Lennox XC21 Installation Instructions Manual page 46

A175 MAIN
CONTROL
VDC
VAC
ONE YELLOW WIRE FROM PS (E24) TERMINAL ON A175 MAIN
CONTROL. AND SECOND YELLOW WIRES ON PIGGYBACK
TERMINALS GOES TO S4 HIGH PRESSURE SWITCH.
GREEN
RED
RED
YELLOW
YELLOW
506518−01
A177 FAN MOTOR CONTROL
PULSE−WIDTH MODULATION (PWM)
BLUE WIRE
24
BLACK WIRE
YELLOW
S4 HIGH PRESSURE SWITCH
A175 MAIN CONTROL
Figure 25. Testing for External Power to A177 Fan Motor Control
CONTROL PANEL
INPUT VOLTAGES DURING DEMAND
ECM/Y1 ONLY − 24VDC
BOTH ECM/Y1 AND ECM/Y2 − 24VDC AT EACH INPUT
ECM/Y2 ONLY − 24VDC
YELLOW WIRE
EXT PWR/R (24VAC INPUT
DURING DEMAND ONLY)
YELLOW
BLUE
BLACK
YELLOW
YELLOW
Page 46
GREEN
RED
RED
B4 FAN
MOTOR
BLACK
BROWN
A177 FAN
MOTOR
SEE TABLE 16 FOR CFM PROFILE
CONTROL
SELECTION OPTIONS.