Quote:
Originally Posted by AC_Hacker
dremd,
The venturi-type vacuum pump you linkled to (HF #96677) is able to hit 28.3" of mercury at sea level. So this would be 'Inches Mercury Gauge' on the chart. Notice that this is around 94.8% vacuum. For HVAC work, we need to pull down to at least 80 microns (99.995% vacuum) and hold it there for a while to let all the moisture that may be in the system turn into vapor and get sucked out by the vacuum pump. It's true that the venturi-type vacuum pump may peg your manifold gauge, but the extra vacuum is where the de-moisturization magic happens.
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I make no claims to the accuracy of my test equipment, nor the performance of my vac pumps; but.
Harbor freight venturi vac pump
http://gallery.me.com/dremd/100071/V...12529717130001
Harbor freight 2 stage vac pump
http://gallery.me.com/dremd/100071/I...12529728370001
Not trying to make any point here; but that's my quasi scientific test results.