How to mod fridge venting

[rockfordroo]

Originally Posted by 270S

My concern are the arrows. The hole would have to go where the red arrow is pointing, but the blue arrow is the depth and the 1st 2" are the outside wall. I don't know if I can access/reach the area further in because that blue area is only a few inches deep at most and not very accessible.

And I then have to run the wire up to the top vent. This project may have to wait until I have the free time to pull the refer out to do proper analysis, allow access, and ….. I learned a long time ago, "Do it right the first time" or just don't do it.

BTW, instead of a switch, I may install a mechanical timer like I do on boats - activates fan to vent generator area during operation/after shutdown. Range minutes - 12hours.

Regarding #2, I wish I had a roof vent. I discovered too late that the only way to avoid 2 vents on the side is to select a floor plan without a refr in the slide.

My fans are at the bottom. The wiring goes from the 2 white connectors over to the switches and then comes back to the connectors, then to the fans.

You can see one fan in the pic in post #25. I just used tie wraps to hold them in place.

[270S]

Originally Posted by SlowrideHD

These are the two computer case fans that I mounted inside my Cedar Creek fridge compartment. I removed the top grill opening for access and dropped the piece of plywood luan out of the way that is blocking most of the top opening. The fans are installed about as far down as I could comfortably reach onto a little shelf. I used epoxy glue to secure them on the shelf. One of the fans is wired to the factory thermistor on the cooling fins so that it comes on when the temperature goes up. The other fan is wired to a manual switch that is shown in the second picture. I have never needed to turn this on, even in the hot Arizona weather.

I also installed a small 2" fan (12volt out of a small inverter that went bad) inside my fridge to circulate air constantly. I pulled power for this fan from the inside light compartment. This little fan runs all the time the fridge is on and does a great job of keeping everything cold.

These two modifications have solved my problems of having noise inside when the old cheap cooling fan would kick on (the new computer case fan is super quiet) and not having adequate and even cooling inside the fridge.

How (where) did you route the power (wires) to the fans above?

[jtatum65]

Take a look at this site. They make cooling units and fan kits for all RV refridgerators. I bought their Dometic add-on Frame Fan bracket, kit 2 fans and the Dometic Evaporator Fan Greater inside Cooling fan kit. And both were easy to install and work great!

https://rvcoolingunit.com

[270S]

Originally Posted by jtatum65

Take a look at this site. They make cooling units and fan kits for all RV refridgerators. I bought their Dometic add-on Frame Fan bracket, kit 2 fans and the Dometic Evaporator Fan Greater inside Cooling fan kit. And both were easy to install and work great!

https://rvcoolingunit.com

That is the company I purchased my internal refer dual-fan from. I have a multitude of fans already that I can use so np need to purchase more. The good news is that by making me look again at his website, it appears he removes the wood POS evaporative cover and replaces it with sheet metal or aluminum. When I have the time, I will do likewise and post up. Thanks for pointing in the right direction.

Nice to know that there is almost nothing behind the wood.
I may add a fan horizontally below the exchanger to aid pushing through and a second vertically above to exhaust the hot air through the vent. That is how you do it professionally with real design features.

Best part is I'll lower the top edge so that there is more room for the hot air to exit properly! POS unprofessional installation by FR! Shown as bottom pic (again).

[tgarson]

I've fought that battle. Initial results were disappointing. I decided that I needed to learn how absorption refrigeration works. Fortunately there were enough resources on the 'net to allow me to do so. Subsequently, I modified my Dometic fridge installation in such a way that it works as well as any reasonable expectations would require.

Stock installation of the Dometic RM2451 refrigerator in our Forest River Wolf Pup travel trailer, performed
according to Dometics installation instructions, resulted in poor refrigerator operation due to accumulation of heat
from the boiler in the top of the back chamber, causing excess heating of the ammonia condensation heat exchanger.
After several hours of refrigerator cooling system operation, with ambient temperature approximately 85 degrees F,
the air temperature in the immediate vicinity of the ammonia condenser was nearly 130 degrees F. The freezing
compartment operated at about 26 degrees F with the refrigeration compartment over 50 degrees F.


A thorough understanding of absorption cooling cycle will greatly help grasping the meaning and import of what
follows. Articles are available* on the web that can provide the needed background,
so I will not go into the why here.


Several steps were required to ultimately remedy the problem, allowing the fridge to operate at the highest possible
level.


The first and foremost problems are heat leakage from the boiler assembly over to the condenser and excess heat from
the boiler exhaust tube dumping into the same chamber. It’s hard to get the system working when you are heating the
condenser almost as much as the boiler! I tried tinkering with adding fans and baffles according to the Dometic
installation guide, and that helped, but not near enough.


To solve this problem, I constructed an angled exhaust director tube out of steel muffler tubing that mounts to the top of the boiler tube and vents hot air and post combustion
gasses straight to the outside world. I then used 3/4” rigid foam to build an insulating shroud around the boiler unit. It is very important to not include the water separator portion of the condenser system, part of which is vertical above the boiler, inside the shroud. Once assembled, I further insulated the boiler by stuffing its cavity with fiberglass.


Next came the necessity of forcing air past all of the other components of the system. I added a 12Vdc squirrel cage
fan near the top to push a high volume of (hopefully cooling) outside air over the condenser plates. A 1/8” plywood
baffle helped. Mounting the fan on rubber dampers and using an adjustable voltage regulator allowed me to fine tune
fan speed vs noise. Two 12Vdc computer fans were installed near the bottom to blow cooling air over the absorber,
these also speed set by their own adjustable voltage regulator.


The piece de’ resistance was to install a thermocouple in the boiler. I did this by first removing the fridge from its
compartment, which allowed me to insert a stainless steel tube, right next to the boiler tube. The thermocouple then
easily slide into place. A temperature monitor and thermostat board was mounted to the bottom of the fridge cavity,
connected into the Dometic controller unit and adjusted to maintain boiler temperature at an optimal 165 degrees
centigrade.


See photos below. There are also a few simple baffles between the plumbing and the outer wall that direct air flow
around the pipes that don’t show in the photos.


Note: I maxed out my files for this post. Will try to do another post with the rest (5 more) of the photos.


Thomas Garson
Ashland, Oregon


* Absorption Cooling by Jeff Santner
Swarthmore College of Engineering

[tgarson]

Here's the rest of the photos of my fridge setup modifications.


It should also be noted that I added insulation to the top and sides of my fridge. See photos.


All electronics and fans came via eBay, except the squirrel cage fan which I ordered from Mouser.



TG

[bpcamper]

Originally Posted by SlowrideHD

I added two computer case fans to my fridge cabinet just below the top vent opening. I did this mainly to rid myself of the racket that the original equipment fan made when it ran. It was very annoying to me. I also dropped the luan piece of wood out of the vent opening because I felt it was a poor design that limited air flow. The computer case fans that I put in there are super quiet (can not hear them run inside my Cedar Creek) and move a tremendous amount of air. I have one fan wired to the factory thermistor on the cooling coil and the other fan on a manual switch that I have never had to use. Even in Arizona heat.

We had same issues and agree very poor design. We removed that wood cutting with jigsaw and have fans as well. All works very well now. No problems. There was so much heat before the microwave was HOT all the time .we had to open door to cool because all the heat built up was trapped. Who would design something like that!!!

[gresper]

thanks for a very informative writeup tgarson (and everyone else). I'm a casual forum lurker and enjoy reading these discussions. I purchased a 5-pack of (12V DC) ARCTIC 120mm Low Noise Case Fans months ago from Amazon http://a.co/3e2rzKW but haven't gotten around to modding my Dometic DM2652 fridge yet. My fridge works pretty good most of the time because Michigan doesn't get a ton of super hot days and I prefer forested campgrounds so am rarely parked in direct sunlight.

Can any of you advise if there is a good place to wire the case fans into the existing circuit panel (wiring diagram attached) in order to have the fans cycle on and off automatically with the heating units? (tap into thermister?)

If automatic cycling is not possible, where would be a good place just to tap into for 12V DC power? Ideally I'd like to tap into one of the panels existing fused outlets. Otherwise, I know that 12V power could be tapped into at the 12V terminal block inlet to the circuit panel but each fan only draws 0.25 amps and has very small gage wiring. Am I correct in thinking that an inline fuse (1 or 2 amp) should be used to protect the fan wiring then?

Picture of the back of my unit, Dometic DM2652 Rearview equipment and wiring diagrams attached for reference. All mod recommendations appreciated.

[garbonz]

For those without the ability or interest to do all the mods tgarson did, an alternative is to invest in the ARPRV module with the fan mods provided. That system provides both protection for the frig itself, as well as an adjusable system to control the boiler temperature and fan controls.

Note that tgarson is using squirrel cage fans, which the ARPRV system advocates, which move infinitely more air than the computer fans. Like 10 times more CFM than any of them.

Just an idea for your consideration. I have used the ARV products on several RV's and the unit is awesome, and customer support is great. The website has a compendium of Information on absorption fridge operation for those inclined.

[bpcamper]

We were lucky i guess, ours had 2 fans but one had stopped working or maybe never did. We got a computer fan replacement, wired it where bad one was and they work fine , cycling on &off as needed but tge biggest improvement was cutting away that board, putting foil insulated tape to block heat from entering walls& interior. It works excellent &much more efficient.

[270S]

Gresper, what model refer do you have? From post and numbers, it appears it is a smaller unit - ?6cuft model DM2652RBX. I have an 8cuft model DM2852LBEX. 6vs 8 after DM2. Not sure what RBX vs LBEX means. But the bottom vent area appears identical.


update - just did a google. Yes 6 vs 8 and the L & R refer to right or left hinge door. Still not sure why I have extra E in LBEX.

[gresper]

My fridge is a DM2652 (6 cu.ft.)
I have attached the Operating Manual I found for it. It is for all of the following Dometic refriferator models:
RM2351
RM2354
RM2451
RM2454
RM2551
RM2554
DM2652
DM2662
DM2663
DM2852
DM2862
NDM1062

[rockfordroo]

Originally Posted by gresper

thanks for a very informative writeup tgarson (and everyone else). I'm a casual forum lurker and enjoy reading these discussions. I purchased a 5-pack of (12V DC) ARCTIC 120mm Low Noise Case Fans months ago from Amazon http://a.co/3e2rzKW but haven't gotten around to modding my Dometic DM2652 fridge yet. My fridge works pretty good most of the time because Michigan doesn't get a ton of super hot days and I prefer forested campgrounds so am rarely parked in direct sunlight.

Can any of you advise if there is a good place to wire the case fans into the existing circuit panel (wiring diagram attached) in order to have the fans cycle on and off automatically with the heating units? (tap into thermister?)

If automatic cycling is not possible, where would be a good place just to tap into for 12V DC power? Ideally I'd like to tap into one of the panels existing fused outlets. Otherwise, I know that 12V power could be tapped into at the 12V terminal block inlet to the circuit panel but each fan only draws 0.25 amps and has very small gage wiring. Am I correct in thinking that an inline fuse (1 or 2 amp) should be used to protect the fan wiring then?

Picture of the back of my unit, Dometic DM2652 Rearview equipment and wiring diagrams attached for reference. All mod recommendations appreciated.

gresper: The white 2-wire connector at the bottom of your 3rd pic is the 12VDC connection. One is positive, the other negative.

Here's a pic of mine with my fans hooked into it (see arrow). I added two other connectors (below the arrow) so I could wire in two lighted switches to turn my two fans on/off.

[270S]

Originally Posted by tgarson

I've fought that battle. Initial results were disappointing. I decided that I needed to learn how absorption refrigeration works. Fortunately there were enough resources on the 'net to allow me to do so. Subsequently, I modified my Dometic fridge installation in such a way that it works as well as any reasonable expectations would require.

If you have seen some of my posts, you are a person of my own thinking and follow through. You have done the "NO Points for Second Place" routine, that I normally do, but even further!

Is this truly necessary though? After I added the internal (inside refer) fan my refer has worked wonderfully, even in Florida 90+ temps. I only started to investigate everything everyone else has done to theirs by chance discovering this subject on this forum.

I felt I could improve moving the air better, but so much of what I have seen others do is beyond what even I would feel necessary - and that is saying something. To those that have done the more involved mods, do you feel they were necessary to the degree done?

[m38mpp]

Originally Posted by zexel

Do not vent into the camper! When the fridge is run on propane you could get gasses in the camper. These units are supposed to be sealed from the interior living space. As far as better air flow on the condenser I had a unit in my previous camper configured the same as your's. I put two fans on the inside of the vent cover blowing out and it worked very well. Sorry I have no pictures and no longer have that unit. By the way I wired the power to the fans thru the thermal switch on the condenser so they only ran when needed.

I did the same on a Georgetown I had wired in a $6.00 120volt fan blowing up the chimney held on and aimed using zip ties. Bought a thermal plug in switch that went on at 110 degrees ,plugged it into the plug that was there for the fridge & then plugged the fan into it. worked great sorry no pics and don't own the coach anymore cost was about $15.00 total hardest part was finding the thermal plug.

[Ree]

We had noticed the wood baffle also and cut it all out. Or refrigerator is in the kitchen slide so no roof vent here. The performance of the cooling fins depends on getting the heat out from the refrigerator compartment. We also added block Styrofoam to seal the top and sides of the refrigerator so the heat stays only in the back and vents out the top opening. We took out the factory fan and replace it with nothing. The proof is in our refrigerator's performance. Pre-cooling the refrigerator before we load it helps. On almost any Florida day the refrigerator loaded stays at 35-38 degrees and the freezer stays at 5-10 degrees loaded !Plus NO fan noise.

[dbbd1]

To those that have wired their fans inside the fridge, what wires did you use? I have a Dometic with the light. I looked at rvcoolingunit site and, right now, their fan for my unit is out of stock. But, I already have some small 12v fans that I can use. Someone else mentioned wiring it into the light switch???

Thanks.

[rockfordroo]

Originally Posted by dbbd1

To those that have wired their fans inside the fridge, what wires did you use? I have a Dometic with the light. I looked at rvcoolingunit site and, right now, their fan for my unit is out of stock. But, I already have some small 12v fans that I can use. Someone else mentioned wiring it into the light switch???

Thanks.

Did you not read post #53?

Update - nevermind, missed "inside.". For inside, most wire to the inside light, BEFORE the door switch.

[dbbd1]

Originally Posted by rockfordroo

Did you not read post #53?

Update - nevermind, missed "inside.". For inside, most wire to the inside light, BEFORE the door switch.

Right. And, I'm no slouch when it comes to wiring and electrical, I was just wondering if someone had specifics. Otherwise, I guess, I'll pioneer this.

[rockfordroo]

Originally Posted by dbbd1

Right. And, I'm no slouch when it comes to wiring and electrical, I was just wondering if someone had specifics. Otherwise, I guess, I'll pioneer this.

I'm attaching a document that shows you how to disable the door heater at the inside fridge light. You can see that you can tie in the +12VDC for your fan at the same place the door heater ties in. I think most people just attach the -12VDC to the condenser coils. I seem to recall someone putting an alligator clip on his -12VDC lead and then he clipped it to the coils to turn the fans on and when he wanted them off, he just unclipped the alligator clip and let it hang down.