How to Convert from Oil Heat to Propane Heat


Homeowners convert from oil to propane heat for a variety of reasons. Some people want avoid the volatility associated with oil prices. Others like the environmentally friendly aspects of heating their home with propane, which is clean and has low emissions. Propane heating systems do not require as much maintenance or repairs as oil-fired systems. The installer has to modify the existing duct work to fit the new system.

Things You'll Need

  • Carpenter's level
  • Plenum
  • Aviation snips
  • Sheet metal screws
  • Foil duct tape
  • Mastic
  • Wood shims
  • PVC Schedule 40
  • PVC fittings
  • PVC primer
  • PVC cement
  • Takeoff
  • Starting collar
  • Foiled-faced fiberglass insulation, 1-inch thick
  • Disconnect switch
  • Thermostat
  • Low-voltage wiring
  • Pressure gauge


  • Determine the local building codes for the installation of a gas propane furnace, including propane tank and gas line installations. Submit an application for a work permit. Start the propane furnace project after receiving approval from the building permit department.

  • Remove the oil furnace and oil line connections. Install the gas furnace in the same location, which minimizes the duct needed to connect to the supply and return duct work systems.

  • Place the carpenter’s level on the top surface of the furnace to ensure it's level. Insert wood shims under any low spots.


  • Follow the installation manual and local building codes for running the vent pipe to the outside through a wall or through the roof. Cut the vent pipe with a hacksaw from Schedule 40 PVC pipe.

  • Clean dirt, grease or burrs from the pipe end. Check the fit of the pipe before permanently installing. Apply a coat of PVC primer inside the fitting and pipe. Spread PVC cement of the end of the pipe. Insert the pipe in the fitting and turn about one-quarter turn to help bond the two components.

  • Connect the pipe to the inlet port on top of the furnace. Install only medium or long radius elbows in the line. Install 1-inch thick foil-faced fiberglass insulation where pipe runs through unconditioned spaces that reach temperatures below freezing.

Duct Work

  • Cut the opening for the return air supply on the appropriate side of the furnace. Mark the outline of the opening on the cabinet and cut with aviation snips. Connect the return air line to the

  • Assemble the supply plenum. This sheet metal box fits on the top of the furnace. Attach the plenum to the flanges around the furnace blower compartment with sheet metal screws.

  • Measure the opening on the plenum for the takeoff or starting collar. Install a takeoff for rectangular ducts and a starting collar for round ducts. Wrap all duct joints in foil duct tape. Apply mastic in gaps and screw holes.

Propane Line

  • Purchase the propane tank and have it installed by the vendor. Check the tank to ensure it has a metal plate with the manufacturer’s nameplate. The nameplate has the manufacturer’s name, contact information, country of origin and date of manufacture etched on the plate.

  • Follow local codes for running a high-pressure underground gas line from the propane tank to the structure. The installer must connect a low-pressure gas regulator at the house connection, which makes the supply safe for residential use.

  • Install the house propane line, which connects to the low-pressure regulator. Consult local building codes for more details on acceptable material and installation methods. Install a gas shut-off valve near the furnace. Test the gas line with a pressure gauge to ensure it meets the local requirement, such as 30 pounds per square inch (PSI), for 15 minutes.

  • Install the liquid propane conversion kit on the furnace. Most units come preconfigured for burning natural gas operation.

  • Test the gas line with a pressure gauge to ensure it meets the local requirement, such as 30 PSI, for 15 minutes.


  • Disconnect the power at the main electrical panel. Flip the circuit breaker to the off position or remove the fuse. Test wires with a voltage tester to verify the power is off before proceeding.

  • Run a separate circuit to the furnace. Install a disconnect switch near the furnace. Run low-voltage wire for the thermostat, which installs in the living space. Follow the installation instruction for the proper location of the thermostat and wiring the terminals. This aspect of the project may require a licensed electrician

  • Install the drain line to the drain pain with copper tubing. Route the line to a floor drain

  • Refer to the installation manual for the checklist for starting up of the unit. Adjust the controls and thermostat to configure the furnace for operation.

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