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Air Conditioning Facts

  • Cool air is heavier than warm air. Your furnace should have a 2-speed blower and large ducts. 4-inch ducts are too small and will cause a shorter equipment life.

  • Household air humidity is between 20-40%

  • 55 degree liquid refrigerant goes into the evaporator, boils at 72 degrees (becomes gas) from the heat it takes from the outside air. The cool air is then blown into the home through the evaporator. The 72-degree gas goes to the compressor and gets compressed to raise the temp to 150 degrees. The 150-degree gas goes to the condenser coils and is cooled to 15-20 degrees warmer than the outside air. The compressed gas goes through the condenser coils that use water or air to cool it to 55 degrees again.

  • 65 ambient degrees is the breaking point. DO NOT OPERATE.

  • Get the original warranty of the compressor manufacturer from the sellers to see if they are transferable.

  • Most compressors have a sump heater so the lubricating oils won’t absorb the refrigerant and therefore not lubricate. The sump heaters are running all the time. A compressor that has been shut down cannot be safely started unless the oil has been purged from the refrigerant. The sump pump must be turned on at least 24 hours before. If the compressor shell is not warm, do not operate the A/C. Not all compressors have a sump pump or oil heater.

  • Some compressors have time delays of 2, 3 or 7 minutes. Also compressors should be free of vibration and perfectly level for proper lubrication.

  • Water-cooled condenser systems can be inside the home and are usually found inside the air handler cabinet. The water should be returned to the ground well. Water cooled systems use a lot of water and is illegal in some towns.

  • About 70 square inches of evaporator are needed per ton of air-cooling. Airflow through the evaporator should be 400cfm/ton of cooling. If the coils are ice covered there may not be enough refrigerant or not enough air volume moving over the evaporator coils.

  • The compressor is usually mounted below the evaporator. If it isn’t, look for a filter that absorbs moisture in the line.

  • Filters are very important for A/C efficiency. If they are dirty you can bet the evaporator fins are dirty and clogged.

  • Supply and return ducts should be equal in cfm.

  • The temperature of the air before and after it passes through the evaporator should be 15-20 degrees colder than the ambient air. If the air leaving the evaporator is over 60 degrees, there may be too little refrigerant or too much air passing over the coils as the result of fan speed that is too high or too large, or the equipment may be too small for the house. Conditions that may cause the air leaving the evaporator to be less than 55 degrees include a dirty filter, clogged evaporator coils, fan speed too low, or a broken fan belt.

  • The evaporator should be mounted downstream of the heat exchanger. If it is upstream, it will be subject to condensation and corrosion.

  • Proper disposal of condensate is necessary because it contains yeasts, bacteria, fungi and other debris you don’t want circulating in the house air. It must be discharged in house drains only.

  • Ideally there should be a return supply in every room located on the lower part of a wall opposite the A/C vent. If returns are not installed in each room, the room doors must be undercut to insure air will reach the return wherever it is.

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