Lennox Mini-Split Service Manual / Page 253
Indoor/Outdoor Units
Communication
Protection
If the indoor units cannot receive the feedback signal from the outdoor units for two
minutes, the AC will stop and display failure.
High Condenser Col
Temp Protection
When T3>149°F (65°C) for three seconds, the compressor will stop while the indoor
fan and outdoor fan will continue.
When T3<125.6°F (52°C), the protection will release and the compressor will retart
after three minutes.
Outdoor Unit Anti-
Freezing Protection
When T2B< 32°F (0°C) for 250 seconds, the indoor unit capacity demand will be zero
and resume to normal when T2B> 50°F (10°C).
Running Rules
1.If the compressor frequency keeps lower than RET_OIL_FREQ1_ADD for RET_
OIL_TIME1_ADD,the AC will rise the frequency to RET_OIL_FREQ2_ADD for RET_
OIL_TIME2_
2.During the oil return process, the EXV will keep 300p while the indoor units will keep
the current running mode.
Compressor Preheating Functions
Preheating permitting
condition
If T4(outdoor ambient temperature)< 37.4°F (3°C) and newly powered on or if
T4<37.4°F (3°C) and compressor has stopped for over 3 hours, the compressor
heating cable will work.
Preheating Mode
A weak current fl ow through the coil of compressor from the wiring terminal of
compressor, then the compressor is heated without operation.
Preheating Release
Condition
If T4>41°F (5°C) or the capacity demand isn’t zero, preheating function will stop.
Compressor Crankcase Heater
Preheating permitting
condition
When T4< 37.4°F (3°C) within 5 seconds of being plugged in, the crankcase heater
will be active.
When T4< 37.4°F (3°C) and the compressor is not running for 3 hours, the crankcase
heater will be active.
Preheating Release
Condition
If T4>41°F (5°C) or the indoor has capacity demand, the crankcase heater will stop
work.
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