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How Does an RV Refrigerator Work? It’s Pretty Cool!

How Does an RV Refrigerator Work? It’s Pretty Cool!

When you’re heading out on a long road trip, nothing beats the convenience of having a fully stocked fridge for the journey. But how does an RV refrigerator work, anyway? And what can you do to keep it running for years to come? Keep reading to find out! 

Salmon in RV Freezer
Yep that’s an RV freezer full of Alaskan Salmon

How Does an RV Refrigerator Work: The Simple Answer

An RV fridge cools your food to a safe temperature for storage just like your fridge at home. Often, it is smaller to fit in the space of the RV and has a few special features, like latching doors and the ability to run on different power sources. Just like your fridge at home, the RV fridge is what’s considered a heat pump because it moves the heat from inside the fridge to outside the fridge.

However, in the case of an RV, “outside” can literally mean outside of the RV as these refrigerators are vented. They also keep food cold or frozen when stationary and when going down the road.  

How Does an RV Refrigerator Work: The Complicated Answer

There are two primary types of refrigerators used in RV’s. The differences can impact your fridge’s size, cooling power, and efficiency.

Compressor Fridge

In this version, the RV refrigerator works by using a small compressor unit to cool. These fridges may use either 12-volt or 110-volt power (or 230-volt if not in North America). This is the same type of fridge commonly used in homes and will be most familiar to users. 

While DC options that can run off the RV’s batteries are less common, they are becoming more popular. These units are extremely efficient and consume very little power. The downside is they are typically more expensive to purchase upfront.

12 volt Efficient DC compressor fridge
Compressor fridges can be 12V ,24V or 120V. This is a 12V unit that runs on our batteries

Compressor refrigerators are more beneficial compared to absorption refrigerators (which we’ll talk about next) because they can usually achieve colder temperatures, even when it is hot outside. It’s a common complaint that RV fridges don’t keep ice cream hard in the freezer, but compressor fridges are your best bet for extreme cold.  

The Compressor Cooling Process

Compressor fridges use a closed-loop cooling system that relies on mechanical compression of gas by way of the compressor. Because of this, it’s sometimes referred to as mechanical refrigeration. There are three primary parts of the cycle.  

  1. Compression: In this stage, the compressor pressurizes the refrigerant vapor to a higher pressure. This high pressure increases the temperature of the refrigerant vapor.   
  2. Condensation: The hot refrigerant enters the condenser where it is cooled.  During the cooling process, the vapor condenses into a liquid just like water vapor condensing on a cold surface.
  3. Evaporation: The high-pressure liquid refrigerant is then forced through an expansion valve or small hole into a larger tube. This lowers the pressure of the liquid to its boiling point. The refrigerant has a very low boiling temperature (-15 to -20F) and this takes heat out of the refrigerator compartment. From here, the vapor makes its way back to the compressor where the cycle starts over.
Check out Wikipedia on vapor compression to learn the details of compressor refrigeration.

Although residential refrigerators also use a compressor, they only function when plugged into the wall. This limits your options as compared to an RV DC-based fridge.

Additionally, a residential 120-volt fridge consumes more power to keep cool than a traditional RV option. A 120-volt option may be cheaper to purchase up front, but the long-term inconvenience and energy usage may not make the initial savings worth it.  

Absorption RV Fridge

This has been the most common fridge style used in RVs over the years because they can run on electricity or propane. You will sometimes hear them referred to as a “2 way” (propane and 110-volt electric) or even “3 way” RV fridge (propane, 110-volt electric, and 12-volt electric) refrigerators.

You can always tell if an RV has this type of fridge because it will have vents on the outside of the RV where the fridge is located. The vents are needed to expel the exhaust and heat when the fridge is running on propane. 

RV fridge open filled with food
You can tell an RV has an absorption style fridge because it has fins at the back of the fridge compartment

It may seem counterintuitive, but this type of fridge burns propane to keep cool using a complicated chemical reaction that takes place in a set of tubes in the back. The heat from the propane is what runs the chemical process. 

The Absorption Chemical Process

An absorption RV refrigerator works by utilizing a combination of heat and chemical reactions between water, ammonia, and hydrogen gas (sometimes helium). The process is complicated, but like the compressor, the fridge is contained in an enclosed system.  There are three primary phases of the cycle. 

The absorption RV fridge cooling process
This is a diagram of the absorption cooling unit process that happens in the back of an absorption RV fridge. Attribution: Goran tek-en
  1. Regeneration (Boiler):  In this state, the refrigerant (ammonia) is mixed with water and placed in a location where it is heated until it boils (heat is by propane or electricity). The ammonia and water have different partial pressures causing them to separate. The water condenses lower in the system, while the ammonia continues to the top of the fridge. There it combines with hydrogen and rejects its heat to the atmosphere while condensing into liquid ammonia. 
  2. Evaporation: In this phase, the liquid ammonia vaporizes in a low partial pressure environment where it absorbs heat from its surroundings. This happens at the back of the fridge’s fins and absorbs heat from the fridge.  
  3. Absorption:  After the ammonia has vaporized back to a gas, it recombines with water vapor, and drips into a pool of liquid water ammonia solution. This solution is then ready to be boiled in the regeneration chamber, where the process starts over again.  

This process happens repeatedly when your RV fridge is running to keep it working and staying cold. One benefit of this process is that it is silent because there are no moving parts. 

RV Fridge Vent
You can always tell if an RV has an absorption RV fridge because it will have vents on the outside.

Using this type of cooling takes longer. If you are heading out on a trip, you should turn on your RV fridge at least 24 hours beforehand to allow the unit to cool down before placing food inside.

RV Refrigerator vs Home Refrigerator

Some RV’s have residential fridges in them and there is no difference between them, but the majority of RV’s have an absorption style fridge that can run off DC power or propane.  

Residential fridge in rv
Residential fridge in RV

Another obvious difference is the size and weight. An RV fridge is typically much smaller than a residential fridge. However, newer RV models are pushing the limits and adding larger and larger fridges. They also design RV fridges to handle bumps on the road with features like ledges on the shelves and latches to keep the doors from swinging open.

Alternative RV Refrigerators

If your RV doesn’t have a fridge (or a working fridge) or if you simply need more storage space for your next trip, here are a few options. 

Mini-Fridge

You can easily add a small mini-fridge to your RV. All you need to do is plug it in when you get to your campsite. If you have solar power, you may also run the fridge while you travel. While a mini-fridge takes up extra space in your rig, they do come in a variety of sizes, have a low price point, and zero installation. Make sure you put it somewhere safe during travel to prevent any mishaps. 

Portable Fridge / Cooler

Another option for gaining extra cooling space is a portable fridge/cooler. You could go the standard route of adding ice to a cooler, but even the best coolers have ice melt and soon your food is soaking in a pool of water.

However, if you go with a portable fridge/electric cooler, you won’t have to worry about that!  Some even have an optional freezer.  These units are also very versatile in terms of their power source.

Dometic CFX coolers, for example, have advanced compressor electronics that allow for minimal power consumption using 100-240V AC, 12/24 V DC, or solar power! You can even digitally control the temperature to get the perfect cool all day long.

Dometic CFX 40W 12v Electric Powered Portable...
  • Your purchase includes one cooler, one manual, one warranty card,...
  • Portable Cooler dimensions: 15.6” W x 18.1” H x 27.2” D |...
  • Additional features: USB Port – 5V, 500mA | Wi-Fi connectivity...

Residential-Style Refrigerator

Some people decide to upgrade their RV fridge to a residential-style refrigerator. This upgrade involves some work to accommodate the larger size and weight. Once completed though, you’ll be able to enjoy the luxury for years to come. 

residential fridge
Open fridge freezer. Side by side stainless steel srefrigerator isolated on white background. 3d illustration

Which RV Fridge Is Right for Your RV? 

Not only is it important to know how an RV refrigerator works, but you also need to know if it works for YOU. If you are in the market for a new RV refrigerator, there are several things you need to think about. How cold do you need to keep your food? Do you want to have a fridge and freezer section? Will you be living in the RV full time or taking long trips? If so, a larger fridge would definitely be convenient if your rig allows for this. 

Salmon in portable cooler
When we went to Alaska we took a portable DC cooler

Also, think about the size of your family. If you bring a large family along for the ride, you’ll go through food quickly. This means you’ll have to restock continually with a small fridge. 

If boondocking is your thing, a fridge that can run on propane will save you a ton of power. A 12-volt DC fridge is usually a great option if you have enough solar power installed. The more power you conserve, the longer you can stay off-grid. 

Pros and Cons

Let’s take a closer look at the pros and cons of the different types of RV fridges. 

Absorption RV Fridge

Pros

The absorption RV fridge type is Silent. When running on propane, it uses very little power. This makes it great for boondocking because it can work on either propane or electricity.

Cons

Absorption fridges are expensive and very inefficient when running on electric power. They do not cool as well as compressor types, are slow to get cold (12-24 hours), and have less food storage capacity. Absorption models are also more susceptible to outdoor temperature swings and can be a fire hazard due to the open flame in the back.

12-Volt Compressor RV Fridge

Pros

The 12-volt compressor RV fridge runs very efficiently on electricity and can usually run on solar. It gets very cold and can cool quickly. Plus, it has more space for food storage.

Cons

12-volt compressor fridges are expensive. They do make some noise while running, and they require a power source all the time.

120-Volt Compressor Fridge (Residential Fridge)

Pros

This fridge has the most powerful and fast cooling abilities compared to the other fridges. Residential Fridges are also less expensive than RV fridges and are usually full-sized, giving you more food storage capacity.

Cons

Residential fridges do make some noise and are not designed for RV use. This means the doors and shelves do not have latching mechanisms to keep them in place while driving. It also uses 120-volt power, so an inverter is needed when off-grid, making it much less efficient on battery power

Absorption to Compressor Conversion Option

So you may have noticed that the DC compressor fridge is a much better option for cooling capacity and electric efficiency. There is a way that you can convert an absorption style fridge to a DC compressor model to keep the same form factor but get better cooling and electrical efficiency. We did this to our fridge and made a video all about it.

The compressor cooling unit was made by an Amish company near Elkhart, Indiana called JC Refrigeration.

Converting our RV Fridge to a High Efficiency DC Compressor- 8x More Efficient! and Better Cooling!

Typical Lifespan of an RV Refrigerator

A traditional RV refrigerator, if regularly maintained, can last at least 15 years. Some can last up to 20 years if you’re lucky or make minor fixes along the way. This is a good thing because replacing them can be pricey! 

Tips for Maintenance and Usage

Here are a few simple tips to keep your RV refrigerator working more efficiently for longer: 

  1. Make sure your RV is level as your fridge will work better this way. This is especially true for absorption refrigerators. If you have a hilly drive, we recommend shutting off your RV fridge entirely rather than running it off the gas. 
  2. Keep your fridge out of direct sunlight. 
  3. Install an RV refrigerator fan to maximize airflow and increase efficiency. We explain the Truth About RV Refrigerator Fans in this article and share a video about our fin fan installation and the kit we used.
  4. Replace the gasket seal on the door to keep cold air from escaping.  
  5. Melt the ice on your fins by defrosting the fridge as needed. 
  6. Defrost your RV freezer to maximize function and space. 
Ice on RV fridge fins
Ice on RV fridge fins

Safety Warning for Absorption RV Fridges 

Absorption RV fridges have a flame in the back of them when running on propane.  Because of this, there is a risk of fire. If birds, insects, or debris get into the fridge’s vent and build up around the burner, it can catch fire.  This is one of the most common causes of RV fires, but it can be prevented.  

Pro Tip: Wipe down the condenser coil and propane components every couple of months and clear any debris, cobwebs, or buildup from the outside vent. This is very important to prevent a possible fire. 

Cleaning RV fridge
Keep the space in the back of your RV fridge clean! There is a flame at the bottom of that silver tube.

Now that you know how your RV refrigerator works, you can take steps to keep it running well for many years. And if the size or capability of your current setup isn’t cutting it, you now have options for added space and functionality.

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About Mortons on the Move

Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of The RVers, producers of “Go North” on Amazon Prime, co-founders and instructors of RV Masterclass, and contributing authors for Hwy.co and an Arizona travel guide.

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Derick Badgley

Tuesday 17th of August 2021

Great article. The chemical engineer in me was having trouble explaining to my dad how his RV refrigerator was working and why it took so long to cool down after running out of propane. You summed it up very well.

Glad to see that you are still enjoying life on the road.

Mortons on the Move

Wednesday 18th of August 2021

Lol, Glad, you found it helpful! Good to hear from ya :) Yea were doing pretty well, busier than ever.

Mortons on the Move

Tuesday 17th of August 2021

Thank you!

Greg

Friday 18th of June 2021

On my absorption refrigerator cooling fins there is a sliding tab with a wire on it typically on the right side. This is used to vary the temperature between the freezer and the refrigerator. With a refrigerator/freezer thermometer in each, and a bit of time (days of various adjustments) you can adjust to your liking.

Diane

Sunday 13th of December 2020

The most important takeaway from this for me was leveling the RV affects the refrigerator. Our RV does not have a leveling system. I did not think it a big deal. Something to adjust to when sleeping.

Yet, another learning opportunity.

Janet Jones

Thursday 9th of September 2021

My fridge just shut down & not being level is the only thing I can think was the problem ?

Diane

Saturday 12th of December 2020

Loved the article. This is something I have been wondering about.

I am such a newbie that only today after five months I figured out how to use battery power.

No idea where condenser coil or propane components are. Need to research which type of refrigerator we have.

I guess I have a new learning opportunity to explore.

Mortons on the Move

Saturday 12th of December 2020

Glad you liked it! There is so much to learn with an RV.

Jeff Callahan

Wednesday 9th of December 2020

Excellent article! You guys rock!

Tom Morton

Wednesday 9th of December 2020

Thanks Jeff! Glad you enjoyed it!

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