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How Does a 3-Way RV Fridge Work?

A 3-way RV fridge is a pretty common option on RVs.  It sounds like a cool idea, so what exactly are they and how do they work?

Rear view of RV fridge with cooling tubes exposed
Discover how a 3-way RV fridge works.

Does your RV fridge say 3-way on it? This is common to see on the front of RV fridges as most RV refrigerators are indeed 3-way fridges. Unlike the fridge in your home which runs solely on AC power, RV fridges are designed for multiple power options.

Having the ability to keep an RV fridge running at all times regardless of your power situation is important. Proper food storage while camping and traveling can be a battle. Having a fridge that can run multiple ways helps ensure your food stays cool and safe.

What is a 3-Way RV Fridge?

As the name implies, a 3-way fridge will operate in 3 different ways. Again, this is important for RVs as we sometimes don’t have shore power available to rely on. 

Your RV has 3 sources of energy to supply its various systems:

  1. 12-volt DC power is supplied by the RV batteries
  2. 240-volt AC power is supplied by shore power when you’re plugged in
  3. Propane supplies gas for the appliances that require it

Not surprisingly, these are also the 3 sources of energy that can power a 3-way RV fridge. Depending on your situation you can use any of the 3 to operate your fridge.

Each method will cool the fridge, however, they are not all equally as efficient. By far the most common method is running the fridge on 110-volt AC which is how it operates when plugged in at a campground.

Sometimes this is not an option and so other methods can be used to keep your fridge running and your food cold. Let’s break down the 3 ways a 3-way fridge can be operated.

12-volt DC Power

Your RV batteries operate anything on the 12-volt system. This includes things such as lights and water pumps. Operating your fridge on the 12-volt system means it’s running off the power of the RV batteries.

This is the least efficient way of running the fridge as it draws a considerable amount of power from your batteries. In the case of RVs with only a single or double battery bank, it can drain all your power pretty quickly.

240-volt AC Power

Another way to power your 3-way fridge is with 240-volt AC. This is the best way to power your RV fridge as it is an unlimited power source and runs the fridge most efficiently.

As long as you have shore power to plug into this is how you want to be operating your 3-way RV fridge. Using up battery power or propane when you could be running off of shore power doesn’t make much sense.

Gas

The last fuel source is by using gas. Your RV has lots of appliances that require propane such as the stove, oven, and water heater in many models. Your RV’s fridge can also be operated on gas when no electric power is available.

Propane burns pretty efficiently and with multiple tanks on most RVs, your propane will last for a reasonable amount of time. That being said, propane is again second to shore power when available.

Propane is more efficient than electricity when evaluating the total energy consumed…propane is 87% efficient; electricity is 32% efficient.

How Does a 3-Way RV Fridge Work?

3-way fridges work on what is known as the absorption principle. Because of their ability to run on gas, 3-way absorption fridges don’t require a power source. In comparison, compression fridges require electricity to power the compressor (which is what cools the unit).

The absorption method instead uses a sealed gas (ammonia) within a winding series of tubes to provide cooling. This gas needs to be heated for the process to work and so the design allows for 3 methods of heating the gas: 2 electrical heating elements, 1 being 12-volt and the other 240-volt, and a flame source. The 12-volt element is heated using battery power, the 240-volt element is heated by using shore power, and the flame source is ignited and burns using propane.

The concept is pretty basic and the fridges have been around for years because they are simple and they work.

Overview of the Absorption Principle

There are 5 main parts in the absorption system:

  1. Generator
  2. Separator
  3. Condenser
  4. Evaporator
  5. Absorber

The generator is filled with an ammonia and water solution. This solution is heated until the ammonia reaches its boiling point.

The ammonia flows into the separator where the ammonia evaporates and separates from the water. The heavier water flows down into the absorber and the lighter ammonia gas rises into the condenser. Without the heat, the ammonia turns back into a liquid.

The liquid ammonia goes into the evaporator where hydrogen gas is present and mixes. The ammonia once again evaporates. This evaporation process in the evaporator removes the heat from inside the fridge causing the fridge to cool down.

As confusing as it may seem, this type of system technically removes hot air rather than making cold air. (Sometimes science is weird.)

Which is More Efficient: Absorption or Compressor?

3-way absorption fridges are not as efficient as compressor fridges and take longer to cool down initially. This is why you have to start cooling your 3-way fridge the night before going camping in most cases.

What is the Best 3-Way RV Fridge?

Like many RV components, there are really only a couple of main manufacturers of 3-way RV fridges. Sunbeam, Norcold, and Dometic are the main manufacturers.

All 3 brands have been making RV fridges for a long time and they all use the same design and technology. Personal preferences aside, they are all basically the same fridge and one is not noticeably better than the other.

What is Better a 2-Way Compression Fridge or a 3-Way Absorption Fridge?

If you are in the market for a new RV fridge the better question to ask is: what is better a 2-way compression fridge or a 3-way absorption fridge?

For those who have access to shore power, a compressor fridge is more efficient, gets colder faster, and is a better option. If you are worried about electricity and want to option to use propane for fridge operation, a 3-way will work regardless of your location or situation.

3-way fridges require a level setup to function properly and are somewhat limited to ambient outdoor temperatures. They can only cool down to a certain temperature if you are constantly in really warm climates.


Keeping food cold while RVing can be a challenge. Having a properly working RV fridge makes travel so much easier. 3-way RV fridges have been used for many years and can provide cooling anywhere you are as long as you have one of the 3 energy sources available.

Do you have a question about your RV fridge? Ask below and we will try to help you learn something new.

 

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