Mitsubishi Heavy Industries FDT28KXE6A Service Manual page 22

(c) Power transistor temperature (PT) protective control (Master unit/Slave unit)
If the power transistor temperature exceeds 75°C, the compressor speed is controlled.
(d) Ventilation fan control for cooling inside control box (Master unit/Slave unit)
If the relationship between the outdoor air temperature (detected with Tho-A) and the inverter frequency (the frequency of
CM1 or CM2, whichever the higher) is in the ventilation fan ON zone in the figure mentioned below and when the CM1
or CM2 is operating, the ventilation fan FMC3 is turned ON.
If once it enters in the zone of ON or OFF, FMC3 control is retained for 1 minute before resetting.
However at the start and stop of compressor, 1 minute retention control is invalid.
When all compressors of the unit are stopped, this control is terminated.
(e) Protection for the number of connected indoor units
(i) When the number of connected indoor units exceeds 80 units, all corresponding units are stopped with the error of
excessive number of connected indoor units.
(ii) The number of connected indoor units is checked when the automatic address setting is completed, or when turning
the power ON or starting operation of indoor units after completion of manual address setting.
(iii) When the error of exessive number of connected indoor units (E43) occurs, the error code (E43) is diplayed up to
allowable maximum connected indoor units + 1unit on the LCD of remote controller, but in case of automatic
address setting E43 is dispalyed on all of connected indoor units.
(iv) After 3 minutes or more has elapsed since power ON, the capacities of connected indoor units are summed, and if the
summed result exceeds the usage limitation in comparison with the capacity of connected outdoor units, it displays
error code (E43) and stops all units.
Retention
Release
72
Power transistor temp. (°C)
Speed is reduced once each minute
75
120
50
20
Outdoor air temperature (°C)
20
- -
Ventilation fan
ON zone
Ventilation fan
OFF zone
35