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Fluctuating pressures, fixed orifice

Discussion in 'Residential' started by doc havoc, Jun 9, 2017.

  1. doc havoc

    doc havoc A cunning linguist

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    Besides noncondensables, what would cause high and low pressures to fluctuate up and down? This is a dry charged r22 condenser using existing evap and line set. Unit was installed, evacuated, and charged. When started, pressures began fluctuating (about 40 psig up and down). Recovered, replaced filter/drier, evacuated and recharged. Same thing. Scroll compressor. That's all the info I received.

    Thoughts?
     
  2. mike1020

    mike1020 entitled millennial

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    Airflow. Is blower dropping out? Heater coming on?
     
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  3. 22blood

    22blood red wire nuts only

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    1,756
    What are your comp amps doing
     
    Last edited: Jun 9, 2017
  4. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    Piston installed correctly?
     
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  5. doc havoc

    doc havoc A cunning linguist

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    Don't know. Former student called me and this is all the info he gave me. He'll get more numbers Monday.
     
  6. doc havoc

    doc havoc A cunning linguist

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    Would "assume" since all they did was disconnect a 23 year old condenser and set the new one.
     
  7. mike1020

    mike1020 entitled millennial

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    They did remember to open the service valves and blow the nitrogen charge out of the condensing unit before pulling a vacuum?
     
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  8. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

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    Does it have a leak?
     
  9. jays 65

    jays 65 New Member

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    nitrogen remaining from condensor
     
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  10. doc havoc

    doc havoc A cunning linguist

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    It was evacuated and charged twice so I'm guessing all nitrogen is long gone.
     
  11. doc havoc

    doc havoc A cunning linguist

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    I can't say for sure. He was taught to use a micron gauge, but who knows.
     
  12. coldsnap

    coldsnap -20 on the money

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    Slightly overcharged will cause that. Have them try taking taking a little gas out.
     
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  13. jays 65

    jays 65 New Member

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    bet they evacuated twice the lineset and coil then opened service valves
     
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  14. Texas-Tech

    Texas-Tech Official Geezer*

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    duhh
    Kink in the lineset going up the wall?
     
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  15. Texas-Tech

    Texas-Tech Official Geezer*

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    duhh
    Back in the 90's we had a system in the attic of a 2 story house that did the same thing. We tried everything but the only thing that stopped it was a txv
     
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  16. newtech

    newtech 636

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    They have a 13seer condenser with probably an 8-10seer evap. Takeout the piston and install a TXV.
     
  17. chesty puller

    chesty puller New Member

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    Had a Goodman 3 ton split a few weeks ago, that had been changed out, fluctuating pressure high and low.. suspected non condensibles, blew charge, noticed a huge amount of oil coming out, isolated evap and condenser, flushed system with nitrogen system had huge amount of oil. Pulled vacuum, no more pressure fluctuating.

    Sent from my Z812 using Tapatalk
     
  18. Jim54

    Jim54 New Member

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    A piece of debris swirling around in the metering device piston chamber would do it possibly. Clogging, unclogging, clogging, unclogging. Saw this one time. On a condenser unit change out. Drove the two guys on the job nuts untill they found it and got it out of there.
     
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  19. frozensolid

    frozensolid Psychologist's Dream

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    Or install the correct piston. The condenser many times has the size required on it.
     
  20. R/HVAC

    R/HVAC selfemployed

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    Was the compressor a Scroll and did they charge with MO99 ? Person said they pulled the charge and recharged with 22 and it worked fine. I thought it was oil or metering device problem though.