76
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Upper limit value
While a pressure value exceeds the upper limit value, the following control operation is repeated.
*The adjustment operation time is a delay time when a compressor is switched from the unloaded operating mode to the
stop mode.
(1) Check whether some compressors with the loaded operating mode exist.
If any, the control target compressor will be one with higher priority. At the next control period, the operation mode is
switched to the unloaded operating mode.
If there is only one compressor with the loaded operating mode, the control will not be executed.
(2) When the delay time (adjustment operation time) passes with the control target compressor keeping the unloaded
operating mode, the target compressor is stopped.
If the pressure value drops to the upper limit value or less before the delay time (adjustment operation time) is over,
the control target compressor will be switched to the loaded operating mode.
(3) Change the control target to a compressor with next higher priority.
Upper limit
value
Compressor 1
Operation (load)
Operation (unload)
Stop
Compressor 2
Operation (load)
Operation (unload)
Stop
Compressor 3
Operation (load)
Operation (unload)
Operation (unload)
Stop
Compressor 4
Operation (load)
Adjustment operation time
Measurement value for
determination
②
③
④
⑥
⑦
Pressure measured value
59 min
①
⑤
<Example of action>
Adjustment operation time: 1 min
Priority
High
Low
00 min
01 min
02 min
03 min
04 min
05 min
06 min
Control target at
the start of control
①
A pressure value exceeds the upper limit value. At the next control period (01 min), a compressor with the highest priority,
compressor 1, will be switched to the unloaded operating mode.
②
The compressor 1 is switched to the unloaded operating mode.
③
Since the adjustment operation time is over, the compressor 1 is switched to the stop mode.
A compressor with the highest priority in compressors with the loaded operating mode, compressor 2, is targeted and switched
to the unloaded operating mode.
④
Since the adjustment operation time is over, the compressor 2 is switched to the stop mode.
A compressor with the highest priority in compressors with the loaded operating mode, compressor 3, is targeted and switched
to the unloaded operating mode.
The pressure value drops to the upper limit value or less. At the next control period (04 min), the compressor 3 will be switched
from the unloaded operating mode to the loaded operating mode.
⑤
Since the pressure value exceeds the upper limit value, at the next control period (05 min), the compressor 3 will be switched to
the unloaded operating mode.
⑥
The compressor 3 is switched to the unloaded operating mode.
⑦
Since the adjustment operation time is over, the compressor 3 is switched to the stop mode.
The compressor 4 is not controlled because at least one compressor should surely remain in the loaded operating mode.
