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.
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RV Refrigerator Tips: The Importance of Leveling
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RV Refrigerator Storage Tips
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RV Refrigerator Troubleshooting Quick Reference Guide
<strong>Ticket 38316 Fridge cooling solution gets warm but no flow or cooling effect
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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
I have a Dometic / Mobilcool 12/24v -3w 80 -mc -065lhI Fridge ,do you know them at all ,Bob
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!
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.
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.
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
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?