Classic MROHC09AS Service Manual Download

Page: 28 / 82

8.3 Main Protection

8.3.1 Three minutes delay at restart for compressor

1 minute delay for the 1

time stand-up and 3 minutes delay for others.

8.3.2 Temperature protection of compressor top

The unit will stop working when the compressor top temp. protector cut off, and will restart after the
compressor top temp. protector restart.

8.3.3 Temperature protection of compressor discharge

When the compressor discharge temp. is getting higher, the running frequency will be limited as below
rules:
---Compressor discharge temp. T5>115°C(239°F) for 5s, compressor stops.
---108°C (226°F)<T5<115°C(239°F), decrease the frequency to the lower level every 3 minutes.
---90°C(194°F)<T5<105°C(221°F), keep running at the current frequency.
----T5<90°C(194°F), no limit for frequency.

8.3.4 Fan speed is out of control

When Indoor fan speed keeps too low (300RPM) for certain time, the unit will stop and the LED will
display the failure

8.3.5 Inverter module protection

The Inverter module has a protection function about current, voltage and temperature. If these
protections happen, the corresponding code will display on indoor unit and the unit will stop working.

8.3.6 Indoor fan delayed open function

When the unit starts up, the louver will be active immediately and the indoor fan will open 10s later.
If the unit runs in heating mode, the indoor fan will be also controlled by anti-cold wind function.

8.3.7 Compressor preheating functions

Preheating permitting condition:
If T4(outdoor ambient temperature)

＜

3°C(37.4°F) and the machine connects to power supply newly or

if T4

＜

3°C(37.4°F) and compressor has stopped for over 3 hours, the compressor heating cable will

work.
Preheating mode:
A weak current flow through the coil of compressor from the wiring terminal of the compressor, then the
compressor is heated without operation.
Preheating release condition:
If T4

＞

5°C(41°F) or the compressor starts running, the preheating function will stop.

8.3.8 Zero crossing detection error protection

If AC detects time interval is not correct for continuous 240s, the unit will stop and the LED will display
the failure. The correct zero crossing signal time interval should be between 6-13ms.

8.3.9 Condenser temperature protection

---55°C(131°F)<T3<60°C(140°F), the compressor frequency will decrease to the lower level until to F1
and then runs at F1.If T3<54°C(129.2°F), the compressor will keep running at the current frequency.
---T3<52°C(125.6°F), the compressor will not limit the frequency and resume to the former frequency.
---T3>60°C(140°F) for 5 seconds, the compressor will stop until T3<52°C(125.6°F).

8.3.10 Evaporator temperature protection

---T2<0°C(32°F), the compressor will stop and restart when T2

≧

5°C(41°F).

---0°C(32°F)

≦

T2<4°C(39.2°F), the compressor frequency will be limited and decreased to the lower

level
---4°C(39.2°F)≤T2≤7°C(44.6°F), the compressor will keep the current frequency.