When you turn on your air conditioning (AC) system during the sweltering hot summer days, you expect it to blow cold air. Most AC systems produce air that’s about 15 to 20 degrees Fahrenheit cooler than the indoor air of the homes in which they are installed. If the air inside of your home is 80 degrees Fahrenheit, for instance, the air coming out of the supply vents should be 60 to 65 degrees Fahrenheit. There are times, however, when your AC system may blow warm air.
Clogged Air Filter
If your AC system has a clogged air filter, it may blow warm air. All centralized, whole-house AC systems have an air filter. Consisting of a rectangular-shaped piece of mesh material — most air filters are made of fiberglass — it’s designed to remove particulate debris from the air. Your AC system will pull air through the return vents and through the air filter before conditioning the air and releasing it back into your home.
With a clogged air filter, your AC system will suffer from restricted airflow. It will reduce the amount of air that reaches your AC system’s cooling equipment. Less air will travel through the filter if it’s clogged, so the cooling equipment may struggle to create cool air.
For optimal cooling performance, replace the air filter once every two to three months. Clean air filters don’t restrict airflow. They’ll catch and remove particulate debris while still allowing air to reach your AC system’s cooling equipment. Air filters, though, require changing every few months to ensure proper airflow.
Dirty coils can cause your AC system to blow warm air. Coils are heat-exchanging devices. They are used to transfer heat from one space to another space, which is essentially how AC systems operate. Your AC system uses coils to transfer heat from the inside of your home to the outside.
If the coils are dirty, they may not transfer a sufficient amount of heat. Your AC system should have an evaporator coil and a condenser coil. The evaporator coil is a piece of indoor cooling equipment, while the condenser coil is a piece of outdoor cooling equipment. If either of them is dirty, they may fail to transfer enough heat to create cool air.
Damage to your AC system’s ductwork can have a negative impact on its performance. Ductwork is the series of wide and hollow ducts through which air travels. Air will enter the ductwork before being conditioning, and it will go back into the ductwork before being released as conditioned air.
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Ductwork damage can cause air to escape. If a duct is torn, air will escape out of it. As a result, the conditioned air may not make it to the supply vents. Some or all of it may leak out of the torn duct. For minor ductwork damage, you may be able to seal the torn area with foil tape. For severe ductwork damage, on the other hand, you may need to replace the torn duct.
Out of Refrigerant
If your AC system is out of refrigerant, it will likely blow warm air. The coils rely on refrigerant to transfer heat out of your home. Most AC systems now use R410A refrigerant, which, like older types of refrigerant, cycles between a gaseous and liquid state. As the R410A flows through your AC system’s evaporator coil, it will pick up heat from the inside of your home. The heat-filled R410A will then flow to the condenser coil, which will release the heat. After being cooled, the R410A will go back into your home where it repeats the process.
Under normal circumstances, your AC system should never run out of refrigerant. The coils and pipes that carry refrigerant are sealed. Leaks, of course, can happen. If your AC system’s evaporator coil or condenser coil is punctured, it may leak refrigerant. Alternatively, a worn pipe gasket can cause a leak. Once your AC system is out of refrigerant, it will no longer create cool air. To solve this problem, you’ll need to get your AC system recharged with refrigerant while also plugging the leak.
Your AC system may blow warm air if it’s the wrong size. AC systems are measured based on their cooling output. More specifically, the size reflects its British Thermal Units (BTUs). Some AC systems have a cooling output of 4,000 BTUs, whereas others have a cooling output of over 20,000 BTUs.
An undersized AC system is a common cause of warm air. If your AC system is too small for your home, for example, it may create warm air. Keep in mind that bigger isn’t always better. While an oversized AC system typically won’t lead to warm air, it can cause other problems like short cycling. Short cycling involves your AC system cooling your home too quickly. It will achieve the temperature on the thermostat, after which your AC system will cut off. The problem with short cycling is that forces your AC system to turn on and off many times throughout the day, thereby exposing it to unnecessary wear and tear.
Wrong Fan Setting
Using the wrong fan setting can cause your AC system to blow warm air. Nearly all programmable thermostats have multiple fan settings, the two most common settings being on and auto. If you use the auto setting, the fan will only turn on when your AC system is running. If you use the on the setting, conversely, the fan will run nonstop. It will only stop running when you change the fan setting.
Fortunately, using the wrong fan setting is easy to fix. You just need to switch the fan setting back to auto.
There’s no better way to beat the heat than by turning on your AC system. Even if it turns on, though, it may not create cool air. AC systems can blow warm air for a variety of reasons. Maybe the air filter is clogged, or perhaps your AC system is the wrong size. By identifying why your AC system is blowing warm air, you can take the necessary steps to fix it.