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  1. #1
    Join Date
    Jul 2012
    Location
    Peace River, Alberta, Canada
    Posts
    46

    rooftop charging in winter?

    any good tips on how to charge a RTU during winter? tried yesterday and set off the freeze stat...

  2. #2
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    5,930
    Quote Originally Posted by Nrmika View Post
    any good tips on how to charge a RTU during winter? tried yesterday and set off the freeze stat...
    Weigh in the charge per nameplate.
    Instead of learning the tricks of the trade, learn the trade.

  3. #3
    Join Date
    May 2000
    Location
    Stafford, Va. USA
    Posts
    215
    Hi Nrmika,
    You must weigh the refrigerant charge into the RTU.

    Keep warm thoughts.
    Good luck,
    Allen
    UA Local 602
    A man who says that he can't learn anything in a class is exactly right.

  4. #4
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    Yep ,easiest way is to weigh it in ,even if you have to recover the remaining charge (if any )

    On a split you can calculate using equipment literature.

    Or you can guess,using your tools ,and probably get pretty close, but that only counts in horshoes and hand grenades
    mikeacman

  5. #5
    Join Date
    Jul 2012
    Location
    Peace River, Alberta, Canada
    Posts
    46
    I was weighing in but it set off the freezestat. Feathering to fast?

  6. #6
    Join Date
    Feb 2007
    Location
    Georgia
    Posts
    167
    You do have to weigh it in

    However you may have to block condenser to keep head up so the suction will stay up so you can get system to take charge without it cycling on freeze stat.

    Using cardboard to block entering air to the condenser usually works great

  7. #7
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    To add ,I use my recovery machine to recharge units . I can weigh it all in before I even start the unit up....

    After all ,its a refrigerant pump....
    mikeacman

  8. #8
    Join Date
    Apr 2011
    Location
    Coastal Maine
    Posts
    888
    Quote Originally Posted by mikeacman View Post
    To add ,I use my recovery machine to recharge units . I can weigh it all in before I even start the unit up....

    After all ,its a refrigerant pump....
    Mike is right. That is how we do it in cold weather. Awful hard to create enough head even with blankets and cardboard when it is below zero. Which means that we wouldn't be able to work on them all winter. So we put the weighed charge in with the recovery machine, then start it up. Never fails, we always have to go back in the summer and trim the charge or adjust the TXV, but it gets us close. Sucks doing AC work when it is below zero.

  9. #9
    Join Date
    Feb 2007
    Location
    Georgia
    Posts
    167
    Wow down here 20f is cold

    I say let's drink some coffee and charge it next summer

    That trick is a first for me I sure hope I never have to use it


  10. #10
    Join Date
    Sep 2006
    Location
    Ohio
    Posts
    498
    If the system was evacuated to 500 microns or lower, You should be able to get most of the charge in without even starting the unit. I will use a torch to warm the refrigerant drum if it won't pull in the entire charge by itself. You could also use a heat gun if you have one, but a MAP gas torch works great.

  11. #11
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    Quote Originally Posted by hands View Post
    If the system was evacuated to 500 microns or lower, You should be able to get most of the charge in without even starting the unit. I will use a torch to warm the refrigerant drum if it won't pull in the entire charge by itself. You could also use a heat gun if you have one, but a MAP gas torch works great.
    that works...

    A lot of the places I service would politely escort you of site and never allow you to return if caught putting a flame to a pressure vessel ....
    mikeacman

  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,607
    Sell them an economizer?

  13. #13
    Join Date
    Sep 2006
    Location
    Ohio
    Posts
    498
    Quote Originally Posted by mikeacman View Post
    that works...

    A lot of the places I service would politely escort you of site and never allow you to return if caught putting a flame to a pressure vessel ....
    They would probably do the same if you were caught with a control panel open and you didn't have your PPE gear on, but that never happens either does it.

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