Outdoor Fan Control; Cooling Mode - Lennox MCA Series Service Manual

Cooling
Modify Rate
When there is more than one indoor unit:
Cooling
Modify Rate
NOTE: The final result is integer.
In low ambient cooling mode, modify rate is fixed as 40%.
According to the final capacity request to confirm he operating frequency, as following table.
Frequency (Hz)
Amendatory capacity
demand
Meanwhile the maximum running frequency will be adjusted according to the outdoor ambient temp.

17.3. Outdoor Fan Control

17.3.1. 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.
>29°C
>84.2°F
100%
>25°C
>77°F
100%
COOL_
0
F1
0 1
T4
28℃
26℃
25℃
23℃
22℃
20℃
19℃
17℃
27
25
20
15
low ambient cooling
Outdoor Temperature (T4)
18°C to 29°C
64.4°F to 84.2°F
60%
Outdoor Temperature (T4)
17°C - 25°C
62.6°F - 77°F
80%
...
COOL_
F2
...
...
2
...
A DC_FAN_HI_SPD_ADD
B DC_FAN_MID_SPD_ADD
C DC_FAN_MIN_SPD_ADD
D DC_FAN_SLOW_SPD_ADD
E DC_FAN_SSLOW_SPD_ADD
High
Low
30
<17°C
<62.6°F
40%
<17°C
<62.6°F
40%
COOL_ COOL_
15 16
15 16