Evacuating a Refrigeration System: Plan Ahead Today. Avoid Contamination Tomorrow

By: Peter Kirtschej, Service Advisor, ABR Wholesalers, Inc.

Evacuating a refrigeration system serves two purposes; it removes non-condensable items and it dehydrates (removes water vapor). Non-condensables are items that should not be inside a refrigeration system such as pieces of solder, braze, soot, and dirt.  These items can plug the metering device and cause txv failures. They contaminate the Freon, and can damage the compressor, making the unit run inefficiently.

When a refrigeration system is installed, the line set is open to the atmosphere which allows moisture in the air to enter the line set.  This moisture will contaminate the refrigerant because there is oil in the refrigerant used to lubricate the compressor.  Oil and water are two liquids that are immiscible – they will not mix together.  If this moisture is not removed, damage to the compressor may occur due to Freon contamination, which can cause premature compressor failure.

To obtain proper evacuation of a refrigeration system, a vacuum pump should be used on every installation.  If you own a single stage pump, I recommend the using the triple evacuation pump down theory.  If you own a 2-stage pump, I recommend the deep vacuum theory.  Either way, you will achieve your goal of 250 microns eventually.  Connect the yellow hose from the gauge set to the micron gauge. Connect the gauge coming out of the micron gauge to the vacuum pump port on the vacuum pump. Next, start the pump and watch the gauges on the manifold – the suction side should start pulling down to a negative. Once the gauge gets down to -30 psi, look at the micron gauge. The magic number that most manufacturers are looking for is 250 microns.  If the system can pump down to this and hold, then – in theory – there is no more moisture or leaks present in the system. In the process of achieving this ultra-low vacuum we are actually boiling off moisture and non-condensable gasses. On several occasions I ran a vacuum pump for 4 hours to achieve this micron reading. It may not seem practical to spend time on this process; however, with a little planning ahead, you can easily integrate this important process into your installation.  If you are installing a furnace and an air conditioner, set the furnace, set the coil, set the condenser, run the line set, and then braze. At this point, set up the evacuation equipment. Let it run for the time that you work on the rest of the install (periodically checking the micron gauge) If it is an air conditioner only installation, set the coil and then work on getting the line sets brazed in so that there is time for  proper evacuation.

Remember, the vacuum pump oil is directly related to how well the pump works. Vacuum pump manufacturers recommend changing the oil between every use. Why? Vacuum pumps do not have a filter – the oil actually acts as a filter. So the oil gets contaminated with whatever was in the system. If the oil is dirty/contaminated, the pump will not evacuate the system efficiently.  An ounce of prevention today is worth a pound of cure tomorrow.  Don’t forget to evacuate the refrigerant system on your next installation.

For more information, or to purchase a UEI (DMG100) micron gauge, contact ABR today.