Page 23
XP15 SERIES
24 TUBES
UP
SLEEVE
AMBIENT SENSOR
− Extend tip
of plastic sensor just outside of
plastic sleeve.
Place ambient sensor and wire
from DCB inside of plastic sleeve
and route through gap between
corner post and coil support as
shown. Secure with wire tie.
WIRE TIE
COIL SENSOR
− Clip coil temperature sensor from the
DCB on the return bend shown on models as follows:
MODELS −024, −036 AND −042
MODELS −048 AND −060
12 TUBES
UP
NOTE − No discharge sensor used;
replaced by 10K resistor.
Figure 32. Heat Pump Unit Sensor Locations
Five−Strike Lockout Safety Function
The five−strike lockout safety function is designed to
protect the unit’s compressor from damage. The DCB
monitors for an active state on the DCB’s Y1 input as
referenced in figure 31 on page 21. When the Y1 input is
active the internal control logic of the DCB will do the
following:
S
Count any HI−PS and LO−PS pressure switch trips
(open and close).
S
If
a pressure switch trips four times during the current
active state on the Y1 input, then the DCB’s control
logic will reset the pressure switch trip counter to zero
at the end of currently active Y1 input state.
S
If the pressure switch opens for a fifth time during the
current Y1 input state, the DCB will enter a lockout
condition.
The system will require servicing to determine the cause of
the pressure switch condition. Once the condition has
been rectified, use the following procedure to reset the
DCB
.
DEFROST SYSTEM SENSORS
Sensors connect to the DCB through a field-replaceable
harness assembly that plugs into the DCB. Through the
sensors, the DCB detects outdoor ambient and coil
temperature fault conditions. As the detected temperature
changes, the resistance across the sensor changes.
Sensor resistance values can be checked by ohming
across pins shown in table 15.
NOTE − When checking the ohms across a sensor, be
aware that a sensor showing a resistance value that is not
within the range shown in table 15, may be performing as
designed. However, if a shorted or open circuit is detected,
then the sensor may be faulty and the sensor harness will
need to be replaced.
Table 15. Sensor Temperature / Resistance Range
Sensor
Temperature
Range °F (°C)
Resistance values
range (ohms)
Pins/Wire
Color
Outdoor
−35 (−37) to 120
(48)
280,000 to 3750
3 and 4
(Black)
Coil
−35 (−37) to 120
(48)
280,000 to 3750
5 and 6
(Brown)
Note: Sensor resistance increases as sensed temperature
decreases.
Ambient Sensor
The ambient sensor as illustrated in
figure 32 on page 23 considers outdoor temperatures
below −35°F (−37°C) or above 120°F (48°C) as a fault. If the
ambient sensor is detected as being open, shorted or out
of the temperature range of the sensor, the DCB will not
perform demand defrost operation. The DCB will revert to
time/temperature defrost operation and will display the
appropriate fault code. Heating and cooling operation will
be allowed in this fault condition.
Coil Sensor
The coil temperature sensor as illustrated
in figure 32 on page 23, considers outdoor temperatures
below −35°F (−37°C) or above 120°F (48°C) as a fault. If the
coil temperature sensor is detected as being open, shorted
or out of the temperature range of the sensor, the DCB will
not perform demand or time/temperature defrost
operation and will display the appropriate fault code.
Heating and cooling operation will be allowed in this fault
condition.
NOTE − Within a single room thermostat demand, if
five−strikes occur, the DCB will lock out the unit. The DCB’s
24 volt power R must be cycled OFF, or the TEST pins on
DCB must be shorted between 1 to 2 seconds to reset the
DCB.
DCB OPERATIONAL MODES
The DCB has four basic operational modes which are
TEST, NORMAL CALIBRATION and DEFROST.
