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Electrical - Circuit Sizing and Wire Routing
In the U.S.A., wiring must conform with current local codes
and the current National Electric Code (NEC). In Canada,
wiring must conform with current local codes and the
current Canadian Electrical Code (CEC).
Refer to the furnace or air handler installation instructions
for additional wiring application diagrams and refer to unit
nameplate for minimum circuit ampacity and maximum
overcurrent protection size.
24VAC Transformer
Use the transformer provided with the furnace or air handler
for low-voltage control power (24VAC - 40 VA minimum).
Thermostat Control and Low Voltage
Control Wiring
Thermostat Control Options
The 4SCU23LX variable capacity units provide two
thermostat control options to provide application and
installation flexibility.
Comfort Sync A3 Communicating Thermostat Control
The 4SCU23LX variable capacity unit may be installed
as a fully communicating Comfort Sync system consisting
of Comfort Sync A3 Communicating Thermostat, a
Comfort Sync-enabled indoor unit and the 4SCU23LX
variable capacity outdoor unit wired with (4) Comfort Sync
communication wires (R, I+, I- and C) connected to the
4SCU23LX Outdoor Unitary Control.
The 4SCU23LX variable capacity unit when wired as a
fully communicating Comfort Sync system will take full
advantage of the advanced diagnostics and control, Wi-
Fi accessibility and system operation parameters. Refer to
the 4SCU23LX field wiring diagram for a Comfort Sync A3
communicating thermostat.
Conventional 24VAC Non-Communicating Thermostat
Control
The 4SCU23LX variable capacity unit may be installed
using a conventional 24VAC non-communicating two-
stage cooling or single-stage cooling thermostat.
NOTE: The conventional 24VAC non-communicating
thermostat must have a compressor minimum on time of
three minutes to prevent compressor short cycling.
The 4SCU23LX unit will provide full variable capacity
operation when installed with a conventional 24VAC non-
communicating two stage cooling or single-stage cooling
thermostat. The 4SCU23LX outdoor control has advanced
control algorithms using the 4SCU23LX suction pressure
sensor to provide true variable capacity operation.
Page 14 of 25
When utilizing a two-stage conventional 24VAC non-
communicating thermostat, four wires are required to
control the outdoor unit (R, C, Y1 and Y2). Refer to the
4SCU23LX field wiring diagram for a conventional 24VAC
non-communicating 2-stage thermostat.
When utilizing a single conventional 24VAC non-
communicating thermostat, three wires are required
to control the outdoor unit (R, C, and Y1) and Y1 is
jumpered to Y2 in the outdoor unit. Note that the published
performance data is based upon the use of a two-stage
thermostat. Refer to the 4SCU23LX field wiring diagram
for a conventional 24VAC non-communicating single-stage
thermostat.
4SCU23LX Low Voltage Control Wiring
Connections
The 4SCU23LX variable capacity units are provided with
(2) RAST 6-Pin connections in the installation instruction
bag for connecting the field low voltage control wiring to the
4SCU23LX harnesses in the low voltage control make-up
box. One RAST 6-pin connector is labeled with terminals
TST, DF, R, I+, I- and C. The second RAST 6-pin connector
is labeled with terminals DS, O, Y1, Y2, L and W.
Electrical Shock Hazard!
Can cause injury or death. Unit must be
properly grounded in accordance with
national and local codes.
Line voltage is present at all components
when unit is not in operation on units
with single-pole contactors. Disconnect
all remote electric power supplies before
opening access panel. Unit may have
multiple power supplies.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
Electrostatic discharge can affect electronic components.
Take care during unit installation and service to protect
the unit's electronic controls. Precautions will help to
avoid control exposure to electrostatic discharge by
putting the unit, the control and the technician at the
same electrostatic potential. Touch hand and all tools
on an unpainted unit surface before performing any
service procedure to neutralize electrostatic charge.
Issue 2231
WARNING
WARNING
508296-01
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