Electrical Connections; Low-Voltage Control Wire Connections; Low-Voltage Control Wire Sizing; Table 13 Design Refrigerant Pressures - Emerson Liebert Prop Fan Condensing Unit Installation, Operation And Maintenance Manual

2.6

Electrical Connections

Each unit is shipped from the factory with all internal wiring completed. All power, control wiring
and ground connections must be made in accordance with the National Electrical Code and local
codes. Refer to equipment nameplate regarding wire size and circuit protection requirements. Refer to
Figures 5, 7 and 8 and electrical schematic (reference Figures 9 through 11) when making connec-
tions. A manual electrical disconnect switch should be installed within 5 feet (1.6 m) of the unit in
accordance with codes.
WARNING
!
Use voltmeter to be sure power is turned off before making any electrical connections.
CAUTION
!
Three-phase power must be connected to the unit line voltage terminals in proper sequence so
that scroll compressor rotates in the correct direction.
The three-phase scroll compressor requires proper phasing to ensure correct motor rotation. The com-
ponent connections have been phase synchronized at the factory. Power phasing should be changed
only at the line voltage supply to the unit. To change phasing, switch any two power leads to the unit.
Observe system pressures to determine whether the unit is operating properly.
CAUTION
!
Apply power to condenser 8 hours before operating system. This time is required to allow
liquid refrigerant to be driven out of the compressor. This is especially important at low
ambient temperatures. The compressor crankcase heater is energized as long as power is
supplied to the unit.
Table 13 Design refrigerant pressures
Suction
Discharge
(At Design Ambient)
High Pressure Cutout
Table 14 Application limits
Input voltage
Minimum
-10%
-5% 208/230V
single-phase
2.6.1

Low-Voltage Control Wire Connections

Field-supplied four-wire control connection (10-wire on 8-ton units) is required between the outdoor
condensing unit and the evaporator. Refer to Figures 5, 7 and 8 and to unit electrical schematic and
Figures 9 through 11.
2.6.2

Low-Voltage Control Wire Sizing

Low-voltage wiring should be sized to allow a 1 volt maximum drop due to line resistance between the
evaporator and condensing unit. Use NEC Class 1 or 2 wiring according to wire routing conditions
chosen, local codes and application limits in Tables 14 and 15.
Table 15 Recommended minimum wire size
Max. Distance*
ft. (m)
50 (15)
100 (30)
150 (45)
* One-way control wire run between outdoor condensing unit and evaporator.
53 - 95 PSIG
(365 to 655 kPa)
280 psig (1930 kPa)
400 psig (2760 kPa)
Dry Bulb Air Temperature at Condenser
Maximum Minimum
+10% -30°F (-34°C)
Min. Wire Gauge
AWG (mm2)
20 (0.75)
18 (1.0)
16 (1.5)
Maximum
115°F (46°C) Std
Ambient & Quiet-Line
125°F (52°C)
High Ambient Models
21
Installation