Defrost Operation - Mitsubishi Heavy Industries V Multi FDC71VNX Technical Manual

(e) Caution at the outdoor fan start control
When the outdoor fan is running at 400min
without starting up the outdoor fan. This is normal.
(f) Snow protection fan control
If the dip switch (SW3-2) on the outdoor 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.

(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 thermistor
(Tho-R1, R2) and the outdoor air temperature
thermistor (Tho-A) become lower than the defrost
operation start 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 (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.
(b) Ending conditions
When any of the following conditions is satisfied, the heating operation starts.
(i) When it has elapsed 8 minutes and 20 seconds after the start of defrost operation. (After 10 minutes and 20 seconds
for FDC250 model)
(ii) When the outdoor heat exchanger temperatures (Tho-R1, R2), whichever the lower, becomes 16 (FDC250:12)°C or
higher for 10 seconds continuously.
-1
before operating the compressor, it may operate with the compressor only,
PSL invalid
-28.6
4
338
- -
Snow protection fan
control ON
3
Outdoor air temperature (°C)
-2
-5
-6
-10
-15
-20
-25
-27
-30
-25 -20 -18 -15 -10
Outdoor air temperature (℃)［Tho-A］
-8
-10
-15
-20
-24
-25
-30
-25 -20 -18 -15 -10
Outdoor air temperature (℃)［Tho-A］
'19 • PAC-T-327
Snow protection fan
control OFF
5
Defrost operation start
temperature zone
-5 0 5 6 10
Defrost operation start
temperature zone
-5 0 5 6 10