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HVAC Refrigeration 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 are for these three reasons.
HVAC Refrigeration Evacuation | Technical Refrigeration
Non-Condensible Gases
- 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 into 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 condense refrigerant in the condenser effectively, and that will reduce efficiency and the ability of the system to cool the space properly. 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.
Refrigerant Oil | 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 the 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 runs. This mix of moisture and oil creates an acid sludge that 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 the 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. That creates a short or what is referred to as a compressor burnout. 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
- Moisture in the refrigeration circuit of 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 causes 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. That 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 Refrigeration 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 Refrigeration 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 systems.
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 from your air conditioner or heat pump.
Related: Read our article about HVAC Refrigeration and Triple Evacuation
HVAC Refrigeration Evacuation
Technical Resource: Refrigeration and Air Conditioning Technology
