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  1. #1
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    Feb 2019
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    Problem holding a vacuum after pump down

    Hi Everyone. I am new to the site but have been reading a number of threads and am finding them very useful. My background is in construction but I decided to branch out and start installing ductless mini-splits. I completed my first install and performed a 40 minute pressure test @ 250psi. I proceeded to the last step of vacuum pump down and this is where I ran into problems. My vacuum setup is as follows: two Appion core removal tools, an Appion 1/2" vacuum hose and CPS vacuum gage. I pulled down under 500 microns quickly and closed the valve to isolate the vacuum pump from the system. The value immediately went up to several thousand and slow increased so I re-opened the valve and allowed it to pump down awhile longer. After several attempts I got it to remain initially at 400um. It didn't stabilize however and kept creeping up around 20-40um per minute. I wasn't sure if it was my system leaking or my connections so I brought my equipment home to see if I could hold a vacuum with a simplier setup. This setup involved one Appion core removal tool, a vacuum gage, a T-valve and about 3' of 1/4" line with plugged flares. I would post a pic but am too new to do so. This time I pressure tested my setup at 620psi for 24 hours. Pressure was good after 24 hours so I released the nitrogen. I started Pulling a vacuum and again when closing the valve the value would creep up. I don't understand why I can't hold a vacuum after holding 620psi after 24 hours. I am not sure if my vacuum gage is the issue or something else. Anyone have any ideas on what I could try next? Your help is appreciated.

  2. #2
    Join Date
    Mar 2019
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    Problem in Vaccum

    Thanks for Sharing the informative post.

  3. #3
    Join Date
    Apr 2010
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    California
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    Quote Originally Posted by shaggs2broke View Post
    Anyone have any ideas on what I could try next? Your help is appreciated.
    "Yes I Do". "Your Tools are only as accurate as the last time they were tested and calibrated" When is the last time you "tested and calibrated" your "gages, vacuum pump, and hoses"? Get in the habit of doing this as much as possible.

  4. #4
    Join Date
    Feb 2019
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    Quote Originally Posted by lzenglish View Post
    "Yes I Do". "Your Tools are only as accurate as the last time they were tested and calibrated" When is the last time you "tested and calibrated" your "gages, vacuum pump, and hoses"? Get in the habit of doing this as much as possible.
    This is excellent advice. I just assumed my equipment was good because it is all new. After hooking up appion valve core tool directly off vacuum pump outlet and adding vacuum gage I still couldn't hold vacuum so knew it was either the valve core tool or vacuum gage. Borrowed a different vacuum gage and could hold vacuum after properly pumping down. Lesson learned verify all your equipment regardless of whether it is new or not.

  5. #5
    Join Date
    Apr 2010
    Location
    California
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    Quote Originally Posted by shaggs2broke View Post
    This is excellent advice. I just assumed my equipment was good because it is all new. After hooking up appion valve core tool directly off vacuum pump outlet and adding vacuum gage I still couldn't hold vacuum so knew it was either the valve core tool or vacuum gage. Borrowed a different vacuum gage and could hold vacuum after properly pumping down. Lesson learned verify all your equipment regardless of whether it is new or not.
    Good deal shaggs ! Welcome, and hope you grab a chair and stick around.....

  6. #6
    Join Date
    Dec 2003
    Location
    Citrus County, Florida
    Posts
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    Pump down and pulling a vacuum are two different procedures. If you are pulling a vacuum and the level rises, try pulling the vacuum for a longer time. Also, to test your set up, pull a vacuum on recovery tank; not a length od tubing.
    Doug

  7. #7
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    6,232
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    Try putting some leaklock on all the fittings. Could also be the core tools are leaking internally. Is this a single head mini and your pulling from both lines? If you only have access to one end of the line length the pressures could just be stabilizing.


    Sent from my iPhone using Tapatalk

  8. #8
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    19,934
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    Quote Originally Posted by shaggs2broke View Post
    Hi Everyone. I am new to the site but have been reading a number of threads and am finding them very useful. My background is in construction but I decided to branch out and start installing ductless mini-splits. I completed my first install and performed a 40 minute pressure test @ 250psi. I proceeded to the last step of vacuum pump down and this is where I ran into problems. My vacuum setup is as follows: two Appion core removal tools, an Appion 1/2" vacuum hose and CPS vacuum gage. I pulled down under 500 microns quickly and closed the valve to isolate the vacuum pump from the system. The value immediately went up to several thousand and slow increased so I re-opened the valve and allowed it to pump down awhile longer. After several attempts I got it to remain initially at 400um. It didn't stabilize however and kept creeping up around 20-40um per minute. I wasn't sure if it was my system leaking or my connections so I brought my equipment home to see if I could hold a vacuum with a simplier setup. This setup involved one Appion core removal tool, a vacuum gage, a T-valve and about 3' of 1/4" line with plugged flares. I would post a pic but am too new to do so. This time I pressure tested my setup at 620psi for 24 hours. Pressure was good after 24 hours so I released the nitrogen. I started Pulling a vacuum and again when closing the valve the value would creep up. I don't understand why I can't hold a vacuum after holding 620psi after 24 hours. I am not sure if my vacuum gage is the issue or something else. Anyone have any ideas on what I could try next? Your help is appreciated.
    Any training, classes, online?

    Where did you purchase this unit?

    Its a waste but at least say your certified!

  9. #9
    Join Date
    Feb 2019
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    Thread Starter
    _

  10. #10
    Join Date
    Feb 2019
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Any training, classes, online?

    Where did you purchase this unit?

    Its a waste but at least say your certified!
    Yes I have had training. Definitely wouldn't attempt installing these without any knowledge. I took Fujitsu 101 in person class and took a handful of classes on their online portal. I also have my EPA 608 type I and II certificate. I also have a bachelors in mechanical engineering so have had thermodynamics classes etc. None get into these types of specifics but you do learn about refrigeration cycles.
    Unit was purchased from RSD.
    I think I have pinpointed my problem, the vacuum gage I purchased new appears to be defective. I suspected it after my overnight 620psi pressure test with no drop. i felt I should be able to hold vacuum with same setup but vacuum gage in place of pressure gage but couldn't say for sure until I used another vacuum gage. I pulled down to 20 microns and held it under 500 microns through 3 feet of 1/4" tubing for over an hour. As soon as I added my other vacuum gage and tried again it wouldn't hold at all. Damn CPS and their vacuum gages!

  11. #11
    Join Date
    Oct 2011
    Location
    Gladstone, Oregon (Portland)
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    Most manufacturers state to hold vacuum for 10 minutes under 1000 microns. Sounds like you have achieved that. What ya sweating?

  12. #12
    Join Date
    Jun 2014
    Location
    Dover, DE
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    Your pressure test is insufficient. Many manufactures call for over 500 PSI for as much as 24 hours.
    “I haven’t failed. I’ve just found 10,000 ways that won’t work.” - Thomas Edison

    “It’s not whether you get knocked down, it’s whether you get up.” - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

  13. #13
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
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    Quote Originally Posted by rider77 View Post
    Your pressure test is insufficient. Many manufactures call for over 500 PSI for as much as 24 hours.
    I doubt thats the case here.


    Sent from my iPhone using Tapatalk

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