77
■
Upper-upper limit value
When a pressure value exceeds the upper-upper limit value, the next control operation is executed once. After that, until
the pressure value drops to the upper limit value or less, the same operation as
■
Upper limit value
is repeated.
After dropping to the upper-upper limit value or less, if the pressure value exceeds the upper-upper limit value again, the
control will be executed again.
*The adjustment operation time is a delay time when a compressor is switched from the unloaded operating mode to the
stop mode.
(1) According to the mode of the control target compressor, the following control operation is executed.
・
When the control target is in the loaded operating mode, it is switched to the stop mode.
After switching to the stop mode, the control target is changed to a compressor with next higher priority.
If there is only one compressor with the loaded operating mode, the control will not be executed.
・
When the control target is in the unloaded operating mode, it is switched to the stop mode.
After switching to the stop mode, the control target is changed to a compressor with next higher priority.
(2) 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.
Upper-upper
limit value
Upper limit
value
Compressor 1
Operation (load)
Operation (unload)
Stop
Compressor 2
Operation (load)
Operation (unload)
Stop
Compressor 3
Operation (load)
Operation (unload)
Stop
Compressor 4
Operation (load)
①
②
③
④
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.
The pressure value exceeds the upper-upper limit value. At the next control period (02 min), the compressor 1 will be switched to
the stop mode regardless of the adjustment operation time.
In addition, the compressor 2 with the highest priority is switched to the unloaded operating mode.
③
Regardless of the adjustment operation time, 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 not over, the control is not executed.
⑤
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 mode.
⑥
Since the adjustment operation time is not over, the control is not executed.
Although the pressure value exceeds the upper-upper limit value, the compressor 4 is not controlled because no compressor with
the unloaded operating mode exists at the next control period (06 min) and at least one compressor should surely remain in the
loaded operating mode.
⑦
The compressor 3 is switched to the stop mode.
Since at least one compressor should surely remain in the loaded operating mode, the compressor 4 is not controlled
*The parts
written in red
indicate the control operation executed in excess of the upper-upper limit value.
⑤
⑥
⑦
<Example of action>
Adjustment operation time: 2 minutes
Adjustment operation time
Measurement value for
determination
Pressure measured value
59 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
