Turning on your air conditioner during a hot and humid day can be a breath of fresh air. Unfortunately, sometimes that air may not be quite as chilly as you'd like. Air conditioner manufacturers design their systems to remove a certain amount of heat from the air, and the result is usually a fairly cold stream flowing from your home's vents. 

There are several possible explanations if the air feels slightly more tepid than you would like. These three questions will help you troubleshoot the issue and determine if you need to call an HVAC technician to investigate the problem.

1. Is Your Interior Air Particularly Warm?

Your air conditioning system works with the concept of a "Delta T," or a change in temperature. The evaporator coil can extract a certain amount of heat energy from the air at once, which means it can only drop the temperature in your home so quickly. Most systems can drop the temperature between about 16 and 22 degrees Fahrenheit.

This temperature drop is the difference between your return and supply vents. In other words, the air from your supply vents won't be as cold if the air in your home is especially hot. In these cases, you'll need to wait a while before feeling ice-cold air from your vents. You can continue troubleshooting if the supply vent temperature still seems warm after the system runs for a while.

2. Does Your System Run For Too Long?

Air conditioning systems normally run in relatively short cycles. Unless you set your thermostat to a very low temperature, your system should usually be able to reach your thermostat setpoint in an hour or less—usually much less. If your system's Delta T is too low, your air conditioner will take too long to bring your home to the correct temperature.

Since your thermostat will continue to request cooling until you reach your setpoint, the result is that your air conditioner will run continuously. If you're noticing warm air from your vents combined with excessively long run times, you may have an issue with your system's performance. An HVAC technician can help investigate this problem to determine if your system is performing as it should.

3. Does Your Vent Air Feel Humid?

Sometimes, you might notice that your vent air is warmer and more humid. Your air conditioner should remove humidity as it operates, so damp air is almost always a sign of trouble. One possibility is a frozen evaporator coil, although you'll usually notice colder air in these cases. However, your vents will produce excessive humidity and warm air if the blower runs without the compressor.

Start by confirming that your thermostat is on "auto" mode since "on" or "recirculate" will cause the fan to run without the compressor. If you have set your thermostat correctly, the problem may be that your compressor is shutting off too soon or not turning on. You will need a professional HVAC technician to perform further diagnosis. 

Contact a local HVAC service, such as Turnbull Heating & Air Conditioning, to learn more.