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Old 06-23-13, 03:17 PM   #56
AC_Hacker
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Quote:
Originally Posted by Elcam84 View Post
...Everyone trusts their gauges to read reasonably accurately which most now are digital and those have even done away with the need for a seperate meter if you are going for perfection. Most everyone goes by the gauge and if the pump pulls down to 30 and holds there for long enough then it's good...
Elcam84, I hope you don't take this personally, but there are many people who come to this site and want to try their hand at doing their own install, or hack some system to behave in a novel way, which we completely support. It is quite likely that this will be their very first experience with vapor-compression machinery. We want them to be successful.

By looking at a standard vacuum gauge, which goes down to 30 (whether analog or digital), they could easily think that when they hit 30, they have achieved a total vacuum, and have removed all air and water from the system, and can safely proceed... not knowing that their gauge is unable to respond to very small, but critical changes at the extreme end.

We have already had lengthy discussions about the important vacuum events that happen at the very low end of the dial... when water actually gets evaporated.

It is for this reason that we are encouraging our readers to beg, borrow or buy a micron gauge when they set up equipment.

Your comment that:

> [using a micron gauge] ...just isn't common practice in the industry.

...does not square with recommendations from professionals I have seen seen on HVAC blogs.

I have no doubt that neither you, nor anyone you work with, uses a micron gauge.

But remember, when you finish with a job, you get to walk away, when our readers finish with a job, they will be living with it for years to come. We want them to know and use the best practices available.


-AC
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