Dometic Refrigerator RM 2852 Questions

[mousepad]

1.  Can the Dometic fridge model RM 2852 be used outside of an RV, hooked up to a 20# propane tank fitted with a regulator set to 11" water column?

2.  Do pretty much all of these RV propane fridges have the same port to receive propane?  The above model has a male flare fitting, though I don't know what size it is.  Could someone please tell me?  I have a PDF of the owners manual.  I can't find the answer I see within its pages. 

Thanks to all in advance.

[TXiceman]

It also has to have 12 VDC to power the controls.

Ken

[lenp]

You will also need some sort of enclosure to ensure air flow over the coils on the back.

Lenp

 

 

[Kirk W]

• If you visit the site of Bryant RV you can download a copy of the service manual, Dometic 12 Series and 52 Series Service manual. Lemp also gave good advice as you could operate it for a short time to test it without any sort of cabinet, but for proper cooling  the air flow must be directed.

[bobsallyh]

mousepad, all the RV refers I have worked on have had a 3/8" flare.

[mousepad]

23 hours ago, lenp said:

You will also need some sort of enclosure to ensure air flow over the coils on the back.

Lenp

 

 

I'm have a very difficult time understanding how an enclosure facilitates air flow.  I assumed it would do the opposite.

13 hours ago, Kirk W said:

• If you visit the site of Bryant RV you can download a copy of the service manual, Dometic 12 Series and 52 Series Service manual. Lemp also gave good advice as you could operate it for a short time to test it without any sort of cabinet, but for proper cooling  the air flow must be directed.

Thanks Kirk.  Although the manual is actually for a model different than the one I own, the DOMETIC MANUAL REFRIGERATOR DIAGNOSTIC MANUAL on page 17 says:

In a good installation there should be as little open space as possible surrounding the sides and top of the refrigerator to achieve proper airflow. All potential dead air pockets should be blocked or baffled to insure that heat from the cooling unit won’t be trapped in these spaces and reduce efficiency. In addition, the cooling unit should be at least one inch from the nearest surface made of combustible materials.Please follow the installation manual for proper dimensions and clearances. . . . The addition of a metal chute the width of the enclosure, that extends from the upper side vent, will help eliminate the possibility of dead air pockets. It helps direct the hot air out the exhaust vent.The best method for venting the absorption refrigerator is with a lower side vent and a roof vent.

Do you think all would be fine were I just to install the fridge in an outdoor open area under cover where it will stay dry and out of direct sunlight?

[Darryl&Rita]

Think of a chimney. Heat out the top draws in cool air to the bottom. 

[mousepad]

Oops, I didn't mean to post yet. 

It seems so counter-intuitive that to insure air flow it is mandatory to have enclosure or constriction of sorts.  I invite someone to attempt to make me understand.  :  ) 

[lenp]

Hot air rises drawing in cool(er) air at the bottom of the enclosure (chimney).  This cooler air helps keep the fins on the back of the unit cool.  If these fins don't get cooled, the unit will not cool properly.  Without the chimney the fins simply generate heat and there is no natural air flow to dissipate it.  Without an enclosure your at the mercy of the wind to cool them.

The unit will still operate out in the open but nowhere near as efficient.  

You could probably make it work by installing a fan to blow cool air over the fins.  Many people (and some RV manufacturers) install 12 volt fans in the "chimney" to improve cooling.  Especially if installed in a slideout. 

I once had to replace the cooling unit on a Dometic and left the unit sitting on the patio overnight to test it.  It would not sufficiently cool the interior sitting outside.  After installing it back in the RV with it's chimney it worked fine.

Hope this helps.

Lenp

[Kirk W]

Keep in mind that an absorption refrigerator operates by convection flow so natural movement of the refrigerant due to heating and cooling is critical to efficient operation. The RV refrigerator is designed to operate inside of a space of specific dimensions in order to direct the air movement to the locations where it is needed and to also keep air movement away from other locations. This type of refrigerator not only requires enough cooling in order to operate properly, excessive cooling will also prevent proper operation. That is the reason that the specs list a minimum ambient temperature for proper operation. 

[mousepad]

Darryl&Rita, thanks for the analogy.  I totally got it.  By the way, nice avatar.  I remember listening to that cassette on a walkman in the 80s!  lenp, thank you for your anecdote.  I actually would have asked if anyone had done what you explained.  Lucky for me, you preempted it.  How right you are Kirk W.  I eventually found the installation and operations manual.  It can downloaded at the below link.

Dometic Americana Model RM2652 & RM2852

The manual even tells you how big the cutouts need to be for the upper and lower vents.

I should have done better researching prior to purchase.  It turns out there is a recall on this model, as explained here at the official Dometic website.  Based on my unit's model and serial numbers, it is affected.  According to the website, a secondary burner housing kit needs to be installed.  The site warns that if there is a yellow residue at the back of the refrigerator then it must be shut down and not operated until the above mentioned installation is completed.  There is a yellow residue on the back of my refrigerator.  Based on the brief research I've done a few days ago, it sounds like that symptom means that it is "toast," and that a replacement cooling unit costs hundreds of dollars and takes hours to install.  That being said, I assume that my fridge will not cool. 

If I get the secondary burner housing kit installed at no cost at the local service center, can I expect my refrigerator to function properly?

[Kirk W]

With the yellow residue, probably not. That yellow stuff is the zinc chromate from the refrigerant that has leaked out. They use a mixture of distilled water, ammonia, and the chromate as corrosion preventive. Most likely your cooling system has already leaked and is dry. 

That update is probably the one that was added several years ago to prevent the boiler from overheating and causing a fire. Am I correct that you just bought this used refrigerator? I hope that you didn't pay much for it.

[mousepad]

9 hours ago, Kirk W said:

Am I correct that you just bought this used refrigerator? I hope that you didn't pay much for it.

Yes.  Unfortunately I did, but fortunately I think I may be able to get a refund.

[mousepad]

You ladies and gents are very knowledgeable and generous in sharing it with me.  Thank you all.  I contacted the folks at https://www.rvcoolingunit.com/ and learned that this model has a PC board and must have DC power to the PC board before anything will work.  I'm embarrassed to say that I don't know what that means.  Could someone please put it terms that this layman might understand?  I'm assuming that it means the refrigerator must either be plugged into a standard household electrical outlet, or it must somehow be connected to a battery (like the kind in an RV or car). 

This (perhaps false) assumption of mine leads me to suspect that the propane is responsible for the cooling whereas the electricity powers the thermostat, on/off switch, and an automatic kill function for the gas supply if the flame goes out.  Am I close?

[Kirk W]

No problem, as we all had to learn sometime.

All of the controls of an RV refrigerator require 12V-DC power in order to operate. If you connect the plug to 120V-AC power it will not solve that problem. The only thing that ever gets power from that cord is the electric heater that can supply heat to the boiler in place of using propane. Look at the installation instructions in the service manual that you downloaded and it should tell you where the positive and negative sides must be connected. 

[mousepad]

So I built a box with the manufacturer prescribed ventilation.  I noticed that the unit's check light came on, which as I understand it is the refrigerator's way of telling me that the fire did not light.  Well the heat coming from the flue tells me otherwise.  Has anyone else experienced this phenomenon in which the check light powers on despite the flame burning well?  Would this interfere with normal efficient operation?

Unfortunately the interior did not get cold, or for that matter even cool.  It seemed to have gotten warmer.  I see that on ebay I can buy a refurbished cooling unit with a 2 year warranty.  Although the price seems fair, I wonder how likely is it that I might take my refrigerator somewhere and have it repaired without having the coils completely rebuilt.  Perhaps this possibility may carry a lower price tag than the $440 + $85 S & H.  Does any have any input they would like to share with me?

Thanks in advanced!

[Kirk W]

10 hours ago, mousepad said:

I noticed that the unit's check light came on, which as I understand it is the refrigerator's way of telling me that the fire did not light.  Well the heat coming from the flue tells me otherwise. 

The check light only means that there is some type of failure in the refrigerator. While a failure to light might cause it to turn on, there are a host of other things which also can do that such as low voltage, poor propane supply, a circuit board failure, or just about anything else. While it is possible that a new cooling unit may resolve the problem, it doesn't come with new circuit boards so it may not be the problem. Based on what you say about it heating up but not cooling, my guess would be that the cause is in the cooling unit, but that is also just a guess.

[Lou Schneider]

JC Refrigeration makes a 12 volt compressor driven replacement cooling units that are much more efficient than the propane units.

But since you're looking for something to use outside the RV, it may be better to look at a compressor powered 12 volt chest refrigerator/freezer.

Here's one example, a Google search will find more:

https://www.homedepot.com/p/Whynter-2-83-cu-ft-Portable-Freezer-FM-85G/202555700

Edited June 15, 2020 by Lou Schneider