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Thread: Bitzer Screw Unloaders
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11-04-2013, 06:43 AM #1
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
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12-04-2013, 02:52 AM #2
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
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15-04-2013, 11:37 AM #3
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.
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22-04-2013, 02:04 AM #4
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.