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.
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
Ticket 38316 Fridge cooling solution gets warm but no flow or cooling effect
Hi Matt! Our experts responded with the following:
If the cooling unit is getting warm there are only a few things that could be causing it to not cool. The first would be low voltage to the heating element, make sure you have good voltage and good connections. It is a resistive load so low voltage will cause the heating element to technically heat up but not enough. You can test the output voltage to the heating element and make sure it is around 120v. Any less than 110v could cause cooling issues. If could be the control board causing the low voltage as well so check the input and output of the board to see where the issue is. If the voltage is fine, test it on gas as well. If gas and electric work fine but there is no cooling then most likely there is a blockage in the cooling unit. If this is the case, the cooling unit will need replaced. I would test it on both heating sources and if they both do the same thing then the cooling unit most likely is the issue.
Sincerely ,Dan RV Repair Club Technical Expert
Thank you!
Might be very useful for folks to understand if the terms in the text actually matched the terms in the illustration used. Add parenthetical references into the document.
Hi, the fridge is working fine. Just after some information.
My name is Don and I have a Dometic Model No RMD 8555 fridge/freezer. The unit works fine. The available information advises that the unit, when operating on 12 volts uses 170 watts. That’s fine. I am also aware of the 5 stage of temperature settings but I understand there is no thermostat as such. I am also aware that the means of cooling is by heating then expanding the refrigerant. However, Can you please advise as to what change occurs when the temperature setting is changed between levels. does the voltage get varied or reduced current (amps) . Does the unit draw less energy (watts) when on lower temperature settings?
any relevant info is appreciated. Don
That’s a great question and we’d love to help!
The ‘Ask an Expert’ section is currently for members to our online community. We do have a promotional offer if you are interested. This would include access to expert advice (like this), plus discounts, hours of Premium videos, etc. Please feel free to take a look. You can message us right back with your question if you decide to become a member and you will have a response within 1-2 business days from our experts!
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Jessica
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I have a Dometic / Mobilcool 12/24v -3w 80 -mc -065lhI Fridge ,do you know them at all ,Bob
Hi there Bob!
We’d love to help! Let us know what we can do to assist you by leaving a reply to this comment!
Sincerely,
Jessica
RV Repair Club Video Membership
Had cooling issue and dealer found upper baffle issue in top vent. Repaired baffle for proper ventilation. I put a small computer fan under the canister at bottom of fridge as I saw video that indicated this would help cooling. Doesn’t seem to help much that I can tell. Fridge is in slide and dealer confirmed that the 4 fans installed at factory are working. I travel with the LP on to try and keep fridge cold but doesn’t seem to help much. I live in Texas and I have talked to several RV folks that have similar problems with with their Dometic staying cold. Several have replaced the Dometic fridge with residential fridge and cooling problems solved. Claim residential gets cold faster, stays cold, recovers faster. They all say residential best for southern heat. Any modifications you can recommend to improve performance in southern heat?? Was considering installing auto radiator fan in top vent to suck air out of top vent and increase air flow over heat exchanger fins. I need to do something to make thisfridge work better or replace it with residential fridge. Thanks for your help!
Hey there Mike!
That’s a great question and we’d love to help!
The ‘Ask an Expert’ section is currently for members to our online community. We do have a promotional offer if you are interested. This would include access to expert advice (like this), plus discounts, hours of Premium videos, etc. Please feel free to take a look. You can message us right back with your question if you decide to become a member and you will have a response within 1-2 business days from our experts!
Please follow the steps below to receive the annual membership at the introductory rate:
1. Click on the email link: https://go.rvrepairclub.com/c18239
2. Click on the Premium Membership offer.
3. The Checkout page will display your Premium Membership purchase.
4. Fill in your Billing Details and create an account password.
5. Fill in your debit/credit card information.
6. Finish by clicking Complete Order.
If you have any further questions, please contact Customer Service at 1-855-706-3536 at your earliest convenience, or chat with us on our site.
We greatly appreciate your business!
Sincerely,
Jessica
RV Repair Club Video Membership
I HAVE A RESIDENTAL FRIDGE FREEZER SECTION GETS DOWN TO 12 DEGREES BOTTOM UNIT WILL GET DOWN TO48 DEGREES AFTER BEING CLOSED ALL NIGHT.ALSO NO ICE CUBES IN ICE MAKER TRAY.FRIDGE DOES NOT WORK ON GAS 110 ONLY.
Hey Jerry!
That’s a great question!
The ‘Ask an Expert’ section is currently for members to our online community. We do have a promotional offer if you are interested. This would include access to expert advice (like this), plus discounts, hours of Premium videos, etc. Please feel free to take a look. You can message us right back with your question if you decide to become a member and you will have a response within 1-2 business days from our experts!
Please follow the steps below to receive the annual membership at the introductory rate:
1. Click on the email link: https://go.rvrepairclub.com/c18164
2. Click on the Premium Membership offer.
3. The Checkout page will display your Premium Membership purchase.
4. Fill in your Billing Details and create an account password.
5. Fill in your debit/credit card information.
6. Finish by clicking Complete Order.
If you have any further questions, please contact Customer Service at 1-855-706-3536 at your earliest convenience, or chat with us on our site.
We greatly appreciate your business!
Sincerely,
Jessica
RV Repair Club Video Membership
installed solar for off grid camping, have a 2500 watt pure sine wave inverter, 600 amp hour battery. inverter burned out after 10 days operation, the frig only draws 440 watts, supplier said that I need a 5000 watt due to start up amps been arguing that there is not 10 times amp for start up
The article doesn’t explain how fridge temperature control works. My unit specs state that it has got temp control when working on mains and on gas (not when working on 12 Volts car battery). I found that when connected to mains, the mains is switched on and off by a thermostat, but I don’t see how the temp control is supposed to work when working on gas. I’d like to understand since the fridge doesn’t perform very well when working on gas, 10°C below outside temp is about the maximum cooling that I get.
Dear Frank,
Thank you for your patience. In response to your question-
It depends on the fridge but some models will use the same thermostat at the electric one. They are in the same system so it will lower the flame to drop the cooling cycle and then enlarge the flame when cooling is called for. There are 3-way fridges that have the gas control on a dial that can be turned to a higher or lower temperature. All this does is adjust the flame. There is a certain range the boiler needs to be at to operate. When on the high setting it boils faster and cools more and is constant. On the lower setting, the flame is smaller and takes longer to get to the range and once there it will only cool so much so it won’t be as cold inside the fridge. Most systems out there work off of just lowering the flame to either stop the cooling process or not allow it to cool as much and then enlarging it cool more.If the fridge isn’t cooling well of gas you would have to check the burner assembly. Any sort of blockage can cause a weak flame or erratic operation. There could be rust in the burner tube, debris on the orifice, bugs or webs creating a restriction or even something in the flue. We do have some great videos showing what to clean and how to trouble shoot this issue. I will post a link below. I hope this helps!
https://www.rvrepairclub.com/videos/rv-refrigerator/
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/c17323
Sincerely,
Dan
RV Repair Club Technical Expert
I was reading my owners manual for the absorption refrigerator in my travel trailer and it states that it shouldn’t be used continuously. Is this true and if so why? I like leaving mine plugged in all the time with the air conditioner and the refrigerator on. Should I shut off power to the refrigerator and leave it open or is it not that big of an issue??
Thank You in advance for your help on this!!
Walt Gaskins
Dear Walt,
Thank you for your patience. In response to your question-
I think they put that in the manual just to be on the safe side. If there happens to be a problem with the system and you aren’t there to know about it, it could cause other problems as well. There are people that live out of RV’s full time and there fridge is always one. I used to have one at a permanent site and would leave it on all summer, I know many people that do this. It doesn’t hurt the system to do this. It is just better to be around if something does go wrong with the system. Just make sure to check the venting regularly to make sure it is clear. Especially the roof vent. If there is a blockage and the fridge can’t remove the heat, it could cause some issues. Other than that, there should be nothing wrong with running the system all of the time. I hope this helps!
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/c16682
Sincerely,
Dan
RV Repair Club Technical Expert
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?
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.
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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!?
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.
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Found information on how to make refrigerator freezer work better
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
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.
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Does a household type refrigerator in an RV had to remain at the same leveling stats as a regular rv refrigerator
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
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?
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
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.
i think this will be a very useful tool, thanks….rookie rv couple
My condenser has a leak. Will “stop Leak” work? what is the psi ?
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.
Just for information