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Scroll compressor issue

leepomy
leepomy Member Posts: 1
in A-C, Heat Pumps & Refrigeration
Went to residence where customer said previous tech says compressor is bad and condensing unit needs to be replaced. I came out next day put gauges on static pressure 210# power up unit and gauges don't move and comp amps 2.5 (1.5 ton unit) concur that compressor is no pumper. Replace compressor and start up same symptoms. Decide I will try to see if it pumps down. Close liquid valve low side pressure starts to drop
open valve back up after low side gets down to 30# pressures go to normal and system running fine now for 2 months. Any idea what could have caused this. TXV in system and subcooling and temp split across coil perfect after pumping down.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,364
    Don't know why the replacement compressor wouldn't pump initally
  • ChrisJ
    ChrisJ Member Posts: 16,260
    EBEBRATT-Ed said:
    Don't know why the replacement compressor wouldn't pump initally
    My first assumption was the first compressor wasn't bad.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    edited October 2020
    I read this last night and have been thinking about it.

    Only thing I can think of (never had it happen) would be the TXV was stuck full open not giving you and differential/restriction. When you pumped it down that made the TXV see much lower pressure than it has seen otherwise and caused it to snap closed and go back to normal operation with flows on the LL etc. 

    However....when you changed the compressor the TXV would have been in a vacuum during evacuation....so that negates the above. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,364
    @Solid_Fuel_Man

    I thought of a TXV issue as well, maybe stuck. But after changing the compressor and you put gauges on you would still get a pressure differential...............unless it was running backwards. Since the OP mentioned residential i am assuming single phase
    Solid_Fuel_Man
  • mattmia2
    mattmia2 Member Posts: 10,820
    EBEBRATT-Ed said:

    @Solid_Fuel_Man

    I thought of a TXV issue as well, maybe stuck. But after changing the compressor and you put gauges on you would still get a pressure differential...............unless it was running backwards. Since the OP mentioned residential i am assuming single phase

    Are run and capacitor reversed on the compressor?
  • Ironman
    Ironman Member Posts: 7,537
    Is it a heat pump? If so, the reversing valve could have been stuck in mid position causing the exact same symptom as a non-pumping compressor.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.

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