Mitsubishi Heavy Industries SRK20ZJ-S Technical Manual page 176

(g) Heating low outdoor temperature protective control
Operating conditions: When the outdoor air temperature (TH2) is lower than - 10ºC or higher continues for 30 sec-
1)
2) Detail of operation:
-10
Outdoor air temperature (°C)
3) Reset conditions:
The outdoor air temperature (TH2) becomes - 7ºC.
a)
b) The compressor command speed is 0 rps.
(h) Compressor overheat protection
Purpose: It is designed to prevent deterioration of oil, burnout of motor coil and other trouble resulting from the
1)
compressor overheat.
2) Detail of operation
Speeds are controlled with temperature detected by the sensor mounted on the discharge pipe.
a)
(Example) Fuzzy
Notes (1) When the discharge pipe temperature is in the range of 100~110ºC, 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 in the range of 90~100ºC even when the compressor command speed is maintained for 3 minutes when the
temperature is in the range of 90~100ºC, the speed is raised by 1 rps and kept at that speed for 3 minutes. This process is repeated until the
command speed is reached.
(4) Lower limit speed
Model
Lower limit speed
If the temperature of 110ºC is detected by the sensor on the discharge pipe, then the compressor will stop immediately.
b)
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.
(i) Current safe
Purpose: Current is controlled not to exceed the upper limit of the setting operation current.
1)
Detail of operation: Input current to the converter is monitored with the current sensor fixed on the printed circuit
2)
(j) Current cut
Purpose: Inverter is protected from overcurrent.
1)
Detail of operation: Output current from the inverter is monitored with a shunt resistor and, if the current exceeds the
2)
onds while the compressor command speed is other than 0 rps.
The lower limit compressor command speed is change as shown in the figure below.
Lower limit 45 rps
Normal operation
-7
When either of the following condition is satisfied.
After lapse of 3 min. or over
After lapse of 3 min. or over
After lapse of 3 min. or over
90
Discharge pipe temperature (˚C)
Item
Cooling Heating
20 rps 30 rps
board of the outdoor unit and, if the operation current value reaches the limiting current value, the
compressor command speed is reduced.
If the mechanism is actuated when the compressor command speed 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
175
- -
'10 • SR-T-091
(1)
4 rps
4 rps
(4)
0 rps
110