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  1. #1
    Join Date
    Sep 2010
    Posts
    66

    HVAC guy needing Comm ref Mech Help

    I am involved in a small frozen food warehouse. The unit is a Tyler has two copeland six cylinder compressors probably about 25 ton. Our companies mechanic that took care of this is no longer with us. The customer lost a compressor. It was vibrating badly and low oil presure. It was replaced about a week ago. I went out on friday on a high temp call. New compressor vibrating badly,low oil pressure.Oil is grey and full of metal. Shut unit down.They have common suction/discharge,an oil seperator,henry oil level control,accumaltor,receiver,three evaporators,R507,oil coolers, timed defrost,
    no unloading. The case is controlled by a temperature controller and compressors cycle on pressure switches. It seems as though the previous compressor and the new have the same problem. What superheat and subcool would I normally see on this freezer application. I am thinking possibly an oil return problem. No level in the Henry cannister. The oil safety was not tripped. Pressure on guages only indicated about 4-5 lbs. Any help is appreciated. Thanks

  2. #2
    Join Date
    Aug 2006
    Location
    Columbus Ohio
    Posts
    1,977
    Grey oil full of metal is about as bad as it gets.

    I wouldn't even think of running that machine(s) without a complete teardown first.
    UA LU189

    10mm, because it's better than .45acp

  3. #3
    Join Date
    Mar 2004
    Location
    Las Vegas, Nevada
    Posts
    1,647
    You got a number of possible suspects on that one bud.

    First off, you need to verify that your oil pressure safety switch is actually working, not bypassed.

    Second, you need to make sure your Liquid Line Solenoid is fully closing when the temp is satisfied and when in defrost.

    Third, you need to make sure your TXVs are not dumping Liquid down the equalizer tubes.

    Do these things prior to replacing that compressor again, let us know what you see.
    The views and opinions posted here are my own. They do not reflect the corporate policies of my employer and will most likely get me fired at some point.

  4. #4
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,933
    Get a new pump because you murdered that last one.

    Install it.

    Replace ALL filters.

    Do an oil change.

    Pull apart the oil separator and clean that.

    PROVE operation of ALL operating and safety controls.

    Verify that you have a solid column of liquid to the TXV. Subcooling isn't normally used on equipment like this, a sightglass is.

    DO NOT walk away until you KNOW what caused the failure. Yes, that means you will have a long, ball-busting day, but Copeland isn't going to warranty incompetence.


    Once you've got all of that done, come on back and tell us what the Superheat is before and after defrost.


  5. #5
    Join Date
    Mar 2004
    Location
    Las Vegas, Nevada
    Posts
    1,647
    Quote Originally Posted by jpsmith1cm View Post
    Get a new pump because you murdered that last one.

    Install it.

    Replace ALL filters.

    Do an oil change.

    Pull apart the oil separator and clean that.

    PROVE operation of ALL operating and safety controls.

    Verify that you have a solid column of liquid to the TXV. Subcooling isn't normally used on equipment like this, a sightglass is.

    DO NOT walk away until you KNOW what caused the failure. Yes, that means you will have a long, ball-busting day, but Copeland isn't going to warranty incompetence.


    Once you've got all of that done, come on back and tell us what the Superheat is before and after defrost.

    Yeah. what he said too.
    The views and opinions posted here are my own. They do not reflect the corporate policies of my employer and will most likely get me fired at some point.

  6. #6
    Join Date
    Sep 2010
    Posts
    66
    Not going to run it. Compressor one week old. Going to have to replace. Just looking for info so we don't loose another.

  7. #7
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,933
    Continuing my prescription....

    Return the following day.

    Replace the oil and all filters.

    Re-check all of your measurements from the day before.


    Return 48 hours later. If the oil has ANY color to it at all, repeat the oil and filter change.

    After 48 hours with no color change to the oil, draw a sample and send it to National Refrigerant's laboratory and follow their recommendations from there.

  8. #8
    Join Date
    Sep 2010
    Posts
    66
    I realize the compressor is done. I am asking about the superheat so, I know I am ok while running. I want to be thorough. I also believe I should check superheat on each of the three evaporators. I am not going to run it,get back on this sight at night, tell the superheat and be wrong. I will not leave it that way.I don't want to be a MURDERER or INCOMPETENT. I just wanted to know what the superheat should be in this application.. The seperator can not be taken apart. I am suspecting an issue with the oil level control/cannister and oil safety not tripping. This is because the seperator has common oil return line to both compressors. The other compressor oil level is ok. Common suction/discharge lines also. I have not performed any diagnosis at this time. Call late friday and shut the compressor down. I always check oil safety on any new compressor intalled. All other safeties are also checked.

  9. #9
    Join Date
    Mar 2004
    Location
    Las Vegas, Nevada
    Posts
    1,647
    Quote Originally Posted by OhioTech View Post
    ...I am suspecting an issue with the oil level control/cannister and oil safety not tripping. This is because the seperator has common oil return line to both compressors. The other compressor oil level is ok. Common suction/discharge lines also. I have not performed any diagnosis at this time. Call late friday and shut the compressor down. I always check oil safety on any new compressor intalled. All other safeties are also checked.
    Gotta say, sounds to me like you got a floodback problem. Copelands like 20 or so deg S/H at the suction endbell.
    The views and opinions posted here are my own. They do not reflect the corporate policies of my employer and will most likely get me fired at some point.

  10. #10
    Join Date
    Sep 2010
    Posts
    66
    The solenoid does shut off. The defrost timer did shut off solenoid valve and pump down while I had just began checking the recent install. The compressor that had been changed, has been down for about a month.The other one has been maintaining the case at 5-6 deg.. From reports I read ,it seems to be the same failure issue.

  11. #11
    Join Date
    Mar 2004
    Location
    Las Vegas, Nevada
    Posts
    1,647
    Quote Originally Posted by OhioTech View Post
    The solenoid does shut off. The defrost timer did shut off solenoid valve and pump down while I had just began checking the recent install. The compressor that had been changed, has been down for about a month.The other one has been maintaining the case at 5-6 deg.. From reports I read ,it seems to be the same failure issue.
    Check your TXVs. The equalizer tubes should not be dumping liquid.
    The views and opinions posted here are my own. They do not reflect the corporate policies of my employer and will most likely get me fired at some point.

  12. #12
    Join Date
    Sep 2010
    Posts
    66
    I will replace the filters. Check safeties. Replace the henry oil level cannister. Replace compressor .Check superheat on each coil and at the compressors. I guess I will have to babysit the old thing a couple days. Thanks

  13. #13
    Join Date
    Mar 2004
    Location
    Las Vegas, Nevada
    Posts
    1,647
    In a freezer, you should be looking at like 6 deg S/H leaving your evaps.
    The views and opinions posted here are my own. They do not reflect the corporate policies of my employer and will most likely get me fired at some point.

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