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3. Check the line voltage connections on the fan
relay to ensure they are tight, in good connec-
tion, and more than 1/4" away from any part of
the appliance enclosure.
4. Plug in the outdoor sensor (if used) and the coil
sensor.
5. Reference the wiring diagrams in Figs. 5 to 8 to
aide in proper appliance wiring.
Table 1. Class 2 Low Voltage Terminations,
24V 60Hz.
Name
R (24V)
24V Hot
C (COM)
24V Common
W
Aux/emergency heat request from
thermostat – W requests will cause
the AUX output to be energized.
Y
Compressor request from
thermostat – Y requests will cause
the COMPR and FAN terminals to be
energized.
O
Reversing valve request from
thermostat – controls the status of
the RV output.
HPC
High pressure cutout/switch – these
(2 Terminals)
terminals must be shorted for
compressor operation. Never
bypass protective pressure
switches.
LPC
High pressure cutout/switch – these
(2 Terminals)
terminals must be shorted for
compressor operation. Never
bypass protective pressure
switches.
AUX
Output to auxiliary/emergency heat
– energized during a defrost cycle or
when requested by W input.
COMPR
Output to compressor contactor –
(2 Terminals)
energized by Y request.
RV
Output to reversing valve –
(2 Terminals)
energized by O input and as
required by a defrost cycle.
INDOOR
DB7110U
EQUIPMENT
AUX
R
C
O/B
W
Y
COIL
AIR
Fig. 5. Wiring diagram with pressure switches
connected to defrost control.
Function
OUTDOOR
EQUIPMENT
FAN
FAN-OUT
L2
FAN-IN
L1
REVERSING
RV
VALVE
COMPR
CONTACTOR
HIGH
HPC
PRESSURE
SWITCH
LOW
LPC
PRESSURE
SWITCH
AIR
SENSOR
(OPTIONAL)
COIL
SENSOR
DB7110U UNIVERSAL HEAT PUMP DEFROST CONTROLLER
INDOOR
EQUIPMENT
AUX
R
C
O/B
W
Y
Fig. 6. Wiring diagram for systems with no low
INDOOR
EQUIPMENT
AUX
R
C
O/B
W
Y
Fig. 7. Wiring diagram for systems with pressure
switches in series with the contactor and no
connection to the defrost control.
M37756
3
DB7110U
FAN-OUT
FAN-IN
RV
COMPR
HPC
LPC
COIL
AIR
pressure switch.
DB7110U
FAN-OUT
FAN-IN
RV
COMPR
HPC
LPC
COIL
AIR
IF THE PRESSURE SWITCH(ES) ARE IN SERIES
WITH THE CONTACTOR, JUMPER THE
ONBOARD CONNECTIONS. DO NOT BYPASS
ANY PROTECTIVE PRESSURE SWITCHES.
OUTDOOR
EQUIPMENT
FAN
L2
L1
REVERSING
VALVE
CONTACTOR
HIGH
PRESSURE
SWITCH
AIR
SENSOR
(OPTIONAL)
COIL
SENSOR
M37757
OUTDOOR
EQUIPMENT
FAN
L2
L1
REVERSING
VALVE
HIGH
PRESSURE
SWITCH
LOW
PRESSURE
SWITCH
CONTACTOR
AIR
SENSOR
(OPTIONAL)
COIL
SENSOR
M37758
34-00032—01
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