Electrical Wiring
28 CG-SVX038A-EN
Research Model 45 Phase Sequence indicator or
equivalent and follow this procedure.
1. Verify that all operating controls for the unit are in the
“Off” position.
2. Disconnect power to the power distribution block in
the unit control panel
3. Connect the phase sequence indicator
leads to the
power distribution block as follows:
4. Turn power on by closing the unit supply power fused
disconnect switch.
5. Read the phase sequence disp
layed on the indicator.
The “ABC” LED on the face of the phase indicator will
glow if phase sequence is ABC.
6. If the “CBA” indicator glows instead, open the unit
m
ain power disconnect and switch two line leads on
the power distribution block in the unit control panel.
Close the main power disconnect and recheck phasing.
7. Open the unit disconnect and re
move the phase
indicator.
Unit Voltage
Electrical power to the unit must meet stringent
requirements for the unit to operate properly. Total voltage
supply and voltage imbalance between phases should be
within the tolerances discussed below.
Voltage Supply
Measure each leg of supply voltage at the line voltage
disconnect switches. Readings must fall within the range
of 187-254 volts for units with a nameplate voltage of
208/230 volt and 414-508 volts for units with a nameplate
voltage of 460 volts. If voltage on any leg does not fall
within tolerance, notify the power company and request
correction of this situation before operating the unit.
Inadequate voltage to the unit will shorten the life of relay
contacts and compressor motors.
Voltage Imbalance
Excessive voltage imbalance between phases in a three-
phase system will cause motors to overheat and
eventually fail. Maximum allowable imbalance is
2 percent. Voltage imbalance is defined as 100 times the
maximum deviation of the three voltages (three phases)
subtracted from the average (without regard to sign),
divided by the average voltage.
Example:
If the three voltages measured at the line voltage fused
disconnect are 221 volts, 230 volts and 227 volts, the
average would be:
221 + 230 + 227
= 226 volts
3
The percentage of imbalance is then:
100 (226-221)
= 2.2%
226
In the preceding example, 221 is used because it is the
farthest from the average. The 2.2 percent imbalance that
exists exceeds maximum allowable imbalance by
0.2 percent. This much imbalance between phases can
equal as much as 20 percent current imbalance with a
resulting increase in winding temperature that will
decrease compressor motor life.
Control Power Supply
A fused, panel-mounted control power transformer is
standard on all units. Replacement fuses are listed on the
“Fuse Schedule” decal located adjacent to the transformer
inside the control box.
External Contacts
Chilled Water Flow Switch
The unit controller has an input that accepts a contact
closure from a proof-of-flow device such as a flow switch
or other factory approved flow proving device. When this
input does not prove flow within a fixed time relative to
transition from enabled to run modes of the chiller, or if the
flow is lost while the chiller is in the running mode of
operation, the chiller will be prohibited from running. The
installer must provide and install this flow proving device.
See also wiring diagrams attached to the inside of the
control panel door. Failure to provide this flow proving
device voids unit warranty.
Phase Seq. Lead Terminal ID
Black (Phase A) L1
Red (Phase B) L2
Yellow (Phase C) L3
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 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.
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