pushed air into the condenser, performance increased. Duty cycle dropped, and noise was considerably less than the VF provided sleeve bearing fan, and it draws 70% less electricity than the VF fan as well!

I'd made a Stainless steel shroud over the cooling unit so that all the air moved by the Noctua fan went across the compressor and compressor controller. I also added some sound dampening material to this protective shroud. This single fan pulls in cool filtered air from the floor below the fridge, pushes it once through the condenser, across the compressor and controller and is forced out the side of the cabinet and cannot be recycled.

This Modification was quite noticeable to both noise and efficiency of the fridge.

I've also added a small 40MM fan to the interior of the fridge which runs 24/7 and blows into the small freezer compartment. I took 12v from the interior light. While this aids in cooling the fridge faster, and items placed within faster, it does not reduce energy consumption. The fan itself adds a very small heat load to the fridge, and for this reason, I found the lowest amp draw fan I could, at 0.03 amps.
The use of this fan allows me to use a setting of ~2.2 out of 7 to maintain sub 35F everywhere in the fridge. With this interior fan turned off, a setting of 4 of 7 is required, and the floor of the fridge will be 31f and the back of the fridge below the compressor will be 44F.

So the internal fan evens out internal temps nicely, and allows for faster cool down of items placed within and allows a lower thermostat setting. When I have a Solar power surplus, I crank the dial to 4, and then at sundown back to 2.2, and for several hours afterward, the duty cycle is reduced, saving some battery power. Smetimes I forget to turn down the thermostat to 2.2 and My milk is slushy in the morning

I can also turn the front loading fridge into a freezer at a setting of 5.5 where without the fan a setting of 7 will only freeze some sections of the fridge box.

Since the Danfoss controller can handle 0.5 amps of fans, one could in theory add 9 of these fans to the one on the condenser to evacuate heat from the cabinet in which the fridge is mounted. Of course this is overkill. But one could also use the Danfoss controller fan output, to trigger a relay to power fans rated at more than 0.5 amps, when the compressor is actually running.

My airflow system does not need more than one fan, and these upgrades, along with the extra insulation mean that ambient temps must exceed 90 degrees before this 1.8 cubic foot, 50 liter fridge exceeds 1 Amp hour per hour in my average usage. In 75 F it uses about 0.75 amp hours of battery capacity per hour, and in winter time average of 55F, it will take 3 days before it consumes more than 24 amp hours in my usage.

And my cheap American swill beer is 33F and gets there quickly!
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Old 01-02-2015, 05:22   #17
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Re: Computer Fan for Refrigerator Cooling?

Greetings and welcome aboard the CF, Sternwake, and Crabber50.
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Old 11-06-2016, 05:53   #18
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Re: Computer Fan for Refrigerator Cooling?

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Originally Posted by Sternwake View Post

I've also added a small 40MM fan to the interior of the fridge which runs 24/7 and blows into the small freezer compartment.
Thanks for the nice post Sternwake
Did you or anyone else for that matter use a NOCTUA 40mm fan inside the fridge?
I can not find any temperature range info at their website and I wonder if a Noctua fan would be ok inside the fridge?
Cheers
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Old 11-06-2016, 09:01   #19
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Re: Computer Fan for Refrigerator Cooling?

I too have used the Noctua fan. In my case, it exhausts the cabinet where the compressor is located. The fan is located at the top of the cabinet, with the make-up air openings located at the bottom.

These are great little fans, utilizing a fluid-filled magnetic bearing. Six year warranty and 150,000 hours MTBF! They are essentially silent, but can be slowed down (and made quieter) by the use of the included resistors. At maximum draw, my fan for example (Noctua NF-A8 FLX, 80 mm), uses less than 1 watt. Slowing the fan rotation with the resistors (which are simple plug-in devices) allows reducing the power consumption to about a half watt. I allow my fan to run continuously since I am primarily in tropical zones. Running at reduced speed keeps the compressor compartment at ambient temperature.

The Danfoss controller allows several ways to connect these fans. They can run continuously whenever the refrigerator is energized, or only run when the compressor is cycling.

In my case, I created a transition between the fan and an existing smaller hole that I used for the fan discharge. This fan has been in full-time operation for about 18 months. Occasionally I will clean the fan blades to remove accumulated dust (see pic). Otherwise, maintenance free. The bearing is sealed.

There are no exposed ferrous materials, but the oil used for the bearing could be affected by very cold temperatures. That would be the only worry I would have for use inside a refrigerator. I would certainly locate it on the refrigerator side, blowing into the freezer if that is the application. If just used for refrigerator circulation, I can't envision a problem.

I think I paid about $16 for my fan. They come in various sizes, and outputs. Highly recommended.
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Old 11-06-2016, 09:37   #20
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Re: Computer Fan for Refrigerator Cooling?

Yes, I already bought the outside fans (Noctua), pending installation. It's the suitability of the Noctua fan for use inside the fridge that I am keen to hear and learn more about. I did send a query to Noctua but while waiting for their reply please feel free to comment anyone.
Good point about the oil, Redsky.
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Old 11-06-2016, 11:17   #21
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Re: Computer Fan for Refrigerator Cooling?

An important item to note is that if the electronic control module of the Danfoss compressor see more than 0.5A from the fan circuit at start-up, it will aboard the start up and give you a 2-LED error flash.

Heat death of the electronic control module (behind voltage spikes) is the No 2 cause of controller death. In fact, the specs from Danfoss call for fan to blow on the heat dissipation fins in tropical environments. So you can never go wrong with keeping the mounting space, control module, and condenser cool in the tropics.
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Old 11-06-2016, 12:33   #22
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Re: Computer Fan for Refrigerator Cooling?

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Originally Posted by SV THIRD DAY View Post
An important item to note is that if the electronic control module of the Danfoss compressor see more than 0.5A from the fan circuit at start-up, it will aboard the start up and give you a 2-LED error flash.

Heat death of the electronic control module (behind voltage spikes) is the No 2 cause of controller death. In fact, the specs from Danfoss call for fan to blow on the heat dissipation fins in tropical environments. So you can never go wrong with keeping the mounting space, control module, and condenser cool in the tropics.

Agreed. In my case, the make-up air enters the cabinet (behind a settee seat back) near the bottom, flows across the refrigeration unit, and exits at the top of the cabinet. Prior to the installation of the fan, I used natural convection to ventilate the cabinet, even opening the cabinet access door when the unit was working hard. Powered ventilation is far superior. Especially for such a minuscule power cost as these fans require.

Every installation is different however, and very few are absolutely ideal. Best bet is to make as many incremental improvements as possible. That includes improved ice box insulation, gaskets, etc. Venting of the heat of compression/rejection is just as important.

Over the years, I have cut my energy consumption for refrigeration by better than half. Can't complain.
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Old 18-06-2016, 14:41   #23
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Re: Computer Fan for Refrigerator Cooling?

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Originally Posted by ErikFinn View Post
Yes, I already bought the outside fans (Noctua), pending installation. It's the suitability of the Noctua fan for use inside the fridge that I am keen to hear and learn more about. I did send a query to Noctua but while waiting for their reply please feel free to comment anyone.
Good point about the oil, Redsky.
I am using a 40MM fan inside my 1.8 cubic foot Vitrifrigo fridge having searched for the lowest amp draw computer fan I could find.

Sunon MagLev-Vapo 40mm x 20mm Fan w/ TAC Sensor Wire - (KDE1204PKV3.MS.AR.GN) - FrozenCPU.com

I emailed Sunon about this fan's ability to handle the temperatures inside the fridge/freezer and the reply was a snarky insulting 'absolutely not', IIRC.

I wired it to the fridge's light 12v power source. It has been running continuously for nearly 4 years without issue. I have it mounted blowing air into the freezer compartment whose flip up door I removed.

Items placed within the fridge have their heat extracted much much quicker with the fan, and internal temps vary only 1.5 degrees f, as opposed to nearly 15 degrees without the fan.

I Really like the Noctua fans, having 120, 80 and 60Mm fans, the 80 and 60mm added to the lid of my Adjustable voltage 40 amp Meanwell power supply( rsp-500-15).

The 120Mm NF-f12 on my fridge pushing air through the condenser( instead of pulling air through it) was an instant improvement in duty cycle for less noise and amp draw. The provided fan was ~72CFM and 0.12a, the Noctua is about 53CFM and 0.05a.

I put a filter on the intake to keep dust build up on fan blades and condenser fins to a minimum.

This is about 6 to 8 months of build up without the filter:



I also made a cooling unit shroud so that ALL the Noctua Fan's airflow is forced over compressor and controller and cannot be recycled, but is instead forced out of the fridge cabinet.

The internal fan allows me to use a setting of ~2.2 of 7 to hold sub 35F temperatures where with fan turned off I need a setting of 4 of 7 to hold everything inside below 40F.
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