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The unit power fused disconnect switch should be
located in the general area of the unit, to comply
with NEC or local codes. Some codes require line-
of-sight disconnect locations. The unit mounted
non-fused disconnect can be used as an emergency
shutdown device.
Scroll Compressor Electrical Phasing
Compressor Damage!
Operating compressors in reverse rotation will
cause damage or failure of the compressor.
It is critical that proper rotation of the scroll
compressors be 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 the inlet
power supply phased “ABC” or “L1, L2, L3”.
The order in which the three voltage waveforms of
a three-phase system succeed one another is called
phase sequence or phase rotation. When rotation is
clockwise, phase sequence is usually called
“ABC” and when counterclockwise, “CBA”.
This direction may be reversed by interchanging
any two of the line wires. The possibility of
interchanging the wiring makes a phase sequence
indicator necessary to quickly determine the
proper phase rotation.
Setting the Proper Electrical Phase Sequence
Proper compressor motor electrical phasing can be
quickly determined and, if necessary, corrected
before starting the unit. Use a quality instrument,
such as an Associated 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. Turn power to FWCD unit “Off” using
supply power disconnect to the unit. Verify
that power to FWCD unit is “Off” and that
there is no voltage on “Line” or entering
side of the FWCD panel mounted unit
disconnect.
3. Connect the phase sequence indicator
leads to the “Load” or leaving side of the
FWCD unit panel mounted disconnect as
follows:
4. Turn power to FWCD unit “On” using the
supply power disconnect to the unit
5. Read the phase sequence displayed 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, turn
power to FWCD unit “Off” using the
supply power disconnect to the unit, then
verify that the power to the FWCD unit is
“Off” and that there is no voltage on the
“Line” side of the FWCD panel mounted
unit disconnect. Reverse two wires on the
“Line” or entering side of the FWCD panel
mounted disconnect switch. Turn power to
FWCD unit “On” and recheck phase
sequence (Step 5 preceding).
7. If phase sequence is correct, turn power to
FWCD unit “Off” using the supply power
disconnect to the unit. Verify that power to
the FWCD unit is “Off” and that there is no
voltage on “Line” or entering side of the
FWCD panel mounted unit disconnect.
Remove the phase indicator and restore
power to the FWCD unit.
Control Power Supply
A fused, panel-mounted control power
transformer is standard. Replacement fuse
information is listed on the “Fuse Schedule” decal
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General