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  1. #1
    Join Date
    Jan 2003
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    Kansas City
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    Fu-sheng compressor

    I have a mammoth unit and the 1st stage compressor constantly loads. On start up, it loads immediately with the load solenoid energized(valve closed). When the control energizes the unload solenoid, the compressor unloads and then immediately loads when the unload solenoid de-energizes. I replaced the load solenoid as the probable culprit and fired the compressor back up. The compressor would not load at all for about 1 hour and then started loading without de-energizing the load solenoid. My next step is to valve off the capillary line that feeds the load solenoid, but I have some time until that can be done...Soooooooo--I wanted to poll the gallery and ask your expert opinions since this is the first Fu-sheng I have worked on. Does this sound like an internal lip-seal type problem and if so, has anyone cracked open one of these compressors?

  2. #2
    Join Date
    Dec 2008
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    Dixiana, AL
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    Let me get this straight - you're saying that the normal operation is: capacity control neutral = load valve energized/unload valve deenergized, cap control loading = load valve deenergized/unload valve deenergized, and cap control unloading = load valve energized/unload valve energized. Correct?

  3. #3
    Join Date
    Jan 2010
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    6,300
    Quote Originally Posted by klove View Post
    Let me get this straight - you're saying that the normal operation is: capacity control neutral = load valve energized/unload valve deenergized, cap control loading = load valve deenergized/unload valve deenergized, and cap control unloading = load valve energized/unload valve energized. Correct?
    Wow say that three times fast !

  4. #4
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    Jan 2003
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    Kansas City
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    Klove--Correct...and when I say I replaced the load solenoid, I mean that I replaced the solenoid and valve and verified that the valve closes when it is energized.

  5. #5
    Join Date
    Mar 2003
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    7,326
    Mammoth units are commonly found to be wired wrong as far as the load/unload solenoids, especially on the larger units say 150 tons and up. Check your wiring first. DO NOT assume it is right until you actuall check it. Is the unit starting with the compressor fully loaded?

  6. #6
    Join Date
    Dec 2008
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    Dixiana, AL
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    Quote Originally Posted by flange View Post
    Mammoth units are commonly found to be wired wrong as far as the load/unload solenoids, especially on the larger units say 150 tons and up. Check your wiring first. DO NOT assume it is right until you actuall check it. Is the unit starting with the compressor fully loaded?
    This is where I was going, James. I rarely make dogmatic statements, and different folks do things different ways, but as a rule, you energize to load/unload. Sounds like you have something crossed up, or you have the wrong valve.

    And VTP - you need to look at where I'm from. I ain't ever said one thing really fast!!!

  7. #7
    Join Date
    Jan 2003
    Location
    Kansas City
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    This is a 160 hp machine so I have 2 other compressors to compare operation sequences. I have also manually energized and de energized the solenoids to try to get it to do what it is supposed to. The load solenoid (SV2) is a normally open valve that closes when energized, so it only deenergizes to load. This valve admits high pressure oil to move the slide to load pushing against spring pressure. The unload solenoid (SV1) is internally tee'd into the oil passage that feeds the slide valve and releases oil pressure when the solenoid valve is energized thus unloading the compressor. I found a rudimentary diagram of the operation sequence and internal design, but I have never heard of them much less opened one up. This compressor is a 25-100% modulating machine.

  8. #8
    Join Date
    Jan 2003
    Location
    Kansas City
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    1,482
    The compressor does not appear to be starting loaded, but it is fully loaded within 5 seconds of starting with the load solenoid hardwired energized(closed). I am making this call based on observing the amp draw on start.

  9. #9
    Join Date
    Dec 2008
    Location
    Dixiana, AL
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    2,610
    Based on that, sounds like you have a 1400 pound doorstop. Maybe it can be fixed, but I've never even heard of a Fu-Sheng, much less been into one.

  10. #10
    Join Date
    Jan 2003
    Location
    Kansas City
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    1,482
    Hey Klove, you wouldn't be in the market for an effective doorstop would you?

  11. #11
    Join Date
    Sep 2002
    Posts
    525

    Fu Sheng Rep

    This is the only rep in the US:


    http://www.avahvacproducts.com/Home_Page.html

    Contact them and they will be happy to help you.

  12. #12
    Join Date
    Jun 2008
    Location
    Florida (Sharpes)
    Posts
    16
    James
    From what you have explained and from working with several of the screw mfg's it sounds like you have a bad slipper seal in the slide valve pistion. Good luck with were you go from here. You do not know untill you get the oil seperator off and the discharge cover plate if you have tired iron. If the slide valve piston chamber is egg shaped it is tired iron
    Robert 1078

  13. #13
    Join Date
    Mar 2005
    Posts
    664
    looks like hitachi screws, i think these are considered unserviceable in field , ie replacement only such as a scroll , could be wrong stan
    Keep it simple to keep it cool!

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