Lennox LIUH018021T431E-1 Service Manual page 109

1. Electrical Control Function
1.1 Abbreviation
T1: Indoor room temperature
T2: Middle indoor heat exchanger coil temperature
T2B: Indoor heat exchanger exhaust coil temperature
T3: Outdoor heat exchanger pipe temperature
T4: Outdoor ambient temperature
T5: Compressor discharge temperature
1.2 Main Protection
1.2.1 Compressor three-minute delay at restart
Compressor functions are delayed for up to one minute upon the first startup of the unit, and are delayed for
up to three minutes upon subsequent unit restarts.
1.2.2 Automatic shutoff based on discharge temperature
When the discharge temperature of compressor rises, the running frequency is limited according to the
following rules:
T5
F
E
D
C
B
A
1.2.3 Automatic shutoff based on compressor top temperature
The unit ceases operation when the compressor top temperature exceeds a pre-determined threshold. The
unit will restart after the temperature guard of the compressor top restarts.
1.2.4 Indoor Fan Delayed Open Function
When the unit starts up, the louver is immediately active . The indoor fan opens 7 seconds later.
If the unit runs in heating mode, the indoor fan is also regulated by the anti-cold wind function.
1.2.5 Fan Speed Malfunction
For console type:
If the indoor fan speed is lower than 300 RPM for certain time, the unit stops and the LED displays the failure
code.
For A6 Duct:
If a fault occurs on the air volume regulator or the regulator enters protection mode, it sends the error
message CF and an instruction to reduce fan speed to the master. The message and the instruction can be
inquired with the remote controller or the wired controller. (Fault and protection information are displayed for
one minute). After a fault occurs, the master unit shows the error code E3 and the fault count for one minute.
If the fault occurs three times, then the fan is unable to resolve the problem independently. External
shutdown by a remote controller, wired controller, or central controller must be used to clear the fan fault and
fault count. The fan runs normally for 5 minutes while clearing fault count.
Electrical Control System
12K
Compressor off
Frequency limit1
Frequency limit2
Frequency holding
Frequencies increase slowly
Normal
16~60K
T5
Compressor off
Frequency limit
Frequency holding
Normal
Electrical Control Function
107