Refrigeration vacuum pumps remove moisture and air from AC/R systems by creating a deep vacuum, boiling water and expelling steam and air. They are typically rotary with two-stage operation and can produce values of 50 microns or less. It is important to use the correct size pump and maintain oil levels.
A refrigeration vacuum pump is a device used to purge air conditioning and refrigeration (AC/R) systems of contaminants such as moisture and air. This purging action is achieved by inducing a deep vacuum in the system by continuously drawing small amounts of gas over an extended period. During this process, the water in the system is boiled and the resulting steam and air are expelled. Refrigeration vacuum pumps are typically rotary variants, many of which feature two-stage operation. The vacuum values involved are expressed in microns with the average two stage vacuum pump capable of producing values of 50 microns or less.
Refrigeration and air conditioning systems often become contaminated with moisture and non-condensable gases such as air. The presence of one or both of these elements in an AC/R system can cause serious problems such as internal ice and corrosion. If signs of these contaminants are found or if the refrigerant charge has been discharged for repairs, the system will need to be purged. This involves connecting the refrigeration vacuum pump to the system and running it until an acceptable vacuum is reached.
A refrigeration vacuum pump serves to remove air and moisture in two ways. The first is the physical withdrawal of air and water vapor from the system along with any residual charge of refrigerant gas. Moisture in liquid form, unfortunately, cannot be drawn out of the system in this way and must be converted into a gas or vapor to facilitate its removal. A refrigeration vacuum pump creates extremely low pressures in the system that cause water to boil at room temperature and be extracted as steam.
Refrigeration vacuum pumps are typically off-axis rotary or scroll pumps. Many deep vacuum pumps feature two stages which are basically two identical pumps operating in series. This type of pump can easily pull a vacuum of 250 microns and can also produce pressures of 50 microns or less. To illustrate the depth of this type of vacuum, the micron pressure of the air at sea level is approximately 760 microns!
Refrigeration vacuum pumps are available in a number of nominal capacities ranging from approximately 1.2 to 10 cubic feet per minute (CFM). It is important to ensure that the vacuum pump used is adequately sized for the particular size of AC/R system in question. Using a pump that is too small can cause unnecessary wear and possible damage. It is also essential to maintain correct oil levels in the refrigeration vacuum pump during bleeding operations.
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