Mitsubishi Heavy Industries FDT71VNXVD Service Manual page 21

(c) Heating high pressure protection
1) Protective control
a) As the indoor unit heat exchanger temperature (Th
(frequency) is controlled to suppress the rise of high pressure.
b) Control value A is updated to an optimum value automatically according to the operating conditions.
Reset
Indoor unit heat exchanger temp. (°C)
2) Anomalous stop control
Operation control function by the indoor unit controller - See the heating overload protection, page 10.
3) Adaptation to existing piping, stop control
If the existing piping adaptation switch, SW5-1 (SW8-1: 71 type), is turned ON, the compressor stops to protect
existing piping when the indoor unit heat exchanger temperature (Th
Reset
47
Indoor unit heat exchanger temp. (°C)
(d) Anomaly detection control by the high pressure switch (63H1)
1) If the pressure rises and operates the high pressure switch (opens at 4.15MPa/closes at 3.15MPa), the compressor stops.
2) Under any of the following conditions, E40 is displayed and it enters the anomalous stop mode.
a) When it occurs 5 times within 60 minutes that pressure rises and the compressor is stopped by 63H1.
b) When 63H1 has been in the open state for 60 minutes continuously, including the stop of compressor.
(e) Low pressure control
1) Protective control
If the value detected by the low pressure sensor (LPT) exceeds the setting value, the compressor speed (frequency)
is controlled to restrain the drop of pressure.
Reduces compressor frequency
at every 30 seconds.
2) Anomalous stop control
a) When a value detected by the low pressure sensor (LPT) satisfies any of the following conditions, the
compressor stops to run for its protection.
When the low pressure drops to 0.079MPa or under for 15 seconds continuously.
At 10 minutes after the start of compressor, the suction overheat becomes 30°C and the low pressure
becomes 0.15MPa or under for 60 seconds continuously.
b) E49 is displayed under any of the following conditions and it enters the anomalous stop mode.
When the low pressure drops 3 times within 60 minutes and the compressor stops under any of the above conditions.
When a value detected with the low pressure sensor becomes 0.079MPa or under for 5 minutes, including
the stop of compressor.
c) However, when the control condition a).
displayed at initial stop and it enters the anomalous stop mode.
(f) Compressor pressure ratio protection control
1) During heating operation, if the indoor unit heat exchanger temperature (Th
temperature (Tho-R) exceed the setting values at 10 minutes after the start of compressor, the compressor speed
(frequency) is controlled to protect the compressor.
2) This control is not performed during the outdoor fan ON and for 10 minutes from the start of outdoor unit fan.
3) This control is not performed during defrosting operation and at 10 minutes after the reset of defrosting operation.
4) When there are 3 indoor unit heat exchanger temperatures (Th
65 °C
33
°C
0.150
Low pressure (MPa)
Reduces compressor frequency
at every 30 seconds.
A
Compressor stop
58
Retention
Reset
0.150 0.189
Low pressure (MPa)
is established during the compressor protection start III, E49 is
Reduces compressor frequency at each minute.
Resert
0.425
- 21
-R) exceeds the setting value, the compressor speed
I
Existing piping adaptation switch: SW5-1 (SW8-1: model 80)
Model OFF (Shipping)
71
125~140
Note (1) Adaptation to existing piping is at ON.
-R) exceeds the setting value.
I
-R) and the outdoor unit heat exchanger
I
-R), the highest temperature is detected.
I
-
'10 • PAC-SM-137A
ON
Control value A (°C)
52~58
46~52
48~54