Installation
28
RRU-SVX01F-EN
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 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 percent.
Measure and record the voltage between phases 1, 2, and
3 and calculate the amount of imbalance as follows:
where
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:
VD (reading farthest from average) = 221
The percentage of Imbalance equals:
The 2.2 percent imbalance in this example exceeds the
maximum allowable imbalance of 2.0 percent. This much
imbalance between phases can equal as much as a
20 percent current imbalance with a resulting increase in
motor winding temperatures that will decrease motor life.
If the voltage imbalance is over 2 percent, 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:
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.
WARNING
Live Electrical Components!
Failure to follow all electrical safety precautions when
exposed to live electrical components could result in
death or serious injury.
When it is 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.
% Volt
a
ge Imb
a
l
a
n
c
e =
100 X
AV - VD where;
AV
AV (Aver
a
ge Volt
a
ge) =
Volt 1 + Volt 2 + Volt 3
3
221 + 230 + 227 = 226 Avg.
3
100 X 226 - 221 = 2.2%
226
WARNING
Hazardous Voltage w/Capacitors!
Failure to disconnect power and discharge capacitors
before servicing could result in death or serious injury.
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.
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
Close the field supplied main power disconnect
switch or circuit protector switch that provides the
supply power to the unit.
WARNING
Live Electrical Components!
Failure to follow all electrical safety precautions when
exposed to live electrical components could result in
death or serious injury.
When it is 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.
