Mitsubishi Heavy Industries FDT71VNXVD Service Manual page 9

3) Operation check mode
There is no communication with the outdoor unit but it allows performing operation in respective modes by operating the
remote controller.
4) Drain pump test run mode
As the drain pump test run is established, the drain pump only operates and during the operation protective functions by
the microcomputer of indoor unit become ineffective.
(n) Cooling, dehumidifying frost protection
1) To prevent frosting during cooling mode or dehumidifying mode operation, the of compressor speed is reduced if
the indoor heat exchanger temperature (detected with Th
compressor operation. If the indoor unit heat exchanger temperature is 1.0 °C or lower after 1 minutes, the compressor
speed is reduced further. If it becomes 2.5 °C or higher, the control terminates. When the indoor heat exchanger
temperature has become as show below after reducing the compressor speed, it is switched to the fan operation. For the
selection of indoor fan speed, refer to item 2).
2) Selection of indoor fan speed
If it enters the frost prevention control during cooling operation (excluding dehumidifying), the indoor unit fan speed is
switched.
(a) In cases of FDU and FDEN
i) When the indoor unit return air temperature (detected with Th
and, as 2 hours elapse after starting the frost prevention control, it is terminated.
ii) If it is detected again within 15 minutes from the start of frost prevention control, the indoor fan speed is raised
by 1 tap to increase the indoor unit fan speed. If it is detected within further 15 minutes, the indoor unit fan
speed is raised by 1 tap more.
Note (1) Indoor unit fan speed can be increased by up to 2 taps.
iii) " FAN SPEED SW VALID/INVALID" of this control is selectable with the function setting of remote
controller.
b) In the case of FDT
i) When the indoor return air detection temperature (detected with Th
exchanger temperature (detected with Th
of indoor unit fan speed is increased by 20rpm.
ii) If the phenomenon of i) above is detected again after the acceleration of indoor unit fan, indoor unit fan speed
is increased further by 20rpm.
Note (1) Indoor unit fan speed can be increased by up to 2 taps.
• Compressor frequency drop start temperature
Item
Temperature - Low (Factory default)
Temperature - High
Note (1) Frost prevention temperature setting can be selected with the indoor unit function setting of the wired remote controller.
(o) Heating overload protection
1) If the indoor heat exchanger temperature (detected with Th
the compressor stops. When the compressor is restarted after a 3-minute delay, if a temperature at 63°C or higher is
detected for 2 seconds continuously within 60 minutes after initial detection and if this is detected 5 times consecutively,
the compressor stops with the anomalous stop (E8). Anomalous stop occurs also when the indoor heat exchanger
temperature at 63°C or higher is detected for 6 minutes continuously.
2) Indoor unit fan speed selection
If, after second detection of heating overload protection up to fourth, the indoor fan is set at Me and Lo taps when the
compressor is turned ON, the indoor fan speed is increased by 1 tap.
-R) drops to 1.0 °C or lower at 4 minutes after the start of
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Cooling operation
Fan operation
1.0 10
Indoor heat exchanger temperature (°C)
-R) detects the compressor frequency drop start temperature A°C+1°C,
I
Symbol
A
1.0
2.5
-R) at 63°C or higher is detected for 2 seconds continuously,
I
Compressor OFF
Compressor ON
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63
Indoor heat exchanger temperature (°C)
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'10 • PAC-SM-137A
-A) is 23°C or lower, this control is invalidated
I
-A) is 23°C or higher and the indoor heat
I