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Old 01-02-2015, 02:36   #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, 04:22   #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, 04:53   #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, 08:01   #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, 08:37   #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, 10:17   #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, 11:33   #22
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Re: Computer Fan for Refrigerator Cooling?

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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, 13:41   #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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Old 26-11-2019, 17:19   #24
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Re: Computer Fan for Refrigerator Cooling?

To revisit this old thread -- I'm thinking about adding an auxiliary fan to our compressor compartment. What I haven't seen are comments on diverting the air inflow vs. outflow.

Our compressor is mounted in a 1 cubic foot locker with open vents on two sides. It has a fan mounted on top of the compressor and in front of the cooling fins. Air is drawn into the top fan housing and exhausts at the bottom sides.

To keep the compressor cool, we've been having to open the top settee.

I want to add another fan on one of the side vents. In post #8 it was pointed out to exchange air you should exhaust. I'm not sure if that will work. I'm picturing the airflow and don't see a clean flow. I'm thinking about adding baffles to separate the cool intake from the hot exhaust.

It would be pretty easy to add a 4" curved baffle from the side vent to the intake fan to draw in cool outside air and add an exhaust fan on the other side vent to exhaust the hot air from the bottom.

Thoughts? Thanks,
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Old 26-11-2019, 18:03   #25
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Re: Computer Fan for Refrigerator Cooling?

If your wanting to cool the compressor, put a fan that blows directly on it, I also put some inexpensive heat sinks meant for stepper motors on mine, figure it can’t hurt.
There are dozens, this is just one example
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Old 27-11-2019, 07:50   #26
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Re: Computer Fan for Refrigerator Cooling?

Getting the heat out of that compartment would be a good thing. Not sure the configuration, but ducting a bit from where the heated air comes off the unit to an exit grill would be a good thing, forcing it out as much as possible. If not that, cool air fan into the cabinet should force some warm air out. You may have a mini thermostat that turns fan air on already, not sure if yours is adjustable. Can you draw cool air from under an adjacent cabinet?
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Old 27-11-2019, 12:26   #27
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Re: Computer Fan for Refrigerator Cooling?

Thanks for the replies. If you look at the way the compressor and cooling condenser are setup, there's cool air drawn in by the top 4" fan and hot exhaust along the bottom. One thought is to run curved duct from one of the side vents to the fan, effectively bringing in cool air from outside the compartment. A flat horizontal flat plate below the fan to exhaust the hot air out. I'd add the aux fan to the other vent for exhaust. I can prototype with light cardboard.
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Old 29-11-2019, 02:20   #28
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Re: Computer Fan for Refrigerator Cooling?

Since my last post in this thread 3.5 years ago, Noctua has come out with new 120mm fans, which outperform the still venerable NF-f12.
I also have developed a lot more experience experimenting with powerful fans and controlling their speeds, and directing their flow.

The Newish Noctua A12x15 now resides on my Danfoss condenser, the 15mm fan width leaves 10 more MM behind my fridge for scavenging air from behind the fan in the cabinet. This fan is also quieter than the NF-f12 but draws more amperage and performs equally well attached to my condenser. I did not take before and after duty cycle measurements when I installed this fan but the overall amp draw remained the same, and it was quieter than the NF-f12.

My NF-F12 is now 6 years old and since aquisition of the A12x15, is relocated to exhaust the adjacent partition of the fridge cabinet, and is on 24/7/365, using the low noise adapters/ inline resistor cables in the winter months.
I've just updated my 1.8 cubic foot Vitrifrigo's door seals with an inner D seal inside the original door seal, and an exterior soft foam door seal cradling the whole door perimeter and other tiny additional insulation miodifications, and my average AH consumed per hour is now 0.42AH each hour , in 75f ambient and 0.46AH in 88F ambinet. Which is down more than 1/3 from before the door seal modifications and significantly better than I hoped for and expected..

Noctua has a newish A12x25 fan, which, when mounted to push air against a resistance like a fridge condenser, they claim outperforms 2 NF-F12s when mounted to a computer heatsink, very similar to a fridge condenser, in a push pull configuration. I've no personal experience with this specific fan, but the computer nerds are raving about it. I hope they make a high rpm industrial version of it soon.

Noctua also has come out with a NA-fc1 PWM speed controller for their PWM fans, or any PWM fans under 2 or 3 amps. One can power PWM fans with higher amp draw than this, directly, just using the output pwm blue wire to control PWM fan speed. PWM fans have 4 wires, Fans with only three wires are not PWM fans, the 3rd wire is to tell the computer mother board the fan rpm, the 4th wire is the PWM signal for controlling fan speed. I have cobbled together a PWM signal generator successfully, but the Noctua speed controller is a way better solution. Noctua's yellow wire is the power +, black the - green and blue are rpm signal and PWM.

Noctua also has 2k and 3K rpm industrial versions of the NF-F12 as well as some other fans, and the 3K rpm NF-F12 version has huge static pressure ratings and ~110CFM. I had issues with the 3K version of the NF-f12 and got 2 warranty replacements, then when those too failed, asked for 140mm versions instead as warranty replacements, and have had no issues with the 140's.
Noctua warranty service is great, I got new Fans delivered from Austria to California or Florida in less than a week after contacting them. They were perplexed by my high failure rate and sent UPS shipping labels so they could inspect the failed units, which I gladly packed up and mailed off at no cost to me.

I recommend users peel back the sticker on the hub of computer fans and cover the solder joints on the circuit board where the wires enter with clear nail polish or something similar, I use Amazing Goop, but its tolulene stank sticks around a bit too long afterwards, if one is sensitive to that. Almost every fan failure I have had is due to corrosion that forms here. Some can be resoldered and function again, some show the corrosion has wicked along the edge of the circuit board, or some other component released its magic smoke.

I love computer fans, and While Noctua design and engineering and warranty service are hard to beat, I am a big fan of high rpm 38mm thick 120mm and 92mm Delta fans. I am not controlling their speed via PWM on the 4th wire on fans designed with such, but using a sub 2$ 5 amp voltage bucker with a XL40015 chip ( much better than the previous LM2596 3 amp chip) , that I remove the tiny 10K ohm, sometimes 50K ohm, voltage trimpot and add wires to a remote 10 turn bourns potentiometer of the correct resistance to get the full range of speed. These are not low power, nor are they quiet fans, at 12 volts, but they will slow to nearly silent and very low amp draws (sub 0.05a, even through the bucker), at around 6.9 volts.

The Xl40015 based voltage bucker loses only 0.3v across it, 12.0v in 11.7v out max. The 0.3v loss is inconsequential but can be negated by fatter wire feeding the fan in most cases if that extra flow is really desired. There are inexpensive voltage buckers employing this chip which also have a current limiting potentiometer, so one could limit current and thus max fan speed, to 0.49 amps or whatever they feel like and use the voltage trim pot to change fan speed from ~0.05 amps upto 0.49 amps though the fan might not start spinning on its own at 0.05 amps/ 7 volts but at 7.75v.
Some of these voltage buckers sold on Amazon or Ebay will come with the little 8.8 x 8.8mm stick on heatsinks linked to a few posts above, which one adheres to the chip's top, but I have found them to stay relatively cool passing half that 5 amp rating. Cool electronics are happy electronics, so I still add the heatsinks, just know some of the voltage buckers sold come with the heatsinks, and some do not.

It is the older LM2595 chip on voltage buckers passing 2/3 of its rating which got quite warm and really benefited from the heatsink, in my experience. One can get 10 of these older LM2596 3 amp voltage buckers for under 12$ and about 5 of the XL40015 5 amp buckers for that, shopping around e Bay, even from US based sellers/shippers. I've had only one failure of about 20 units, and it could have been induced by me overheating the CB when removing the trimpot and adding wires, and or overloading it with 6 amps worth of fans.

At 12vDC, and these Delta fans have no issues with 14.7v in my experience, they are monsters. Extremely powerful and loud with huge static pressure ratings. Dual ball bearing of course.

The Delta FFB1212EHE, my current favorite all time fan, is rated at 3 amps but draws 1.68a at 11.7v and moves 190 CFM, and has a huge static pressure rating, and responds wonderfully to voltage based speed control.

Delta has an even more powerful, ridiculously powerful 252 CFM 120x38mm fan too, but beware, this monster will not respond nicely to voltage based speed control, it will simply shut off at ~7 volts and be spinning way too fast and loud and drawing over 2 amps at 7.01 volts. It has a PWM 4 wire version but I never succeeded in controlling it via a PWM signal on that wire. Others have. I gave up.

The ~200 cfm Delta FFB1212EHE seems to move just as much air at 14.4v as the 252 cfm fan does at 12.0v, and I also employ 10 amp voltage buck boost step up step down converters on 24v E Papst fans with great success and airflow for less noise and amp draw than their smaller 12v counterparts.

The the amp draw of the delta 12v fans I've tested, nearly doubles at 14.7v so using a buck boost module is not desirable, nor really needed in any application I envision, but.........The potential is there to feed a 12v fan on a buck boost voltage converter and limit voltage by potentiometer value, or by the current limiting potentiometer, and get that extra power above battery voltage.

The massive potential airflow of the high CFM Delta fans is not needed for compressor/ condenser cooling, but they, and the voltage bucker and even a 10 turn bourn's 10 turn potentiometer can be had for less than one Noctua, if one shops on Ebay and can wait for free shipping from Asia which has been about 2.5 weeks average order to door in California.
While the Danfoss compressor controller can handle switching only 0.5 amp of fan, and the high power Deltas easily exceed this amount, one can trigger them with a relay and then control their speed with a bucker. Hot days loading the fridge down hard with warm items, crank it up and then back down once things are cooled down and extreme airflow is not required.
One could perhaps even have fan speed throttled automatically with ambient temperature.

One other thing I want to mention, for people who made it this far, about many of these Delta fans, is they have steering vanes comprising the hub support, in front of the impellers. These steering vanes keep the high velocity airflow in a nice tight column with little spread, whereas fans with 4 hub supports only send off air in 4 hot spots of flow, at much wider angles.
The steering vanes can blow through a condenser and then across the compressor and controller without the baffling required to do so with a regular 4 hub support fan. I have an Enermax rotatable grill attached to one Delta fan which redirects air at ~ a 30 degree angle from the face of the fan, and the 4 hub support fans have the significantly reduced flow spread wide and flat and slower, where as the equal CFM Delta fan sends a thin narrow fast moving column of air out at 30 degrees with little extra noise and seemingly no lost flow. I was so extremely impressed with this Delta FFB1212EHE fan's performance, I ordered 3 more the next day even though I don't really need them.

Glad to answer any questions and If I don't have any experience, or Don't know the answer, I'll say so.
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Old 29-11-2019, 02:40   #29
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Re: Computer Fan for Refrigerator Cooling?

Quote:
Originally Posted by ErikFinn View Post
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
sorry I did not see your post back in 2016.

I contacted Sunon who makes my internal 40mm MAGLEV fan about the fan being used blowing into the freezer compartment. The reply was an emphatic NO!
Mine has been running since october 2013 blowing air into freezer compartment 24/7/365 instead of cycling on and off with the compressor.

If it were switched on only with the compressor then i bet it would not be a happy fan, but running continuously it has had no issues. My specific 0.03 amp fan is discontinued and I've found nothing 12v with equally low amp draw without using resistors, but I've not really searched either.
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Old 29-11-2019, 07:49   #30
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Re: Computer Fan for Refrigerator Cooling?

Quote:
Originally Posted by Sternwake View Post
Since my last post in this thread 3.5 years ago, Noctua has come out with new 120mm fans, which outperform the still venerable NF-f12.
I also have developed a lot more experience experimenting with powerful fans and controlling their speeds, and directing their flow.

The Newish Noctua A12x15 now resides on my Danfoss condenser, the 15mm fan width leaves 10 more MM behind my fridge for scavenging air from behind the fan in the cabinet. This fan is also quieter than the NF-f12 but draws more amperage and performs equally well attached to my condenser. I did not take before and after duty cycle measurements when I installed this fan but the overall amp draw remained the same, and it was quieter than the NF-f12.

My NF-F12 is now 6 years old and since aquisition of the A12x15, is relocated to exhaust the adjacent partition of the fridge cabinet, and is on 24/7/365, using the low noise adapters/ inline resistor cables in the winter months.
I've just updated my 1.8 cubic foot Vitrifrigo's door seals with an inner D seal inside the original door seal, and an exterior soft foam door seal cradling the whole door perimeter and other tiny additional insulation miodifications, and my average AH consumed per hour is now 0.42AH each hour , in 75f ambient and 0.46AH in 88F ambinet. Which is down more than 1/3 from before the door seal modifications and significantly better than I hoped for and expected..

Noctua has a newish A12x25 fan, which, when mounted to push air against a resistance like a fridge condenser, they claim outperforms 2 NF-F12s when mounted to a computer heatsink, very similar to a fridge condenser, in a push pull configuration. I've no personal experience with this specific fan, but the computer nerds are raving about it. I hope they make a high rpm industrial version of it soon.

Noctua also has come out with a NA-fc1 PWM speed controller for their PWM fans, or any PWM fans under 2 or 3 amps. One can power PWM fans with higher amp draw than this, directly, just using the output pwm blue wire to control PWM fan speed. PWM fans have 4 wires, Fans with only three wires are not PWM fans, the 3rd wire is to tell the computer mother board the fan rpm, the 4th wire is the PWM signal for controlling fan speed. I have cobbled together a PWM signal generator successfully, but the Noctua speed controller is a way better solution. Noctua's yellow wire is the power +, black the - green and blue are rpm signal and PWM.

Noctua also has 2k and 3K rpm industrial versions of the NF-F12 as well as some other fans, and the 3K rpm NF-F12 version has huge static pressure ratings and ~110CFM. I had issues with the 3K version of the NF-f12 and got 2 warranty replacements, then when those too failed, asked for 140mm versions instead as warranty replacements, and have had no issues with the 140's.
Noctua warranty service is great, I got new Fans delivered from Austria to California or Florida in less than a week after contacting them. They were perplexed by my high failure rate and sent UPS shipping labels so they could inspect the failed units, which I gladly packed up and mailed off at no cost to me.

I recommend users peel back the sticker on the hub of computer fans and cover the solder joints on the circuit board where the wires enter with clear nail polish or something similar, I use Amazing Goop, but its tolulene stank sticks around a bit too long afterwards, if one is sensitive to that. Almost every fan failure I have had is due to corrosion that forms here. Some can be resoldered and function again, some show the corrosion has wicked along the edge of the circuit board, or some other component released its magic smoke.

I love computer fans, and While Noctua design and engineering and warranty service are hard to beat, I am a big fan of high rpm 38mm thick 120mm and 92mm Delta fans. I am not controlling their speed via PWM on the 4th wire on fans designed with such, but using a sub 2$ 5 amp voltage bucker with a XL40015 chip ( much better than the previous LM2596 3 amp chip) , that I remove the tiny 10K ohm, sometimes 50K ohm, voltage trimpot and add wires to a remote 10 turn bourns potentiometer of the correct resistance to get the full range of speed. These are not low power, nor are they quiet fans, at 12 volts, but they will slow to nearly silent and very low amp draws (sub 0.05a, even through the bucker), at around 6.9 volts.

The Xl40015 based voltage bucker loses only 0.3v across it, 12.0v in 11.7v out max. The 0.3v loss is inconsequential but can be negated by fatter wire feeding the fan in most cases if that extra flow is really desired. There are inexpensive voltage buckers employing this chip which also have a current limiting potentiometer, so one could limit current and thus max fan speed, to 0.49 amps or whatever they feel like and use the voltage trim pot to change fan speed from ~0.05 amps upto 0.49 amps though the fan might not start spinning on its own at 0.05 amps/ 7 volts but at 7.75v.
Some of these voltage buckers sold on Amazon or Ebay will come with the little 8.8 x 8.8mm stick on heatsinks linked to a few posts above, which one adheres to the chip's top, but I have found them to stay relatively cool passing half that 5 amp rating. Cool electronics are happy electronics, so I still add the heatsinks, just know some of the voltage buckers sold come with the heatsinks, and some do not.

It is the older LM2595 chip on voltage buckers passing 2/3 of its rating which got quite warm and really benefited from the heatsink, in my experience. One can get 10 of these older LM2596 3 amp voltage buckers for under 12$ and about 5 of the XL40015 5 amp buckers for that, shopping around e Bay, even from US based sellers/shippers. I've had only one failure of about 20 units, and it could have been induced by me overheating the CB when removing the trimpot and adding wires, and or overloading it with 6 amps worth of fans.

At 12vDC, and these Delta fans have no issues with 14.7v in my experience, they are monsters. Extremely powerful and loud with huge static pressure ratings. Dual ball bearing of course.

The Delta FFB1212EHE, my current favorite all time fan, is rated at 3 amps but draws 1.68a at 11.7v and moves 190 CFM, and has a huge static pressure rating, and responds wonderfully to voltage based speed control.

Delta has an even more powerful, ridiculously powerful 252 CFM 120x38mm fan too, but beware, this monster will not respond nicely to voltage based speed control, it will simply shut off at ~7 volts and be spinning way too fast and loud and drawing over 2 amps at 7.01 volts. It has a PWM 4 wire version but I never succeeded in controlling it via a PWM signal on that wire. Others have. I gave up.

The ~200 cfm Delta FFB1212EHE seems to move just as much air at 14.4v as the 252 cfm fan does at 12.0v, and I also employ 10 amp voltage buck boost step up step down converters on 24v E Papst fans with great success and airflow for less noise and amp draw than their smaller 12v counterparts.

The the amp draw of the delta 12v fans I've tested, nearly doubles at 14.7v so using a buck boost module is not desirable, nor really needed in any application I envision, but.........The potential is there to feed a 12v fan on a buck boost voltage converter and limit voltage by potentiometer value, or by the current limiting potentiometer, and get that extra power above battery voltage.

The massive potential airflow of the high CFM Delta fans is not needed for compressor/ condenser cooling, but they, and the voltage bucker and even a 10 turn bourn's 10 turn potentiometer can be had for less than one Noctua, if one shops on Ebay and can wait for free shipping from Asia which has been about 2.5 weeks average order to door in California.
While the Danfoss compressor controller can handle switching only 0.5 amp of fan, and the high power Deltas easily exceed this amount, one can trigger them with a relay and then control their speed with a bucker. Hot days loading the fridge down hard with warm items, crank it up and then back down once things are cooled down and extreme airflow is not required.
One could perhaps even have fan speed throttled automatically with ambient temperature.

One other thing I want to mention, for people who made it this far, about many of these Delta fans, is they have steering vanes comprising the hub support, in front of the impellers. These steering vanes keep the high velocity airflow in a nice tight column with little spread, whereas fans with 4 hub supports only send off air in 4 hot spots of flow, at much wider angles.
The steering vanes can blow through a condenser and then across the compressor and controller without the baffling required to do so with a regular 4 hub support fan. I have an Enermax rotatable grill attached to one Delta fan which redirects air at ~ a 30 degree angle from the face of the fan, and the 4 hub support fans have the significantly reduced flow spread wide and flat and slower, where as the equal CFM Delta fan sends a thin narrow fast moving column of air out at 30 degrees with little extra noise and seemingly no lost flow. I was so extremely impressed with this Delta FFB1212EHE fan's performance, I ordered 3 more the next day even though I don't really need them.

Glad to answer any questions and If I don't have any experience, or Don't know the answer, I'll say so.
Wow, we now have a fan guru aboard! Thanks for all the info.

I had a cooling fan fail on me last season, only thing I had access to was a cheap chinese PC cooling fan w cheesey LED lights...it worked...and now I can tell when the compressor is running by the glow of the multicolored LEDs!

With your posted research maybe I will upgrade my provisional solution this season.

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