Installing a furnace into a home, whether new or pre-existing, is not a quick and easy task. When installing a furnace, you must do many things to properly function.

The average time to install a furnace is 4-10 hours. The installation in new construction will likely take less time because there is no pre-existing unit to remove. Depending on the adjustments needed to install the furnace, properly installing it in an existing home can take longer.

Read on to learn about the steps involved and the time required to install a furnace into new construction and existing homes.

Installing a Furnace in a New Construction

Before the actual furnace installation, all of the sizing and ductwork must be completed. It is also essential to make sure the correct electrical components are installed. If these things are completed first, the installation will likely be delayed. On the day of installation, there are several steps the HVAC technicians will follow.

Install Furnace Cabinet

Before you can hook up the furnace, the furnace cabinet will need to be installed. The purpose of the furnace cabinet is to hold the basic working components of the furnace in place. Sometimes the cabinet will be attached to the floor with bolts, while other times, installers will place it on risers to lift it from the floor.

Connect Ducts

Once the furnace is securely in place, the unit will need to be hooked into the existing ducts. Because it is a new build, the ducts have likely been precisely placed for the unit so connecting them won’t be an issue.

Connect Power

After the ducts are attached, and the unit is fully in place, it is time to connect the unit to the power source. They can program the thermostat to test the furnace when the power is attached.

Test the Furnace

The final step is to test the furnace to ensure everything is working.

Installing a furnace in new construction is usually much easier because there aren’t as many obstacles to work around.

Installing a Furnace in an Existing Home

The process of installing a furnace in an existing home can be a bit more complex because there are likely several things that the installers will need to work around, including previously installed ductwork.


When placing a new furnace into an existing home, you must measure the area correctly to ensure the furnace fits appropriately. This is particularly important if you are updating your furnace because the cabinet size may be larger than the original.

Install the Cabinet

The first thing that you will install is in the furnace cabinet. It may be installed on the floor or elevated depending on the airflow needs. The HVAC technicians will determine which option is best for your unit.

Attach the Ducts

The next thing that will happen involves attaching the new unit to the existing ductwork. Sometimes this can be challenging because you are running the ducts to a new unit with a different configuration.

If the existing ducts don’t match the new furnace, it may be necessary to run extra piping or remove some of the pipes. This will ensure the furnace is attached correctly to heat the home accordingly.

Connect the Power

After the furnace is attached to the ducts, they will connect the power to the unit to be tested. This will also allow the technicians to set the thermostat.


Once the unit is fully set up, the technicians will test it to ensure it is working correctly. The thermostat will be adjusted to ensure the house is being heated properly.

Why Does an Installation Take So Long?

The installation process may seem straightforward, so it may leave you questioning why it takes so long to do. There are several reasons a furnace installation may take longer than you anticipated.

Unit size: If the installed unit is larger than the initial furnace, it may take longer to install the cabinet and run the proper ductwork.

Location: The location of the furnace will determine if it can be installed quickly or if it will take extra time. If you install the furnace in an open area, it will be much easier than in a small space. Depending on the space, it could add days or hours to the installation time.

Timing: If you are trying to install a furnace during peak season, it may take longer than expected to install it because of the demand for HVAC technicians.

Things to Know

It is essential to understand that there will be an odor the first time the furnace is turned on. This odor is entirely typical and will disappear after a few minutes. There is a coating on the furnace parts that will burn off after the first few times the furnace runs. To help prevent the smell from being overpowering, opening the windows will help.

Smells That are Dangerous

Smells after the furnace is initially used are common, but some things cannot be ignored and indicate a serious problem.

Plastic: If you smell an odor of burning plastic or rubber, you need to contact the HVAC company because there can be a wiring or electrical issue.

Gas: If you smell gas, you likely have a significant problem that needs to be addressed immediately. The most important thing is to call the gas company and leave the house. They will come to determine if a gas leak is present.

Once the gas company has determined the house to be safe, it would be wise to contact the HVAC technician to have them check out the connections on the furnace to make sure there are no leaks that they can find.

(Source: Lycoming Heating)

If you smell anything that is concerning, you must contact the HVAC company that installed the furnace. Even if it is nothing to be worried about, they will likely be willing to come to check it out to put your mind at ease.

Final Thoughts

The time it takes to install a furnace is dependent on many different factors, but you can expect the installation to take at least four hours. If the installation location is challenging to access, it will likely take longer to install.


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