Man opening an RV fridge door

How to Keep Your RV Fridge Cold While Driving

Share on Facebook Share on Twitter Share on Pinterest

There’s nothing like a cold fridge full of your favorite foods to make you marvel at how far science and engineering have come – except, perhaps, a cold RV fridge that travels with you wherever you go!

Life on the open road involves making some trade-offs; you’ll have to forgo your china cabinet and hot tub when you live in an RV, but some creature comforts just can’t be left behind. For many RV owners, a fridge is one of these necessities. Sure, it’s possible to live off non-perishables, but if fresh produce, meats, dairy products and cold beverages are on your menu, you simply can’t go without a refrigerator.

Running your RV fridge when you’re stationary is simple: just set it to your preferred power source, turn it on and it’ll handle the rest automatically. But when it’s time to pack up and head off to your next destination, things can get a little tricky. Fridges use a lot of energy and, depending on the power source, may even be dangerous to run while your RV is in motion.

So what’s a traveler to do with a fridge full of cold food and an eight-hour drive to undertake? The answer is highly debated and depends heavily on your unique RV setup. Let’s take a look at both sides of the RV fridge dilemma and find out how to keep your food cool when your engine heats up.

Refrigeration Explanation: How RV Fridges Work

Your typical RV fridge works very differently from a residential refrigerator. Understanding the refrigeration process will help you get the most out of your RV fridge and keep it running in top shape.

Household Fridges

Shiny chrome residential fridge in a clean white kitchen

A household fridge runs on 120V AC power and uses a cooling method called vapor-compression refrigeration. It has three main components: refrigerant, a compressor and a series of coils that run both in and out of the fridge.

The refrigerant starts out as a gaseous vapor. The compressor pressurizes the refrigerant, heating it up before sending it through the outer (condenser) coils. The cool air on the outside of these coils causes the gas to release heat – heat transfers itself into any colder temperatures it comes in contact with.

As the refrigerant loses more and more heat, its molecular activity decreases, causing the gas to condense into a liquid. It’s still highly pressurized but it’s cooled down so much that it’s no longer a vapor, similar to how hot water stops producing steam as it cools. The liquefied refrigerant now passes through an expansion valve, where it’s depressurized before entering the inner (evaporator) coils of the fridge.

Depressurizing the refrigerant causes it to become very cold – even colder than the inside of the fridge. Just as heat transferred out of the refrigerant when met with cold air, so too does heat transfer out of the fridge and into the cold refrigerant. As liquid absorbs heat it evaporates into a gas, so the refrigerant becomes increasingly gaseous as it travels through the evaporator coils.

Having removed all the heat from the fridge on its journey through the evaporator coils, the refrigerant has now come full circle. It’s back in its vaporized form, ready to enter the compressor and begin the cycle anew.

RV Fridges

RV fridge with the door open and filled with bottled beverages

Vapor-compression refrigeration may be efficient but it’s impractical for RV fridges. The compressor motor is loud and power-hungry, full of moving parts that can easily be damaged by the motion of a moving vehicle. RV fridges ditch the compressor and utilize another cooling method: absorption refrigeration.

Absorption refrigeration depends on heat and chemical reactions, specifically the reactions between ammonia, water and hydrogen gas. A solution of ammonia and water is heated in a generator chamber until the ammonia becomes gaseous. The ammonia gas is then separated from the water and sent through the condenser coils, where it releases its heat and cools back to a liquid – much like the condensing that takes place during vapor-compression refrigeration.

The depressurized liquid ammonia travels through the evaporator coils on the inside of the fridge, combining with hydrogen gas in the process. This hydrogen-ammonia mixture absorbs heat, becoming gaseous as it cools the fridge compartment. From there it enters the absorber, which contains the water that was separated from the ammonia earlier in the process.

As the ammonia and water recombine into a solution, they release the hydrogen gas back into the evaporator coils. The remaining mixture is then sent back to the generator chamber to be reheated and continue the cycle.

So the basic process of absorption refrigeration is very similar to that of vapor-compression refrigeration – cool the refrigerant so it absorbs heat from the fridge, then heat it up so it releases heat outside the fridge. The biggest difference is that absorption refrigerators don’t need a mechanical compressor, as the chemicals themselves do all the work once they’re heated up.

Heat Sources

It may seem counterintuitive to think of heat as the key to refrigeration, but without a steady heat source, your RV refrigerator would simply be a fancy cabinet. There are three potential heat sources that an RV fridge can use: propane, 120V AC and 12V DC. Your RV fridge can run on two or three of these sources depending on its type.

Two-way RV fridges are the most common type, running on propane or 120V AC power. Electricity is limited when you’re traveling in an RV, so these fridges can receive their heat from your propane tank to conserve energy. If you’re running your generator or plugged into the grid at a campground, you can switch the fridge to 120V AC; heat will come from an electric heating element rather than a propane flame.

Three-way RV fridges can be switched between all three power sources depending on your needs. In addition to running on propane and 120V AC, a three-way fridge can power its heating element with 12V DC power from your RV’s battery bank. Due to the limitations of 12V DC power, these fridges tend to be smaller than two-way fridges and are usually found in older RVs, pop-up campers, and small trailers.

Each power source has its pros and cons. Propane is a dangerous substance but it can be used when electricity is limited or nonexistent, while 12V DC is safer but can quickly drain your RV’s batteries. 120V AC provides consistent cooling but requires a connection to the power grid or your generator; it’s possible to run a fridge on 120V AC through your RV’s inverter but you’ll need a lot of battery capacity to handle it.

You’ll want to switch your source as needed to suit your current resources. Many modern RV fridges have an automatic setting that detects power availability and switches the source accordingly.

Refrigeration on the Road: Ways to Run Your RV Fridge While Driving

So you’ve got your refrigeration situation all figured out while you’re parked, but now it’s time to roll out and you’ve got a fridge full of cold food that you’d like to remain that way. What’s a traveler to do? There are several possible solutions; the right one for you will depend on your power supply, your thriftiness and your risk aversion.

#1 – Propane in Motion?

Fridge with the door open and stocked with canned beverages and condiments

It’s one of the biggest debates between RV owners, with opinions being split pretty much right down the middle: can you run propane while driving your RV? Some say it’s simply too dangerous and would rather be safe than sorry, while others swear by it and claim that the benefits outweigh the risk. Let’s hear both sides so you can decide for yourself.

The dangers associated with propane are due to its high flammability. Because the gas catches fire so easily it’s a great source of heat for your fridge, water heater and furnace… assuming nothing goes wrong.

Hitting a pothole or making a sharp turn could jostle the propane tank and its lines; should a line come loose or disconnect, the gas would leak out. Not only would this be wasteful, but it would also be quite hazardous – if there’s propane in the air, any spark could start a fire or explosion. Inhaling propane gas can cause headache, dizziness, irregular heartbeat, difficulty breathing, seizures, and even unconsciousness.

Though many manufacturers advise against running propane while in motion, it’s generally not expressly forbidden to do so. If you choose to run your fridge on propane while driving, you’ll need to take a few extra precautions to stay safe.

All RV owners should inspect their propane system regularly, ensuring that everything is tightly connected and free of damage, but this is especially important if you leave your propane on while driving. By law, you’ll need to turn the propane off while at fuel stations and while going through tunnels – the high flammability and close quarters of these places are recipes for disaster if there’s a propane flame nearby.

So if you’re willing to assume the additional risks and responsibilities associated with using propane while driving, you can keep your RV fridge cold while you’re on the road. If you’d prefer to take a safer approach to powering your fridge, read on – propane isn’t the only way!

#2 – Generators on the Go

Your generator, whether built-in or external, can certainly provide enough 120V AC power to run your fridge while driving. If you choose to do this, you’ll need to make sure that you’re fueled up before you hit the road. Generators that share your RV’s gas supply will typically shut off automatically when you fall below a quarter tank of fuel, so don’t expect to power your fridge until you fill up again.

If your generator runs on propane, you’ll have to follow the same laws as if you were using a propane tank. Shut off the generator before pulling up to the fuel pump and while going through tunnels. Some roads and bridges also have propane restrictions; these will usually be stated on signage before you reach the prohibited area.

Generators can be quite loud while they’re running. This probably won’t present a problem on noisy highways, but if you’re driving through a quiet suburban area with a roaring generator you might draw attention from police. For the sake of politeness – and of noise ordinances – you might not want to run your generator in these sorts of locations.

Some generators limit the amount of power they supply while the RV is in motion for safety and fuel conservation purposes. Because a fridge draws so much power, your generator may not be able to run it while you’re driving. You’ll need to try another method of keeping your fridge cool instead.

#3 – Time for 12V

If you have a three-way RV fridge that you want to run while you’re driving, you’re in luck – that third power option is there specifically for this purpose. You won’t need to run your propane tank or your generator to keep your fridge cold; just switch it to 12V DC and you’re all set! Since your engine recharges your batteries as it runs, you won’t drain them anywhere near as fast as you would if you were running the fridge on 12V DC while parked.

Unfortunately, three-way fridges are found few and far between these days. As RVs have gotten bigger, so too have their fridges, and 12V DC can only provide so much power. Most modern RV fridges are simply too much for a 12V DC connection to run; you’ll find three-way fridges mainly in small campers and older RVs.

Assuming you have a three-way fridge, there’s still one downside to powering it with 12V DC: it can be tough on your alternator and batteries.

Your RV’s alternator converts energy from your engine into charge for your batteries as needed. If your fridge is continuously draining your batteries, your alternator will need to run continuously to replenish the charge, which can shorten its lifespan significantly over time. You may want to add a second alternator to your RV if you plan to run your fridge on 12V DC frequently to reduce the strain on your RV’s power system.

RV batteries also have a finite lifespan. After a certain number of charge-discharge cycles, their capacities will drop, eventually getting so low that the battery dies completely. The more you use the batteries the quicker they’ll die, so running a power-hungry appliance like your fridge off them could mean more frequent trips to the battery aisle.

If you run your fridge on 12V DC, keep an eye on temperatures both inside and outside. When it’s hot outside, batteries drain faster and can overheat very easily, especially when a high-powered appliance like a fridge is drawing power from them. To avoid damage and potential fires, avoid heavy battery usage when temperatures are high.

#4 – Go Powerless

If you’re willing to get a little inventive and limit your fridge usage while your RV is in motion, you may not need to power your refrigerator at all while driving. It may sound unlikely but it’s true: if your fridge is functioning properly, all gaskets are in place and it’s already at its proper temperature before you hit the road, temperatures shouldn’t rise more than 4 degrees Fahrenheit over six to eight hours.

RV fridge cooling isn’t the most efficient process, but these fridges are designed to compensate for that by holding their temperature extremely well – as long as the door stays shut. Consider keeping a cooler filled with ice in your RV and filling it up each day with the food and drinks you plan to consume on the road. That way you can keep the fridge door closed until you’re ready to power it up again.

You can help your fridge hold its temperature throughout the drive by getting it as cold as possible before taking off. Set the thermostat as low as it can go and fill any empty space with ice-cold beverages, freezer packs, or bags of ice – the colder the better!

Remember that hot air rises, so the bottom of the fridge will stay cooler than the top. Arrange your food accordingly – put the most perishable items, like meat and dairy products, on the bottom shelves and the least perishable items, like cans of soda and fruits, on the top shelves.

Using these tips and tricks, you should have no problem driving for up to eight hours without running your fridge at all. Even if you do plan to power your RV fridge on the road, you may not need to do so for your entire drive if you take a few simple steps to reduce your usage and plan ahead. RV living is all about efficiency, after all, and there’s no better place to start than with your fridge.

Keeping it Cool: RV Fridge Maintenance Tips

Whether you’re on the road or boondocking, your RV fridge will stay cooler for longer if it’s properly maintained. Follow these tips to optimize your fridge’s efficiency and help it hold its cold in regardless of its power supply.

#1 – Vital Circulation

Your household fridge has a built-in fan that helps circulate the cold air throughout the refrigerator, keeping everything at the same temperature and preventing hot and cold spots from forming. Most RV fridges, on the other hand, don’t have fans. This causes inconsistent temperatures from shelf to shelf and can result in frost collecting on the evaporator coils, which further impairs efficiency.

Fortunately, there’s an easy remedy for this. Small “muffin” fans are inexpensive, easy-to-find devices that are designed to mount in the back of your fridge near the evaporator coils. These fans serve the same purpose as the built-in fans found in residential fridges: circulate air to stabilize temperatures.

Some muffin fans run on D batteries; others can be wired into the same 12V DC lines that power your fridge’s light. 12V DC fans are convenient as they need no maintenance once installed, but they require some basic electrical wiring know-how. Battery-powered fans require a monthly battery change but are ideal for those who don’t fancy themselves amateur electricians.

To really maximize airflow in your RV fridge, you can purchase a second muffin fan and install it on the outside of your fridge, near the rear condenser coils. This extra breeze will greatly improve the efficiency and longevity of your fridge, reducing its power consumption and boosting its cooling ability.

#2 – Spring Cleaning

You probably clean the inside of your fridge pretty regularly, but how about the outside? Believe it or not, the condition of your fridge’s exterior has a big impact on its functionality and efficiency.

Once a year or so, open your fridge’s outside vent cover and take a look inside. You’ll probably find some dust, dirt and debris as expected – it’s an exterior vent, after all – but you may see some surprising things in there as well: cobwebs, bird nests, beehives and wasp nests have been found in fridge vent compartments! Aside from being creepy or gross, these unwanted vent tenants block airflow to your fridge, causing it to overheat, operate poorly or even break altogether.

Keeping your fridge vent clean and clear is critical to its proper functioning. Remove any nests or debris from the compartment and clean off dust and grime with a wet cloth or alcohol wipe. You can use compressed air to remove cobwebs and tidy up any hard-to-reach spots.

#3 – Leveling Off

There’s no mechanical pump in your RV fridge; the flow of refrigerant through the cooling system occurs thanks to the natural force of gravity. Thus the fridge’s functionality is dependent on it being properly aligned with the ground. If it’s not level, then gravity won’t pull the chemicals through the system correctly, reducing the fridge’s efficiency and even preventing it from functioning altogether.

Whenever you’re able to do so, run your fridge when you’re on level ground. If you’re traversing a mountain pass, it might be a good idea to power your refrigerator down until the road levels out. Try not to park on hills if you can avoid it; if you’re in doubt, place a simple bubble level on your fridge to see if you’re properly positioned.