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Thread: AIRFLOW TROUBLESHOOTING

  1. #1
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    AIRFLOW TROUBLESHOOTING

    I think I have an airflow issues, low superheat low suction pressure. 3 stage package unit r 22 50psi on suction 32 line temp. 30 degree supply air temp, every package unit on whole building is tripping on freeze stat. There is not really a duct system just opened tap, like in walmart. Thought it might be airflow but don't see where I could be getting restrictions. What else could be the problem?

  2. #2
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    Quote Originally Posted by anders13 View Post
    I think I have an airflow issues, low superheat low suction pressure. 3 stage package unit r 22 50psi on suction 32 line temp. 30 degree supply air temp, every package unit on whole building is tripping on freeze stat. There is not really a duct system just opened tap, like in walmart. Thought it might be airflow but don't see where I could be getting restrictions. What else could be the problem?
    check return air temp at the unit and filters in unit.

  3. #3
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    Amperage on blower motor.

    Static Pressure

    SC

    Blower clean

    Evaporator clean

  4. #4
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    I assume this is not residential

    The basics- Delta T Subcooling and superheat?...........How many stages are running and @ what load.......If all 3 stages are calling and there is no load I would start there- If all units are doing the same thing probably simple

  5. #5
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    Is it one 3 stage unit or a bunch of units having a problem? Either way... Check economizer dampers and make sure either the osa dampers or the return air dampers are not both closed at the same time and check the fire dampers to make sure a detector didn't trip somewhere.
    Still Crazy after all these years.

  6. #6
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Amperage on blower motor.

    Static Pressure

    SC

    Blower clean

    Evaporator clean

    Evap a little dirty, didn't check amp draw on motor, because all the units are doing something so I don't think all blower motors are bad. I think equipment might be ovrrsized, but even when I run 1 stage I still have low suction pressure and I know charge is dead on.

  7. #7
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    Thread Starter
    ** all units are doing same thing not something.

  8. #8
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    Seeing every unit's doing it... there's possibility someone didn't think there could be filters inside the RTU.

  9. #9
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    Did the use to work or is this a new install- You can't know charge is dead on without knowing a lot of missing parameters

  10. #10
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    I know charge is dead on because I pulled it and weighed it in myself. It is not a new install, and filters are in every unit and are clean.

  11. #11
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    Weight on a name plate means nothing as the conditions change- 1) verify air flow ( plot it on a chart with static if you have to) if TXV charge to sub cooling........Did you pull and weigh in the charge after this problem occurred? If you cant check static at least check the load on the blower, you may have dampers that have slammed shut

    We do refrigerant charge verifications on factory charged units all the time- rarely is it spot on

  12. #12
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    Well, check the entering temperature as close as possible to the actual unit. That'll tell you something about the entering air.


    Quote Originally Posted by lkapigian View Post
    Weight on a name plate means nothing as the conditions change
    It's an RTU. Can't get better than weighing in.

  13. #13
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    Quote Originally Posted by ICanHas View Post
    Well, check the entering temperature as close as possible to the actual unit. That'll tell you something about the entering air.




    It's an RTU. Can't get better than weighing in.
    We agree to disagree You will find that even on RTU's there are charge adjustments that need to be made from nameplate-- --I know, we weigh in as well, but when doing refrigerant charge verifications they are rarely spot on. Nothing beats charging to target subcooling with proper verified airflow

  14. #14
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    Ande, did you check the dampers yet?
    Still Crazy after all these years.

  15. #15
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    Quote Originally Posted by koolaid747 View Post
    Ande, did you check the dampers yet?
    NO DUCTS JUST OPENED TAPPED THROUGH ROOF OF BUILDING

  16. #16
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    possible mixing air..supply and return in curb ???just a quik thought

  17. #17
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    30° supply air temp. Is there any rubber left on the belts?

  18. #18
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    Quote Originally Posted by swift one View Post
    possible mixing air..supply and return in curb ???just a quik thought
    This is what you can figure out by measuring return air. He probably has those diffuser thing that looks like a big speaker embedded in the ceiling. Maybe the system isn't even designed correctly to have the units run on 3rd stage.

  19. #19
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    Quote Originally Posted by ICanHas View Post
    This is what you can figure out by measuring return air. He probably has those diffuser thing that looks like a big speaker embedded in the ceiling. Maybe the system isn't even designed correctly to have the units run on 3rd stage.
    agreed, or the building just did a remodel and decided that it was ok to cut off that ugly supply diffuser all together. Love it when this gets done.

  20. #20
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    maybe 3 phase blower running backward,power to whole building miswired.

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