Stay Cozy on the Road: Know Your RV Heating Systems!

Are you tired of waking up to a freezing tent and struggling to light a fire for your morning coffee? That’s where the beauty of RV camping comes in – reliable heating and cooling! Most RV furnaces operate on DC power even when your RV is plugged into shore power, allowing them to work at a campground or when camping off-grid. And just like your home’s heating system, your RV furnace requires regular maintenance to keep it running smoothly. If you’re not sure how your RV furnace works, don’t fret! We’ve got you covered. In this guide, we’ll dive into everything you need to know about operating and servicing, your RV furnace to ensure you stay cozy and comfortable no matter where your adventures take you.

Know The Basics Of How RV Heating Systems Work

As an RV owner, it’s important to know how your RV heating system works. There are two main types of RV heating systems: forced air furnaces and hydronic heating systems. Each has its own unique way of heating your RV, so understanding how they work will help you keep your RV warm and cozy during colder temperatures.

First, let’s take a look at forced air furnaces. In this type of system, outside air for combustion is force-fed through a sealed combustion chamber assembly and discharged to the exterior. Meanwhile, interior air of the RV is moved across a heat exchanger. This design ensures that no products of combustion are mixed with the interior air, making it a safe option for heating your RV.

Heat is distributed throughout your RV using a blower fan that’s powered by a small motor. Most forced air furnaces burn propane to heat air, but some utilize diesel fuel (more common with hydronic heating systems). It’s important to note that forced air furnaces use a sail switch and a limit switch as safety mechanisms. The sail switch is the first safety switch in an RV furnace. It prevents your furnace from attempting the ignition sequence if the blower motor isn’t running at a minimum of 75% of its rated speed. The limit switch, on the other hand, opens at a preset temperature to prevent overheating. The limit switch is mounted on the heat exchanger or the burner assembly housing. It shuts off the burner but allows the combustion blower to continue running to lower the equipment temperature.

If your blower never shuts off, but your burner is cycling on and off at regular intervals, your RV should be inspected by a qualified RV technician immediately. This is a symptom of an overheating limit switch, which could result from blockages, faulty components, or LP gas adjustment issues that create a very dangerous situation.

Now, let’s take a look at hydronic heating systems. These systems use a heated surface to heat water that is distributed to radiators throughout the RV. That surface can be heated by burning fuel (i.e., propane or diesel), an electric element, or using primary engine coolant to heat that surface. Some hydronic heating systems heat potable water and can be used for engine preheating.

Hydronic heating systems are a bit more complex than forced air furnaces. Instead of using a blower fan to distribute heat, hydronic systems use a pump to circulate hot water throughout the RV. This means that hydronic systems are quieter than forced air systems, making them a great option for RVers who prefer a quieter living space.

When it comes to safety mechanisms, hydronic systems also have a sail switch and a limit switch. The sail switch ensures that the pump is running before the burner ignites, while the limit switch prevents overheating. Hydronic systems also have a pressure relief valve that opens to release pressure if the system becomes over-pressurized.

If you’re looking to use your RV heating system to heat potable water or preheat your engine, a hydronic system may be a better option for you. However, if you’re looking for a simpler, safer option, a forced air furnace may be the way to go.

No matter which type of RV heating system you choose, it’s important to understand how it works and to keep it properly maintained. Make sure to have your system inspected by a qualified technician regularly to ensure that it’s working properly and safely. With the right knowledge and care, you can enjoy a warm and cozy RV all winter long.

When you turn on your RV furnace, here’s a general overview of what happens if it’s working properly:

1. The thermostat is turned on and signals for heat.
2. An electrical current is sent from the thermostat to the time delay relay built into the circuit board, which closes to energize the blower motor after a delay of 10-20 seconds. If the motor isn’t reaching 75% of its rated speed, potential issues include low DC power, a faulty motor, a blocked return air inlet, or a blocked exhaust. 
3. When the motor comes up to speed, the sail switch is moved by the airflow to close a micro-switch and continue the circuit. The micro-switch is set to require a minimum fan speed to close. If the motor isn’t running fast enough, you have a sticky switch, or there’s an airflow blockage that doesn’t allow the switch to close – the current will be interrupted. This circuit is independent of the thermostat and motor circuit.
4. The sail switch closes, sending power to the limit switch, which then sends power to the circuit board. Under normal operation, the limit switch is closed and opens at a preset temperature to prevent overheating.
5. The circuit board delays ignition for 10-20 seconds, allowing the blower motor to purge any gas remaining in the combustion chamber.
6. The circuit board opens the gas valve and sends a high-voltage current to the electrode.
7. If ignition occurs, the electrode senses the flame and sends a current back to the control board, stopping the high-voltage spark and keeping the gas valve open
8. If ignition doesn’t occur, the board will go into lockout mode and need to be reset before trying again. Most circuit boards will pause for 20 seconds, then try for 7 seconds. They’ll repeat this three times before going into lockout.

How to Reset an RV Furnace

As an RV owner, resetting your furnace is a simple process. First, locate the power switch or main breaker for your furnace. If your furnace doesn’t have a power switch, turn off the main breaker for the furnace. Wait about 10 seconds before turning the power back on. If you can’t find a breaker, check the fuse corresponding to your furnace. If needed, remove and reinstall the fuse. This is why labeling your RV’s circuit breaker panel is essential. With these steps, you can quickly reset your RV furnace and restore its functionality.

Where Is The RV Furnace Located?

The location of your RV furnace will vary depending on the manufacturer and the floorplan. Keep in mind that the furnace itself will not be visible, but you will be able to see a return air vent or vents inside your RV and the air intake/exhaust vent on the exterior of the RV. When shopping for an RV, consider looking for a model with an exterior access panel to service the furnace. Keep in mind that not all RVs, particularly entry-level travel trailers, have this panel.

Know How Much Propane Your RV Furnace Uses

It’s crucial to ensure that your furnace has an adequate propane supply. However, you may be wondering how much propane your furnace uses. The amount of propane consumed by your RV furnace largely depends on its BTU rating.

BTU stands for British Thermal Units and is a unit of heat that measures the amount of heat required to raise one pound of water by 1℉ at sea level. The higher the BTU rating of your furnace, the faster it will burn propane.

To determine your furnace’s BTU rating, you need to measure it in BTUs per hour. Once you know your furnace’s BTU rating, you’ll have a better idea of how much propane it consumes.

Before using your RV furnace, it’s essential to learn how to connect and turn on propane in your RV. Proper knowledge and understanding of propane usage will ensure that you have a safe and comfortable RV experience.

Lie your furnace in your home, your RV furnace will cycle on and off to regulate the temperature inside your RV. This is critical to remember when calculating how much propane your RV furnace uses.

Here is a typical example:

RV and Furnace Specs (let’s use specs for the Keystone Cougar 30BHS)

• Propane Capacity: 60 pounds
• Furnace BTU Rating: 30,000 BTUs/hr
• Electric Fireplace BTU Rating: 5,500 BTUs/hr

RV Furnace Propane Consumption Calculator

To start, propane containers can only be filled to 80% of their total capacity. So while the Cougar’s advertised propane capacity is 60 pounds, its actual capacity is 48 pounds (60 x 0.8 = 48).

We can calculate the total BTUs of 48 pounds of propane from there.

1 pound of propane = 21,548 BTUs

48 pounds of propane = 1,034,304 BTUs

If the total propane supply accounts for 1,034,304 BTUs, you divide that by the furnace’s BTU rating to estimate how many hours the furnace would run before that supply is exhausted.

1,034,304 BTUs / 30,000 BTUs/hr = ~34.48 hours

If you run the furnace and electric fireplace simultaneously, you can actually reduce your rate of propane consumption because you’re also relying on electric heat:

30,000 BTUs – 5,500 BTUs = 24,500 BTUs

1,034,304 BTUs / 24,500 BTUs/hr = ~42.22 hours

You can insert the appropriate figures from your RV into the example above to calculate how much propane your RV furnace uses. But remember that these calculations are based on 100% run time operation.

Other variables, such as cold weather and your desired temperature setting, impact your furnace’s potential operating hours on a full LP supply. For instance, you can roughly double the number of hours your furnace will operate if you estimate a 50% duty cycle (i.e., your furnace will run for half the time you’re camping).

Keep Your RV Furnace Clean

It’s important to keep your RV in top shape to ensure that everything runs efficiently. One component of your RV that requires regular cleaning is the furnace. Pet hair, dust, and debris can accumulate and cause problems for your furnace, but with proper cleaning techniques, you can keep it in good condition.

To start, it’s recommended that you clean and disinfect your RV after each trip to prevent any buildup. Inside your RV, use an RV vacuum to keep dust and dander to a minimum. You can also remove the return air vent to vacuum around your furnace unit on certain floor plans, but make sure to turn off the furnace first.

Outside your RV, use a portable air compressor to remove any dust, debris, pet hair, or insect nests from your furnace’s exhaust tube. This is especially important to add to your seasonal maintenance list when winterizing your RV in the fall and de-winterizing it in the spring before heading out for camping season.

By taking the time to clean your RV furnace regularly, you’ll ensure that it runs smoothly and efficiently, and you’ll be able to enjoy a comfortable and safe RV experience for you and your rental guests.

PS, Evaluate Proper Airflow

Proper airflow is crucial for an RV furnace to work efficiently and effectively. To evaluate your RV furnace’s airflow, follow these steps:

1. Open all discharge registers and closeable registers inside your RV to verify air discharge. You can do this by feel or use an airspeed indicator.
2. Check that no obstacles such as throw rugs or floor coverings are hindering airflow. This can cause the limit switch to open, and check the air filter to ensure it is clean and free from debris. A clogged air filter can restrict airflow and reduce the furnace’s efficiency.
3. Inspect the furnace ductwork for any obstructions or damage that could impede airflow.
4. Verify that the discharge is warm and conduct a carbon monoxide test to check for the presence of carbon monoxide.
5. Check the opening size for the furnace’s return airflow, ensuring that it matches your unit’s operating manual specifications.
6. Measure the temperature difference between the furnace inlet and outlet to ensure that the furnace is producing the desired amount of heat.

If you notice any issues with your furnace’s airflow, it’s best to consult with a professional HVAC technician with experience in RV units to address the problem and ensure proper airflow is maintained. By following these steps, you can ensure that your RV furnace runs efficiently and effectively, providing you with a comfortable and safe RV experience.