How Do RV Propane Furnaces Work?

How To Keep Them Hot!

RV propane furnaces work with both propane (to create heat) and electricity (for the ignition and fans). The process starts when the thermostat is turned on and turns on the combustion chamber where gas is burned to heat the air in the heat exchanger before warm air is blown into the RV via a duct system.

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Only when the right temperature is reached will the blower fan turn on. If the blower fan doesn’t reach the right speed, the sail switch turns off the furnace. And if the furnace gets too hot, another safety feature called the limit switch will shut down the combustion chamber.

With the built-in safety features and regular maintenance, this allows RV propane furnaces to be 100% safe and efficient. Furnaces also heat the basement storage, which help prevent pipes and water from freezing.

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What Are The Parts On An RV Propane Furnace?

The general components of a propane furnace system and how each one works:

  • Thermostat. It can be analogue or digital, and it turns on the system to heat the air to the desired temperature. Only when the temperature in the heat exchanger is warm enough will it trigger the blower.
  • Combustion chamber. This is where propane gas is burned to create heated air with an electronic ignition.
  • Blower fan. It has to reach a 75% of air flow capacity before it can trigger the sail switch to turn on. The blower can get filled up with debris, lint, dust, leaves, nests, etc. from the air intake or pests.
  • Sail switch. It’s an electronic safety device that shuts off the furnace to prevent overheating if the air intake is blocked or the blower fan doesn’t have enough speed. It’s also affected by low DC voltage.
  • Circuit board. This is the heart of the furnace since it controls the propane valve and burner.
  • Limit switch. This shuts down the combustion chamber if it gets too hot. It also allows cooler air to go back into the furnace via the cold air return duct.
  • Stainless steel vent. Serves as chimney to allow fumes out via the exhaust.
  • Ducting. It’s made of flexible reinforced aluminum tubes that is routed into the different sections of the RV. The minimum number of ducts required by the propane furnace are indicated in the user manual.
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How To Keep Your RV Furnace Running Efficiently?

Keeping your RV furnace running efficiently will ensure that there is plenty of heat when you need it the most, especially if you are doing some winter camping. Here’s the things that are needed:

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  1. Have enough propane. Make sure there’s enough propane for your furnace, and all other propane-appliances. You can do one (or all) of the following:
    • Compute how much propane’s needed. Each propane appliance (check the owner’s manual and look for the BTU rating) needs to operate for the duration of the camping trip. See next section on how to compute for this.
    • Use an accurate propane gauge, scale or indicator. Knowing how much propane you have allows you enough time to go buy some more. Some tanks already have a gauge built into them (or can be purchased separately) to see how much is left. Using a propane tank scale, whether analog or a smart wireless one, is also a good idea to know if you’re about to run out of it. Other options could include a magnetic gas level indicator too.
    • If necessary, have a spare tank. Depending on your RV, some towable models will be able to accommodate another 20-30lb propane tank.
  2. Ensure annual servicing & regular maintenance is done. This is necessary to make sure the furnace not only works properly when you need it, but also makes it last longer.
    • Always check if intake/exhaust vents are clean/debris free
    • Ducting should be properly connected to the furnace
    • Check if ducts don’t have any holes
  3. Depending on your RV, having separate heating zones are useful to allocate the heat properly. Some RVs have multiple heating zones. Not all sections of the RV will need heat at various times of the day (or night).
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If your furnace is not providing enough, consider supplementary heating options to help.

Small electric heaters can provide that additional heat as needed and or the use of electric blankets.

How Often Does Your RV Furnace Need Maintenance?

Depending on how frequent you use your rig, An RV furnace needs to be checked at least once a year. Ideally before the season starts so that there won’t be any issues when you need to use it. If you use it more frequently maybe a monthly inspection of the parts to ensure everything is working in top shape.

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How Much Propane Is Needed To Run An RV Furnace? (How Much Propane Does An RV Furnace Use?)

Since a furnace (30,000 BTU) doesn’t run continuously (it will switch on/off to maintain the desired temperature), one (1) gallon of propane can last 4.5 days (or 3 hours if it runs continuously off a 20lb tank).

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Remember though that the total amount of propane needed will depend on the number and type of propane appliances you have, how you use them, and the weather conditions (if it gets colder, it will take longer to heat the furnace or water). Checking the owner’s manual to determine the BTU of each appliance or trying a fuel consumption calculator can help with this task.

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1 gallon propane = ~92,000 BTU

20pound propane tank = 4.6gallons propane = 423,200BTU

Is A Carbon Monoxide Detector/Fire Detector Required In Your RV?

As part of local or state regulations, carbon monoxide, propane, smoke detectors and fire extinguisher(s) are required in your motorhome. These devices are a must:

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  • Carbon monoxide (CO) detector: As per the Consumer Product Safety Commission, a CO detector should be mounted near the sleeping area – 4-18 inches from the ceiling). Carbon Monoxide is a tasteless, colorless, odorless poisonous gas and is considered the #1 for poisoning annually in the US. RV furnaces and generators commonly generate a lot of carbon monoxide. Check the CDC CO Poisoning Prevention for more details.
  • Propane detector: A propane detector is mounted around 4-18 inches off the ground, near the sleeping area.
  • Fire Detector
  • Fire Extinguisher
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Common Issues

Some issues may arise when using a propane furnace. In the article “Troubleshooting Guide: RV Furnace blowing cold? (Or Not blowing at all?)” it will list the signs and their most probable cause that can be checked to fix it, or determine if a professional may need to see what’s going on.

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