If your furnace is blowing cold air it can be really frustrating. Not only is your building not staying warm, but because the furnace is still on and running, you’re wasting money on pumping your building full of cold air. Whether it’s an office, a classroom, or another public space, having adequately heated space is essential for the comfort and safety of everyone in it. 

In this article, our team at Tri-Tech Energy has put together a list of some of the most common reasons why your furnace is blowing cold air. 

A Cracked Heat Exchanger May Lead To Cold Air Coming From The Vents When The Heat Is On 

The most important thing to understand about a cracked heat exchanger is that it puts you at risk for carbon monoxide poisoning. This is extremely serious and needs to be fixed immediately, so if your furnace suddenly starts blowing cold air, turn your whole system off and call an HVAC technician right away. They need to inspect the heat exchanger to ensure it’s not cracked, and if it is damaged, it needs to be replaced immediately. 

Heater Not Blowing Hot Air Due To Faulty Main Limit 

There’s a safety feature located inside each furnace called a main limit. When your furnace overheats, it triggers the main limit which activates a safety mode that turns off the ignition. If your furnace frequently overheats and the ignition is switched off, you’ll notice that it starts blowing cold air. 

Just like all components of your heating system, over time the main limit can become worn out and dirty. The main limit switch can also be faulty and can activate your furnace’s safety mode when it’s not necessary, causing your furnace to switch off unnecessarily and begin blowing cold air. It’s important that your main limit switch engages only when your system is actually overheating, otherwise it’ll shut down your furnace frequently for no reason. 

You Have Cold Air Blowing Out The Vents When The Heat Is On Because Of A Dirty Air Filter

We understand that your heating system is out of sight, out of mind, but dirty air filters are the cause of so many issues with heating and cooling systems. Think about how much air passes through the vents on a daily basis, then think about how much dust, dirt, and other debris must also pass through those same vents. Your air filters work to prevent this debris from entering your building and you must change them regularly, our recommendation is once every three months. 

When your furnace filters become dirty and clogged, it stops the air from flowing into the furnace which results in your heater blowing cool air. Changing your furnace filters is something you can do yourself, so set a reminder to replace them every three months to prevent any issues. 

When All Else Fails, Call an HVAC Professional

While it’s possible to troubleshoot your furnace yourself, we recommend calling your HVAC technician if the problem persists. The last thing you want is for your entire heating system to break down, so the sooner your HVAC technician can identify and fix the problem, the better. We also recommend investing in regular furnace maintenance, even during the warmer months when your furnace is resting, to ensure it’s in top condition and ready to fire up come winter time. 

For more information about how to fix your furnace when it’s blowing cold air, or if you have any other HVAC questions, please contact our team at Tri-Tech Energy today or visit us at: https://www.tritechenergy.com/