Defrost Termination; Outdoor Fan Control - Lennox MPA009S4S Service Manual

31.4. Defrost Termination

Defrost will terminate if:
T2 is greater than 64.4°F.
T3 is between 64.4°F and 43.4°F for 80 seconds.
System has been in defrost for 10 minutes.
Run-time count starts
0
This formula depends on humidy. The higher the humidity, the more frequent the defrost cycles. With no humidity, there
will be less frost build-up. Defrost is a function of humidity.

31.5. Outdoor Fan Control

31.5.1. Cooling Mode
Normally the system will choose the running fan speed according to ambient temperature:
Compressor
X1 10S
4-Way valve
Outdoor fan
After 29 min-
utes of run-time
T3 time
mea-
and T3+5.4°F is
sured
still less than or
and T3
equal to T30.
temp
deter-
mined
14 minutes
15
10
After first 15 minutes of
operation, if T3 <
19.4°F then defrost,
otherwise monitor T3
for next 14 minutes.
T4
A
28℃
26℃
B
25℃
23℃
C
22℃
20℃
D
19℃
17℃
E
X2
10S
T3 < 19.4°F
After 40 minutes of run-time
T3 < 11.2°F.
6 min
5 min
35
29 < 30 40
After 36 minutes of
run-time T3 < 23°F and
T3+5.4°F is still less than
or equal to T30.
DC_FAN_HI_SPD_ADD
DC_FAN_MID_SPD_ADD
DC_FAN_MIN_SPD_ADD
DC_FAN_SLOW_SPD_ADD
DC_FAN_SSLOW_SPD_ADD
164
2 Hours
2 hours have passed
and T3 < 5°F.