Mitsubishi Heavy Industries FDUA160AVSAVH Service Manual page 32

(e) Snow protection fan control
If the DIP switch (SW3-2) on the outdoor unit control PCB is turned ON, the outdoor fan is operated for 30 seconds at 4
tap speed once in every 10 minutes depending on the outdoor air temperature (detected with Tho-A) in the stop mode or
anomalous stop mode.
( f ) Caution at the outdoor fan start control
When the outdoor fan is running at 400min
without starting up the outdoor fan. This is normal.
(5) Defrost operation
(a) Starting conditions
If all of the following defrost conditions A or conditions B
are satisfied, the defrost operation starts.
(i) Defrost conditions A
1) Cumulative compressor operation time after the end
of defrost operation has elapsed 37 minutes, and the
cumulative compressor operation time after the start
of heating operation (remote control ON) has elapsed
30 minutes.
2) After 5 minutes from the compressor ON
3) After 5 minutes from the start of outdoor fan
4) After satisfying all above conditions, if temperatures
of the outdoor heat exchanger temperature sensor
(Tho-R1, R2) and the outdoor air temperature sensor
(Tho-A) become lower than the defrost operation
starting temperature as shown by the right figure for
15 seconds continuously, or the suction gas saturation
temperature (SST) and the outdoor air temperature
(Tho-A), which are obtained from the value detected
by the low pressure sensor (LPT) stay for 3 minutes
within the range below the defrost operation start
temperature as shown by the right figure. However, it
excludes for 10 minutes after the start of compressor
and the outdoor air temperature is as shown by the
lower figure.
LPT detection
2
Outdoor air temperature (°C)
(ii) Defrost conditions B
1) When previous defrost ending condition is the time out of defrost operation and it is in the heating operation after
the cumulative compressor operation time after the end of defrost operation has become 30 minutes.
2) After 5 minutes from the start of compressor.
3) After 5 minutes from the start of outdoor fan.
(b) Ending conditions
When any of the following conditions is satisfied, the heating operation starts.
(i) When it has elapsed 10 minutes and 20 seconds after the start of defrost operation.
(ii) When the outdoor heat exchanger temperatures (Tho-R1, R2), whichever the lower, becomes 12°C or higher for 10
seconds continuously.
Snow protection fan
control ON
3
Outdoor air temperture (°C)
-1
before operating the compressor, it may operate with the compressor only,
LPT invalid
4
31
- -
Snow protection fan
control OFF
5
-2
-5
-6
-10
-15
-20
-25
-27
-30
-25 -20 -18 -15
Outdoor air temperature (℃)［Tho-A］
-8
-10
-15
-20
-24
-25
-28.6
-30
-25 -20 -18 -15
Outdoor air temperature (℃)［Tho-A］
'21 • PAC-SM-398
Defrost operation start
temperature zone
-10 -5 0 5 6
Defrost operation start
temperature zone
-10 -5 0 5 6
10
10