Tip & How-To about Heating & Cooling

Accurate Charging Methods of Central Air Conditioners

The charging (of an air conditioning system) alone can have a substantial impact on system operation costs. A few percentage points of over-or undercharge can raise electricity consumption significantly and shorten the life of the compressor." You must invest in the proper tools, training and methodology to accurately charge an Air Conditioning system so that it works at maximum efficiency. Using the Thermocharge method to charge your air conditioning systems to the exact charge needed will save hundreds to thousands of dollars in electricity and maintenance costs over the years!
Thermocharging method

Skilled technicians will "Thermocharge" your air conditioning system with an exact refrigerant charge. This procedure produces an exact charge . . .not approximate, but exact. The Thermocharge method requires special equipment and training to use. Your installer uses the following instruments:


  • 1. An electronic thermometer
  • 2. Sling psychrometer or electronic humidity measuring device
  • 3. Refrigerant pressure gauges
  • 4. Accucharge slide rule calculator

Here the tech is using the sling psychrometer to obtain the indoor humidity and indoor air temperature. He will double-check his figures with the electronic thermometer laying on the table. He will also verify the readings with an electronic psychrometer.

After recording the indoor humidity and temperature the tech will go to the outside condensing unit to take additional readings. These are the following:

  • 1. Outdoor temperature
  • 2. Indoor humidity
  • 3. Temperature difference, between air entering the evaporator coil, and the air leaving the evaporator coil
  • 4. Suction line temperature
  • 5. Suction line pressure
  • 6. Liquid line pressure (smaller copper line)

Enter this information into his special slide rule calculator to determine the exact amount of refrigerant to put into your air conditioner.

Let it run for about ten minutes to verify his figures. If there are any discrepancies, start the procedure all over again from the beginning.

This Thermocharging method of charging an air conditioning system takes time and patience, but it guarantees that theair conditioning system will operate at peak efficiency all season long.
How does accurate refrigerant charging help?

  • Improved comfort - A improperly charged air conditioner will not dehumidify properly.

  • Lower maintenance costs - A poorly charged system will not properly cool or lubricate the compressor . . .significantly shortening its life.

  • Better cooling and efficiency - Improper charging means that the air conditioner will not provide enough cooling on hot days, causing the system to run longer.

  • Improved efficiency and lower electric bills - Poor heat transfer from improper charging results in increased power consumption. A 15% undercharge or overcharge can result in a 25% decrease in efficiency. This means that the homeowner's electric bill will be 25% higher than necessary. As the charge drops farther, efficiency decreases faster to 50% or more.

  • Increased reliability - A poorly charged system will not properly cool or lubricate the compressor . . . significantly shortening its life. Even if you have extended warranty by a heating company, you will either be greatly inconvenienced or even end up paying for the repair if the company stalls and you end up paying another company for the work . . .a $300-$700 repair that will void the warranty.

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