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Pulling down a system help..,

So I charge the small system (1.5 ton) to 350# of co2 and it holds for an hour. I release that and hook up 2 pumps to pull it down to 200 microns. The second I kill the pumps it jumps to way over 10k microns and then crawls back down. Brand new digital gauge. When I run the pumps again it jumps back down to 400 microns in seconds.



Any thoughts??????



Thanks, Tim
Just a guy running some pipes.

Comments

  • Ironman
    Ironman Member Posts: 6,359
    Vacuum

    What size hose(s) are you using and how many are connected to the system? If you're only pulling with one 1/4" hose and two pumps, that could be the reason.



    Also, If there's moisture in the system, the microns will level off when the pump is stopped but they won't come down until the moisture is removed.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Techman
    Techman Member Posts: 2,144
    edited August 2011
    Wacky readings.

    Hi Timco. Why two evac pumps? What size are the evac pumps ? Where is the micron guage hooked up to? What size hoses from the system? What size hoses are connected to the pumps? Are the Schrader inserts still in place? Do you isolate the evac pumps from the manifold/micron guage/system before killing the pumps?
  • Timco
    Timco Member Posts: 3,025
    Pulling down

    I use two pumps because I bought both very cheep and they are new but low cfm. I do not isolate the pumps when I check microns, just shut them down. I do have a vac pump tree but am not sure I am doing this exactly right. I put one pump to each gauge hose (4 port gauge with large vac hose and regular refrig hose) and take the gauge off the tree on the pump that has the large hose.



    Thanks, Tim
    Just a guy running some pipes.
  • JStar
    JStar Member Posts: 2,752
    edited August 2011
    Set up.

    You need to isolate the pumps from the system with a valve. If you don't, you'll only be reading how well the pumps perform, and not the state of the system.



    The picture is how I have my lines set up.
  • Techman
    Techman Member Posts: 2,144
    edited August 2011
    Vacumm

    Colored hoses are not for pulling deep vac's , black hoses are .The 4 port evac mainfold has two 1/4" hoses (hi/lo sides) and one 3/8" hose that goes to the 3/8" fitting on the vac pump.The vac pump(s) should be isolated from the micron guage to get a reading of the system's micron reading.The Schrader inserts in place make for a much longer pulldown, so remove them.If you can , hook up a 2nd micron guage to the Schrader on the suction filter/drier or install a  3/8 Schrader wrot T ( less than 4$) in the liquid line. As they say "Seeing is beleaving ".The micron guage connected to the system will be higher than the micron guage connected to the manifold or vac pump,in this application. I think the vacpumps pulled a deeper vac in the hoses/manifold than in the system.
  • Techman
    Techman Member Posts: 2,144
    How's this

    for an evacuation manifold? All brass. Five port ! The hoses in the case are 1/2 " S.A.E braided copper,the  yellow 3/8 hose is evacuation grade. The evac pump is big! It has a 1/2 " pipe fitting , as is the bottom fitting of the manifold . That's my trusty dog Freon in the back.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Is it time?

    I think it's time for new hoses Terry....lol  I cannot even tell what color they are any more..



    Peace



    Mike T.
  • Timco
    Timco Member Posts: 3,025
    Thanks for the advise!

    So I bought a JB 7CFM pump and could not be happier. The other two were 5 CFM and super heavy. This pump is lighter than one of the other! Anyway, it pulled down to 120 microns when I went to get a cold drink. The pump itself has a ball valve isolator. I am starting to enjoy the AC thing.......



    Tim
    Just a guy running some pipes.
  • Techman
    Techman Member Posts: 2,144
    Hoses

    Mike T, -Those babies are 30 years old ! Whats that stuff ? Tarnex  ? NnOoTt ! Tim,like that soot on your face in your photo, think BLACK (1/4 & 3/8 ) or YELLOW ( 3/8 ) evacuation hoses.
  • Techman
    Techman Member Posts: 2,144
    edited September 2011
    Colored Hoses

    for evacuation . Up until 2008 or so all colored hoses were for pressure only. Then Goodyear Rubber come out w/ a BYR set but they have ball valves in them , and they are vacuum rated . Imperial Eastman also came out w/ a colored, balled valved set of hoses. Strangly though, the Blue and Yellow hoses are evac rated but the Red hose IS NOT ! Go figure ! The Black hoses are superior to ANY colored hose according to Goodyear and Imperial.The inside diameter of the 3/8 hose is pretty much equal to the ID of both of the 1/4 "hoses combined . Where as a 1/4" hose pulling thru two 1/4" hoses takes longer to pull down . But if you get 350 -500 microns ,then that is what counts!
  • Techman
    Techman Member Posts: 2,144
    One more tidbit

    the 1/4" non-evacuation colored hoses have a "shrinkage" problem! The ID of the hoses DECREASES under a vacuum due to a "weak wall" construction. So that 1/4" ID hose will become smaller and/or even collapse in on itself ! The "smaller hose" makes for a longer evac time. but , somehow the "collapsed " hose makes for a shorter evac time. And a  "bigger is better" vacuum pump will increase the hose shrinkage/collapse problem. Now ,that horse is dead!
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