Lennox XP21 Series Installation Instructions Manual page 49

Table 15. Fan Motor Control RPM, LED Code and DC Voltage Output
CFM Profile Pin Select
Application
4
XP21−024 ON
XP21−036 ON
XP21−048 ON
XP21−060 ON
* LED Code indicates Fan Motor Control LED flash sequence. For example, LED Code 9 indicates 9 slow flashes and pause.
Table 16. Fan Motor Control Error/Fault LED Codes
Unit Status Motor Control LED
Fast flash with no
Mismatched RPM
CRC Failure Constant ON.
Table 17. Fan Motor Control Stage LED Indicator
Unit Status Unit Status
Low Stage
ECM1/Y1 ONLY
High Stage
Two Stage
ECM1/Y1 and
Operation
ECM2/Y2
EDA Operation
ECM2/Y2 ONLY
Table 18. Fan Motor Control Flash and Pause
Durations
Flash or Pause State
Flash Flash
Slow Flash
Short Pause
Long Pause
Testing
Use the following information to verify and test the fan
motor control (A177).
Verify Jumper Settings (J2)
The unit is shipped from the factory with the default fan
motor speed setting (in RPMs) required for each model.
Use table 15 to verify that jumpers are set correctly for the
unit being installed.
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
3 2 1 RPM
ON OFF ON
OFF ON ON
OFF OFF ON
OFF OFF OFF
Possible Cause
Internal feedback,
PWM does not
pause
match target
Microcontroller CRC
failure
Codes
Motor Control LED
One slow flash, then
short pause
Two slow flash, then
short pause
Three slow flash,
then short pause
Duration
Three flashes per second
One flash per second
Two seconds of OFF time
Five seconds of OFF time
Table 19. Fan Motor Control Voltage Inputs
Low Stage ECM1/Y1
Only
LED
DC Volt RPM
Code
425 6 13.6
525 7 16.8
600 8 19.2
625 8 20.0
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 in sequence. Two−stage units have
various fan motor speed operations available (see table
15).
Verify 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 15 to verify that all
four jumper terminals are set correctly for the specific
unit.
2. Verify that the fan motor speed / RPM indicator is
displaying the correct flash sequence for the specific unit
(see table table 15).
3. Test DC voltage output on the fan motor control's J2
terminals (see figure 35) while under full load. The actual
voltage tested should match the voltage listed in table 15
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.
Verify Correct Input Voltage
ECM C AND EXT ECM/R) Terminals
Use a voltmeter to check voltages on the following fan
motor control inputs, using table 19. Voltage will only be
present during a thermostat demand. See figure 36 for test
example.
If correct voltages are detected at the applicable inputs
during a demand, and no voltage is present at the J2
terminals, then the fan motor control should be replaced.
Thermostat Demand Voltage Present
YES Between 24VDC and 32 VDC
NO NONE
YES Between 24VDC and 32 VDC at each input
NO NONE at each input
YES Between 24VDC and 32 VDC
NO NONE
YES 24VAC
NO NONE
Page 49
High Stage ECM1/Y1
and ECM2/Y2
LED
DC Volt RPM
Code
500 7 16.0
600 8 19.2
675 9 21.6
700 10 22.5
Verify LED Status Codes
EDA Operation
ECM2/Y2 Only
LED
DC Volt
Code
200 3 6.3
225 3 7.0
225 3 7.0
225 3 7.0
(ECM/Y1, ECM/Y2,
XP21 SERIES