What is Evacuation?

Evacuate is the term used to remove any non-condensable, moisture, air and trapped refrigerant from the system after it has been recovered. The purpose of a vacuum pump is quite often misunderstood, its job is to remove moisture and air from an A/C system. Moisture in a refrigeration system, directly or indirectly, is the cause of most problems and complaints. “Freeze Up” is not the only problem caused by moisture. It can also result in corrosion, the effects of which are not apparent until the real damage has occurred. Also, refrigerant oil rapidly absorbs moisture. Water formed acids combine with the refrigerant, forming a closely bonded mixture of fine globules. The effect is called sludging and it greatly reduces the lubricating ability of the oil.

A vacuum pump removes troublesome moisture by lowering the pressure within the system and vaporizing (or boiling off) the moisture, then exhausting it along with air.

Robinair recommends changing your vacuum pump oil every 10 hours. What most people don’t realize is how important the oil quality is. The oil creates an important part of the sealing within the pumping elements, as well as lubrication. An effective vacuum pump will be rated between 25 and 50 microns, with contaminated or old oil this can drop to 10,000 micron or more, severely reducing the ability of your vacuum pump to lower the pressure enough to boil off moisture trapped in the system, not to mention the extra wear caused to the pump form poor lubricant. A vacuum pump properly serviced will give many years of reliable service.