Announcement

Collapse
No announcement yet.

3-phase Conversion for chiller...

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 3-phase Conversion for chiller...

    I'm installing a 3-phase chiller in a small facility with only single phase available. 3-phase compressor is less than 5hp. Condenser fans and control system are single phase. So I'm running a dedicated 110v single phase circuit for fans and control system and another dedicated 2-pole 220v circuit to run the compressor with a VFD as a phase converter installed after the contactor. I think my math & logic will work; anyone else have other experiences? I've not programmed a VFD for a refrigeration compressor before. I assume there would be some advantage to a fast ramp on startup/shutdown as a form of soft-start? Another advantage is delayed startup on power restoration. That's an easy one to save your refrigeration compressor when local power goes out. Upon power restoration, the first 10 seconds of brown power will cause the relatively high load of the compressor to overheat windings. Should I run this in "sensorless vector" mode? Any torque boost? What other parameters should I pay special attention in order to provide maximum protection and benefit? Thanks for your help!
    Phillip Kelm--Palau Brewing Company Manager--

  • #2
    Control Voltage

    Phillip, if you have a 208-230V unit, your control circuit needs to be the same at 208-230 instead of 115.
    Your fan motors will be 208-230V Single phase and your relay control coils should be the same.
    Copeland and others are running VFD controlled compressors now on some of their gear. I have not laid hands on any, but I would not want a contactor ahead of the drive because it will make for too much power cycling of it and they do not do well with that historically. It could make your control sequence lag and could lead to flooded starts and other weirdness.
    You need control logic that integrates with the drive. I would look for some current diagrams on those style units being used in the field and see whats being done there. I think they are using some outboard control modules that serve this purpose and possibly with some of this being built into special purpose drives which can be gotten.
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    The Thought Police are Attempting to Suppress Free Speech and Sugar coat everything. This is both Cowardice and Treason given to their own kind.

    Comment


    • #3
      Thanks!

      My control circuit is simply one phase and neutral for simple 110v operation. Likewise the fans are single phase and neutral. So I'm planning on running those two on a separate 110v breaker as independent loads. The compressor will have separate power to the VFD. Although the Danfoss VLT drive unit I have may be switched at the mains without damage to the unit, I think you bring up a good point--if I eliminate the contactor altogether, then I may use the drive in that capacity. I can start/stop the vfd through dry contacts on a control relay in the control circuit. This might be relatively straightforward....
      Phillip Kelm--Palau Brewing Company Manager--

      Comment


      • #4
        Considerations

        Never seen a 3 Phase condensing unit with 115V fans. Interesting.
        Reciprocating compressors have a cirtical RPM threshold both regarding gas cooling [ mass flow ] and lubrication.
        I am looking at whats being done with primarily larger rack systems. Some of it is quite a trick with unexpected changes such as doing away with resilient mounting of semi hermetic machines.
        I'd be interested to hear details on operation.
        Soft start is a plus.
        Warren Turner
        Industrial Engineering Technician
        HVACR-Electrical Systems Specialist
        Moab Brewery
        The Thought Police are Attempting to Suppress Free Speech and Sugar coat everything. This is both Cowardice and Treason given to their own kind.

        Comment

        Working...
        X