gForce Ultra IOM
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Fixed Speed Scroll Compressor Phase Check
Since the fixed speed, scroll compressors are phase dependent, the easiest way to check proper
phasing is to check the rotation of the fixed speed scroll compressor (if available) on the evaporator
section of dual circuit units by momentarily energizing the COOL 2 (fixed speed compressor) under the
dap4 Menu I – Manual Control (Service Level). See dap4 IOM instructions for details. As soon as the
compressors comes on, observe the compressor pressure difference for a few seconds and then turn
the Cool 2 OFF.
An out of phase fixed speed scroll compressor will draw relatively low amps and both suction and
discharge pressures will remain nearly equal. If necessary, reverse any two of the three input line
voltage wires at the line voltage field connection point to change the compressor rotation.
Although fixed speed scroll compressors are phase dependent, units shipped from the factory are run
tested, ensuring the compressor rotation is consistent with evaporator fan motor. However, a field
change-out of a compressor may require checking proper phase.
Variable Speed Compressor Phase Check
The gForce Ultra unit has a Variable Speed Compressor (VS Compressor) with a Variable Frequency
Drive (VFD) which is factory wired and run tested to governor the phasing and rotation direction. The
wire connections between the VS Compressor and the VFD have very specific connections, and these
are shown on the wire diagrams. The only time a phase check is needed is when a VS Compressor or
VFD is during a field change-out. An out of phase VS Compressor will not turn ON and the VFD will
show an error message.
To phase check the VS Compressor, under the dap4 Menu I – Manual Control (Service Level), turn the
VS Compressor ON by momentarily energizing Cool 1. See dap4 IOM instructions for details. As soon
as the VS Compressors comes ON, observe the VFD display for any error message then turn the Cool
1 OFF.
If a VFD error message is observed, review the electrical wiring diagram to make sure the proper
connections between the VFD to the VS Compressor are correct.
Figure 15 Typical VFD to VS Compressor Wiring
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