Introduction: Why Fuel Conversion Matters
I’m Tony Marino. Over my 20-plus years in the HVAC trade, I’ve seen plenty of homeowners and technicians face the decision to convert a boiler’s fuel type. It could be because natural gas has become available to a neighborhood, or maybe LP fuel prices have risen sharply.
Weil-McLain offers certified gas conversion kits that let you safely change your boiler’s fuel from natural gas to propane (LP) or propane to natural gas without replacing the entire unit. This is a cost-effective way to adapt to changing fuel availability or prices.
But conversion isn’t just a simple swap — there are important considerations, codes to follow, and safety protocols. This guide will walk you through everything you need to know.
When Should You Consider a Fuel Conversion?
1. Availability and Cost of Fuel
If your area suddenly gets natural gas service and you’ve been running on LP, converting can save you money. Natural gas often costs less and burns cleaner than propane. Conversely, if natural gas lines are unavailable or expensive, switching to LP might make sense.
According to the U.S. Energy Information Administration, natural gas is typically the least expensive heating fuel in many regions, but propane is popular where gas infrastructure is limited.
2. Environmental and Efficiency Concerns
Natural gas generally produces fewer carbon emissions per unit of heat than propane. So, switching fuels can help reduce your home’s carbon footprint if you choose natural gas.
3. Equipment Age and Condition
If your existing boiler is older but still in good condition, conversion kits provide a smart alternative to full replacement.
What Are Weil-McLain Gas Conversion Kits?
Weil-McLain’s conversion kits include all necessary components—jets, orifices, regulators, and sometimes valves—to switch between fuels safely. The kits are designed specifically for each boiler model to maintain proper combustion and ensure warranty compliance.
Popular kits include:
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KIT-C NG/LP CGI6 S3 (for CGi6 Series 3 boilers)
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Other model-specific kits depending on your boiler type
All Weil-McLain conversion kits come with detailed instructions. It’s vital to follow them closely.
For technical details, you can review Weil-McLain’s product manuals and specs.
How Does Fuel Conversion Work?
Converting fuel primarily involves:
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Replacing Burner Orifices: These control fuel flow; propane orifices are smaller than natural gas due to higher energy content.
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Adjusting Gas Regulators: To set proper inlet pressure for the new fuel type.
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Calibrating Combustion: Adjusting air-to-fuel ratio to ensure efficient, clean burning.
This process must be done carefully, or else you risk incomplete combustion, carbon monoxide production, or inefficient operation.
Step-by-Step Guide to Fuel Conversion
Step 1: Verify Boiler Model and Serial Number
Before ordering a conversion kit, confirm your boiler’s exact model and serial number. This info is usually on the boiler label.
Step 2: Obtain the Correct Conversion Kit
Use Weil-McLain’s catalog or talk to your dealer to get the right kit. Using the wrong kit can cause performance issues and void your warranty.
Step 3: Turn Off All Power and Fuel Supply
Safety first. Shut down electrical power and close the fuel supply valve.
Step 4: Remove the Burner Assembly
Access the burner compartment carefully. Wear gloves and eye protection.
Step 5: Replace Orifices and Adjust Regulator
Swap out the gas orifices and adjust the gas regulator as per the instructions.
Step 6: Reassemble and Turn On Fuel and Power
Make sure all components are secure.
Step 7: Test Combustion
Use a combustion analyzer to check CO, CO2, and O2 levels, and adjust the burner for safe and efficient operation.
Safety and Code Compliance
Fuel conversion work is regulated and should comply with local codes such as the National Fuel Gas Code (NFPA 54). Improper conversion can cause dangerous conditions including carbon monoxide leaks and fire hazards.
According to the National Fire Protection Association (NFPA), only qualified personnel should perform fuel conversions.
Always get your work inspected by local authorities when required.
Common Questions About Weil-McLain Fuel Conversion Kits
Can I do the conversion myself?
If you’re a trained HVAC technician, yes. For homeowners, it’s best to hire a pro.
Will my boiler warranty remain valid after conversion?
Yes, but only if you use Weil-McLain-certified kits and follow installation instructions exactly.
How long does the conversion take?
Usually 1–3 hours depending on model and technician experience.
Does conversion affect boiler efficiency?
Properly done, efficiency remains the same. Poor conversions can reduce efficiency and increase emissions.
Cost Considerations
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Conversion kits themselves can cost anywhere from $100 to $400 depending on the model.
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Labor costs vary by region and complexity but expect $200–$600 for professional service.
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Savings from switching to a cheaper fuel can offset these costs over time.
For a deeper dive into cost and benefits of fuel switching, check out Home Comfort Practice’s fuel conversion cost guide.
Advantages of Weil-McLain Certified Conversion Kits
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Maintains Manufacturer Warranty
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Precisely Engineered for Your Boiler
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Includes All Necessary Components
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Supports Safe and Efficient Operation
Tips for Maintaining Converted Boilers
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Schedule annual tune-ups to check combustion and safety controls.
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Inspect venting regularly for corrosion or leaks.
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Monitor for unusual odors or soot build-up.
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Upgrade controls if possible for better fuel management.
Alternative: Replacing Your Boiler Instead of Converting
In some cases, especially for very old or inefficient boilers, replacement might be more cost-effective long-term. New high-efficiency models can drastically cut energy use.
You can learn more about your options in this detailed Energy.gov guide to home heating systems.
Summary: Is Fuel Conversion Right for You?
Switching fuels using a Weil-McLain conversion kit is a practical option when:
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Your fuel supply or cost changes significantly
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Your boiler is in good shape and compatible
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You want to avoid the cost and hassle of a full replacement
But, always ensure the work is done by a qualified professional who follows code.
Final Thoughts from Tony Marino
Fuel conversion is a smart way to keep your Weil-McLain boiler working efficiently in a changing energy landscape. Use certified kits, follow instructions carefully, and don’t cut corners on safety.
For help choosing the right conversion kit or professional service, reach out—I’m happy to guide you through the process.
