Outdoor Fan Control - Lennox MMA018SM4 Service Manual

19.8. Outdoor Fan Control

19.8.1. Cooling Mode
Normally the system will choose the running fan speed according to ambient temperature:
When low ambient cooling is valid:
Outdoor fan speed control logical (low ambient cooling).
When T4 <15°C (59°F) and T3 < 30°C (86°F), the unit will enter into low ambient cooling mode. The outdoor fan will
choose speed according to T3.
When T3≥38°C (100.4°F) or when T4≥20°C (68°F), the outdoor fan will choose the speed according to T4 again.
T4
A
28℃
26℃
B
25℃
23℃
C
22℃
20℃
D
19℃
17℃
E
High
27
25
20
Low
15
low ambient cooling
Exit low ambient cooling
mode , run with high fan
38
for 1 minute
27
Low
off
82
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
30
23