Troubleshooting Tips For Furnace Draft Problems

Posted on: 20 December 2021


Although nearly all modern furnaces include them, draft inducers are still a relatively new component in the heating world. Old furnaces were relatively inefficient, which meant that the exhaust gases carried away a substantial portion of the combustion heat. Hot gases will naturally rise, allowing them to escape through a simple roof flue.

However, higher-efficiency furnaces extract far more heat from the combustion gases. As a result, they require a separate fan motor to induce a negative pressure or "draft." This draft pulls the exhaust gases away from the furnace and through a PVC exhaust pipe.

What Are Furnace Draft Problems?

A modern furnace can't safely operate if there's no draft to pull exhaust gases away from the combustion chamber. Leftover gases can lead to less efficient combustion and even allow carbon monoxide to enter your home. Your furnace contains a few safety measures to help ensure that the draft system is operating correctly and prevent these eventualities.

In a typical furnace, you'll need your draft inducer motor and pressure switch to be working correctly for your furnace to ignite. The draft inducer produces the negative pressure necessary to pull combustion gases away from the furnace, while the pressure switch proves that the inducer is operating. If either one fails, your furnace will not ignite.

How Do You Know If Your Furnace Has a Draft Problem?

Furnaces can fail to ignite for many reasons, so how can you know if your draft inducer or pressure switch is to blame? While the best option is always to rely on a professional diagnosis, you can use a few clues on your own. Start by listening to your furnace when the thermostat calls for heat. Can you hear a fan motor turning on?

Your draft inducer should be the first thing to turn on when your furnace begins its ignition sequence. If you can't hear the draft inducer, that can mean the motor isn't working correctly. Note that there may also be other issues at play, such as a pressure switch that's stuck closed. The control board will confirm the switch is open before turning the motor on, so a closed switch can stop your furnace cold.

On the other hand, you may hear the draft motor run, but the furnace never ignites. In these cases, you may have a switch that's stuck open, preventing the igniter from ever turning on. An HVAC technician can test the switch to ensure that it's working correctly and rule out any other problems that may be stopping your furnace from igniting.

Remember that your furnace's draft system is critical for safe and efficient operation. Never attempt to bypass a failing draft inducer motor or pressure switch. If you suspect your furnace's draft motor may be failing, contact a professional for furnace repair as soon as possible to get the problem fixed.