Pre-Start; Voltage Imbalance; Electrical Phasing (Three Phase Motors) - Trane YHC092E Installation, Operation And Maintenance Manual

Pre-Start

Use the checklist provided below in conjunction with the
"General Unit Requirements" checklist to ensure that the
unit is properly installed and ready for operation.
WARNING
Hazardous Voltage w/Capacitors!
Disconnect all electric power, including remote
disconnects and discharge all motor start/run
capacitors before servicing. Follow proper lockout/
tagout procedures to ensure the power cannot be
inadvertently energized. Verify with an appropriate
voltmeter that all capacitors have discharged. Failure to
disconnect power and discharge capacitors before
servicing could result in death or serious injury.
For additional information regarding the safe discharge
of capacitors, see PROD-SVB06A-EN
Verify that the condenser airflow will be unobstructed.
WARNING
Rotating Components!
During installation, testing, servicing and
troubleshooting of this product it may be necessary to
work with live and exposed rotating components. Have
a qualified or licensed service individual who has been
properly trained in handling exposed rotating
components, perform these tasks. Failure to follow all
safety precautions could result in rotating components
cutting and slashing technician which could result in
death or serious injury.
• Verify that the condenser fan and indoor blower turn
freely without rubbing and are properly tightened on
the shafts.
• Check the supply fan belts for proper tension and the
fan bearings for sufficient lubrication. If the belts
require adjustment, or if the bearings need lubricating,
refer to the maintenance section of this manual for
instructions.
• Verify that a condensate trap is installed and the piping
is properly sized and pitched.
• Verify that the correct size and number of filters are in
place.
• Inspect the interior of the unit for tools and debris and
install all panels in preparation for starting the unit.

Voltage Imbalance

Three phase 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
42
within the proper tolerances, notify the power company to
correct this situation before operating the unit.
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:
100 x AV - VD
% Voltage Imbalance=
Volt 1 + Volt 2 + Volt 3
AV (Average Voltage)=
V1, V2, V3 = 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 + 227
= 226 Avg.
3
VD (reading farthest from average) = 221
The percentage of imbalance equals:
100 x 226 - 227
= 2.2%
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 is over 2%, notify the proper agencies
to correct the voltage problem before operating this
equipment.
Electrical Phasing (Three Phase
Motors)
The compressor motor(s) and the supply fan motor are
internally connected for the proper rotation when the
incoming power supply is 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:
• Turn the field supplied disconnect switch that provides
power to the main power terminal block or to the
"Line" side of the optional factory mounted disconnect
switch to the "Off" position.
• Connect the phase sequence indicator leads to the
terminal block or to the "Line" side of the optional
factory mounted disconnect switch as follows;
Black (phase A) to L1
Red (phase B) to L2
Yellow (phase C) to L3
where;
AV
3
RT-SVX21K-EN