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  1. #14
    Join Date
    Sep 2011
    Location
    Vancouver, WA
    Posts
    261
    At the end of a call for cooling is it pumping down? What is your crankcase pressure prior to start up? When the compressor 1st starts up, what is the oil pump temp, is it cold? Even with operating crankcase heaters, refrigrant can still condense in the crankcase.

  2. #15
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    The condensing unit is on the ground. The evap. unit is elevated about 15-20 ft.
    I haven't installed the delay on make timers yet. I have purchased them, but they are still on my desk. The unit has locked out on circuit 1 this morning. I will check the cc pressure, pump temp., and check to see if it pumps down after I reset the unit. Thanks for all the info.

  3. #16
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    The Crankcase temp. is 100.3 degrees f.
    Crankcase pressure when unit is off is 105 psig.
    Crankcase pressure when unit is running is 75 psig.
    Unit shut down after 2 minutes, so I didn't notice a pumpdown.

  4. #17
    Join Date
    May 2011
    Location
    Fort Worth, Texas
    Posts
    49
    I'm assuming you've already done this, however have you valved-off your compressors and cleaned all your screens and tested and removed and checked your attached oil pumps?

    I only ask because you didn't mention it!

    I've seen that long screen (pump inlet screen) on the bottom left of Carlyles appear clean from the outside but be filthy when you remove the sleeve.

  5. #18
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    I have not checked the pumps and screens on the compressors. I do have 20 plus psig on oil pressure. Thanks for the info. I will check into this.

  6. #19
    Join Date
    Sep 2011
    Location
    Vancouver, WA
    Posts
    261
    I had a problem like this with a Trane self contained water cooled 25ton at a bank. During long off cycles, the crankcase would have refrigerant in it. At start up the compresser would loose oil pressure.
    The compresser cc heaters worked but there was no pump down. The cc pressure was above the condensing temperature of the oil so during a long off cycle the refrigerant would condense in the crankcase. I made some wiring changes. I wired the control circut for compresser through the safties and low pressure control. I wired the liquid line solonoid so on a demand for cooling it would energize the valve. At the end of a cycle the compresser pumped down. I never saw this problem again. Hope this helps.

  7. #20
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,723
    Quote Originally Posted by zorrithod View Post
    I have not checked the pumps and screens on the compressors. I do have 20 plus psig on oil pressure. Thanks for the info. I will check into this.
    What does the oil pressure safety look like ? Old style or new style?
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  8. #21
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,723
    Quote Originally Posted by Williamsma View Post
    I had a problem like this with a Trane self contained water cooled 25ton at a bank. During long off cycles, the crankcase would have refrigerant in it. At start up the compresser would loose oil pressure.
    The compresser cc heaters worked but there was no pump down. The cc pressure was above the condensing temperature of the oil so during a long off cycle the refrigerant would condense in the crankcase. I made some wiring changes. I wired the control circut for compresser through the safties and low pressure control. I wired the liquid line solonoid so on a demand for cooling it would energize the valve. At the end of a cycle the compresser pumped down. I never saw this problem again. Hope this helps.
    If he has mechanical unloaders he won't be able to perform a pumpdown.
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  9. #22
    Join Date
    Sep 2011
    Location
    Vancouver, WA
    Posts
    261
    Quote Originally Posted by thegoodlistener View Post
    If he has mechanical unloaders he won't be able to perform a pumpdown.
    Why not? Unloaders on compressers are there for capacity control. Even if the compressor has unloaders (suction cut off, hot gas by-pass, or electro-mechanical) there is still at least 1 bank of cyclinders with out an unloader. This still leaves the compresser the ability to pump down the system. I see this all the time with Carlyle, Copeland, and Trane compressors. A pumpdown at the end of a cycle prevents a flood back at compresser start up.

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