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Typical
Thermostat
Connections
C
G
W2
(Note 2)
W1
O/B/Y2
(Note 1)
Y1
R
Notes:
1. Typical multi-function marking. Follow manufacturer's configuration
instructions to select Y2. Do not configure for O output.
2. W2 connection not required on units without electric heating.
Field Wiring
Fig. 27 — Typical Low-Voltage Control Connections
Thermostat Wiring, Units Without Thru-Base Connection Kit
Pass the thermostat control wires through the hole provided in the
corner post; then feed the wires through the raceway built into the
corner post to the control box. Pull the wires over to the terminal
strip on the upper-left corner of the Controls Connection Board.
See Fig. 28.
NOTE: If thru-the-bottom connections accessory is used, refer to
the accessory installation instructions for information on routing
power and control wiring.
RACEWAY
HOLE IN END PANEL (HIDDEN)
Fig. 28 — Field Control Wiring Raceway
Central
Terminal
Board
X
C
T
H
G
E
R
W2
M
O
W1
S
T
Y2
A
T
Y1
R
19
HEAT ANTICIPATOR SETTINGS
Set heat anticipator settings at 0.14 amp for the first stage and 0.14
amp for second-stage heating, when available.
COMMERCIAL DEFROST CONTROL
The Commercial Defrost Control Board (DFB) coordinates ther-
mostat demands for supply fan control, 1 or 2 stage cooling, 2
stage heating, emergency heating and defrost control with unit op-
erating sequences. The DFB also provides an indoor fan off delay
feature (user selectable). See Fig. 29 for board arrangement.
Fig. 29 — Defrost Control Board Arrangement
The DFB is located in the 549J unit's main control box (see
Fig. 30). All connections are factory-made through harnesses to
the unit's CTB, to IFC (belt-drive motor) or to ECM (direct-drive
motor), reversing valve solenoids and to defrost thermostats. Refer
to Table 3 for details of DFB Inputs and Outputs.
Reversing valve control
The DFB has two outputs for unit reversing valve control. Opera-
tion of the reversing valves is based on internal logic; this applica-
tion does not use an "O" or "B" signal to determine reversing
valve position. Reversing valves are energized during the cooling
stages and the defrost cycle and de-energized during heating cy-
cles. Once energized at the start of a cooling stage, the reversing
valve will remain energized until the next heating cycle demand is
received. Once de-energized at the start of a Heating cycle, the re-
versing valves will remain de-energized until the next cooling
stage is initiated.
Compressor control
The DFB receives inputs indicating Stage 1 Cooling, Stage 2
Cooling and Stage 1 Heating from the space thermostat or unit
control system (PremierLink™ controller or RTU Open control-
ler); it generates commands to start compressors with or without
reversing valve operation to produce Stage 1 Cooling (one com-
pressor runs), Stage 2 Cooling (both compressors run) or Stage 1
Heating (both compressors run).
DIP
Switches
Speed-Up
Jumpers
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