How to Convert Natural Gas Furnace to LP

The Big Switch: Converting Your Natural Gas Furnace to LP (or Vice Versa!)

Hey there! So, you're probably here because you're thinking about, or have been told you need to, convert your natural gas furnace to LP. Maybe you're moving to a rural area without natural gas lines, or perhaps you just bought a property that has LP (liquid propane) and a natural gas furnace, and you're scratching your head wondering if you need a whole new heating system. Good news: often, you don't! But it's definitely not as simple as flipping a switch. Let's dig into what this whole process entails, why it matters, and why you probably shouldn't try to tackle it yourself on a Saturday afternoon.

Hey There, Why Are We Even Talking About This?

You know, it's pretty common for folks to find themselves in this exact situation. Maybe you've landed a sweet deal on a new property, only to realize the existing furnace is set up for natural gas, but your new home runs on a big ol' LP tank. Or maybe, vice versa, you're transitioning from LP to natural gas because new utility lines just became available in your neighborhood. Whatever your personal "why," the core issue is the same: you have a furnace designed for one type of fuel, and you need it to safely and efficiently burn another. It's a critical change, and understanding the nuances can save you a lot of headache (and potentially, danger!).

Natural Gas vs. LP: What's the Real Difference Under the Hood?

Okay, let's get a little bit technical, but I promise to keep it friendly. Think of natural gas and LP as cousins – they both burn, they both create heat, but they're definitely not identical twins.

The biggest differences we care about for your furnace are:

Energy Content (BTU Value): LP packs a lot more punch per cubic foot than natural gas. It's denser and contains more energy.
Pressure: LP is stored as a liquid and then vaporizes, coming out at a higher pressure than your typical natural gas line.
Air-to-Fuel Ratio: Because of these differences, LP needs a different mix of air to burn completely and cleanly compared to natural gas. Get this wrong, and you're looking at incomplete combustion, soot, inefficiency, and worst of all, potential carbon monoxide production. Yikes!

So, you see, you can't just hook up an LP line to a natural gas furnace and expect it to work safely. The furnace's components are specifically sized and calibrated for the particular fuel it's designed to use. That's where the conversion process comes in.

Is It Even Possible? The "Yes, But" Answer

Absolutely, in most modern furnaces, converting your natural gas furnace to LP (or LP to natural gas) is totally possible! Manufacturers design many of their units with this flexibility in mind. However, and this is a huge "however," it almost always requires a specific manufacturer-approved conversion kit. You can't just wing it or buy generic parts. Your furnace's model and serial number are key to getting the right kit.

Think of it like getting new shoes for your car. You wouldn't just buy any old tires; you'd get the ones specifically designed for your car's make and model, right? Same principle applies here, but with much higher stakes!

What's Actually Involved in the Conversion Process? (The Nitty-Gritty)

So, what exactly does this conversion kit contain, and what does a technician actually do when converting a natural gas furnace to LP? Let's break down the main components that need to be swapped or adjusted:

The Key Components You'll Be Touching (or Rather, Your HVAC Pro Will Be!)

Burner Orifices: This is probably the most crucial part of the conversion. Natural gas orifices are larger because natural gas needs more volume to deliver the same amount of heat as LP. LP orifices are smaller to restrict the flow of the higher-BTU, higher-pressure LP gas, ensuring the correct air-to-fuel mixture for proper combustion. It's like changing the nozzle on a hose – different flow for different needs.
Gas Valve/Regulator: The gas valve controls the flow of fuel to your burners, and it often includes a pressure regulator. For an LP conversion, this regulator needs to be set to a different outgoing pressure than for natural gas. Some conversion kits might include an entirely new gas valve, while others might involve adjusting or replacing specific regulator springs or components within the existing valve.
Pilot Light Orifice (if applicable): If your furnace has an older-style standing pilot light (most modern furnaces have electronic ignition, thankfully!), its tiny orifice will also need to be swapped out for one suitable for LP. Don't forget this little guy!
Burner Air Shutters (sometimes): In some furnace designs, there are adjustable air shutters at the base of the burners. These might need to be opened or closed slightly to allow the correct amount of primary air to mix with the LP for optimal combustion. It's all about getting that perfect blue flame!

The "How To" (But Seriously, Don't Do It Yourself)

The general steps for converting a natural gas furnace to LP look something like this:

Safety First! Turn off all power to the furnace and shut off the gas supply. Seriously, don't skip this.
Access: Open up the furnace to get to the burner assembly, gas valve, and other components.
Swap Orifices: Carefully remove the existing natural gas burner orifices and replace them with the smaller LP orifices from the kit.
Gas Valve Adjustment/Replacement: Either adjust the pressure regulator on the existing gas valve or replace the entire valve with the LP-specific one from the kit.
Pilot Orifice (if needed): Swap out the pilot orifice.
Air Shutter Adjustment (if needed): Adjust the burner air shutters.
Reassembly & Leak Check: Put everything back together carefully and, critically, perform a thorough leak check on all gas connections using a specialized leak detection solution.
Test & Calibrate: Restore power and gas, then ignite the furnace. This is where the true pro work comes in: the technician will use instruments like a manometer (to check gas pressure) and a combustion analyzer (to measure exhaust gases for efficiency and safety) to ensure everything is burning perfectly and safely. This step is non-negotiable.

Why This Isn't a DIY Project for the Faint of Heart (or Uncertified)

I cannot stress this enough: converting a natural gas furnace to LP is NOT a DIY project for the vast majority of homeowners. I know, I know, YouTube makes everything look easy, but this is a whole different ballgame. Here's why you absolutely, positively need to call a certified HVAC professional:

Safety, Safety, Safety: We're talking about flammable gas, high pressures, and combustion. Messing this up can lead to gas leaks, fires, explosions, or the production of deadly carbon monoxide. This isn't just about your furnace; it's about the safety of your entire home and everyone in it.
Precision and Expertise: It's not just swapping parts. It's about precise gas pressure adjustments, air-to-fuel mixture calibration, and thorough leak detection, all of which require specialized tools (like manometers and combustion analyzers) and years of training. An eye-ball test simply won't cut it.
Warranty Issues: Attempting a DIY conversion will almost certainly void your furnace's warranty. If anything goes wrong down the line, you'll be footing the bill for repairs that would have otherwise been covered.
Local Codes & Regulations: In many areas, gas appliance work is regulated and must be performed by a licensed professional to meet safety codes. Your home insurance might even have stipulations about this.
Efficiency: A poorly converted or adjusted furnace will run inefficiently, costing you more in fuel bills and potentially shortening the life of your unit.

Honestly, the peace of mind knowing your heating system is safe and running optimally is worth every penny of a professional's fee.

Finding the Right Conversion Kit: Your Furnace's Best Friend

As we mentioned, the conversion kit is central to this whole process. Don't even think about trying to source individual parts.

Model Specificity is Crucial: The conversion kit must be specifically designed for your exact furnace make and model. You'll find this information on a label inside your furnace cabinet. Give these details to your HVAC technician.
Where to Get Them: Typically, your HVAC professional will order the correct kit directly from the furnace manufacturer or through their authorized distributors. These aren't usually items you can pick up at a big-box hardware store.
What's Usually Included: A kit will generally contain the LP-specific burner orifices, possibly a new gas valve or regulator components, any necessary gaskets or seals, and, importantly, detailed installation instructions for the technician.

What to Expect When Hiring a Pro

When you decide to convert your natural gas furnace to LP and call in a professional, here's a rough idea of what the process will look like:

Initial Assessment: The technician will inspect your furnace, confirm its model, and verify that a conversion kit is available.
Kit Sourcing: They'll order the correct manufacturer-approved conversion kit.
The Conversion Work: On the scheduled day, they'll perform the steps we outlined earlier: safely shutting down the system, swapping components, adjusting pressures, and reassembling.
Post-Conversion Testing: This is the critical safety and efficiency check. They'll use their specialized tools to verify gas pressure, check for leaks, and perform a combustion analysis to ensure your furnace is burning cleanly and efficiently on LP. This step is vital for your safety and comfort.
Cost: Expect to pay for the conversion kit itself (which can range from $100-$500 or more, depending on the furnace) plus several hours of skilled labor. It's an investment in your home's safety and comfort.

Beyond the Furnace: Other Considerations

Remember, converting the furnace is one thing, but if you're truly switching fuel types, there are broader implications:

LP Tank Installation: If you don't already have one, you'll need an LP tank installed, which involves trenching, pad construction, permits, and a whole separate set of safety regulations.
Gas Line Sizing: Ensure your existing gas lines (if you're repurposing them) are appropriately sized for LP, which runs at higher pressures.
Cost Implications: While LP offers flexibility, its price per BTU can fluctuate and is often higher than natural gas in many regions. Factor this into your long-term heating budget.

The Final Word: Don't Skimp on Safety and Expertise

Whether you're looking to convert a natural gas furnace to LP or the other way around, the takeaway message is clear: it's a completely achievable task, but it absolutely requires the hands of a qualified and certified HVAC professional. Don't risk your safety, void your warranty, or compromise your furnace's efficiency by attempting this complex conversion yourself.

Invest in peace of mind. Give your local HVAC experts a call, get the right kit, and let them handle the technicalities. You'll be warm, safe, and happy knowing your heating system is running exactly as it should be.