Looking for a way to cut down your energy bills? Converting your furnace from propane to natural gas could be a smart move. Many people see their gas expenses decrease significantly, often by a third, after the first year.
But it’s not just about saving money. It’s also about choosing a cleaner, more reliable way to keep your home cozy and warm. While you would typically want to hire a licensed contractor to convert your furnace, there’s a way to do this conversion yourself.
In this guide, we’ll walk you through how to convert your propane furnace to natural gas, and we’ll make it simple with easy steps you can follow to make the switch.
Let’s get started on making your home heating better and more budget-friendly!
How to Convert a Propane Furnace to Natural Gas
This guide is designed to help you but is not expert advice. Converting your furnace from propane to natural gas involves working with gas lines, modifying the internal components of your gas furnace, and adjusting gas pressures.
It should only be attempted by those with experience and knowledge of gas appliances.
Make sure you read the manual for your heating system because not all gas furnaces are the same, and the conversion requirements can vary. Always get a licensed technician involved if you don’t have any experience with this type of work.
Step 1: Make Sure Your Propane Furnace Can be Converted to Natural Gas
First, you need to check and make sure your furnace can actually be converted from propane to natural gas. Most of the time, this boils down to how old your furnace is.
If your furnace or gas pack is under 20 years old, a conversion kit should be available. However, if your heating system is 20-30 years old, some manufacturers may have discontinued the conversion kits for your specific system.
To find out if a conversion kit is available, locate the rating plate on your heating system. The rating plate will show your unit’s model and serial number, along with the manufacturer and when it was made. Call the manufacturer directly and provide them with your specific model and serial number. With this information, they’ll be able to let you if a conversion kit is available.
In some cases, they may have discontinued making them but can provide you with a distributor near your location you can call to check availability with them. If the manufacturer doesn’t give you anywhere else to look, that doesn’t mean you’re out of luck.
There are a couple of websites you can also check that might have your conversion kit available – RepairClinic.com and HVACdirect.com. Just search for your furnace model number and see what they have available.
You can also check with your local HVAC or plumbing supply stores to see what they have in stock.
If you still can’t find the conversion kit for your furnace, another option would be to either find a contractor who can drill out your propane orifices to the correct size for natural gas or do it yourself. Because propane operates at a higher pressure than natural gas, your orifice holes will need to be larger.
Keep in mind, some companies don’t want to take on the liability of drilling out orifices, so your only option may be to do it yourself.
If you want to try drilling out the orifices, you’ll need to know the converted natural gas orifice size for each burner in your furnace. Your owner’s manual might tell you what orifice size is required but if not, look for the number of BTUs each burner uses so you can match that up with the correct orifice size in a gas orifice conversion chart.
Once you know what size hole to drill for natural gas, you’ll need to use a micro drill bit to slowly drill out the hole with your hand. Don’t use a power drill for this. The hole must stay clean and even all the way around.
If you want more in-depth instructions on how to drill out a propane orifice for natural gas, we cover that in our grill conversion guide.
If your furnace is 20+ years old and you can’t find a conversion kit, it may be time to replace your unit.
That’s because the older your furnace gets, the more likely you are to spend money just to keep it operational year after year. You also run the risk of having a cracked heat exchanger, which can release carbon monoxide into your home.
But even if you do have to come out of pocket for a new heating system, there’s still good news!
Many manufacturers offer rebates for certain natural gas furnaces, and there are also federal tax credits you can receive once you install a high-efficient natural gas furnace.
The permit application may require you to provide the following information about the work:
- The scope of the job (LP to NG furnace conversion)
- The budget of the job (cost of materials, conversion kit, etc.)
- If any subcontractors will be used to do any part of the work
To find out what your local jurisdiction charges for the permit, you can google “(city or town) permit fees”. Sometimes, they’ll name this “permit fee schedule,” so if you see that, it should take you to where you need to be.
Once you have your permit, you can schedule the inspection. The inspection is when a local inspector comes out to look at your work to make sure it was done correctly and is up to code.
When it comes time to sell your home, you may need to provide proof that the work you did was inspected before closing on the home.
Step 3: Gather the Tools Needed
To convert a heating system from propane to natural gas, you will need certain tools to complete the job. Here’s a list of tools you’ll need:
- Screwdriver – Flat head and Phillips head
- Socket wrench
- Channellock’s
- Pipe dope
- Teflon tape
- Manometer
- Micro drill bit set – if necessary
Step 4: Turn Off the Power and Gas to Your Furnace or Gas Pack
To turn off the power to your unit, locate the breaker inside your panel box labeled for your furnace and switch that to the off position.
To turn off the gas to your furnace, locate the gas shut-off valve. This is typically in line with the gas piping before it enters the heating system. Turn the valve 90 degrees to the off position.
For reference, see the diagram below showing how a valve should look when turned off.
Step 5: Remove the Access Panel and Disconnect Gas Piping from the Gas Valve
Using a screwdriver, remove the access panel on your heating system. Once removed, you should be able to see where the gas piping comes into the gas valve.
It might be a good idea at this time to take a picture or create a drawing so you can remember how everything is laid out internally. Having this visual aid when putting everything back together helps a lot, especially if you have to remove any wiring or Molex connectors to get where you need to be.
Follow the gas piping from the gas valve over to the burners. You may need to disconnect more gas piping on this side of the gas valve to give yourself more room to work. If the burner box is sealed, remove the screws so you can access the burner assembly and get to the orifices.
Step 6: Replace the Orifices on Each Gas Burner
Carefully remove each burner retainer by unscrewing them from their position. This allows you to access the orifices on the orifice manifold.
Using the correct-sized socket, carefully remove the propane orifices. Before you install the new natural gas orifices that came in your conversion kit, wrap their threads with Teflon tape (PTFE sealing tape).
After installing your orifices, reconnect the burners and any gas piping you removed from the burner assembly to the gas valve. Use pipe dope on the threads of the gas pipe to ensure there are no gas leaks.
Once taped, install the new natural gas orifices that came in your conversion kit. Make sure you don’t overtighten these as it could cause them to bind up.
Step 7: Replace the Spring Inside the Gas Valve
Locate the cap screw that holds your adjustment spring inside your gas valve. Turn out the cap screw and plastic adjustment screw to remove the old propane gas spring.
Insert the new natural gas spring and re-install your plastic adjustment screw. Don’t screw the cap back on just yet. You may need to use the adjustment screw to set the outlet pressure. This is explained further in the next step.
Reconnect any wiring or gas piping back to the gas valve to tie everything back in. Again, make sure to use pipe dope for the pipe threads.
Step 8: Set the Gas Pressures with a Monometer
Remove the gas inlet pressure port on the furnace’s gas valve and connect one end of the manometer tube to the port and the other end to the manometer to test the incoming gas pressure.
With your cap screw still disconnected from your gas valve, you now need to adjust your gas pressures for the inlet and outlet side of your gas valve. To do this, you’ll need a manometer.
Once connected, turn the gas ball valve to the on position to allow gas to flow into your furnace. Refer to your instruction manual to determine what the incoming gas pressure needs to be set at and adjust as needed.
The incoming gas pressure should typically be between 4.5” and -11” W.C. (water column).
- Adjust the Appliance Regulator: If your home uses a 2lb gas pressure, you will have an appliance regulator in line with the gas piping going to your furnace. You can adjust the outlet pressure of this regulator down or up to get to the required gas pressure. To do this, remove the cap on top and use a screwdriver to turn it left or right. Turning right gives you more gas pressure, and turning left gives you less. Watch your manometer and stop adjusting once it’s in the required pressure range.
- Call Your Local Gas Company: If you don’t have an appliance regulator, that means your pipe system is set up for a lower pressure. To change the gas pressure on these systems, you’ll need to call your local gas company so they can make the adjustments on their end.
Once your inlet pressure is set, turn off the gas ball valve and close the gas inlet pressure port. You can now hook up your manometer to the outlet pressure port on the gas valve.
Turn the power back on to the unit and go to your thermostat to turn the heat on. Make sure to set the temperature high enough so the burner stays on while you set this pressure.
Your conversion kit should have come with a sticker showing that the unit uses natural gas or has been converted from propane to natural gas. Make sure to stick this to the gas valve, as your local inspector will look for that when they inspect your work.
Once that’s done, you can close your unit back up and enjoy your new source of heat.
If DIY isn’t your thing, don’t hesitate to call in a professional. Whether you do it yourself or need a licensed contractor’s help, one thing is certain—you’ll benefit from a heating system that’s more efficient and reliable.
Refer to your manual again to determine the outlet pressure of the gas valve for natural gas. Most natural gas furnaces operate with a gas pressure between 3.2” and 3.7” W.C. (water column).
You can adjust this pressure by turning the plastic adjustment screw that controls the new natural gas spring you installed earlier. For more gas pressure, turn the adjustment screw to the right clockwise. For lower pressure, turn it left or counterclockwise.
Once the pressure is set, you can turn the gas ball valve off, close your outlet pressure port and re-install your cap screw. You can then turn the gas ball valve back on.
Final Thoughts
By following the detailed steps in this guide, you should now understand how to convert a propane furnace to natural gas. With this conversion behind you, you can move on to converting your other propane appliances.
And we’re here to help with those too! You can start by checking out our guide on how to convert a propane grill to natural gas.
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