Electrical Phasing; Voltage Supply And Voltage Imbalance - Trane Voyager CV Installation And Maintenance Manual

Startup

Electrical Phasing

Unlike traditional reciprocating compressors, 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 Ideal - Sperry 61-520
Phase Sequence Indicator and following the steps below:
WARNING
Hazardous Voltage!
Disconnect all electric power, including remote
disconnects before servicing. Follow proper lockout/
tagout procedures to ensure the power can not be
inadvertently energized. Failure to disconnect power
before servicing could result in death or serious injury.
• Open the disconnect switch or circuit protector switch
that provides the supply power to the unit's power
terminal block or to the unit mounted disconnect
switch.
• To be consistent with the compressor leads, connect
the phase sequence indicator leads to the terminal
block or unit mounted disconnect switch as follows;
Table 29. Phase sequence leads
Phase Sequence Leads
Red (phase A)
Blue (phase B)
Black (Phase C)
• Turn the "System" selection switch to the "Off"
position and the "Fan" selection switch (if Applicable)
to the "Auto" position.
• Close the disconnect switch or circuit protector switch
that provides the supply power to the unit's power
terminal block or unit mounted disconnect switch.
WARNING
Live Electrical Components!
During installation, testing, servicing and
troubleshooting of this product, it may be necessary to
work with live electrical components. Have a qualified
licensed electrician or other individual who has been
properly trained in handling live electrical components
perform these tasks. Failure to follow all electrical safety
precautions when exposed to live electrical
components could result in death or serious injury.
HIGH VOLTAGE IS PRESENT AT TERMINAL BLOCK HTB1
OR UNIT DISCONNECT SWITCH.
54
Unit Power Terminal
L1
L2
L3
• 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 main electrical power and recheck phasing. If
the phasing is correct, open the disconnect switch or
circuit protection switch and remove the phase
sequence indicator.

Voltage Supply and Voltage Imbalance

Supply Voltage
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.
Voltage Imbalance
Excessive voltage imbalance between phases in a three
phase system 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:
% Voltage Imbalance = where;
AV (Average Voltage) =
Volt1
+
---------------------------------------------------------------
Volt 1, Volt 2, Volt 3 = Line Voltage Readings
VD = Line Voltage reading that deviates the farthest from
the average voltage.
Example:
If the voltage readings of the supply power measured 221,
230, and 227, the average volts would be:
221 230
+
---------------------------------------------- -
3
VD (reading farthest from average) = 221
The percentage of Imbalance equals:
226 221
–
---------------------------- 
226
The 2.2% imbalance in this example exceeds the
maximum allowable imbalance of 2.0%. This much
imbalance between phases can equal as much as a 20%
current imbalance with a resulting increase in motor
winding temperatures that will decrease motor life.
If the voltage imbalance at the job site is over 2%, notify the
proper agencies to correct the voltage problem to within
2.0% before operating this equipment.
Volt2 Volt3
+
3
227
+
226Avg
=
100 2.2percent
=
RT-SVX34F-EN