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The Beginner’s Guide to RV Furnaces

The Beginner’s Guide to RV Furnaces

Whether you want to purchase a new unit or want to know more about RV furnaces, you’ve come to the right spot. This beginner’s guide will help you understand how to use them, why they’re essential, basic maintenance, and what to do if your furnace doesn’t work correctly. Let’s get started. 

Why Does Your RV Need a Furnace?

An RV furnace is the primary heat source for your motorhome, trailer, or truck camper. Although you won’t need one during the warmer summer months, a heater allows you to enjoy your RV during the winter

RV furnace vent in a travel trailer
Without an RV furnace, you would not be able to camp during the winter months.

An RV furnace can keep your interior toasty warm when it’s freezing outside. But even more important than your comfort, an RV furnace keeps essential water functions, such as supply lines and collection tanks, from freezing. 

Does an RV Furnace Run on Propane or Electric?

Most RV furnaces run off of propane. The average RV is manufactured with a propane furnace unless you opt for an alternative, such as a heat pump. Its uncommon but there are a few RV furnaces that have electric heating element options in addition to the propane and can switch between electric and propane heat.

Some RV furnaces also use diesel heat. Many of the parts of a diesel heater are the same as propane that we are focusing on here.

Unfamiliar with RV heat pumps? Here’s what you need to know: How Does an RV Heat Pump Work?

Does an RV Furnace Need Electricity?

Even though an RV furnace runs off of propane, it still needs electricity to run. For example, vent fans and ignition require electricity to function. Usually, a 12V battery will run these functions. However, you need to make sure to keep your battery warm and charged. 

RV propane tanks
RV furnaces run off of propane, so make sure you keep your tanks filled while winter camping.

How Much Propane Does an RV Furnace Use?

The average RV furnace uses between 20,000 and 50,000 BTUs. However, the actual amount of propane an RV furnace uses depends on its size. The larger the unit, the higher the BTUs and the more propane used and heat produced. In general, one gallon of propane will fuel 92,000 BTUs. 

Therefore, to determine the amount of BTU hours available in your propane tank, you must multiply 92,000 BTUs per gallon on your tank. Then divide that number by the BTUs used by your furnace. 

For example, a 20 lbs propane tank contains 4.6 gallons of propane or 423,000 BTU hours. A 20,000 BTU furnace could last almost a day if running constantly. However, furnaces rarely run all day, so the unit in this scenario would work for a couple of days cold weather.

Keep in mind that RV’s are not thermally efficient and the BTU rating on the furnace is input BTU. Most RV furnaces are only about 60% efficient so much of that heat is lost in exhaust. To avoid condensation these furnaces intentionally run the exhaust hot. Some of the higher efficiency RV frunaces like the trauma vario heat do require condensation vents.  

Truma furnace condensation
The small round thing on the side of the RV is a Truma furnace exhaust. It drips condensate out and you can see the drip marks down the RV.

Parts of an RV Furnace You Should Know

A furnace has many parts, and you could spend hours learning about each one. However, unless you are a certified mechanic, you probably don’t need to know everything about every part. 

But, some aspects of it you should understand better. So, continue reading to learn about some of the basic elements, how to use them, and why they matter. 

Dometic Thermostat
Some RVs have manual thermostats, while others have digital thermostats like this Dometic model.

RV Thermostat

The RV thermostat is the unit inside the RV that controls the furnace. With the thermostat, you can set the desired temperature. It’ll monitor the interior temperature, signal the furnace to kick on when the inside gets too cold, and signal it to shut down when it reaches the set temperature.

An RV thermostat is very similar to what you have in your home, but the wiring and power source is different. Usually, home thermostats do not work in RV’s without some special conversion wiring.

Intake & Exhaust Vents

You can find the intake and exhaust vents on the outside of the RV. The intake vent, similar to the cold air returns in a residential furnace, brings fresh air into the RV furnace so it can run efficiently. 

Like the flue in a residential furnace, the exhaust vent sends water vapor and poisonous gases, such as carbon dioxide and carbon monoxide created during the combustion process, outside of the RV. Expelling these gases is vital because they can cause severe sickness or death.

Intake/exhaust vent on an Airstream trailer
Intake vents are located on the exterior sidewalls of campers. If you see the word “HOT” on the vent, you know you’ve found it!

Heat Duct

Heat ducts are the pathways used to carry the heat from the RV furnace to different areas. These ducts usually have reinforced aluminum and connect the furnace to each register. 

Usually, these are located beneath the floor in the frame.

Furnace ducting
This is an example of furnace ducting in an under-sink cabinet in a Bigfoot truck camper.

Furnace Fan

Furnaces have different fans that circulate air throughout the system. The intake fan brings outside air to create burning in the combustion chamber. 

One returns air from the interior of the RV. Another pushes dangerous gases out of the exhaust. It may have other fans within the ducting system to help send the heated air to the multiple registers.  

When the fan runs the air pushes up what’s called a sail switch. This switch indicates to the furnace that its fan is operating properly. It’s critical for the fan to run otherwise it could overheat and catch fire. Sail switches are a potential failure point in a furnace and they are designed to fail off. If your furnace starts up but shuts down quickly, the sail switch might be to blame.

Burner

The burner is the part of the furnace that combusts fuel. Usually, there is a nozzle at one end that shoots a flame into a tube. The burner is usually a squiggly shaped pipe that sits inside an air exchanger. Cool RV air is blown over the hot burner to heat the air and pass it into the RV. Inside air and burning air do not mix.

Usually, the burner is ignited with an electric spark, but some older models use a pilot light that needs to remain lit and burning all the time. The electric igniters use a high voltage solenoid to create a spark and usually, you can hear it ticking as it ignites. This too like the sail switch is a common failure in furnaces. If you find your furnace starts up but won’t ignite (and usually you smell a little propane) check the igniter.

RV furnace burner
If you were to open the furnace during operation you would see a blue flame like this.

How to Control Your RV Furnace

You can control the RV furnace by using the thermostat. Once you set the desired temperature, it will tell the furnace when to turn on and shut off when it reaches the set temperature. 

Usually, after setting it, nothing else is required. The unit will function on its own. However, if you feel too cold or hot, you can adjust the temperature on the thermostat at any time. 

What Size Furnace Do I Need for My RV?

You will need to find the right RV furnace size to ensure it heats efficiently. If you have a larger RV, you will need a larger unit. Many larger RV’s even have multiple furnaces. When sizing a trailer, you will need to know the required BTUs to heat the whole area comfortably. 

RV furnace vent
This is a furnace in a hybrid RV. A hybrid RV has the body of a travel trailer with canvas pop-outs on each end like a pop-up camper.
Hybrid RV
When you have pop-outs with canvas sides, a furnace is critical even in mildly cold temperatures.

But be careful — if you oversize your furnace, you may have problems with rapid cycling and getting too hot. 

If you replace an older or non-working unit, you can find the BTU requirement on a data plate located on the original furnace. If you don’t have that information, you can calculate your BTUs yourself. 

Warmer climates usually require about 25-30 BTUs per square foot, whereas cooler climates require more BTUs and typically range between 45-60 BTUs per square foot. 

Basic RV Furnace Maintenance

Just like with any other machine, an RV furnace also needs periodic maintenance. Although you can take your RV into a dealership or certified mechanic, you can complete most basic maintenance yourself. 

But, whether you do it yourself or hire someone, don’t forget to get it done. Basic furnace maintenance can ensure your furnace runs safely and efficiently. 

Check Internal and External Vents & Burner for Bugs, Soot, & Dirt

You can locate the internal and external vents on the RV’s exterior. Make sure to clean out the vents. Wind can blow in dirt and leaves, and animals can crawl inside. 

Sometimes, a bird can even try to build a nest, especially when in storage. Make sure to check these vents periodically and at least annually to remove any foreign substances. Blocked ducts can reduce efficiency or cause a malfunction. 

Keep RV Batteries Charged

Although most RV furnaces run on combustible fuel, they still have many components that use electricity. For example, the motor fans won’t function if hooked to a dead or low-powered battery. 

And, if the fan does not properly run, the whole RV furnace will not operate. Therefore, it is critical to keep your batteries charged

Test Carbon Monoxide Detector

Your furnace releases carbon monoxide as a by-product of the combustion process. Carbon monoxide is a dangerous gas that can lead to death if inhaled in large doses.

RV carbon monoxide and propane detector
Always keep your RV carbon monoxide detector in good working order.

Even in small quantities, one can become very sick. Test your RV carbon monoxide detector often to avoid these potential dangers. 

Run Annually (At Least)

Even if you live in a warm climate or camp in areas that don’t require a furnace to keep warm, you should still run it at least annually. Try to find a cool day and open the windows. Turn on the heater and run it full-blast throughout the whole RV. 

Heat should reach every corner. You may smell something weird or aversive. Don’t panic! A dusty smell is normal for the first run of the season.

RV 101® - RV Furnace Operation & Preventive Maintenance

How Much Is an RV Furnace?

The cost of an RV furnace depends on the size of the unit. Prices for a motorhome furnace range between $950 and $1200. 

However, a smaller RV, such as a travel trailer, will not require a large furnace and may cost less. Do your research to find the best furnace for your RV at the best price. 

Forest River No Boundaries Travel Trailer
Smaller travel trailers are easier to heat than large fifth wheels or motorhomes.

Best (And Most Common) RV Furnace Brands

You can choose from many RV furnace brands. However, some of the best and most common ones include Truma, Suburban, and Atwood. Let’s look at each one in more detail.

Truma: Combi & VarioHeat

Truma, established in 1949, received its first patent in 1950. Over 50 years later, it’s still going strong. Two of its popular models include the Truma Combi and VarioHeat. Either of these models may work for your RV.

We had a Truma VarioHeat installed in the Lance truck camper we used for our Go North expedition, and it worked great! We have also experienced the truma combi when renting RV’s overseas as they are commonly found in European models.

Truma furnaces tend to be the most expensive, but also the most efficient and quietest options available currently.

Building the Lance Truck Camper & Pickup Out for Our Expedition North | Go North Ep 2

Suburban

Suburban, another well-known brand, has RV furnaces ranging between 16,000 and 40,000 BTUs per hour. You can also get them in various sizes, making it easy to find the perfect unit for your RV.

Atwood (Now Dometic)

Atwood is well known for specialized RV water heaters, but this brand has excellent furnaces too. They boast lightweight, fuel-efficient, easily serviced units that can withstand difficult travel conditions. This makes Atwood furnaces ideal for any weather or situation you may encounter with your RV.

As of 2017, all Atwood products are now Dometic. However, you can still find original Atwood furnaces in many RV’s manufactured prior to that year.

RV Heating Alternatives & Supplements

Although most RVs come installed with a furnace, you can consider alternative heating systems, especially when you just need a little extra heat in one area. For example, electric space heaters and blankets may work well. 

Electric Space Heaters

You can use electric space heaters wherever you need them. They can also increase the immediate area’s temperature while running the furnace at a lower temperature. 

RV space heater
On really cold days, a space heater is a good supplemental heating option.

Additionally, running at a lower temperature allows the furnace to use less propane, which you may like if you have limited access to fuel.

Speaking of propane…RV propane heaters are another popular heating option for winter camping, but are they safe? Find out here: Are RV Propane Heaters Safe?

Electric Blankets

You can use cozy electric blankets to warm you up, especially during the night. Usually, you don’t need temperatures as high during the night, and with an electric blanket, you can turn the thermostat down. 

However, don’t turn the furnace off. Ensure that you keep overall RV temperatures above 32 degrees to avoid freezing your water lines or tanks. 

Keeping Warm with Your RV Furnace

Whether planning to purchase a new furnace or getting to know the one you already have, it’s important to know how they work. The more you understand your RV furnace, the better you will care for it and the better it will care for you. 

Tom and Cait cold weather camping
Whether you’re road-tripping to the Arctic Ocean or winter camping in the lower 48, you’ll be a happy camper with an RV furnace!

We know winter seems to drag on forever, but eventually, the sun does shine again. When the temperatures start to rise, you’ll need to know how your RV AC works. Get started here: The Complete Guide To RV Air Conditioners

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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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James Harvey

Saturday 16th of October 2021

Thank you for writing this post, it is really useful for me. I am looking to equip my RV with an efficient propane RV furnace that keeps the air temperature inside the RV warm even in cold weather.

James Harvey

Friday 29th of October 2021

I found the right furnace for my RV, thanks for your helpful info.

Dave Pellegrino

Sunday 19th of September 2021

Good article, I was hoping to see/hear more about replacing common items such as the sail switch, igniter etc...

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