It's frustrating when you turn on your home's air conditioning (AC), only to discover that it's blowing warm air. The primary function of an AC unit is to circulate cool air throughout the home.So, if it's pushing out warm air, it's not going to create a cooler and more comfortable environment for you and your family.
Frozen Evaporator Coils
The evaporator plays a key role in the function of an HVAC system by absorbing heat from the air into the refrigerant. However, it's not uncommon for evaporator coils to freeze solid, causing the system to blow warm air.
During operation, the evaporator coils pull moisture vapor from the air, which drips to a pan below where it's guided outside through a PVC pipe. If condensation accumulates around the coils instead of draining, though, it can freeze when the AC is turned on.
Factors that may increase the risk of frozen evaporator coils include the following:
- Dirty air filter
- Obstructed return vents
- Dirty evaporator coils
- Low refrigerant
Perhaps the most common cause of an AC blowing warm air is a refrigerant leak. AC units use refrigerant to absorb heat, transferring that heat outside. As the refrigerant collects heat from inside the home, it turns from a gas to a liquid state. And once the refrigerant reenters the system, it's converted back to a gas state.
AC systems are designed to be closed, meaning that refrigerant levels should never drop under normal conditions. However, systems can leak and refrigerant can escape; thus, causing the system to blow warm air. If this is the underlying cause of your AC problem, you need to fix the leak as well as recharge your system with more refrigerant. Adding refrigerant without stopping the leak is only a temporary solution.
There are three primary types of refrigerant used in AC systems:
- Chlorofluorocarbons (CFCs)
- Hydrochlorofluorocarbons (HCFCs)
- Hydrofluorocarbons (HFCs)
Keep in mind that older AC unit using CFCs won't support newer refrigerant types; therefore, you need to choose the right refrigerant for your respective unit. Of course, this is something a qualified HVAC technician can assist you with.
Incorrect Thermostat Setting
While this may sound like common sense, another possible cause of an AC blowing warm air is an incorrect thermostat setting. If your thermostat was accidentally turned to the fan-only mode, for instance, it may blow room temperature air throughout your home. So, before attempting to troubleshoot some of the bigger problems, check your thermostat to ensure it's set to cool.