Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 28

SRK-GZ
(9) Economical operation (ECONO button on remote controller: ON)
Pressing the economy button initiates a soft operation with the power suppressed in order to avoid an excessive cooling or heating.
The unit operates 1.5ºC higher than the setting temperature for the LO air flow during cooling or 2.5ºC lower than that during
heating.
(10) Protective control function
(a) Frost prevention for indoor heat exchanger (During cooling or dehumidifying)
(i) Operating conditions
(i) Indoor heat exchanger temperature (detected with Th2) is lower than 2.5ºC.
(ii) 10 minutes elapsed after the start of operation.
(ii) Detail of anti-frost operation
Inverter command speed
Indoor fan
Outdoor fan
4-way valve
(iii) Reset conditions: Indoor heat exchanger temperature (Th2) is higher than 8˚C.
(b) Indoor fan motor protection
When the air conditioner is operating and the indoor fan motor is turned ON, if the indoor fan motor has operated at 300 rpm
or under for more than 30 seconds, the unit enters first in the stop mode and then stops the entire system.
Timer lamp illuminates simultaneously and the operation lamp flashing 6 times at each 8-second.
(c) Continuous low Hz operation protection
When the command frequency from the indoor control has been suppressed at 18rps (40 Hz) or under (other than 0 rps(Hz))
for more than 15(45) minutes in order for the reverse feed of oil to the compressor, the compressor is operated forcibly at
30rps (60Hz) for 20(30) seconds (1 minutes). However, the speed of indoor fan is not changed.
Notes (1) If a command exceeding 30rps (60 Hz) is received during the forced operation at 30rps (60 Hz), the command governs the operation.
(2) Value in ( ) indicates 25, 35 models.
(d) Current safe
(i) Purpose: Current is controlled not to exceed the upper limit of the setting operation current.
(ii) Detail of operation: Input current to the converter is monitored with the current sensor assembled on the printed
circuit board of the outdoor unit and, if the operation current value reaches the limiting current value, the inverter
frequency is reduced.
If the mechanism is actuated when the frequency of outdoor unit is less than 25:28 Hz, 35:34 Hz, 50:30 rps, the compres-
sor is stopped immediately. Simultaneously, a red LED on the printed circuit board provided on the outdoor unit
controller flashing 3 times for 0.5 second at intervals of 8 seconds. Operation starts again after a delay time of 3 minutes
but, if the mechanism is actuated again at less than 25:28 Hz, 35:34 Hz, 50:30 rps, the operation does not start on the
third time.
(e) Current cut
(i) Purpose: Inverter is protected from overcurrent.
(ii) Detail of operation: Output current from the converter is monitored with a shunt resistor and, if the current exceeds
the setting value, the compressor is stopped immediately. Simultaneously, a red LED on the printed circuit board
provided on the outdoor unit controller flashing for 0.5 second at intervals of 8 seconds. Operation starts again after a
delay time of 3 minutes but, if the current cut mechanism is actuated again before it reaches less than 25:28 Hz, 35:34
Hz, 50:20 rps, the operation does not start on the third time.
(f) Heating overload protective control
(i) Operating conditions: When the unit is operating with the outdoor unit frequency other than 0 Hz(rps) or when the
outdoor temperature thermistor temperature rose beyond 17ºC for 2 minutes continuously.
(ii) Detail of operation
1) Indoor fan speed is raised forcibly by 1 step.
2) Taking the upper limit of control frequency range at 25,35:60 Hz, 50:70 rps, if the output frequency obtained with
the fuzzy calculation exceeds the upper limit, the upper limit value is maintained.
(iii) Reset conditions: When the outdoor thermistor temperature drops below 16ºC.
26
0Hz
2nd speed
OFF
Stop mode