What is the recommended evacuation procedure to remove moisture from a system?

• A. Triple evacuate the system to 500 microns with a deep vacuum pump
• B. Evacuate once to 1000 microns
• C. Evacuate to 2000 microns
• D. Use a standard air compressor only

Answer: (A)

Moisture in a refrigeration system is removed by creating a deep vacuum so water vapor boils off at a lower pressure and can be drawn out of the oil and passages. The recommended procedure is to triple evacuate to about 500 microns using a deep vacuum pump. Doing multiple evacuations helps because each pull expels moisture that may outgas from oils and surfaces, then the subsequent deeper vacuum reaches residual moisture that the earlier pulls couldn’t remove. A single evacuation to around 1000 microns isn’t deep enough to guarantee dryness, while stopping at 2000 microns is far too shallow. Using a standard air compressor cannot create the necessary vacuum and would introduce air and moisture into the system.