Carrier 42QZA009DS-1 Service Manual page 65

17.5.4 Compressor current limit protection
Temperature interval.of current limit is same as range of T4 limited frequency.
Cooling mode:
Heating mode:
17.5.5 Indoor / outdoor units communication protection
If the indoor units cannot receive the feedback signal from the outdoor units for 2 minutes, the AC will stop
and display the failure.
17.5.6 High condenser coil temp. protection.
17.5.7 Outdoor unit anti-freezing protection
When T2<4℃ for 250 seconds or T2<0℃, the indoor unit capacity demand will be zero and resume to
normal when T2>8℃ and the time of protection is no less than 3 minutes.
17.5.8 Oil return
Running rules:
1. If the compressor frequency keeps lower than setting frequency for setting time, the AC will rise the
frequency to setting frequency for setting time and then resume to former frequency.
2. The EXV will keep 300p while the indoor units will keep the current running mode.
T4
T4
T3
Off
Decrease
Hold
Resume
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CoolZone5
CoolZone4
CoolZone3
CoolZone2
CoolZone1
HeatZone4
HeatZone3
HeatZone2
HeatZone1