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C09276
Fig. 27 -- Defrost Control Board (DFB) Location
Table 9 – 548J Defrost Board I/O and Jumper Configurations
Inputs
Point Name Type of I/O Conne ction Pin Number Unit Connection Note
GFan DI, 24 --- vac P2 --- 3 LCTB --- G
Y1 Cool 1 DI, 24 --- vac P2 --- 5 LCTB --- Y1
Y2 Cool 2 DI, 24 --- vac P2 --- 4 LCTB --- Y2
W1 Heat 1 DI, 24 --- vac P2 --- 7 LCTB --- W1
W2 Heat 2 DI, 24 --- vac P2 --- 6 LCTB --- W2
RPower 24 --- vac P3 --- 1 CONTL BRD --- 8
C Common 24 --- vac P3 --- 2 CONTL BRD --- 4
DFT1 DI, 24 --- vac DF T --- 1 to DFT --- 1
DFT 2 DI, 24 --- vac DF T --- 2 to DFT --- 2
Output s
Point Name Type of I/O Conne ction Pin Number Unit Connection Note
IFO F an On DO, 24 --- vac P3 --- 9 REHEAT --- 2
OF OD Fan On DO, 24 --- vac OF OFR
RVS1 DO, 24 --- vac P3 --- 7 to P3 --- 5 Energize in COOL
RVS2 DO, 24 --- vac P3 --- 6 to P3 --- 4 Energize in COOL
COMP 1 DO, 24 --- vac P3 --- 10 FPT --- REHEAT --- 6
COMP 2 DO, 24 --- vac P3 --- 8 REHEAT --- 8
HEAT 2 DO, 24 --- vac E --- HEAT HC --- 1 (TB4 --- 1)
COM 24 --- vac P3 --- 3 HC --- 1 (TB4 --- 3)
Configuration
Point Name Type of I/O Conne ction Pin Number Unit Connection Note
Select Jumper 24 --- vac P1 --- 1
2 Compresso r 24 --- vac P1 --- 3 Use for 548J***D
Speed--Up Configuration
Point Name Type of I/O Conne ction Pin Number Unit Connection Note
Speed---Up Jumper JMP17
Speed---Up Jumper JMP18
Jumper for 1--3 secs: Factory Test, defrost runs for 9 secs
Jumper for 5--20 secs: For ced Defrost, defrost runs for 30 secs if DFT2 is open
Reversing valve control — The DFB has t wo outputs for
unit re versing valve control. Operation of the re versing
valve s is based on internal logic; this appl ication does not
use an “O” or “B” signal to determine reversing valve
position. Reversing valves are energized during the
Cooling stages and de--energized during Heating cyc les.
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 reversing valves will
remain de -- energized until the next Cooling stage is
initiated.
Compressor control — The DFB receives i nputs
indicating Stage 1 Cooling, Stage 2 Cooling (sizes 08 and
09 only) and Stage 1 Heating from t he space thermostat or
unit control system (RTU--MP); it generates commands to
start compressors with or wit hout reversing valve
operation to produce Stage 1 Cooling (one compressor),
Stage 2 Cooling (both compressors run) or Stage 1
Heating (both compressors run).
548J