How to Charge AC Units


Home air conditioning units require occasional charging in order to continue work efficiently. Older air conditioning units are usually filled with Freon, a type of refrigerant that is often used as a propellant in aerosol cans. If the AC units in your home do not have enough Freon, it may not be able to function well and provide enough cool air for your home. If you want to avoid these kinds of problems, you can charge your AC unit by follow a few easy steps.

Things You'll Need

  • Digital psychrometer
  • Digital thermometer
  • Thermocouple
  • Tap valve
  • Bottle of Freon
  • Check the air flow of the AC unit over your evaporator and condenser in order to make sure that it is right for the system. Use your digital psychrometer, which measures air temperature and humidity, to get a temperature reading by measuring the airflow while your unit is running. This will allow you to take the indoor air wet bulb temperature. The wet bulb temperature is lowest temperature reached by the air condition unit as water evaporates from the system. You need this to check against the dry bulb temperature reading, which is temperature of air without moisture.

  • Take the temperature near the AC unit condenser coil inlet with your digital thermometer to determine the dry bulb temperature.

  • Measure the suction line temperature of your AC unit. Attach your thermocouple to the suction line of your AC unit and insulate it. The unit suction line is the longer of two lines leading to your unit's compressor. Get the reading closest to your evaporator to obtain greater accuracy.

  • Charge the home AC unit while it is running and attach your unit's manifold to the blue tap valve. Attach the high side hose of the gauge to the compressor's other line, and attach the yellow manifold line of the unit to your Freon bottle.

  • Start the AC unit and open the valve to your refrigerant, tap valve and manifold. Make sure that the pressure on your manifold reaches 40 to 50 pounds maximum for every square inch.

  • Check the superheat temperature and make sure that it reaches at least 2 degree Fahrenheit, before removing the manifold and replacing your caps for the lines.

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