External fans for Norcold fridge

[garyemunson]

Gary Munson
10 hrs
In September we took a trip from Nevada to Florida. For most of the ride we encountered unseasonably hot weather. Kept having the problem of the freezer and fridge running warm (10 degrees freezer, 45 fridge). At night, with cooler air, the freezer would go to 0 and 35 for the fridge. Examining things, it became obvious that while driving, there just was not enough air circulating through the rear of the fridge area. I'd previously replaced the sensor for the original fans but the little computer size things just were not doing the job. And, yes, the recommended shrouding was in place. I decided to install more robust fans that will exhaust directly out of the rear compartment top vent. I found these on eBay for about $25. They are small automotive radiator fans. I found wiring them in series cut the speed down and made them very quiet and also reduced current draw to less than 4 amps. They still move a LOT of air. I used flat aluminum stock from Home Depot to make the support brackets. As the RV wall is plywood over foam, I Liquid Nailed a couple strips of 3/4" wood to the inside of the wall to provide something solid to screw the rails to. I'll probably have to wait until next summer to see how this will work but I'm optimistic!

[garyemunson]

My Norcold has 2 computer type fans. I removed them when I did this mod as they just were not doing the job. Maybe newer coaches have 3 because of this reason. Hadn't seen the 200mm computer fans however I think I still would have bought the automotive ones as they are probably going to be longer lived in this application as they are made to not be damaged by water. Not that the area gets wet but it would expose them to high humidity on damp days. With the volume of air these new fans move,I'm doubting direction of airflow will make any difference. We camp year round so at the moment the fans are not in use here in the cool Reno fall. Hadn't thought about the flue issue. In testing with the snap disk jumped it did not seem to be affecting the flame. My short "testing time" probably didn't prove whether the airflow is going to also cool the flue and affect the cooling. Next summer will tell the tale. If needed I'll reverse the fans.

[CincyGus]

For those of you looking for bigger fans, I know they sell 200mm one for top of computer cases to exhaust the rising hot air. Thermaltake 200mm Fan Looks like $13.19 gets you on your way.

[momentum_rv]

If it's a 4 door Norcold it should have 3 fans already in the back. Airflow bottom to top. Adding more fans reversing the flow will be fighting existing fans.

[2012Coleman]

So how loud are they?

[CA_Traveler]

garyemunson

After mulling over your fan arrangement I’ve concluded that the cooling will be reduced by your fans. Here’s why:

Your high volume downward draft fans will likely do a good job cooling the fins. But the flue is another matter. The flue is designed for the heat to flow up and the baffle helps to circulate and distribute the heat throughout the flue. Your fan arrangement is going to blow the flue heat downwards resulting in inadequate flue heat and hence inadequate cooling. There is also the possibility that your high volume air may blow out the propane. But for either propane or AC there will be less flue heat for cooling.

Even with a upward draft the air flow can be to much and not allow the flue heat to work. Perhaps even your series connected fans would have to much air flow. Don’t know.

Two other minor points: A downward flow might raise the electronics temperature. And using fans to create a positive pressure will cause hot air to enter into the rig inside if there are any air leaks.

This is based on my understanding of how absorption refers work so let us know what happens next summer.

[CA_Traveler]

I also have the plywood baffle and slide mounted refer. And will look into alternate 12V fans, perhaps a single 14" fan.

[2012Coleman]

CA Traveler wrote:
Read his second post.

Oh - OK, missed that. I agree then. Suck the hot air out of the top. I have the same issue on my new fifth wheel. Fridge is in the slide so no roof vent. They made a chimney out of plywood and have 4 computer fans about midway up, but fridge still performs poorly in the summer heat. It gets hot up over the coils at the top.

Still going to do this mod - but am going to suck hot air out at the top.

[gatorcq]

garyemunson wrote:
I ended up with the fans intaking at the top and blowing the hot air out the bottom. I can reverse this if I find it's not working next summer.
Fans I used..
https://www.ebay.com/itm/2x-10-inch-Universal-Slim-Fan-Push-Pull-Electric-Radiator-Cooling-12V-Mount-Kit/151521113218?epid=502641911&hash=item23475cb482:g:Ho0AAOSwuMFUlG0W:rk:7:pf:0&vxp=mtr

Hot air rises - The Norcold book states this - reverse fan

[Old-Biscuit]

garyemunson wrote:
I was going to have them blow out the top at first but noticed that I'd have to reverse the blades for that to be efficient (and reverse polarity). Thought I'd try the top down first. When the snap disk doesn't turn them on, convection will do the cooling (bottom to top). I really do not think it is going to make a difference when they are on considering the amount of air they are moving. Individually the fans draw about 8 amps and are far too noisy and move much more air than is needed. In series they work just right for me and use 1/2 the current.

Can't you just turn fans around?

And they may enhance cooling due to size/CFM of fans BUT
NO...blowing air down top to bottom is NOT how an absorption fridge gets rid of heat.
But it's your fridge ---have at it.

[doxiemom11]

We had to add computer fans at the bottom, blowing up because of the hot sun and temps in N Mex this summer. Also able to put the awning out after springs winds stopped to help shade the frig area. Those 2 things made the frig more efficient and ran 10-15 degrees cooler on the same setting. That was a 4 door Norcold.

[garyemunson]

I was going to have them blow out the top at first but noticed that I'd have to reverse the blades for that to be efficient (and reverse polarity). Thought I'd try the top down first. When the snap disk doesn't turn them on, convection will do the cooling (bottom to top). I really do not think it is going to make a difference when they are on considering the amount of air they are moving. Individually the fans draw about 8 amps and are far too noisy and move much more air than is needed. In series they work just right for me and use 1/2 the current.

[CA_Traveler]

bob213 wrote:
Please correct me if I'm wrong (but agreeing with Old-Biscuit about draft) if you reverse the pos. and neg. wires the fans should push air up the stack rather than pull it out. Or..turn the fans around.

DC motors will reverse direction with reversed polarity so he could just reverse the wires. However his picture suggests to me that the blade design is such that he should turn them around for better efficiency.

[bob213]

Please correct me if I'm wrong (but agreeing with Old-Biscuit about draft) if you reverse the pos. and neg. wires the fans should push air up the stack rather than pull it out. Or..turn the fans around.

[CA_Traveler]

Do you know what the amp draw is for 1 fan?

I like those fans and amp draw is a secondary consideration vs better cooling for me. My plan is to have a on off on toggle switch inside a cabinet that will turn the fans on, off or on using a snap disk. Plus a small LED to indicate when the fans are running.