Fridge Vent Fan Questions

[TURNKEY]

Two questions, and I would appreciate the wisdom of the crowd:

1-I want to add vent fans to my small 5ver's fridge 'chimney' to improve cooling. I intend to use 2-3 computer fans. I assume it would be better to mount them at the very top of the chimney,(just under the bug screen that caps the chimney below the top roof cap) so as to 'pull' the air up, rather than on the inside of the bottom vent or below the cooling unit and try to "push the air up.

This is based on my belief that the heat generated by the fridge will naturally rise and will build up from the top down in the chimney. Just like an attic fan will cool your house better than trying to push air into your basement with a fan.

2-I don't want the fans to run if it isn't necessary. (We are off grid 95% via solar and I HATE all generators. Even mine.) Therefore I intend on installing a thermo switch to control at what temperature the fans will kick off and on. What temperature should it be rated? And where should it be placed?Norcold 6.3 foot reefer.

Thanks for your help.

[trail-explorer]

Norcold sells a thermal switch... part number 618093

[Gjac]

TURNKEY wrote:
I appreciate all the suggestions people have been giveng but I'm still looking at:
1-Is it better to pull air or push air?????


2-What temperature should a thermo switch be rated? And where should it be placed?Norcold 6.3 foot reefer.

I think pull or push makes little difference but CFM does. Having said that I believe a turbulent flow from a fan at the bottom cools better than a laminar air flow from natural venting or small fans at the top. A "fan in a can" produces more directional air than just a fan given the same CFM. I installed a bilge fan off a boat that I had (fan in a can) at the bottom of mine pushing up for that reason. It moves much more air than the small computer fans. I rarely use it because I also added a section of .020 FG sheet to the top to improve the natural venting of the air out the top vent as others have mentioned.

[sullivanclan]

I purchased one of RV fan kits, installed at top of fridge near coils and upper vent. Dropped temp nearly 10 degrees. Instructions said the fan was set to go on at 100 degrees inside that area.

I also purchased a switch so that I could turn it off when we boondocked but never bothered to install it. (I could easily disconnect fan power wire by removing lower vent if needed.)

I also do a good cleaning of fins and back of fridge each Spring.

[doxiemom11]

Check out a Norcold manual. The preset temps for the already installed vent fans are much much higher. We spent summer 2018 in N Mex and with the sun, our frig could not stay cool enough. We added a computer fan at the bottom of the exterior access blowing upward helping the hot air to move up and out thru the roof venting. After making this alteration, we were able to keep the frig at a good temp. Now that cold weather has arrived we have shut that fan off as you do need some heat for the frig to function properly and in extreme cold may even need to partially block the opening so that there is enough heat.

[Wild_Bill_888]

Fans will move cold dense air better than warm less dense air. The motors will age slower in cool air.

Suggest mounting small fans below coils, pointing straight up. The jets from these fans will move much more air than just the air that goes through the fan cages, and allow air to move freely when the fans are off.

Make some electronic savvy friends. They can make a cheap field effect transistor work as a voltage controled relay to turn the fans on/off without drawing any current from the solenoid circuit.

You can add a thermal switch in line with the FET in the range of 80-90F on the cold side, but you can find inexpensive adjustable thermostats on eBay and Amazon that would allow you to fine tune with experience.

Clean the dust off the coils and make sure ducting is well sealed and shaped to manufacturers specs and you should not need fans unless you spend a lot of time in hot weather.

[enblethen]

It would be better to suck in clear air and blow out dirty air. Fan would last longer.
I would turn it on around eighty degrees.

[TURNKEY]

I appreciate all the suggestions people have been giveng but I'm still looking at:
1-Is it better to pull air or push air?????


2-What temperature should a thermo switch be rated? And where should it be placed?Norcold 6.3 foot reefer.

[toddb]

The foil switch on the top controls my fans, came on the norcold fridge.

todd

[folivier]

Since you have solar what about wiring the fan power to the "load or street light" terminal on the solar controller?
That way the fans will only run when the sun is shining.
This terminal normally only sends power when the solar panels are delivering power, but check your manual.

[Chris_Bryant]

You could install a fan control ARP fridge defender and kill two birds with one stone.

[ScottG]

You could use the gas solenoid circuit to power a relay but I would not use it to power the fan(s) themselves.

[TURNKEY]

Wow...THAT is a cool idea 😉 (pun intended). The fans would pull a lot of power from the circuit board but what about only powering a small solenoid to switch the fans???

Also I'm surprised Son Of Norway you went full bore on the fan mount board such that you HAVE to run the fans to cool the fridge. I just don't think there would be enough draft through those 3 small obstructed holes without the fans running.

[Big_Dog2]

I have a Norcold model N81I in a 2007 Colorado fifth wheel. I installed a computer fan below the cooling fins. It is switched and in my opinion helps the refrigerator run more efficiently in hot weather. Previous to the installation I operated the refrigerator on # 4 setting (1 to 5 settings with 5 being the coldest). I now operate on # 3. I boondock 75% of the time and run the fan constantly in hot weather but occasionally shut it off in the evening if it cools off. The fan draws 0.5 amps.

I thought about controlling the fan operation by tapping into the wires that operate the propane solenoid. That way, the fan would only operate when the burner was on. I do not know how or if the circuit board would be affected and did not want to take a chance damaging something.

I wrote to Norcold for information: (cut and paste from my email to them - I have a Norcold refrigerator SN XXXXXX model N811 in a 2007 Colorado fifth wheel trailer. I installed a small computer fan outside the refrigerator to help cool the unit during hot weather. The fan draws about .5 amp (12 volts). The fan is wired into the "hot" feed for the fridge. With this arrangement, the fan runs constantly whether the propane flame is on or not. My question is: Would any damage occur to the circuit board if the fan was connected to the propane control valve? This would turn on the fan only when the propane burner is on.)

Their reply was: Hello,

SN XXXXX

Ref # 1021446

We do not recommend altering your unit in any way, that includes adding additional fans. Altering your unit violates your warranty and we have made notes in our warranty system. Please take you unit to an Authorized Norcold Dealer service center for all repairs.

If you have additional questions, please contact us.

Thank you,

Rhonda
Consumer Service
Thetford Corp/Norcold Inc.
800-543-1219 Opt. 1

I am not sure what the warranty threats are about, (info request made Oct 2017) since the trailer was ten years old at the time of request and obviously out of warranty. Not a very helpful reply since they made no attempt to answer the question.

I did not wire the fan to the solenoid so do not know the repercussions (if any) of that. I run the fan manually. I also installed a smaller fan (0.25 amp draw) in the interior of the fridge. I believe this helps to circulate the cold air within the fridge for more uniform cooling, especially when full.

We will be passing through Saskatoon mid June and mid July. If you are interested in seeing or discussing what I have done, PM me.

[ScottG]

I was going to use some foam insulation but the dimensions didn't add up right. I ended up spacing the back wall inward 1.75" by using 1X2's and luan paneling. Then I used the same .2" thick paneling to create a flue that directs exhaust out the roof.

[Son_of_Norway]

I did this project with 3 computer fans and a "Bayite" DC digital temperature controller that I found on Amazon. I leave the controller set at 75 deg. I used a piece from a plastic cutting board for the mount. This project works well and keeps the fridge 5-10 deg cooler.



The vent cover goes over the top of the assembly in the picture. (Hope this picture isn't too big. Still trying to figure out the RV.NET Photo Posting App.)

By the way, making sure that your refrigerator install has the specified gap in the back is a good first step.