Results 1 to 15 of 15
  1. #1
    Join Date
    Oct 2007
    Location
    Mexico
    Age
    44
    Posts
    158
    Rep Power
    17

    Low Superheat Compressor Rack System



    Hello everyone!

    I'm in this project where a 5 compressors Rack system is used to cool 7 rooms, each room with 2 evaporators.

    The Rack has beeing working like 3 months but suddenly I noticed that the Superheat at the Compressors inlet is getting very low, some times short periods of time but sometimes considerable periods of time, as low as barely having superheat at all.

    Have you ever deal with a situation like this???

    Hope you can help!



  2. #2
    Join Date
    Apr 2006
    Location
    UK
    Age
    55
    Posts
    1,920
    Rep Power
    29

    Re: Low Superheat Compressor Rack System

    check the expansion valve bulb for good contact and insulation

  3. #3
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Low Superheat Compressor Rack System

    How evaporators are defrosted?
    Are they full of ice or clean of ice.
    Does all fans are operational.
    Check individual superheat of all evaporators.
    Last edited by nike123; 04-08-2011 at 09:48 AM.

  4. #4
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    48
    Posts
    1,044
    Rep Power
    19

    Re: Low Superheat Compressor Rack System

    george,

    What you consider low superheat? Do you have notice any sign of trouble at the compressors?
    To make progress is never good enough, I want to do better and better and better

  5. #5
    Join Date
    Oct 2007
    Location
    Mexico
    Age
    44
    Posts
    158
    Rep Power
    17

    Re: Low Superheat Compressor Rack System

    Thanks to all!!
    Unfortunately there was a broken compressor before we could get there to check the entire system, we found a non operational TXV at one evaporator, it got stuck wide open so liquid refrigerant got to the compressors manifold, apparently the closest compressor to that circuit pipe suctioned the liquid and went out of oil until it broke down.

    Do you know why a TXV would ever get stucked after months of correctly operation????

  6. #6
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    48
    Posts
    1,044
    Rep Power
    19

    Re: Low Superheat Compressor Rack System

    Maybe because a not well cleaned system and debris get in to the spindle and spindle liner...
    To make progress is never good enough, I want to do better and better and better

  7. #7
    Join Date
    Apr 2006
    Location
    UK
    Age
    55
    Posts
    1,920
    Rep Power
    29

    Re: Low Superheat Compressor Rack System

    Quote Originally Posted by georgedvf View Post
    Do you know why a TXV would ever get stucked after months of correctly operation????
    Could just be the same reason we have service engineers, mechancal items will not last for ever - wear & tear

    I have been asked by customers in the past to change just the internals(tight wads), but I always try to change the whole valve as the body wears aswell

  8. #8
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    48
    Posts
    1,044
    Rep Power
    19

    Re: Low Superheat Compressor Rack System

    Quote Originally Posted by chillerman2006 View Post
    Could just be the same reason we have service engineers, mechancal items will not last for ever - wear & tear

    I have been asked by customers in the past to change just the internals(tight wads), but I always try to change the whole valve as the body wears aswell
    I think the rack is too young to suffer normal wearing, don't you think?
    To make progress is never good enough, I want to do better and better and better

  9. #9
    Join Date
    Oct 2007
    Location
    Mexico
    Age
    44
    Posts
    158
    Rep Power
    17

    Re: Low Superheat Compressor Rack System

    Yes, I think chillerman2006 missed the 3 months of operation data...

    We replaced the TXV and run the Rack with the 4 working compressors and seems to be ok. Superheat in compressors manifold is between 25º - 29ºF.

  10. #10
    Join Date
    Apr 2006
    Location
    UK
    Age
    55
    Posts
    1,920
    Rep Power
    29

    Re: Low Superheat Compressor Rack System

    Quote Originally Posted by Sandro Baptista View Post
    I think the rack is too young to suffer normal wearing, don't you think?
    Yep..guilty as charged... lept before i looked

  11. #11
    Join Date
    Oct 2007
    Location
    Mexico
    Age
    44
    Posts
    158
    Rep Power
    17

    Re: Low Superheat Compressor Rack System

    I guess then we can only assume a fabrication defect???

  12. #12
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    48
    Posts
    1,044
    Rep Power
    19

    Re: Low Superheat Compressor Rack System

    Quote Originally Posted by georgedvf View Post
    Yes, I think chillerman2006 missed the 3 months of operation data...

    We replaced the TXV and run the Rack with the 4 working compressors and seems to be ok. Superheat in compressors manifold is between 25º - 29ºF.
    I think the superheat is a little high unless you have an heat exchanger liquid-suction and/or an high DT on the evaporators or lack of feed on the evaporators.
    To make progress is never good enough, I want to do better and better and better

  13. #13
    Join Date
    Sep 2007
    Location
    Split Croatia
    Age
    57
    Posts
    6,175
    Blog Entries
    6
    Rep Power
    36

    Re: Low Superheat Compressor Rack System

    Quote Originally Posted by Sandro Baptista View Post
    I think the superheat is a little high unless you have an heat exchanger liquid-suction and/or an high DT on the evaporators or lack of feed on the evaporators.
    I think that one compressor out off order and some pressure drop and heat gain on long pipe runs could give such numbers (12-15K) without heat exchanger and at full load.
    Last edited by nike123; 05-08-2011 at 09:39 AM.

  14. #14
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    48
    Posts
    1,044
    Rep Power
    19

    Re: Low Superheat Compressor Rack System

    Quote Originally Posted by nike123 View Post
    I think that one compressor out off order and some pressure drop and heat gain on long pipe runs could give such numbers (12-15K) without heat exchanger and at full load.
    Okay, but it will be high non useful superheat and/or high pressure drop. Let see: If if you have an DT=8K » useful superheat about 6 K. Maybe the TEV should be better regulated to performance the plant.
    To make progress is never good enough, I want to do better and better and better

  15. #15
    Join Date
    Oct 2007
    Location
    Mexico
    Age
    44
    Posts
    158
    Rep Power
    17

    Re: Low Superheat Compressor Rack System

    Yes, I agree with that, I meant it was ok because no liquid refrigerant was coming back to the compressors so I was reliefed. We will get the new compressor and after installation we will adjust all TEV's superheat.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •