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  1. #1
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    MTS-YORK SCREW COMPRESSOR IN YCIV CHILLER

    The MTS screw compressor in the YCIV York chiller, I was told by a contractor that this MTS MODEL VSD compressor was not built without backpressure valve as built like CHHA trane or 06T carrier, its function is that the discharge gas will not return to screw housing and prevent revers rotation when compressor going to switch off. Recently some screw compressors from YCIV makes noise after the 8-year partial operation. Have anybody noticed? Thank you

  2. #2
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    Look at York form 201.23-NM-156 (6/30/2016) and look at page 216 there is a color picture of the compressor parts. There is no check valve.


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  3. #3
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    You can purchase a suction check valve from Frick that fits those compressors or you can fit a standard Danfoss NRV in the discharge line between the oil separator outlet and condenser inlet , that will stop any backspin, especially as you are possibly in a high ambient area.


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  4. #4
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    Thread Starter
    the reverse rotation technically is not good for screw compressor. then why they omitted this check valve on discharge pipe? I rechecked and found looks like a check valve on discharge pipe-pic attached. I don’t know whether that is check valve and the manual also mums about witch.
    Attached Thumbnails Attached Thumbnails YORK.jpg  

  5. #5
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    There is always going to be a certain amount of reverse rotation even with the check valve. I have several without the check valve that are too big for their load. They cycle very frequently and haven’t had any problems.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  6. #6
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    Can you explain why the reverse rotation when slowing down is not good for the compressor ?

  7. #7
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    Quote Originally Posted by moideen View Post
    the reverse rotation technically is not good for screw compressor. then why they omitted this check valve on discharge pipe? I rechecked and found looks like a check valve on discharge pipe-pic attached. I don’t know whether that is check valve and the manual also mums about witch.
    That is the discharge isolation ball valve. Normal shut down is at a reduced load ,minimum speed 50 Hz. , so head pressure is low and backspin is little to none. Even a emergency shut down the is still oil flow. It just sounds bad. We have a early vintage YCAV from 2007 running on the original compressors. It has had a lot of high head shut downs due to dirty coils.

  8. #8
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    Quotation from York s manual - When a compressor stops, back-spin of the compressor will often occur as the pressure differential between discharge and suction equalizes. This should not be a cause of concern.

  9. #9
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    Thread Starter
    Quote Originally Posted by Sserrviceman View Post
    Quotation from York s manual - When a compressor stops, back-spin of the compressor will often occur as the pressure differential between discharge and suction equalizes. This should not be a cause of concern.
    york s manual? can you attach the page here..thank you

  10. #10
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    You can find such manuals easily in google. For example Form 201.23-NM1 (616). Page 233.

  11. #11
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    Thread Starter
    Quote Originally Posted by Sserrviceman View Post
    You can find such manuals easily in google. For example Form 201.23-NM1 (616). Page 233.
    thank you serviceman. i had this document in my file. but couldn't find the exact location in the file. yes, york doesn't concern as the the backspin. it might be the part of their design.
    Attached Thumbnails Attached Thumbnails BACKSPIN.jpg  

  12. #12
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    those units are on speed drives......at shutdown, they should drop to minimum HZ before shutdown. if they come to a controlled stop, you should have very little backspin.

    if you have a unit that needs shutdown, and don't want to use the unit switches or panel switch, just raise the CHW setpoint above the differential.

  13. #13
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    I was in one of the early training sessions when this machine was introduced . Even then we were instructed it was not a problem . ( It can be as loud as an AIR RAID SIREN under certain conditions )

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