Bryant Legacy 549J 12 Series, Руководство по установке

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Fig. 34 — Typical Low-Voltage Control Connections
COMMERCIAL DEFROST CONTROL
The Commercial Defrost Control Board (DFB) coordinates
thermostat demands for supply fan control, 1 or 2 stage cool -
ing, 2 stage heating, emergency heating and defrost control
with unit operating sequences. The DFB also provides an in -
door fan off delay feature (user selectable). See Fig. 35 for
board arrangement.
The DFB is located in the 549J unit’s main control box (see
Fig. 2 and 36). All connections are factory-made through har -
nesses 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 6 for details of DFB Inputs and
Outputs.
Fig. 35 — Defrost Control Board Arrangement
Reversing valve control
The DFB has two outputs for unit reversing valve control. Oper -
ation of the reversing valves is based on internal logic; this appli -
cation does not use an “O” or “B” signal to determine reversing
valve position. Reversing valves are energized during the cool -
ing stages and the defrost cycle and de-energized during heating
cycles. Once energized at the start of a cooling stage, the revers -
ing valve will remain energized until the next heating cycle de -
mand is received. Once de-energized at the start of a Heating cy -
cle, the reversing 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 (RTU Open controller); it generates commands
to start compressors with or without reversing valve operation
to produce Stage 1 Cooling (one compressor runs), Stage 2
Cooling (both compressors run) or Stage 1 Heating (both com -
pressors run).
Auxiliary (Electric) Heat control
The 549J unit can be equipped with one or two auxiliary elec -
tric heaters, to provide a second stage of heating. The DFB will
energize this Heating System for a Stage 2 Heating Command
(heaters operate concurrently with compressor(s) in the Stage 1
Heating cycle), for an Emergency Heating sequence (compres -
sors are off and only the electric heaters are energized) and also
during the Defrost cycle (to eliminate a “cold blow” condition
in the space).
X
C
G
W2
R
C
W2
G
W1
O/B/Y2
Y2
W1
R
Y1 Y1
Typical
Thermostat
Connections
T
H
E
R
M
O
S
T
A
T
(Note 1)
(Note 2)
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
Central
Terminal
Board
NOTES:
DIP
SWITCHES
SPEED-UP
JUMPERS