Is It Legal to Install Your Own Furnace

Is your furnace outdated and old? Is it making weird, creaking noises? Are there visible cracks or signs of rust on the unit? If you answered ‘yes’ to any of these questions, it might be time for a new furnace. Many homeowners take pride in doing repair jobs (including their furnace) to keep their house in tiptop condition. Yet, few ask the all-important question: is it legal to install your own furnace?

Just a quick heads-up, it’s illegal to install a furnace without a permit or licensed professional. Each state has its own regulations regarding big home repair projects to ensure that the job gets done with the care and expertise it requires.

man installing furnace

Even if you are a diehard DIYer, keep reading. This is one post you don’t want to miss!

How Does a Furnace Work

A furnace is a box-shaped heater connected to several pipes and tubes. Gas and electricity flow in, heating the metal exchanger.

This heat exchanger warms up the cool air coming in from the bottom of the furnace. Next, the warm air is pushed towards the blower, while the exhaust is pushed out of the flue pipe.

Finally, the blower pushes the heated air out through the ductwork and circulates it in your home.

The Permit Zone

Furnace installations are within the ‘permit zone,’ as professionals call it. This zone includes big construction projects, like removing walls and insulation, or installing water heaters and furnaces.

A permit guarantees that the technician installing your furnace is fully experienced. It also ensures that there won’t be any safety hazards or technical difficulties once the furnace is in place.

Relying on Licensed Professionals

So, is it legal to install your own furnace? No, it’s not.

It can be tempting to try and get the job done yourself. However, installing a furnace is a large home repair job that requires knowledge of sheet metal, plumbing, and electrical work. If the furnace is powered by natural gas, that makes things even more complicated.

This is why installing a furnace requires a licensed technician with HVAC certification. These experts go through a diligent certification process after completing their associate degrees.

Applying for a Permit

For a licensed specialist to install your furnace, you need to apply for a low-voltage permit in your city. It’s basically an application that describes what kind of work will be done in your home in detail. It should also include the names of the professionals working on the project.

Besides the permit, you’ll need the following documents:

  • A floor plan that shows the furnace, as well as the return air and heat registers
  • Electrical plans showcasing how the furnace will be powered
  • Plumbing plans to show the gas piping system
  • Compliance with combustion air requirements
  • Compliance with minimum installation requirements

Out With the Old, In With the New

Now that you have your permit ready, it’s time for the installation to begin. The first thing you have to do is shut off all the gas and electrical supply lines. Leaving them turned on during this project can be a serious health hazard for the contractor as well as your home.

Before they start, the HVAC system technician needs to put on their protective gloves and gear to prevent injuries. Then, they begin by loosening the clumps and bolts connecting the furnace to the ducts and vents.

Next, they carefully pull up the old furnace from its resting place. Once it’s removed, the contractor cleans and vacuums the entire area.

The next step is to set the new furnace in place. Next, they attach the wires, pipes, and ductwork. The final step is to connect the thermostat to the new unit.

After that, the technician will turn the gas and electricity back on. Then, they’ll test the system and make sure there are no leaks in the ductwork or the gas supply pipes.

Common Installation Problems

Installing a furnace can be deadly if it’s not done the right way. Specialists need years of experience and hours of training to be qualified for large construction jobs. Even with that, they’re still liable to make mistakes, even if they’re few and far between. 

Nevertheless, it’s good to have a basic idea of some common installation problems that may occur.


Almost all furnace manufacturers rely on trained technicians to carry out installations. This ensures that their product is in good hands. It also guarantees that your furnace remains covered by the warranty.

However, if someone without a license installs the unit, the manufacturer can cancel your warranty. In other words, you could end up paying a hefty sum in repairs even if it’s the manufacturer’s fault.


Picking the right-sized furnace ensures that it’ll do its job efficiently and safely. When choosing a furnace, keep certain factors in mind, such as:

  • Square footage of your home and its layout
  • The quality of insulation
  • The number of rooms
  • Window sizes
  • Ceiling Height


When the furnace isn’t fitted and sealed properly, it can cause a gas leak. This can be either carbon monoxide or natural gas.

Breathing in carbon monoxide can lead to severe health problems, such as dizziness, nausea, and blurred vision. It can also lead to loss of consciousness and even death.

Similarly, natural gas can also cause severe health complications. This can range from nosebleeds to a reduced appetite to sharp pain in your chest. Furthermore, it can cause an explosion or a fire outbreak.


Simply put, installing a furnace without a permit and a licensed professional is illegal. 

With such a large project, you have to turn to the experts, as they have the needed experience and knowledge to handle all the ins and outs of a project like this. Even if a problem comes up, they’re equipped with the right skills and tools to handle them.

The good news is that paying a contractor to install your furnace is typically a one-time expense. Just make sure you take good care of your HVAC system, and in return, you’ll enjoy many years of use.

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