# Thread: What does a micron vacuum gauge do???

1. Regular Guest
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I know all the basics because I do alot of reading, but what does a micron guage read, total vacuum depth or total moisture in the system that is being vacuumed? On a puron system with POE oil, what is a good number to use? 200 microns?

Thanks,
Dan

2. it measures the level of vacuum wich in turs lets you know if there is moisture in the system

check with manufacture specs but for the most part 500 is deep enough

3. Banned
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I copy and pasted this response to basically the same question that you are asking. These ARE NOT my words but I think it is a pretty accurate descritpion of the MG. Hope it is helpful to you.

A manifold compound gauge uses the barometric pressure as a reference that varies with altitude and the weather and the American unit of measurement of inches of mercury displacement. You may pull 29.95"/Hg at sea level, but since pressure drops about 1"/Hg per 1,000' of altitude, you would only pull about 20"/Hg at 10,000'.

All kinds of units of measurement for pressure and that is exactly what a vacuum is, pressure or more precisely lack of it, either mercury or water in a tube can be used and any measurement for lenght, inches, meters, centimeters, millimeters or even micrometers. HG seems to be the standard so we will stick with that, though pascals can be used as well.

1" euals 2.54 centimeters, but also equals 25,400 micrometers, microns is actually a shortened name for micrometers, so that is how that comes into play. Just saying microns is not correct, it is actually microns of Hg, and as you can see, it is a much smaller unit of measurement than an inch.

The big difference with a so-called micron vacuum gauge is that it is referenced against a perfect vacuum that is the zero point, a vacuum pump that can pump DOWN to 25um/Hg is darn good, but typical practical vacuum pull down ranges are in the 500-1000 um/Hg range or in incorrect jargon shop talk, it pulls down to 500-1000 microns. The point being, you want the least amount of microns as possible and require a gauge capable of this very fine resolution.

I can easily pick off 0.1"/Hg from my 3" vaccum gauge that is equivalent to 2500 microns, and that is good enough for me and a calibrated aircraft altimeter set to my altitude tells me exactly what the barometric pressure is. If you try to pull a system down to 25um/Hg, you may go crazy doing so. Just my opinion. The EPA says within 2"/Hg of barometric, but what do they know about AC? That is a tad bit too sloppy.

4. POE oil will absorb moisture from the air. A vacuum pump will not remove moisture from oil. That is what a liquid and or suction drier will do. Unless there are heavy contaminants, flushing may do very little.

A vacuum pump will remove airborne moisture and or non-condensable properties from the refrigeration system. It will boil off moisture or changes it state to a gas allowing it to be pulled out.

The deeper the vacuum the lower the micron level. You will not be able to pass 29.999 “/HG because 30 “/HG is perfect and it does not exist within the power of these instruments. (See NASA for 30” /HG)

Anything below 500 microns on your residential system even after all of the acid that has run through the old compressor as explained in the other thread will not help your situation.

As discussed… rely on a set of driers and Acid-a-way to sweet’n the PH .

I didn’t want to butt in on the other thread but… If it were me… I would hire another company to replace my condenser, line set and coil. Convert your house to being comfortable first then let the lawyers fight it out. It will not get past the first few *****’n letters anyway. There will be a settlement and everyone will loose a little and win a little.

Good luck

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a vacuum pump removes gases from a space, just as does the common vacuum sweeper.

for a HVAC system, the pump removes the gases, hopefully to low enuf level to also allow any moisture vapors to be extracted; then that negative pressure level is checked after a holding period to determine leakage in the piping after the field connections were made.

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Originally posted by cem-bsee
a vacuum pump removes gases from a space, just as does the common vacuum sweeper.

for a HVAC system, the pump removes the gases, hopefully to low enuf level to also allow any moisture vapors to be extracted; then that negative pressure level is checked after a holding period to determine leakage in the piping after the field connections were made.
Vacuuming a system is not used to pressure test linesets, it is used to remove moisture and non-condensibles. If that were the case, you are only using 14.7 psi as a pressure test. The nitrogen test is your pressure test when used at pressures above 150 PSI for a length of time.

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I hear ya Lusker. Why settle for a scratch & dent when you deserve the full monty. The contractor can get a spanking new unit with in a few days.

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