Lennox XC21 Series Unit Information page 41

Field Configuration and Testing
This section provides procedures for configuring, adjusting
and testing various components of this unit.
S
Fan Motor (B4) Test Procedure
S
Fan Motor Control (A177) Configuration and Testing
S
Top Grille and Fan Motor Mounting Adjustment (Fan
Clearance)
S
Heat Pump Control (A175) Unit Nominal Capacity
Code configuration
B4 FAN MOTOR TEST
See figure 24 for procedures on test the B4 fan motor.
FAN MOTOR CONTROL (A177) LED CODES AND
SEQUENCE OF OPERATION
AND LATER
During start up, the LED:
1. Display error conditions (see table 13), if present
2. If no errors are detected, then the LED code indicating
stage operation (see table 14) will display the
applicable code and then a long pause.
3. The fan motor speed / RPM (revolutions per minute)
indicator is displayed next (see table 15).
4. After the RPM indicator is displayed, there is a short
pause. The sequence repeats if a thermostat demand
is still present. See figure 21 for LED sequence. See
table 12 for description of flash and pause durations.
FAN MOTOR CONTROL TROUBLESHOOTING
XC21−XXX−230−05 AND LATER
Use the following subsections to verify and test the fan
motor control (A177).
Verifying Jumper Settings (J2)
The unit is shipped from the factory with the default motor
RPM setting required for the specific model size. Use the
table 15 for two−stage operation 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
display any error conditions. If error conditions exist
then no other codes will display. If no error
conditions are present, then the stage status and and
RPM indicator are displayed. Two−stage units have
various fan motor speed operations available (see table
15).
XC21−XXX−230−05
Page 41
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.
1. Use the information provided in table 11 to verify that
all four jumper terminals are set correctly for the
specific size unit.
2. Verify LED RPM indicator is displaying the correct flash
sequence for the applicable size unit (see table table
15).
3. Test DC voltage output on the fan motor control's J2
terminals (see figure 22) while under full load and verify
the voltage read to the voltage listed in table 15 for the
applicable size unit.
4. If no voltage is detected at the J2 terminals, verify there
is a Y1 demand at the thermostat and applicable
voltages detected all fan motor control voltage inputs,
see table 11.
NOTE Voltage will be present at specific inputs
depending on the type of demand (low or high stage
and EDA operation).
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)
XC21−XXX−230−05 AND LATER
Using a volt meter, check voltages on the following fan
motor control inputs using table 11. Voltage will only be
present during a thermostat demand. See figure 23 for test
example.
If correct voltages are detected at applicable inputs during
a demand, and no voltage is present at the J2 terminals,
then fan motor control should be replaced.
Table 11. 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
Thermostat Voltage
Demand Present
YES 24VDC
NO NONE
24VDC at each
YES
input
NONE at each
NO
input
YES 24VDC
NO NONE
YES 24VAC
NO NONE
XC21