It's a common misconception that air conditioning systems "create" cold air, but how these systems work is far more interesting and clever. A typical residential system continually cycles the same air through your home, passing it through a cleaning filter each time. The warm air travels from your return ducts to your air handler, where the evaporator coils absorb heat (energy) and move it outside.

Of course, removing heat isn't enough. The system must also push the cooler air back into your living space by moving it through your ductwork to your supply vents. The refrigerant in the evaporator coils can absorb a certain amount of energy at once, so there's an expected temperature drop ("delta T") between the return and supply vents. If the supply vent temperature is too high, something is wrong.

What Should You Expect?

Simply put, you should expect the air from your supply vents to be noticeably colder than the air entering your return vents. You can check this with a thermometer, but you'll often be able to feel any significant problems. Even on hot days, the air at your supply vents should be much cooler than the surrounding air.

The exact temperature of the delta T will vary depending on your system, environment, and other factors. An HVAC tech may perform a delta T calculation when servicing your system to check for efficiency issues and confirm that everything is working correctly.

What If Your Temperatures Are High?

If the temperature at your AC vents seems too high, there are a few things you can check before assuming your system has an issue. First, confirm that your thermostat's fan setting is on "auto." The "on" setting will force the fan to run while the AC compressor is off, blowing warm air through your house. Always use the "auto" setting when using your air conditioner in the summer.

Low airflow is another culprit and the likely problem if there doesn't seem to be much air moving through your vents. Check your filter and replace it if necessary. The evaporator can't absorb enough heat without adequate airflow, and you'll feel lukewarm air. This step will not only restore your AC's cooling, but it will protect critical components.

These two steps will likely resolve many problems, but what should you do if your vent temperature still seems high? At that point, it's time to call in a professional. You may have issues with refrigerant charge, a restriction in the system, or even a problem with the condenser coils on your outdoor unit. Numerous problems can affect AC efficiency, so it's critical to have an expert perform an in-depth diagnosis.

Contact a company like Big Rock Service Company LLC for more information.