Page 21
XP15 SERIES
LSOMLED Functions
IMPORTANT
This monitor does not provide safety protection.
The monitor is a monitoring device only and cannot
control or shut down other devices
.
See table 13 on page 20 for the complete explanation of
troubleshooting codes.
LED
Color
Function
Description
Green
Power
Indicates
voltage within the range of
19−28VAC is present at LSOM con-
nection.
Yellow
Alert
Communicates an abnormal system
condition through a unique flash code.
The alert LED flashes a number of
times consecutively; then pauses;
then repeats the process. This
consecutive flashing correlates to a
particular abnormal condition.
Red
Trip
Indicates there is a demand signal
from the thermostat but no current to
the compressor is detected by the
LSOM.
Resetting Alert Codes
Alert codes can be reset manually or automatically:
Manual
Cycle the 24VAC power to LSOM off and on. Af-
ter power up, existing code will display for one
minute and then clear.
Automatic
After an alert is detected, the LSOM continues
to monitor the compressor and system. When/if
conditions return to normal, the alert code is
turned off automatically.
LSOML Terminal Connection
The L connection is used to communicate alert codes to
the room thermostat. On selected
Lennox SignatureStat
t
thermostats, a blinking check LED will display on the room
thermostat and on select White-Rodgers room
thermostats, an icon on the display will flash. Either will
flash at the same rate as the LSOM yellow alert LED.
NOTE − ROOM THERMOSTATS WITH SERVICE OR
CHECK LIGHT FEATUREThe room thermostat may
blink the Check or Service LED or it may come on solid.
Confirm fault by observing and interpreting the code from
the LSOM yellow alert LED at the unit.
Defrost System
DEFROST CONTROL BOARD (DCB) FUNCTION
The DCB measures differential temperatures to detect
when the system is performing poorly because of ice
build−up on the outdoor coil. The DCB self−calibrates when
the defrost system starts and after each system defrost
cycle. The DCB components are illustrated in figure 31.
24V TERMINAL
STRIP
CONNECTIONS
DIAGNOSTIC
LEDS
PRESSURE
SWITCH
CIRCUIT
CONNECTIONS
TEST PINS
Note − Component Locations Vary by Board Manufacture
r.
SENSOR
PLUG IN (COIL
AND AMBIENT
SENSORS)
REVERSING
VALVE
DELAY
PINS
LOW
AMBIENT
THERMOSTAT
PINS
DEFROST
TERMINATION
PIN SETTINGS
Figure 31. Defrost Control Board (DCB)
The DCB monitors ambient temperature, outdoor coil
temperature, and total run time to determine when a
defrost cycle is required. The coil temperature probe is
designed with a spring clip to allow mounting to the outside
coil tubing. The location of the coil sensor is important for
proper defrost operation.
NOTE − The DCB accurately measures the performance of
the system as frost accumulates on the outdoor coil. This
typically will translate into longer running time between
defrost cycles as more frost accumulates on the outdoor
coil before the DCB initiates defrost cycles.
Pressure Switch Connections
The unit’s automatic reset pressure switches (LO PS − S87
and HI PS − S4) are factory−wired into the DCB on the
LO−PS and HI−PS terminals, respectively.
Pressure Switch Event Settings
The following are the auto reset event values for low and
high pressures thresholds:
S
High Pressure
(auto reset) − trip at 590 psig, reset to
418 psig.
S
Low Pressure
(auto reset) − trip at 25 psig, reset to 55
psig.
