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Thread: Carrier 50DD044

  1. #1
    Join Date
    Nov 2003
    Montreal, Qc.

    Carrier 50DD044

    Hi all,

    I lurk here quite a bit but rarely post.
    I now have a problem that has me scratching my head.
    I have 2 identical Carrier packaged rooftop units on a building.
    Each unit has 2 Carlyle 06E compressors.
    Stage 1 has 2 12T TX valves while Stage 2 has 2 10T TX valves in parrallel.

    The units have gone through a refresh with new compressors, TX valves, liquid line shutoff valves, driers etc.
    The evaporators, condensers and blowers were thouroughly cleaned.

    On the first unit stage 1 is running excessively high condensing pressure (275psig) while stage 2 is running 220psig.
    On the 2nd unit stage 2 is running excessively high condensing pressure (300psig) while stage 1 is running 225psig.
    This is on a 78F day.

    All circuits were charged by weight according to the dataplate and the sight glasses give every indication that the charge is correct.
    Superheat at the TX valves is 10F and suction pressure is around 65psig with a 73F return.
    All condenser fans are running and are single phaze 347v so rotation is not an issue.
    All are using identical blades which appear to have quite a shallow pitch.

    If it were the condenser fan blades I would need to assume that all circuits would be running higher condensing pressures.

    What can be causing this?

  2. #2
    Join Date
    Mar 2005
    non condensibles?
    Keep it simple to keep it cool!

  3. #3
    Join Date
    Nov 2003
    Montreal, Qc.
    Quote Originally Posted by stanbyyourword View Post
    non condensibles?
    That's the first thing that comes to mind but I can't see when or how they could have entered the system.
    Vacuum was pulled down to >500 microns and isolated for 15 minutes. None of the circuits went over 1000 microns.
    I change the oil in my vac pump after every vacuum. I'm a little anal about these types of things.

    I ordered 3 new condenser fan blades today. 30", 4 blade, 27º pitch, 11,000cfm.
    I'll be damned if these systems get the better of me.

  4. #4
    Join Date
    Jul 2008
    You have the superheat what's the subcool and are thier unloaders on the heads

  5. #5
    Join Date
    Feb 2007
    Northern Ontario

    clean condensers

    Im not sure but i have cleaned certain carrier condensers thinking they were perfectly clean later to find they have a split condenser which has to be separATED and cleaned between... could have caused compressor probs?

  6. #6


    You stated that the superheat was 10 degrees but there are 4 circuits,what is the superheat and the subcooling per circuit, have you taken the bulbs off the TXV's and warmed them to see whether or not the TXV's are responding to temp, i know you said they were new but if overheated during installation they could have damaged them.

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