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Thread: How low do you pull vaccum?

  1. #101
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    Quote Originally Posted by matcolecat View Post
    Thats awesome! Part of the key to a good vacume is clean oil
    I have not used them since fall so I thought it would be a goo time to change it. Usually change it after each use.
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  2. #102
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    Quote Originally Posted by marvin View Post
    if your pump does that well i would try vacuuming with copper tube
    really sounds like a hose problem. other posssibility is moisture in system,
    or not enough time
    I saw yellow Jacket makes stainless hoses. Do you think they are worth th money? I mostly use them for residential work.
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  3. #103
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    Quote Originally Posted by qwerty hvac View Post
    I saw yellow Jacket makes stainless hoses. Do you think they are worth th money? I mostly use them for residential work.
    i have mixed feelings about the stainless hoses. normally i will buy several sets of hoses a year & always have a new one on standby if i need it.
    i usually test them with my vac. pmp & a micron gage. i have been getting away from the y/j products as i dont feel that the quality is what it used to be. have a set of npr right now that seem to be holding up fairly good.
    also have a set with no markings at all that have been good for over a year. no idea where i got them. all black with chrome ends & med. weight hose.

  4. #104
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    Quote Originally Posted by qwerty hvac View Post
    I saw yellow Jacket makes stainless hoses. Do you think they are worth the money? I mostly use them for residential work.
    I have a pair and yes. they are worth it They cost more, but they last longer and you can reach very low vacuum with them.

  5. #105
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    Hello gentlemen,
    I am a professional and have worked on everything from an itty bitty ice maker to a 500 ton centrifigul chiller. Here is my humble opinion on the subject. There is no definite answer to the question with so many varying circumstances. I had a 50 ton system one time with 150 foot of line set. We put 2-5 cfm pumps on it in the morning and went to a different area to work. It looked like everything was going good until lunch. This was a spring project and the system was coming down slow. The outdoor air temp was about 65 degrees faren. and dropped to 58 degrees by noon. We checked again and the micron gauge said 400 microns. Through experience I didn't believe what I was seeing , it came down to fast. I noticed a 20' sect of copper looked like it was sweating on the bottom not to far from the cond. I grabbed a torch and heated the pipe and lost the micron reading it went off the chart. Due to the weather change and the speed of the evacuation process we actually froze moisture in the system which fooled the micron gauge reading.
    So sometimes micron readings don't mean much and sometimes they do. Sometimes speed of change and common sense and a watchful eye can mean the difference between fixed and uh oh. So again there is no one formula, one time interval, one micron level or one situation. Unless you are in a lab with all variables controlled and unchanging and that just don't happen in the real world with the boss breathing down your neck.
    Then there is the { I'm losing money on this , just fill er up and get the heck outa there! }

  6. #106
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    Quote Originally Posted by geno54 View Post
    When I first started I was taught to open the liquid line and purge three times for one minute each. No need for a vacuum pump. Shortly thereafter I got educated and learned the proper methods and why.

    For those of you who are members of RSES there was a Q & A (MSAC) in the Jan 2010 edition of the Journal regarding just this by Jamey Hale, CM, Technical Support Supervisor, ICOR International.
    http://www.rses.org/assets/journal/0110_MSAC.pdf
    Geno...definately worth the read, they have one at least once a year..For a very good reason. Still feel strongly not enough attention paid to maintenance of tools used though. Digital Gauges are nice, but you know what, have found a few sets guys used in the field that not maintained gave some very false readings. Technology has indeed improved things and made things quicker, but do not ever let go of the philosophy behind the principle otherwise the tools will make you look like an idiot.

  7. #107
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    Quote Originally Posted by boscohvac View Post
    Due to the weather change and the speed of the evacuation process we actually froze moisture in the system which fooled the micron gauge reading.
    you knew something was wrong!

    these are scenario's that are almost impossible to teach



    .

  8. #108
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    The wisdom of experience

    Quote Originally Posted by boscohvac View Post
    Hello gentlemen,
    I am a professional and have worked on everything from an itty bitty ice maker to a 500 ton centrifigul chiller. Here is my humble opinion on the subject. There is no definite answer to the question with so many varying circumstances. I had a 50 ton system one time with 150 foot of line set. We put 2-5 cfm pumps on it in the morning and went to a different area to work. It looked like everything was going good until lunch. This was a spring project and the system was coming down slow. The outdoor air temp was about 65 degrees faren. and dropped to 58 degrees by noon. We checked again and the micron gauge said 400 microns. Through experience I didn't believe what I was seeing , it came down to fast. I noticed a 20' sect of copper looked like it was sweating on the bottom not to far from the cond. I grabbed a torch and heated the pipe and lost the micron reading it went off the chart. Due to the weather change and the speed of the evacuation process we actually froze moisture in the system which fooled the micron gauge reading.
    So sometimes micron readings don't mean much and sometimes they do. Sometimes speed of change and common sense and a watchful eye can mean the difference between fixed and uh oh. So again there is no one formula, one time interval, one micron level or one situation. Unless you are in a lab with all variables controlled and unchanging and that just don't happen in the real world with the boss breathing down your neck.
    Then there is the { I'm losing money on this , just fill er up and get the heck outa there! }
    boscohvac, thanks for this great post! I am looking forward to reading more of your posts in the future.
    "I aint going to spit on 30 years of my life" Monte Walsh


  9. #109
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    Quote Originally Posted by boscohvac View Post
    You are in a lab with all variables controlled and unchanging and that just don't happen in the real world
    too--shaay



    .

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