Mitsubishi Heavy Industries FDT200VSAWPVH Service Manual page 35

(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 start temperature as shown by the right
figure for 55 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 (PSL)
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.
PSL 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.
(iii) Defrost condition C
After 12 minutes from the start of compressor with SW4-4 ON
(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
(c) Switching of defrost control with SW3-1
(i) If SW3-1 on the outdoor unit control PCB is turned to ON, it becomes easier to enter the defrost operation. Use this
when installing a unit at snowing regions.
(ii) Control contents
1) It allows entering the defrost operation under the defrost condition A when the cumulative heating operation time
becomes 30 minutes. It is 37 minutes at SW3-1 OFF (Factory default).
2) It allows entering the defrost operation under the defrost condition B when the cumulative heating operation time
becomes 25 minutes. It is 30 minutes at SW3-1 OFF (Factory default).
3) It allows the defrost operation with the outdoor heat exchanger temperature (Tho-R) and suction pressure
saturation temperature (SST) being higher than normal.
PSL invalid
-28.6
4
34
- -
-2
-5
-6
-10
-15
-20
-25
-27
-30
-25 -20 -15 -10
-18
Outdoor air temperature (℃)［Tho-A］
-8
-10
-15
-20
-24
-25
-30
-18
-25 -20 -15 -10
Outdoor air temperature (℃)［Tho-A］
'21 • PAC-SM-383
Defrost operation start
temperature zone
-5 0 5 6 10
Defrost operation start
temperature zone
-5 0 5 6 10