Mitsubishi Heavy Industries FDT28KXE6A Service Manual page 7

(11) Drain motor (DM) control [Applicable type: FDT, FDTC, FDTW, FDTS, FDTQ, FDUM, FDQS and FDU90～140]
(a) Drain motor (DM) start operation at the same time when compressor ON at cooling and dehumidifying mode and
keeps operating for  minutes after operation stop, the anomalous stop, thermostat OFF and switching from cooling or
dehumidifying operation to fan or heating operation.
Stop
Compressor ON
Compressor OFF
(i) Control A
1) If the float switch detects any anomalous draining condition, the unit stops with the anomalous stop (displays E9)
and the drain pump starts.
2) The drain motor keeps operating while the float switch is detecting the anomalous condition.
(ii) Control B
If the float switch detects any anomalous drain condition, the drain motor is turned ON for 5 minutes, and at 10 seconds
after the drain motor OFF it checks the float switch. If it is normal, the unit is stopped under the normal condition or, if
there is any anomalous condition, E9 is displayed and the drain motor is turned ON. (The ON condition is maintained
during the drain detection.)
(b) Drain motor (DM) interlock control
(i) Start conditions
Depending on the function setting of the remote controller, the drain motor is turned ON under either one of the
following conditions.
1) During heating operation (Both the thermostat ON/OFF)
2) During heating operation (Both the thermostat ON/OFF) + Fan operation
3) Fan operation
(ii) Stop conditions
The drain motor is turned OFF  minutes after the stop of operations 1) to 3) above.
(12) Operation check/drain pump test run operation mode
(a) If the power is turned on when the dip switch (SW7-1) on the indoor PCB is ON state, it enters the mode of operation
check/drain pump test run. It is ineffective (prohibited) to change the switch after turning power on.
(b) When the communication with the remote controller has been established within 60 seconds after turning power on by the
dip switch (SW7-1) ON, it enters the operation check mode. Unless the remote controller communication is established, it
enters the drain pump test run mode.
Note (1) To select the drain pump test run mode, disconnect the remote control connector (CNB) on the indoor PCB to shut down the remote controller
communication.
(c) Operation check mode
There is no communication with the outdoor unit but it allows performing operation in respective modes by operating the
remote controller.
(d) Drain pump test run mode
When the drain pump test run is established, only the drain pump operates, and during operation the protective functions
by the microcomputer of indoor unit become ineffective.
(13) Indoor heat exchanger anti-frost (anti-frost control)
Thermostat OFF control
1) Thermostat is turned OFF depending on the temperature detected with the heat exchanger sensor (Th
during "Cooling" and "Dehumidifying" operations.
Forced thermostat OFF
2) For 4 minutes after the thermostat ON, the forced thermostat OFF control for the anti-frost protection is not effective.
a) When temperatures detected by the heat exchanger sensors Th
temperature at 4 minutes after the thermostat ON, the detection starts from the state of thermostat ON.
3) If the temperature detected with the heat exchanger sensor Th
temperature (-0.5°C) continuously for 5 minutes after 4 minutes of the thermostat ON operation, then the thermostat is
turned OFF forcibly.
The thermostat will be turned ON if temperatures detected by Th
4) "Anti-frost" signal is sent to the outdoor unit.
Indoor unit operation mode
(1)
Cooling Dehumidifying
Control A
Control B
5-min timer
1.0 10°C
(2)
Fan Heating
Thermostat ON OK
Heat exchanger temperature
-R1 and R2 are higher than the anti-frost protection
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-R1 or R2 has stayed below the anti-frost protection
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-Ra and R2 picked up in the thermostat ON range.
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Note (1) Including the stop from cooling, dehumidifying,
fan and heating operation and the anomalous stop.
(2) Including the "Fan" operation according to the
mismatch of operation modes.
Temperature drop
Temperature rising
-R1, R2)
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