Lennox XP21 Series Installation Instructions Manual page 52

HEAT PUMP
CONTROL (A175)
VDC
VAC
ONE YELLOW WIRE FROM PS (E24) TERMINAL ON HEAT PUMP
CONTROL. AND SECOND YELLOW WIRES ON PIGGYBACK
TERMINALS GOES TO S4 HIGH PRESSURE SWITCH.
GREEN
RED
RED
YELLOW
YELLOW
Figure 36. Testing for External Power to Fan Motor Control (A177)
506601−01
FAN MOTOR CONTROL (A177)
PULSE−WIDTH MODULATION (PWM)
BLUE WIRE
24
BLACK WIRE
YELLOW
S4 HIGH PRESSURE SWITCH
HEAT PUMP CONTROL
CONTROL BOX
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 52
GREEN
RED
RED
BLACK
BROWN
FAN MOTOR
CONTROL
SEE TABLE 15 FOR CFM PROFILE
SELECTION OPTIONS.
B4 FAN
MOTOR