How do I Install a Goodman Two-Stage Furnace?

Homeowners may replace their furnace because the previous unit no longer works, or to obtain energy savings from more energy-efficient models.

Installing a Goodman Two-Stage Furnace

Be sure the chimney liner is in good condition.Be sure the chimney liner is in good condition.
Regardless of the reason, be sure the person installing the new furnace, homeowner or qualified technician, is familiar with the procedure, local codes and safety measures surrounding the installation of a new gas appliance.

Acquire building permits to install the furnace.

Read the entire furnace manual. Even if you have installed furnaces previously, the particular model may have specific requirements that differ from other models. Those differences can sometimes be related to safety measures that are vital for protecting the occupants of the home.

Turn off the gas from the meter and replace the manual shutoff gas valve if it appears to be worn. It is good practice to replace the manual shutoff for every install even though it is usually not required by code. Make sure the electrical wire from the switch does not have current running through it by flipping the breaker at the breaker box.

Line up the furnace with the supply plenum and attach the transition to connect the furnace to the supply plenum. Attach the return air plenum to the furnace. If the return plenum does not line up, it may need to be moved or an offset attached to allow for proper fit.

Check the entire return air system from the furnace to the returns grills throughout the house. Air entering the return grill must be sealed for the complete path to the furnace. Use appropriate sealers or tape to prevent air outside of the return air system from entering.

Attach the venting to the chimney if it is a natural draft furnace. Be sure to check the chimney liner to verify it is in good condition. If it is in good condition, it can be reused with this new furnace. If the furnace is direct vent, then drill the appropriate size holes in the wall to allow combustion air to enter the furnace and exhaust air to the outdoors. If the furnace is high efficiency, then a condensation drain needs to be attached to the furnace to drain into a floor drain.

Attach the gas pipe to the furnace. If the furnace is the same size and design as the previous furnace, then everything should line up properly.

Attach the electrical wire to the furnace. It should be on its own breaker that is dedicated to the furnace. The ground will attach to the screw in the junction box inside of the furnace. The black connects to black and white to white. Make sure that proper wire nuts are used and tightened so that they cannot be pulled out. Attach the thermostat wire to the furnace.

Check for any loose fittings or connections. Turn on the gas and purge the line of air. Perform a soap-and-dial test using approved soap solution that will help detect any gas leaks on joints. To perform a dial test, turn off gas to all other appliances other than the furnace. Make sure the furnace is turned off and watch the dial on the outside meter for 10 minutes to see if the dial is moving. The slightest movement indicates a leak, and a quality gas detector should be used to identify the location.

Turn on the power to the furnace and set the thermostat to heat.

Things You Will Need

  • Pipe wrenches
  • Screwdriver
  • Wire nuts
  • Wire strippers
  • Multimeter
  • Transition kit

About the Author

Eric Jonas has been writing in small-business advertising and local community newsletters since 1998. Prior to his writing career, he became a licensed level II gas technician and continues to work in the field, also authoring educational newsletters for others in the business. Jonas is currently a graduate student with a Bachelor of Arts in English and rhetoric from McMaster University.