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Low suction

Discussion in 'Residential' started by jamesyarbrough, Sep 22, 2017.

  1. jpb2

    jpb2 Dog Tard *

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    65 was spec with RCBA series coils both 2.5 and 3 ton for many years. I dont think the piston is the issue. Im with air flow. If its the UBHA,B,C series there is a good chance its ducted wrong. Fickle design ( shitty).
     
  2. jpb2

    jpb2 Dog Tard *

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    If i recall. 89 for 5. 82 for 4 . 78 for 3.5. 65 for 2.5 and 3. 57 for 2 and 53 for 1.5. Rarely did they get changed to match
     
  3. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    It's a 3 ton. My chart says 73 but the oem says 65. So I went with the oem. Besides more refrigerant isnt going to fix the problem. I can just dump more gas in it to get the pressure up. What about superheat?


    I just wanna say give it more air. But I think there's also more to it
     
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  4. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    I did.
     
  5. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    Im no rheem expert, but I can tell you it had a TINY blower. It's half the size of my 2 ton blower. Very narrow. Maybe 6 inches wide and 10 inches in diameter. I didn't measure tho
     
  6. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    It's the extra shitty design where the heat strips are in the blower housing.
     
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  7. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    and here's another thing. It had a delta t of 15! Wtf? Low cfm gives high delta. But it's not a restriction because I have low sh.
     
  8. jpb2

    jpb2 Dog Tard *

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    And my bet is the plenum is not the outlet size. Probably much bigger. The outlet is approx 8x18. If the plenum is way over sized the airflow will be an issue. Like I said poor design. It works well if you rtfm but really is different
     
    tuna likes this.
  9. knave

    knave Undeterred

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    Did you change the compressor?
    Does it have new gas?
    Or maybe a mix of R290 or who knows.
    Valve off the condenser and run the cond fan for 10 min then check against a PT chart.
     
  10. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    no I didn't change the compressor. Someone else did.

    They wouldn't give me any history. New customer. Not cooling well. I found a 17 year old pos.
     
  11. Septua

    Septua New Member

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    Jpb2 has a good point. The Rheem marketing literature always bragged about the air handlers being short so you could get 'em in short places...then the install manual said to add a 3' extension to the outlet to improve the air "dynamics". So much for the low profile feature...

    They did say if 3' wasn't possible, any length you could manage would help...I usually managed 12-18". But, I also did a few without an extension, so it may not be the explanation.

    Those units also came with a dinky, washable factory filter installed...found a lot of those over the years that were never removed...forgot to remove a couple myself. :D
     
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  12. R2D2-TX

    R2D2-TX New Member

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    Possible non- condensables.. Air or other blends mixed..???
     
  13. knave

    knave Undeterred

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    With your numbers the split should be higher across the coil.
     
  14. Anita sannich

    Anita sannich Exceptionally average

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    Return air blocked? Supply diffusers covered? What's the airflow reading at the farthest diffuser?
     
  15. Daryl_Dixon

    Daryl_Dixon New Member

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    In the good old days, 17-21 across the evap was spec. Over 21, possibly insufficient airflow. Under 17, possibly too much airflow.

    I know this is an oversimplification. But with a Delta-T of only 15, I can't see how adding more airflow through the evap improves anything.

    Idk though...

    I've been out of the loop on the running characteristics of modern residential stuff for a while.
     
  16. Anita sannich

    Anita sannich Exceptionally average

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    Time to change the tstat
     
    Last edited: Sep 23, 2017
  17. tuna

    tuna New Member

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    I would like to see the iom if you have it handy. I think you are saying you need to transition from fan outlet size rather than just put an oversized plenum on the box.
     
  18. jpb2

    jpb2 Dog Tard *

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    Pm me an address. I will send. They recomend the same size as outlet for i believe a min. Of 18 or 24"
     
  19. jpb2

    jpb2 Dog Tard *

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    Yes that is what i am saying
     
  20. HMD

    HMD does it matter?

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