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HVAC Refrigerant Evacuation | Technical Refrigeration - Why is it necessary to evacuate a refrigeration system before charging it with refrigerant? Because all systems are designed to operate without moisture or non-condensable gas in the system. If your air conditioner or heat pump was installed without a proper evacuation the system it will not function as designed and will likely fail prematurely.

A new air conditioning, heat pump, or refrigeration system is installed and the piping is soldered together and pressure tested with nitrogen to ensure there are no leaks. Nitrogen is also used to remove moisture from the system. The three major reasons for making sure a proper refrigeration evacuation is done is for these three reasons.

HVAC Refrigerant Evacuation | Technical Refrigeration

  • Non-condensable gases will not condense in the condenser and will use up this space in the condenser that would otherwise be used to condense refrigerant from a gas to a liquid. The air conditioning or heat pump system is soldered at a few places on a new installation. At the evaporator coil where the air handler is located, at the condenser to the line set which runs to the evaporator coil, and a filter drier is soldered in to the system usually on the liquid line near the condenser. After all this is done there will remain in the piping and the evaporator coil air. Air contains nitrogen and oxygen both of which are non-condensable gases. Again, these non-condensable gases, if not evacuated from the system, will take up space in the evaporator coil and limit the amount of condensing of the refrigerant in the condenser coil. In other words, the condenser will not be able to effectively condense refrigerant in the condenser and that will reduce efficiency and the ability of the system to properly cool the space. Non-condensable gases will also cause higher operating temperatures and pressures in the system which will make the compressor work harder. A proper evacuation will remove all the non-condensable gases from the system as long as the evacuation is done properly.
  • HVAC Refrigeration Evacuation

    R-22 Refrigerant and a Vacuum Pump

    Moisture in the system can be detrimental to a major component in the air conditioner or heat pump refrigeration system. Moisture in the form of vapor is a natural part of air. Moisture in an air conditioning or heat pump refrigeration circuit will mix with the oil which is in the refrigeration system to lubricate the compressor. This oil migrates throughout the whole air conditioning and heat pump refrigeration system circuit as the air conditioner or heat pump run. This mix of moisture and oil creates an acid sludge which will eventually kill the compressor. The oil in the system always migrates back to the compressor. The oil bathes the inside of the air conditioner or heat pump refrigeration compressor with necessary lubrication to keep it running. The oil also ends up running over the windings of the electric motor built into the compressor. If the oil has acid in it, which it will if moisture is in the system, the acid eats at the shellac covering over the windings. When the shellac is gone the windings touch and this creates a short or what is referred to as a compressor burn out. The compressor is considered condemned and requires a replacement compressor. The compressor is one of the most expensive components in the air conditioner and heat pump refrigeration. If the evacuation is not done after installation the air conditioning and heat pump system will eventually fail because of this problem.

  • Moisture in the refrigeration circuit of an air conditioning and heating will also cause problems at the refrigeration controls especially the metering device. The moisture will freeze inside these controls and cause a restriction which cause the refrigeration system to malfunction and cause little or no cooling. This restriction of ice in the refrigeration system will cause the pressures to build up to very high levels on the high side of the refrigeration circuit. This is yet another reason to perform the HVAC system evacuation properly following all the basic rules of performing an evacuation including installing the new filter driers anytime the refrigeration circuit has been comprised in any way.

HVAC Refrigerant Evacuation - System Cleanliness

One of the leading causes of air conditioning or heat pump failures happens because the refrigeration system is not properly evacuated before being put into service. Moisture, copper particles or shavings, flux, flakes from brazing the copper, and particulates end up in the system and can cause severe damage to compressors or clog metering devices (or make the metering device function improperly). All of these things can lead to a failure of the air conditioner or heat pump system and all of these things can be avoided if proper evacuation techniques are used before the systems are put into service.

HVAC Refrigerant Evacuation - Conclusion

There is never any guarantee that any part of the system will fail at any time. That is why air conditioning and heat pump manufacturers offer warranties. Getting a proper installation from the beginning is important to the efficiency and effectiveness of the air conditioning and heat pump system. That is the reason why many of the larger air conditioner and heat pump manufacturers require their dealers to offer training for the technicians who install and repair air conditioner and heat pump system. Make sure your air conditioner or heat pump is installed properly by hiring a qualified air conditioning and heat pump professional to do the job and you will enjoy years of comfort form your air conditioner or heat pump.


Do you have a heat pump instead of an air conditioner? See our comprehensive heat pump category for help with heat pumps:


Furthermore, additional heat pump resources here:

Read our article about HVAC Refrigeration and Triple Evacuation

HVAC Refrigerant Evacuation - High Performance HVAC

HVAC Refrigerant Evacuation

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