Unit Voltage Power Supply - Trane CGAM Installation & Operation Manual

Pre-Start Checkout

Unit Voltage Power Supply

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.
Voltage to the unit must meet the criteria given. Measure
each leg of the supply voltage at the unit's main power
fused-disconnect. If the measured voltage on any leg is not
within specified range, notify the supplier of the power
and correct the situation before operating the unit.
NOTICE:
Equipment Damage!
Inadequate voltage to the unit may cause control
components to malfunction and shorten the life of
relay contact, compressor motors and contactors.
Unit Voltage Imbalance
Excessive voltage imbalance between the phases of a
three-phase system can cause motors to overheat and
eventually fail.The maximum allowable imbalance is 2
percent. Voltage imbalance is determined using the
following calculations:
1V x
= phase with greatest difference from V
regard to sign)
For example, if the three measured voltages are 221, 230,
and 227 volts, the average would be:
The percentage of imbalance is then:
This exceeds the maximum allowable (2%) by 0.2 percent.
122
Unit Voltage Phasing
It is important that proper rotation of the compressors be
established before the unit is started. Proper motor
rotation requires confirmation of the electrical phase
sequence of the power supply.The motor is internally
connected for clockwise rotation with the incoming power
supply phased A, B, C.
Basically, voltages generated in each phase of a polyphase
alternator or circuit are called phase voltages. In a three-
phase circuit, three sine wave voltages are generated,
differing in phase by 120 electrical degrees.The order in
which the three voltages of a three-phase system succeed
one another is called phase sequence or phase rotation.
This is determined by the direction of rotation of the
alternator. When rotation is clockwise, phase sequence is
usually called "ABC" , when counterclockwise, "CBA" .
This direction may be reversed outside the alternator by
interchanging any two of the line wires. It is this possible
interchange of wiring that makes a phase sequence
indicator necessary if the operator is to quickly determine
the phase rotation of the motor.
Proper compressor motor electrical phasing can be quickly
determined and corrected before starting the unit. Use a
quality instrument, such as the Associated Research
Model 45 Phase Sequence Indicator.
8. Press the Stop key on the Clear Language Display.
9. Open the electrical disconnect or circuit protection
switch that provides line power to the line power
terminal block(s) in the starter panel (or to the unit
mounted disconnect).
10. Connect the phase sequence indicator leads to the line
power terminal block, as follows:
11. Turn power on by closing the unit supply power fused-
(without
ave
disconnect switch.
12. Read phase sequence on indicator.The "ABC" LED on
the face of phase indicator will glow if phase is "ABC" .
13. If the "CBA" indicator glows instead, open the unit
main power disconnect and switch two line leads on
the line power terminal block(s) (or the unit mounted
disconnect). Reclose the main power disconnect and
recheck the phasing.
Equipment Damage!
Do not interchange any load leads that are from the
unit contactors or the motor terminals.
14. Reopen unit disconnect and disconnect phase
indicator.
Phase Sequence Lead
Black (Phase A)
Red (Phase B)
Yellow (Phase C)
NOTICE:
Terminal
L1
L2
L3
CG-SVX17E-EN