RT-SVX24Q-EN
105
Electrical Phasing
Scroll compressors are phase sensitive. Proper phasing
of the electrical supply to the unit is critical for proper
operation and reliability. The compressor motor is
internally connected for clockwise rotation with the
incoming power supply phased as A, B, C.
Proper electrical supply phasing can be quickly
determined and corrected before starting the unit by
using an instrument such as an Associated Research
Model 45 Phase Sequence Indicator and following the
steps below:
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IImmppoorrttaanntt:: HIGH VOLTAGE IS PRESENT AT TERMINAL
BLOCK OR UNIT DISCONNECT SWITCH.
☐ Turn the field supplied disconnect switch that
provides power to terminal block or to the unit-
mounted disconnect switch to the “Off” position.
☐ Connect the phase sequence indicator leads to the
terminal block or unit-mounted disconnect switch
as follows:
Phase Sequence Leads
Unit Power Terminal
Black (phase A)
L1
Red (phase B)
L2
Yellow (phase C)
L3
☐ Close the disconnect switch or circuit protector
switch that provides the supply power to the unit
terminal block or the unit mounted disconnect
switch.
☐ Observe the ABC and CBA phase indicator lights on
the face of the sequencer. The ABC indicator light
will glow if the phase is ABC. If the CBA indicator
light glows, open the disconnect switch or circuit
protection switch and reverse any two power wires.
☐ Restore the main electrical power and recheck the
phasing. If the phasing is correct, open the
disconnect switch or circuit protection switch and
remove the phase sequence indicator.
Voltage Supply
Electrical power to the unit must meet stringent
requirements for the unit to operate properly. Measure
each leg (phase-to-phase) of the power supply. Each
reading must fall within the utilization range stamped
on the unit nameplate. If any of the readings do not fall
within the proper tolerances, notify the power
company to correct this situation before operating the
unit.
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Voltage Imbalance
Excessive three phase voltage imbalance between
phases will cause motors to overheat and eventually
fail. The maximum allowable voltage imbalance is 2%.
Measure and record the voltage between phases 1, 2,
and 3 and calculate the amount of imbalance as
follows:
UUnniitt SSttaarrttuupp
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