Midea Aurora MOF-24HFN1-QRD0GW, Service Manual

Page: 26 / 46

8.3 Main Protection
8.3.1 Three minutes delay at restart for
compressor
1 minute delay for the 1
st
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
℃
(239°F) for 5s, compressor stops and restarts
up till T5<90
℃
(194°F)
---110<T5<115
℃
(239°F), decrease the
frequency to the lower level every 2 minutes.
---
105(221°F)<T5<110
℃
(230°F), keep running
at the current frequency.
----T5<105
℃
(221°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 7s
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 Sensor protection at open circuit and
breaking disconnection.
When there’s one temperature sensor in
malfunction, the air conditioner will display error
code and will not stop immediately, to avoid the
case that the air conditioner is in urgent need.
Fault
temp.
sensor Operation in
cooling, drying
and fan only
mode Operation in
heating mode
T1 Run supposed
T1=26
℃
high
fan speed
Run supposed
T1=26
℃
medium
fan speed
T2 Normal Normal
T3 Run with
compressor
frequency
≤
F14
3 minutes’
defrosting every
40 minutes when
T4<7
℃ ; 2 minutes’
defrosting every
90 minutes when
T4≥7
℃
.
T4 Run supposed
T4=50
℃
Run supposed
T4=15
℃
TP Run supposed
T4=50
℃
Run supposed
T4=15
℃
8.3.9 Zero crossing detection error
protection
If AC can not detect zero crossing signal for 4
minutes or the zero crossing signal time interval
is not correct, the unit will stop and the LED will
display the failure. The correct zero crossing
signal time interval should be between 6-13ms