Auxiliary fridge fans for Dometic 8CF fridge

[Yoda]

Yoda Keith, Pulling air across a radiator is more efficient than pushing (think air compressor, compressed air is warmer than non compressed air and vacuum air is cooler than non vacuum air). I dis like the fan setup on the camper. Will evaluate the fans in the spring and consider moving them up.

As for computer fans, the 3 pins are bat + Bat -, and speed. (not necessarily in that order in the plug). Most modern computers use PWM to control fan speed and use the 3rd wire to monitor fan speeds.

Thanks Joseph. To verify what your saying is the mounting location Scott did is better than my location below? Unfortunately there is not enough room in front of the fins to mount the fans. The outside vent cover is just too close, and cutting it would allow water into the area behind the fridge. There is also no room above either that I can tell. No way to blow out to the vent. The top baffle is in the way too - hard to see in the photos.

I could go to 140MM (about 108 CFM - 71 CFM for the 120mm) units, but they would need to be angled about 30 degrees (tilted towards fridge) to fit the 5" space between the fridge and side wall. Could be done, but I was concerned about the angled mount. The air flow would be directly at the cooling fins though. from the back of the fridge.

140MM units measure 5.51 x 5.51 x 0.98 inches 120MM units measure 4.72 x 4.72 x 0.98 inches so the will fit mounted flat towards the fridge (actually the mount will be just touching the back of the fridge).

Do you have any suggestions or ideas on other options?

Thanks for the help.

Keith

[Scott'n'Wendy]

In my opinion, if you can manage to mount extra fans horizontally, blowing up directly onto the cooling fins, it would be just as effective as the ones I have pulling the air across the cooling fins (blowing out). If there is a difference, it wouldn't be very much of a difference.

I like where I mounted my extra fans because I can swap in replacements in a couple minutes. I have extra fans with the quick disconnect bullet connectors pre-crimped on. So I shouldn't have to get really involved with a fan replacement while on a trip.

[Scott'n'Wendy]

How I wired in the extra fans.
One amp fuses in the ASK-1 fuse blocks.

[Yoda]

How I wired in the extra fans.
One amp fuses in the ASK-1 fuse blocks.

Thanks Scott - you picture answers a lot of question I had.

[Yoda]

I was researching more possible 120mm fans and found different IP ratings. First I cant find a IP rating for the stock fan Dometic part number 3851183016, I have found several with an IP52 ratings (dust and water resistant) and IP67 (dust and water proof to 3m), I am lacking in understand all of this, so What do I really need?

Then I ran across and interesting discussion on supplying constant 12V power as many of the fans cant handle much more. Don't know if this is true or not, but with my luck and my system charge voltage of 14.4V I would probably fry everything. Anyone know the real answer of typical voltage limits for these PMW fans?

So as it was raining and cold today I looked up 12V voltage regulators. Something simple that will deliver constant 12V regardless of input voltage like 14.4v. That's when I learned my knowledge is totally lacking.
This is what I found
https://www.amazon.com/dp/B09H264Z61..._rd_w=mz6u3&am

https://www.amazon.com/DROK-Converte...8743736&hv

https://www.amazon.com/Voltage-Stabi...8550635&hv

https://www.amazon.com/DROK-Waterpro...ds=dc%2Bvoltag

So can an electronics wizard decipher this if I do need constant 12V for theses fans. All the fans I am looking at draw less than 1 amp total per pair - closer to 0.5 amp.

I have sent off several email to the various manufactures asking for better definition of operating voltages, especially with charge voltage hitting 14.4v. No information yet.

Thanks in advance for educating me - and yes I understand the danger in this

One fan I am considering now (yes it can be loud at full power) is this one
https://www.amazon.com/dp/B00KFCRATC/ref=emc_b_5_t

It can put out 110CFM if needed.

Thanks
Keith

[Scott'n'Wendy]

14.4 volts is of no concern to a 12v (nominal) cooling fan. Handle up to a bout 20-22v with no issue. For years.
PMW means nothing to your application. It's just a method of varying speed....which you won't be doing.

The fan you are considering looks like it is noisy and overpriced. Just my opinion.

Remember, you won't be controlling the speed of the fan, so why buy the capability?

[Yoda]

14.4 volts is of no concern to a 12v (nominal) cooling fan. Handle up to a bout 20-22v with no issue. For years.
PMW means nothing to your application. It's just a method of varying speed....which you won't be doing.

The fan you are considering looks like it is noisy and overpriced. Just my opinion.

Remember, you won't be controlling the speed of the fan, so why buy the capability?

Thanks Scott
I am looking at controlling fan speed manually using the controller https://www.amazon.com/Noctua-NA-FC1..._dp&th=1&psc=1 and only use the extra fans when needed so I can control the noise. When traveling it not an issue. The existing fan is loud. Coolerguys https://www.coolerguys.com/ have some interesting IP67 fans too with a 3 pin speed controller that will work with them. One up to 157CFM
https://www.amazon.com/dp/B07P46D62Q...NsaWNrPXRydWU=

Thoughts?
Keith

[Scott'n'Wendy]

Well I think that controlling the fan speed is fine, I just wouldn't bother. The fans I'm using have a switch on them to change the speed, or can use pwm. What I found is on max speed I can only hear them if I stand right beside the fridge vents. So I leave them on max. The more airflow the better.
No one has ever commented that my fridge seems noisy.
So any fan you get you will just likely leave it on high...I think.

[Yoda]

I just heard back form Noctua Support-Team
"Can your components withstand that voltage?" referring to the 14.4 charge voltage
They can withstand that voltage, but it has a big impact on the lifetime of the fan. It is important to note that, running the fan out of its specifications voids its warranty.

I wonder if the other brands are the same. Makes me wonder if installing a voltage regulator might be prudent. Yes I am probably over thinking this, but would not want to damage anything.

Thanks
Keith

[Scott'n'Wendy]

The cheap fans I use lasted over 5 years in the 13-15 volt range before the bearing became noisy necessitating their replacement. Motor was still fine. Voltage impairing the motor windings was not an issue. They lasted much longer than the factory installed fans...so....

Either noctua is a pretty poor fan or their warranty department is just covering their, uh, butt.

Probably just a standard disclaimer for them.

IMHO...remember...... this is just a cooling fan....not a life support system..

[Todd_P]

This is the fan set-up I put together for my trailer. We were still making ice cubes in the trays and had rock solid ice cream when it was 97 degrees and no shade!

[Yoda]

Well to update this I got two of the following
https://www.amazon.com/dp/B00KFCRIQM/ref=emc_b_5_t

and the controller
https://www.amazon.com/Noctua-NA-FC1...tronics&sr=1-3 With this I can vary the speed as needed. I plan to put it on a simple switch so I can totally turn it off when not needed.

I also got some extra cabling. I am going to mount below the cooling fins pushing air up. Using two separate mounts located in the area shown in post #19. There is some existing wiring I need to avoid. Worst case Ill extend it to clear the area I need. Now to figure out the direction of air flow when the fan is running before I install.

Thanks for the help everyone.

[Yoda]

OK update on this project. I got the fans, mounts, extension cables, and controller and as it was a nice day yesterday (40's) I took a look at my mounting location again.

I need some advice on the wires that may be in the way that cut across the mounting path.


Starting at the top right the red wires that attach to some sort of sensor angle down to the left.There is zero slack in these wires and are currently very tight where they attach to the sensor. I am wondering what theses wires do and can they be extended? I was thinking of using Wago connectors, or crimp terminals - not sure which would be better given the vibration. Maybe heat shrink but connectors and put additional heat shrink tubing over the connection?


This shows the wires angling down above the stock fan. There is basically no way to get to these without pulling the fridge as they are behind the top baffle that was installed from the inside.

It appears they pass through a zip tie and run down to the lower access area. I don't see any slack. I also cant find them in the lower opening. To get the photo I had to stick the camera lens behind the baffle. There is no way for me to get my hand in behind there.


Not much to see here, but I was expecting to find them on the left side in the wire bundle, but no such luck. Does anyone know where to look or where they might terminate?

I was thinking of mounting the NA-FC1 speed controller (no mounting holes on it) using double faced tape to the cover of the black box in the lower left corner, or to the sheet metal cover below the drain pan pipe (below bottom label), but not sure how hot the metal gets.

Thanks for any help or suggestions

Keith

[Scott'n'Wendy]

That sensor is what turns the fans on/off.

[Yoda]

That sensor is what turns the fans on/off.

Thanks
So they should tie into the covered control board below? Sure seem like heavy gauge wiring.
Thanks for the help