Component Field Configuration And Troubleshooting - Lennox Signature XP21 Series Installation And Service Procedure

Component Field Configuration and
Troubleshooting
FAN MOTOR CONTROL (A177)
This section provides procedures for testing the fan con-
trol.
FAN MOTOR CONTROL LED CODES, JUMPER SET-
TINGS AND SEQUENCE OF OPERATION
During start up, the LED:
1. Display error conditions (see table 15), if present
2. If no errors are detected, then the LED code indicating
stage operation (see table 16) will display the applica-
ble code and then a long pause.
3. The fan motor speed / revolutions per minute (RPM) in-
dicator is displayed next (see table 17).
4. After the RPM indicator is displayed, there is a short
pause. The sequence repeats if a thermostat demand
is still present. See figure 20 for LED sequence. See
table 16 for description of flash and pause durations.
FAN MOTOR CONTROL TROUBLESHOOTING
Use the following subsections to verify and test the fan mo-
tor control (A177).
Verifying Jumper Settings (J2)
The unit is shipped from the factory with the default fan mo-
tor speed setting (in RPMs) required for each specific
model. Use table 17 to verify that jumpers are set correctly
for the specific size unit.
Verifying LED Status Codes
During start up, the fan motor control LED will dis-
play any error conditions. If error conditions exist
then no other codes will display. If no error condi-
tions are present, then the stage status and and RPM
indicator are displayed. Two−stage units have various
fan motor speed operations available (see table 17).
Verifying Correct DC Output Voltage (J2)
The following three methods can be used to determine
whether the fan motor (B4) is operating at the correct
RPMs based on unit size.
XP21
1. Use the information provided in table 17 to verify that
all four jumper terminals are set correctly for the specif-
ic unit.
2. Verify that the fan motor speed / RPM indicator is dis-
playing the correct flash sequence for the specific unit
(see table table 17).
3. Test DC voltage output on the fan motor control's J2
terminals (see figure 21) while under full load. The ac-
tual voltage tested should match the voltage listed in
table 17 for the specific unit.
4. If no voltage is detected at the J2 terminals, verify there
is a Y1 demand at the thermostat.
If there is a demand, proceed to the next section for further
testing.
VERIFYING CORRECT INPUT VOLTAGE (ECM/Y1,
ECM/Y2, ECM C AND EXT ECM/R)
Use a voltmeter to check voltages on the following fan mo-
tor control inputs, using either table 13. Voltage will only be
present during a thermostat demand. See figure 22 for test
example.
If correct voltages are detected at the applicable inputs dur-
ing a demand, and no voltage is present at the J2 terminals,
then the fan motor control (A177) should be replaced.
Table 13. Fan Motor Control Voltage Inputs
Input
ECM/Y1 and ECM C
(Low Stage)
ECM/Y1 − ECM/Y2 and
ECM C
(High Stage)
ECM/Y2 and ECM C
(EDA Operation)
EXT ECM/R and ECM C
Page 38
Thermostat Voltage
Demand Present
Between
24VDC and 32
YES
VDC
NO NONE
Between
24VDC and 32
YES
VDC at each
input
NONE at each
NO
input
Between
24VDC and 32
YES
VDC
NO NONE
YES 24VAC
NO NONE