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Service Manual VMH SerieS Heat Controller, Inc.
8.5.5 Indoor / outdoor units communication protection
If any indoor unit can not receive the feedback signal from the outdoor unit for 2 minutes, the AC will stop
and display the failure code.
8.5.6 High condenser coil temp. protection.
When T3>149°F(T3>65°C) for 3 seconds, the compressor will stop while the indoor fan and outdoor fan will
continue.
When T3<126°F(T3<52°C), the protection will release and the compressor will restart after 3 minutes.
8.5.7 Outdoor unit anti-freezing protection
When T2B<32°F(T2B<0°C) for 4 minutes, the indoor unit capacity demand will be zero and resume to
normal when T2B>50°F(T2B>10°C).
8.5.8 Oil return
Running rules:
1. If the compressor frequency remains lower than RECOILINFRE for 2hours,the AC will increase the
frequency to RECOILFRE for 3mins and then resume to the former frequency.
Model
RECOILINFRE
A-VMH18DC-1 45
A-VMH27TC-1 45
A-VMH36QC-1 40
2. During the oil return process, the EXV and indoor units continue with the current running mode, the
frequency will not be limited by the compressor discharge temp. or the current.
8.5.9 Compressor preheating functions
----Preheating permitting condition:
If T4(outdoor ambient temperature) T4＜37.4°F(T4＜3°C) and newly powered on or if T4＜37.4°F(T4＜3°C)
and compressor has stopped for over 3 hours, the compressor’s crank case heater will begin to operate.
----Preheating mode:
A weak current flow through the coil of compressor from the wiring terminal of compressor, heats the
compressor without it operating via the crankcase heater.
----Preheating release condition:
If T4>41°(T4>5°C) or the compressor starts running, preheating function will stop.
8.5.10 Compressor crankcase heater
When T4<37.4°(T4<3°C) and the compressor is not running, the crankcase heater will be active.
When T4≧41°(T4≧5°C) or the compressor starts up, the crankcase heater will stop working.