The deep vacuum method requires a two-stage vacuum pump and a quality gauge that can measure microns. The technician would then repeat this again,spending close to 3 hours for the effort! Although very effective at removing moisture, this process is very time consuming and likely not needed with today's two-stage pumps. Since it takes time to absorb the moisture, the nitrogen must remain in the system for an hour. So, you would pull a vacuum to 28" Hg, operate the pump an additional 15 minutes, and then break the vacuum with dry nitrogen until you reached 2 psig (Source: Carrier Installation Manuals). Since there is no way to make that elusive 500 microns with the older technology, and it isn't always 100F+ when installing A/C's, we used to have this method of removing the moisture with dry nitrogen. In order for water to boil off and be removed from the system, the temperature must be above 100F 28" Hg. You see, this type of pump can only pull a vacuum to 28" Hg (Mercury). The triple evacuation method, developed very early on in our industry, is used with single stage vacuum pumps. Maybe my confusion started because I kind of used a hybrid to maximize my time on the job site. The Deep Vacuum and the Triple Evacuation methods are not one in the same.
#Deepvacuum free#
Little did I know, call it that HVAC Tech's ignorant moment, there are actually two different types of methods of evacuating a system free from non-condensables.
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