수리 사례

2026. 6. 30. 작업

증상

Cannot pull a "deep" vacuum on AC system

처리 내용

I don't know the devices used for this job, but due to the negative sign, the pressure seems to be relative, i.e. difference to ambient pressure. (When the device is disconnected and doesn't run, the gauge should show a pressure of zero, too) The absolute air pressure at altitude is shown in this plot: (Sorry for the odd values, but I'm used to SI units...) 30inHg is the absolute air pressure at sealevel at standard conditions. At your altitude, the absolute pressure is 25inHg. (Sanity check: Denver Airport (1656m) currently has 832hPa, which fits really good into the curve.) So you can't pull 30inHg, since then you would have a negative amount of gas molecules inside the system. The highest value you can get is 25inHg. You get 21inHg which corresponds to an altitude of about 11,000ft, so this can't be explained by you being at not exactly 5,000ft. Since the system holds the vacuum, I'd say there's a problem with the device. Either the pump itself or the pipes between pump and valve ha