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  1. #1
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    Bitzer Screw Unloaders



    Hi, I am monitoring a couple low and medium temp hill phoenix racks. Both have Bitzer screw compressors with two unloaders on each compressor staging capacity at 50%, 75%, and 100%. I have had great success in removing unloaders from capacity control on Carlyle screws because of their inefficiencies. I don't know much about the Bitzers yet and was wondering if anybody had any experience or data on Bitzer screw unloaders and efficiencies?

    Bitzer HSN5343-25 Low temp
    Bitzer HSK5343-30 Med temp



  2. #2
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    Re: Bitzer Screw Unloaders

    generally the unloaders open a bypass port on the screw length. Disconnect power to each solenoid coil will keep compressor fully loaded. Ramp speed up and down with a VSD would be more efficient, minimum hertz for oil flow is around 30 Hertz

  3. #3
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    Re: Bitzer Screw Unloaders

    Quoting Magoo. Unloaders simply creates by-pass which means you spend power in compressing and then you by-pass what you compressed ... very poor efficiency. VSD is the way.

  4. #4
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    Re: Bitzer Screw Unloaders

    Hi Joel404a
    Do you not need capacity control for you application? It would be interesting to see the difference between running a lower SST due to less staging VS the Parasitic losses of utilizing the Unloaders.

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