How Does an RV Refrigerator Work Using Absorption?

Back in the early days of RVing, ice was used to cool food and beverages much as it was in homes, before the advent of modern refrigeration. Mechanical refrigeration systems using compressors are noisy and require a lot of electrical energy, but provide fast cool down. This method has been almost universally adopted for household and commercial use, including refrigerators, freezers, and air conditioners.

Essentially, what refrigeration systems do is provide cooling effect by moving heat from where it’s not wanted, to where it doesn’t bother anything. This is the case for both mechanical and absorption-type refrigerators. Absorption cooling was invented by a French scientist in 1858, using water and sulphuric acid as the heat transfer medium. In 1922 Swedish scientists improved the technology with a three-fluid mix.


Related video: Why an RV Refrigerator is Best


For the RV market, the decade of the 1960s saw the gradual introduction of so-called absorption refrigeration systems, which somewhat magically chilled food and even made ice from heat! These units are quiet, have no moving mechanical parts, and require less energy, although they don’t cool as quickly as systems with compressors. The company AB Electrolux sold RV refrigerators under the Dometic brand and in 2001, Dometic became a separate company and now makes the majority of RV refrigerators.

Differences Between Compressor and Absorption Refrigeration

Both compressor-type and absorption refrigerators employ a refrigerant gas that has a very low boiling point temperature. In either type, when the refrigerant boils as it is exposed to heat, it carries heat away with it and then condenses. This change of state between a gas and a liquid provides the cooling effect.

The main difference between how absorption refrigeration works versus a compressor-type is how the refrigerant is converted from a gas back into a liquid, which allows the cycle to repeat. Absorption refrigerators change the gas into a liquid by employing only heat, with no moving parts other than the refrigerant gas, which goes around in a circle of tubes.

absorption-refrigerator
Photo credit: Dometic

The absorption cooling cycle consists of three phases: Liquid refrigerant evaporates in a low pressure vessel, picking up heat from the interior of the refrigerator. Due to the low pressure, heat required for evaporation is low. Next, the now-gaseous refrigerant is absorbed by a special salt solution. Then the refrigerant-saturated liquid is heated, causing the refrigerant gas to evaporate out. This hot refrigerant gas passes through a heat exchanger, transferring its heat to the outside ambient-temperature air. This heat loss causes the gas to condense back into a liquid, which then supplies the evaporation phase, as the cycle starts over and continues to do this as long as it has heat applied to the burner or heating coil.

RV absorption refrigerator coils are typically heated by either LP-gas burner or 120-volts AC and some may also use 12 volts DC electricity for heating, with the control circuit always powered by 12 volts DC from the coach battery. The circuit boards draw a slight current even when in storage, which along with other parasitic draws, can run batteries down. Therefore, during extended storage a battery maintenance charger should be used, or during shorter storage the batteries should be disconnected to prevent deep discharge which is harmful to batteries.


Related article: RV Battery Basics: A Beginner’s Guide


RV refrigerators perform better when there is sufficient airflow over the heat exchanger coils, especially in hot weather. Some refrigerators come from the factory with small air circulation fans behind the units to aid air circulation. If yours doesn’t have one, they can be purchased at RV supply stores. If your coach is plugged in to shore power most of the time, a fan that is powered by 12 volts from the battery may be fine. If you dry camp a lot (off the grid) a fan powered by a small solar panel may be best.

Tips to Improve Cooling Performance

RV refrigerator doors shouldn’t be left open for long; plan what you are going to do and move quickly to keep them cold inside. Other ways to improve cooling performance are to park so the sunlight does not shine directly on the side of the coach where the refrigerator is located. Also, before going on a trip, put ice in the refrigerator to speed up the cooldown process when it is started up. Check that the door gasket is sealing properly by slipping a piece of paper between gasket lips and then close the door on it. Try to drag the paper around the perimeter of the door; lack of drag will indicated places where the gasket is not sealing well.


Related video: Simple Tips for Keeping RV Refrigerators Efficient


Leveling is one of the requirements for proper operation of absorption refrigerators. Proper leveling must be maintained to provide the correct refrigerant flow. Without proper leveling, refrigerant within the cooling unit will collect and stagnate at certain areas. Without proper refrigerant flow, the cooling process will stop. To ensure proper leveling, the vehicle needs to be leveled so it is comfortable to live in. (No noticeable sloping of floor or walls.)

Final Thoughts

Looking to the future, it’s quite possible that solid-state electronic devices may be introduced to provide the cooling in RV refrigerators. But modern absorption refrigerators work well when used properly and will likely handle your cooling needs for years to come.

Have something to add to the story? Leave a comment below.

More related videos:
RV Refrigerator Tips: The Importance of Leveling
Diagnosing an Inefficient RV Refrigerator
RV Refrigerator Storage Tips
RV Refrigerator Replacement in a Few Easy Steps
RV Refrigerator Troubleshooting Quick Reference Guide

Discussion
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16 Responses to “How Does an RV Refrigerator Work Using Absorption?”
  1. Brett Austin

    RV Make: Monaco, RV Model: Windsor, RV Year: 2002, Brand: Norcold, Model Number: 1200 LIR

    My condenser has a leak. Will “stop Leak” work? what is the psi ?

    Reply
    • Customer Service

      Hi Brett. Thank you for visiting the RV Repair Club and the opportunity to assist with your refrigerator cooling unit. Stop leak will not work for a couple reasons, first the system is a closed set of pipes and tubes and there is no place to introduce the stop leak product. Second, Stop Leak plugs holes but also plugs the pipe and it would cause the solution in your cooling unit to get blocked and not work. If you have a leak, shut the refrigerator off immediately and take it to a qualified service center as the chemicals leaking out could create a fire. You will need to replace the cooling unit or the entire refrigerator if it’s an older unit. Check out the videos in the appliance section on the Norcold recall to see if your unit may fall within the recall serial numbers.

      Reply
  2. kim brown

    RV Make: palomino, RV Model: thoroughbred, RV Year: 2009

    i think this will be a very useful tool, thanks….rookie rv couple

    Reply
  3. George Edwards

    RV Make: Holiday Ramber, RV Model: Vacationer, RV Year: 2002, Brand: Norcold, Model Number: 120X-IMXX

    My unit after driving with gas on will go out,with no power to unit for about one hour then will start. Even went on 110V.The controller on the door will power that first hour can you help. Thanks George

    Reply
    • Customer Service

      Hi, George. Thank you for visiting the RV Repair Club site and the opportunity to assist with your refrigerator issue. To provide more specific technical information we need the make, model, and year of your refrigerator and RV as well. What it sounds like is a temperature “open” in the module board. If it only happens while driving using the propane and not when parked using electricity, something is getting hot and creates an open circuit that does not allow power to go through. As it cools, it closes and works? Another condition could be the house batteries? When running on propane, the refrigerator needs 10.5 volts from the house batteries to operate and even when running on electricity as the inside monitor panel runs on 12-volt power. If your batteries are not in good condition, they may be draining while driving down the road and when you stop and wait 1 hour the converter charges them back up? Take a multimeter and check the battery voltage during the time they are not working.

      Reply
  4. William

    RV Make: Open Range, RV Model: FR316RLS, RV Year: 2017, Brand: Norcold, Model Number: 8 cu feet model

    During a driving rain storm I noticed a puddle of water inside the coach on the floor near our Norcold refrigerator. The coach had been parked. As is standard with this refrigerator, it has two access/vent panels on the outside. After checking for the source of the leak – windows, roof, slide, etc., it appears that the source may be the lower vent panel. I added sealant to the inside of the panel trim ring, but would like to add a positive drain. Do you have a recommendation to add a drain to the acess panel or its trim ring?

    Reply
  5. raymond

    RV Make: sunnybrook, RV Model: 24ck fs, RV Year: 1999

    ac on roof doesn’t make any cold air. the fan blows good evaporator and condenser clean compressor wont come on. cant tell what brand the ac is

    Reply
  6. Denny

    RV Make: Tiffen, RV Model: Phaeton, RV Year: 2010, Brand: General Electric

    Does a household type refrigerator in an RV had to remain at the same leveling stats as a regular rv refrigerator

    Reply
  7. Marc Lobelle

    RV Make: SIBIR, RV Model: propane only, RV Year: 1965 ?, Brand: SIBIR

    I would like to convert it to electricity. I found the gaz boiler and the refrigerant pipe going trough it. this place was surrounded by rockwool. Is it possible to convert it to electricity by adding a resistance controlled by a thermostat in the frige ? What power should be the resistance ? Do you have something to recommend ?

    Thanks

    Marc

    Reply
    • Customer Service

      Hello Marc,

      To provide more specific information we need the make, model and year of your rig as well as what component you are referring to?

      Thanks,

      David
      RV Repair Club Video Membership

      We’d love to have you be a part of our community. We are convinced you will enjoy the benefits of becoming a member and having access to the best instructional how to videos and professional tips. We would like to offer you a special promotion for your first year membership.
      https://go.rvrepairclub.com/C11605

      Reply
  8. Betty

    RV Make: Forest River , RV Model: Cardinal, RV Year: 2014, Brand: Domestic , Model Number: RM1350

    Found information on how to make refrigerator freezer work better

    Reply
  9. Dick Bellows

    RV Make: Winnebago , RV Model: Journey 40L, RV Year: 2010, Brand: Norcold , Model Number: 1211

    My refer has a leak. The yellow fluid is showing in the outside panel of the frigi an amp is smell inside. How can I get it repaired!?

    Reply
    • Customer Service

      Hello Dick,

      The cooling unit has to be replaced. You can’t repair the leaks, they are sealed systems from the factory. If you are smelling ammonia and seeing residue, there is definitely a leak. The cooling unit isn’t too hard to replace though. It does take some time but it’s really just disconnecting some wires, removing the control board and the gas ignition system etc and then removing the cooling unit and installing everything is reverse. You may need a caulking gun for one part of install. The fridge will have to be pulled out of the compartment to do all of this too. If you decide to do it I would be more than happy to help guide you through the process, I would just need the make and model of the fridge and I can walk you through it.

      Hope this helps,

      Dan
      RV Repair Club Video Membership

      We’d love to have you be a part of our community. We are convinced you will enjoy the benefits of becoming a member and having access to the best instructional how to videos and professional tips. We would like to offer you a special promotion for your first year membership.
      https://go.rvrepairclub.com/C13778

      Reply
  10. Paul

    RV Make: keystone, RV Model: 220 RBI Bullet, RV Year: 2017, Brand: Dometic fridge, Model Number: DM2652LBFX

    THIS FRIDGE MAKES A HIGH PITCHED WHINE. Not all the time but seems to be when it is working hard to get the temp down.
    any suggestions of why that is or what to dao about it?

    Reply
    • Customer Service

      Hi Paul,

      Is this an RV absorption fridge or a residential fridge? A residential fridge can make high pitch noises like that from a faulty compressor. An absorption fridge should not be making any noise but what you may be hearing is the condenser fan kicking on. Some units have a fan on the back to blow more air across the condenser to release more heat, causing the unit to get colder faster. The fan could be going bad or have a problem with the install. Take the outside panel off and see if you can trace it. Sometimes you can get access to the fans through an upper outside vent, roof vents can be hard to reach and the fridge may need pulled if it’s in a hard to reach place.

      I hope this helps!

      Dan
      RV Repair Club Video Membership

      We’d love to have you be a part of our community. We are convinced you will enjoy the benefits of becoming a member and having access to the best instructional how to videos and professional tips. We would like to offer you a special promotion for your first year membership.
      https://go.rvrepairclub.com/C13778

      Reply