Mitsubishi Heavy Industries SRK20ZG-S Tech Manual page 25

(7) Compressor overheat protection
(a) Purpose: It is designed to prevent deterioration of oil, burnout of motor coil and other trouble resulting from the compressor
overheat.
(b) Detail of operation
1) Speeds are controlled with temperature detected by the sensor mounted on the discharge pipe.
(Example) Fuzzy
Notes (1) When the discharge pipe temperature is in the range of 100(90) to 125(110)ºC, the speed is reduced by 4 rps.
(2) When the discharge pipe temperature is raised and continues operation for 20 seconds without changing, then the speed is reduced again by 4 rps.
(3) If the discharge pipe temperature is still 90 (80) ºC or greater but less than 100 (90) ºC even when the inverter command speed is maintained for 3
minutes when the temperature is 90 (80) ºC or greater but less than 100 (90) ºC, the speed is raised by 2 rps and kept at that speed for 3 minutes. This
process is repeated until the command speed is reached.
(4) Lower Limit Speed
20, 25, 35 type
(5) Values in ( ) are for Type 50.
2) If the temperature of 125 (110)ºC is detected by the sensor on the discharge pipe, then the compressor will stop immediately.
When the discharge pipe temperature drops and the time delay of 3 minutes is over, the unit starts again within 1 hour but
there is no start at the third time.
(8) Current safe
(a) Purpose: Current is controlled not to exceed the upper limit of the setting operation current.
(b) Detail of operation: Input current to the converter is monitored with the current sensor fixed on the printed circuit board
(9) Current cut
(a) Purpose: Inverter is protected from overcurrent.
(b) Detail of operation: Output current from the converter is monitored with a shunt resistor and, if the current exceeds the
(10) Outdoor unit failure
This is a function for determining when there is trouble with the outdoor unit during air conditioning.
The compressor is stopped if any one of the following in item 1), 2) is satisfied. Once the unit is stopped by this function, it is not
restarted.
1) When the input current is measured at 1 A or less for 3 continuous minutes or more.
2) If the outdoor unit sends a 0 rps signal to the indoor unit 3 times or more within 20 minutes of the power being turned on.
(11) Inching prevention
When the compressor goes into the thermo operation within 10(5) minutes since operation start or becomes various dehumidifying
operations, the operation is continued with the lower limit speed forcibly.
Note (1) Values in ( ) are for Type 50.
After lapse of 3 min. or over
After lapse of 3 min. or over
After lapse of 3 min. or over
90
(80)
Discharge pipe temperature (˚C)
Cooling Heating
20 rps
50 type
22 rps
of the outdoor unit and, if the operation current value reaches the limiting current value, the outdoor
unit speed is reduced.
If the mechanism is actuated when the speed of outdoor unit is less than 30 rps, the compressor is
stopped immediately. Operation starts again after a delay time of 3 minutes.
setting value, the compressor is stopped immediately. Operation starts again after a delay time of 3
minutes.
(3)
(3)
Lower limit
(3)
100
(90)
30 rps
38 rps
22
- -
4 rps (1)
4 rps
(4)
0 rps
125
(110)