Installation, Operation and Maintenance 3 - 3
Other Supply Power Components
Fused Disconnect Switches
Size fused disconnects in accordance with NEC
Article 440-22(a).
Compressor Motor Phase Sequencing
Always verify that proper rotation of the Series R
compressor is established before the machine 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 incoming power supply phased A, B, C.
To confirm the correct phase sequence (ABC), use a
Model 45 Associated Research Phase indicator or
equivalent.
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.
Correcting Improper Electrical Phase
Sequence
Proper compressor motor electrical phasing can be
quickly determined and corrected before starting the
unit. If using an Associated Research Model 45
Phase Sequence Indicator, follow this procedure:
1 Press the STOP button to insure the unit will not
attempt to start the compressor.
2 Open the electrical disconnect or circuit protection
switch that provides line power to the line power
terminal block in the control panel (or to the unit-
mounted disconnect).
3 Connect the phase sequence indicator leads to
the line power terminal block (or the unit mounted
disconnect) as follows:
4 Turn power on by closing the unit supply power
disconnect switch.
5 Read the phase sequence on the indicator. The
“ABC” indicator on the face of the phase indicator
will glow if phase is “ABC”.
WARNING
Hazardous Voltage! Disconnect all
electrical power, including remote
disconnects before servicing. Fail-
ure to disconnect power before
servicing can cause severe per-
sonal injury or death.
6 If the “CBA” indicator glows instead, open the unit
main power disconnect and switch two line leads
on the line power terminal block (or the unit
mounted disconnect). Reclose the main power
disconnect and recheck phasing.
7 Reopen the unit disconnect and disconnect the
phase indicator.
Compressor Motor Power Wiring
Provide line voltage wiring from the starter/control
panel to the proper terminals in the compressor
motor junction box. See
Figure 22
and
Table 12
for
motor wire sizing information.
Terminal Lugs.
Proper starter/control panel line-side lug sizes are
specified on the starter submittals. These lug sizes
must be compatible with conductor sizes specified by
the electrical engineer or contractor. Appropriate lug
sizes are provided.
Rated Load Ampacity (RLA)
The compressor motor RLA for a particular chiller is
determined by the field selection program and
indicated on the compressor nameplate.
Phase Seq. Lead 1TB1 Terminal
Black (Phase A) L1
Red (Phase B) L2
Yellow (Phase C) L3
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