DB7110U UNIVERSAL HEAT PUMP DEFROST CONTROLLER
3 34-00032—01
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.
Fig. 5. Wiring diagram with pressure switches 
connected to defrost control.
Fig. 6. Wiring diagram for systems with no low 
pressure switch.
Fig. 7. Wiring diagram for systems with pressure 
switches in series with the contactor and no 
connection to the defrost control.
Name Function
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
(2 Terminals)
High pressure cutout/switch – these 
terminals must be shorted for 
compressor operation. Never 
bypass protective pressure 
switches.
LPC
(2 Terminals)
High pressure cutout/switch – these 
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
(2 Terminals)
Output to compressor contactor – 
energized by Y request.
RV
(2 Terminals)
Output to reversing valve – 
energized by O input and as 
required by a defrost cycle. 
LPC
HPC
CONTACTOR
AUX
REVERSING
VALVE
FAN-IN
FAN-OUT
R
C
O/B
W
Y
AIR
SENSOR
(OPTIONAL)
COIL
SENSOR 
INDOOR
EQUIPMENT
OUTDOOR
EQUIPMENT
FAN
DB7110U
L1
L2
COMPR
RV
HIGH
PRESSURE
SWITCH
LOW
PRESSURE
SWITCH
AIR
COIL
M37756
LPC
HPC
CONTACTOR
UX
REVERSING
VALVE
FAN-IN
FAN-OUT
R
C
O/B
W
Y
AIR
SENSOR
(OPTIONAL)
COIL
SENSOR 
INDOOR
EQUIPMENT
OUTDOOR
EQUIPMENT
FAN
DB7110U
L1
L2
COMPR
RV
HIGH
PRESSURE
SWITCH
AIRCOIL
M37757
LPC
HPC
CONTACTOR
AUX
REVERSING
VALVE
FAN-IN
FAN-OUT
R
C
O/B
W
Y
AIR
SENSOR
(OPTIONAL)
COIL
SENSOR
INDOOR
EQUIPMENT
OUTDOOR
EQUIPMENT
FAN
DB7110U
L1
L2
COMPR
RV
HIGH
PRESSURE
SWITCH
LOW
PRESSURE
SWITCH
AIRCOIL
IF THE PRESSURE SWITCH(ES) ARE IN SERIES 
WITH THE CONTACTOR, JUMPER THE 
ONBOARD CONNECTIONS. DO NOT BYPASS
ANY PROTECTIVE PRESSURE SWITCHES. 
M37758