Lennox MCFA Service Manual page 97

Heating
Modify Rate
When there more than one indoor unit:
Heating
Modify Rate
NOTE:
The final result is integer.
Then modify it according to T2 average (correction):
NOTE: Average value of T2: Sum T2 value of all indoor units)/ (indoor units number). According to the final capacity
request to confirm the operating frequency, as following table. Heating capacity improved in low ambient heating.
In heating mode, when T2<T2_ExitT4LowFre_ADD , and T4<-4°C, there is frequency elevation: elevated frequency=
Recent frequency * 110%
When T2> T2_ExitT4LowFre_ADD-2 and T4>-6, the highest frequency can't exceed F17
When T2> T2_ExitT4LowFre_ADD-4 and T4>-8, the highest frequency can't exceed F18
When T2> T2_ExitT4LowFre_ADD-6 and T4>-10, the highest frequency can't exceed F19
In the other conditions, the highest frequency is F20.
Frequency (Hz)
Amendatory capacity
demand
Outdoor Temperature (T4)
<0°C <12°C
<32°F <53.6°F
120%
Outdoor Temperature (T4)
<0°C <12°C
<32°F <53.6°F
120% 100%
HEAT_
0
F1
0 1
53.6°F to 77°F
80%
53.6°F to 62.6°F
HEAT_
F2
2
97
12°C to 17°C
40%
12°C to 17°C
80%
...
HEAT_
15
...
...
15
...
≥17°C
≥62.6°F
20%
≥17°C
≥62.6°F
60%
HEAT_
16
16