6 Best Furnaces For 5Th Wheel That Seasoned Nomads Recommend
Choosing a furnace for your 5th wheel? Discover the top 6 models that seasoned nomads trust for efficient heating and long-term durability on the road.
There’s a specific kind of quiet that falls over a campsite when the temperature plummets and the snow starts to fly. It’s the moment you’re most grateful for the gentle hum of your furnace kicking on. But if that hum turns into a clank, a squeal, or worse, silence, your cozy winter retreat quickly becomes a race against the cold. Choosing the right furnace for your 5th wheel isn’t just about comfort; it’s about safety, efficiency, and the freedom to chase adventure in any season.
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Why Upgrading Your 5th Wheel Furnace Matters
The furnace that came with your rig was likely chosen for one reason: it met the manufacturer’s budget. It works, but "working" isn’t the same as "working well." An upgrade is your chance to choose a unit based on your needs, not the builder’s bottom line.
A better furnace transforms your living experience. We’re talking about tangible benefits like lower propane consumption, which means fewer trips to town and more money in your pocket. It also means a quieter environment. Factory-installed units can sound like a jet engine taking off, while modern or specialized options prioritize silent operation for a more peaceful night’s sleep.
Most importantly, an upgrade is an investment in reliability and safety. Newer models feature more advanced sail switches, better circuit boards, and more efficient heat exchangers. This translates to more consistent heat, better performance at high altitudes, and the peace of mind that comes from knowing your primary heat source is a dependable workhorse, not a ticking-time-bomb of deferred maintenance.
Suburban SF-35FQ: The Industry Standard Workhorse
If you’ve ever looked at an RV furnace, you’ve probably seen a Suburban. The SF-35FQ, a 35,000 BTU ducted unit, is the undisputed industry standard for mid-to-large 5th wheels. Its ubiquity is its greatest strength. You can find parts for it in nearly any RV supply store from coast to coast, and any mobile tech worth their salt knows how to work on one.
This furnace is a direct-fit replacement for the majority of factory-installed units, making the upgrade process relatively painless. It connects to your existing ductwork, distributing warm air through the floor vents to heat the main living space, bathroom, and bedroom. Crucially, this ducted air also helps keep your underbelly and water tanks from freezing in sub-zero temperatures—a non-negotiable for winter camping.
The tradeoff for this reliability and serviceability is a lack of refinement. The SF-35FQ is effective but not particularly quiet or efficient by modern standards. It draws a significant amount of 12V power to run its large blower fan, which is a major consideration for anyone who spends time off-grid. Think of it as a trusty V8 engine: powerful, simple, and reliable, but thirsty for both propane and battery power.
Dometic Atwood DFMD: Reliable Ducted Performance
The Dometic DFMD series is the Suburban’s lifelong rival, and for good reason. It offers similar performance, fits comparable cutouts, and is another go-to for OEM installations and aftermarket replacements. Many seasoned RVers have a strong preference for one brand over the other, but in practice, they are both highly capable and proven designs.
One key difference often cited by technicians is the heat exchanger design. Dometic uses a tubular heat exchanger, which some argue is more durable and less prone to cracking over time compared to Suburban’s clamshell design. While failures are rare in both, it’s a point of distinction for those planning on heavy, long-term use.
Ultimately, the choice between a Dometic DFMD and a Suburban SF often comes down to what your rig already has. Sticking with the same brand usually guarantees a perfect fit for the exterior vent and internal mounting points. If you’re starting fresh, you can’t go wrong with either. They are both loud, powerful, and dependable ducted furnaces that get the job done.
Propex HS2211: Quiet Heat for Off-Grid Living
While a Propex heater is more commonly found in a van or truck camper, it’s a brilliant strategic upgrade for a 5th wheel, especially for boondockers. The Propex HS2211 is a small, propane-fired furnace that is exceptionally quiet and incredibly efficient with 12V power. It sips electricity, allowing you to run it all night without making a dent in your battery bank.
This is not a direct replacement for your main 35,000 BTU furnace. With a heat output of around 7,500 BTU, it’s designed for smaller, well-insulated spaces. However, it’s a perfect solution for creating a "zone" of heat. Many nomads install one in the bedroom to keep it toasty overnight without having to run the massive main furnace, saving an enormous amount of propane and power.
The installation is more involved, as it requires its own thermostat, fuel line, and small-diameter ducting. But the payoff is huge. Imagine silent, steady warmth in your sleeping area while your main furnace stays off. For full-timers who prioritize off-grid capability and a quiet night’s sleep, adding a Propex as a secondary heater is one of the best quality-of-life upgrades you can make.
Suburban NT-20SEQ: A Compact Direct Vent Solution
A direct vent furnace is a self-contained unit that heats a single area directly, without connecting to a central duct system. The Suburban NT-20SEQ is a fantastic example of this technology. It’s compact, reliable, and because it doesn’t use a large blower fan, it’s significantly quieter than a ducted furnace.
This type of heater is an ideal problem-solver. Is the garage in your toy hauler always freezing? Does a specific slide-out never seem to get warm enough? Installing an NT-20SEQ provides a dedicated, powerful heat source right where you need it. It’s also a great choice as a primary furnace for smaller or older 5th wheels that may not have been built with extensive ductwork in the first place.
The major limitation is its inability to heat your entire rig or, more importantly, your underbelly. A direct vent furnace won’t protect your tanks and water lines from freezing. Think of it as a space heater, not a central heating system. It excels at its specific job but can’t replace the whole-house functionality of a ducted furnace in a four-season setup.
Dometic Mojave: Next-Gen High-Efficiency Option
The Dometic Mojave represents the next step in RV furnace technology. It’s designed from the ground up to be more powerful, more efficient, and smarter than the legacy models that have dominated the market for decades. For the full-timer who spends significant time in cold weather, the Mojave is a compelling, premium upgrade.
Its two biggest advantages are efficiency and comfort. The Mojave features a redesigned heat exchanger and a variable-speed fan. This means it can modulate its output, running at a lower, quieter speed to maintain temperature instead of the all-or-nothing blast of a traditional furnace. This provides more even heat, uses less propane, and consumes less 12V power over time.
This advanced performance comes at a cost. The Mojave is more expensive upfront, and because it’s a newer product, finding a technician familiar with it or sourcing parts in a remote location could be more challenging than for a standard Suburban. It’s an investment in long-term efficiency and comfort, best suited for the dedicated RVer who will see a real return on that investment through fuel and power savings.
VEVOR Diesel Heater: A Top Frugal Alternative
You can’t talk about RV heat today without mentioning the wildly popular Chinese diesel heaters, often sold under brands like VEVOR. These units are incredibly inexpensive to purchase and operate. They run on diesel, which is often easier to source than propane, and they produce an intense, dry heat that is excellent for combating RV condensation.
For the off-grid nomad, these heaters are a dream. They use a minuscule amount of 12V power and sip fuel, allowing you to stay warm for days on end without worrying about your resources. Many full-timers install one as a secondary heat source, using it to do the heavy lifting of keeping the rig warm while reserving the propane furnace for extreme cold snaps and keeping the underbelly thawed.
However, it’s critical to understand the tradeoff. These are not RV-certified appliances. Installation requires careful planning to safely route the hot exhaust pipe away from combustible materials and to ensure the fuel system is leak-proof. You are trading the plug-and-play safety and certifications of a Dometic or Suburban for rock-bottom operating costs. For the skilled DIYer, it’s an unbeatable value; for the novice, it can be a risky project.
Matching BTU Output to Your 5th Wheel’s Size
BTU stands for British Thermal Unit, and it’s simply a measure of heat output. Choosing the right BTU rating is crucial for an efficient system. Many people assume bigger is always better, but installing a furnace that’s too powerful for your space is a common and costly mistake.
An oversized furnace will "short cycle." It will blast your rig with a huge amount of heat, satisfy the thermostat in a few minutes, and then shut off. This constant on-off cycle is incredibly inefficient, hard on the furnace components, and creates a drafty, uncomfortable environment with wide temperature swings. You want a furnace that can run for longer, more gentle cycles to provide steady, even heat.
While every rig is different, here are some general guidelines to get you started. Always consider your insulation quality and the climate you travel in.
- Under 30 feet: A 20,000 to 30,000 BTU furnace is typically a good match.
- 30 to 40 feet: This is the sweet spot for the popular 35,000 to 40,000 BTU models.
- Over 40 feet / Toy Haulers: Look for 40,000+ BTU units, or consider a dual-furnace setup or supplementing with a secondary heater like a diesel unit.
Remember, a well-insulated, four-season 5th wheel in Wyoming needs more heating power than a standard-build rig of the same length that spends its winters in Florida. Don’t just shop by length; shop for your specific rig and your travel style.
Ultimately, the best furnace isn’t the one with the highest BTU rating or the most features. It’s the one that aligns with your life on the road. Whether you need the rock-solid reliability of a Suburban for worry-free resort hopping or the frugal efficiency of a diesel heater for deep-woods boondocking, making a conscious choice empowers you to build a more comfortable and capable rolling home.
Frequently Asked Questions (FAQs)
What size furnace for a 5th wheel is needed for cold weather?
A 5th wheel typically requires a 30,000 to 42,000 BTU furnace to stay comfortable in freezing temperatures. Trailers between 30 and 36 feet usually perform well with a 30,000 or 35,000 BTU unit like the Suburban SF-35F. Larger rigs over 38 feet, especially those with multiple slide-outs, require 40,000 to 42,000 BTUs to maintain interior temperatures around 68 degrees Fahrenheit when outside ambient temps drop below 20 degrees.
What does a sail switch do in a 5th wheel furnace?
The sail switch in a 5th wheel furnace acts as a safety sensor that confirms the blower motor is pushing enough airflow before allowing propane ignition. If the fan runs too slowly or if hair, lint, and dust block the paddle, the switch contacts stay open. This prevents the gas valve from opening and stopping unburned propane buildup. Cleaning the switch with compressed air often restores normal operation without needing parts replacement.
How do I clean the burner tube on a 5th wheel furnace?
Cleaning a 5th wheel furnace burner tube requires turning off the propane, removing the exterior access panel, and brushing out rust, soot, or insect nests. Use a flexible bore brush or compressed air canister to clean through the intake and exhaust chambers. Spiders frequently build webs inside the orifice, which starves the flame of air and causes yellow, uneven burning. Reassemble the intake plate tightly and test for gas leaks using soapy water before relighting.
How long does a 30 lb propane tank last running a 5th wheel furnace continuously?
One 30-pound propane tank lasts roughly 22 to 30 hours of continuous furnace burner run time. A standard 30-pound cylinder contains about 7 gallons of propane, totaling approximately 640,000 BTUs of fuel energy. If a 35,000 BTU furnace runs non-stop, it consumes about one gallon every two and a half hours. In typical sub-freezing conditions where the furnace cycles on and off, a single tank normally lasts two to three days.
Propane furnace vs diesel air heater for a 5th wheel, which is better for boondocking?
Diesel air heaters are generally better for off-grid boondocking than factory propane furnaces because they consume significantly less battery power and use cheaper fuel. A standard RV propane furnace draws 7 to 11 amps of 12-volt DC power, quickly draining lead-acid house batteries overnight. In contrast, an auxiliary diesel heater draws just 1 to 3 amps while running and provides drier radiant heat that reduces indoor condensation during damp winter stays.
How much does a replacement furnace for a 5th wheel cost including installation?
Replacing a 5th wheel furnace costs between $800 and $2,200 for parts and professional labor combined. The furnace unit itself, such as a Dometic or Suburban 35,000 BTU model, ranges from $550 to $1,300 depending on dimensions and duct configuration. RV service centers charge between $150 and $200 per hour for labor, with typical installation taking two to four hours to secure venting, test gas connections, and wire the thermostat.
Why does a 5th wheel furnace blow cold air and then shut off?
Furnaces in 5th wheel trailers blow cold air and shut down when the system fails to detect airflow or establish a stable flame ignition. When you call for heat, the blower motor runs for 15 to 30 seconds to purge the combustion chamber. If the sail switch fails to engage, the high-limit switch trips from overheating, or the electrode fails to spark the propane within three tries, the control board locks out to prevent gas accumulation. Low battery voltage below 10.5 volts is another frequent culprit.
Is it safe to run a 5th wheel propane furnace overnight while sleeping?
Operating a factory 5th wheel propane furnace overnight is completely safe as long as the RV has functioning smoke and carbon monoxide detectors. Modern RV furnaces use a sealed combustion design where propane combustion takes place entirely isolated from the interior living space, venting toxic exhaust gases outside. Test your carbon monoxide detector monthly, verify that exterior exhaust vents remain free of snow or insect debris, and never substitute an unvented portable propane heater for your built-in furnace while sleeping.
