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7.8
Compressor Control
Compressor control is a function that executes energy saving operation by switching the operation modes of a compressor
(loaded operating mode, unloaded operating mode, and stop mode) in order to optimize the pressure of piping.
One control unit in the system controls one compressor
’s operation mode.
The number of controllable compressors is two to four units.
In order to execute the compressor control, the valid and invalid time periods are set for control execution with the calendar
setting. When the present time of the control unit becomes arbitrary times set in advance, the compressor control is executed.
The control is executed by monitoring the upper/lower limit of piping pressure.
The piping pressure is measured by the analog input unit (Model: EMU4-AX4) connected to the control unit.
According to the result by monitoring the upper/lower limit of measured pressure values, the operation mode of the
compressor is controlled.
Caution
<Precautions for connectable/controllable compressors>
This function controls the operation modes of a compressor (loaded operating mode, unloaded operating mode, and
stop mode) by using the three contacts. Therefore, connectable/controllable compressors are limited to the ones that
can move to each operation mode at the corresponding contact state as the following table.
Operation mode of
compressor
Contact
Loaded
operating mode
Unloaded
operating mode
Stop mode
Loaded/Unloaded
ON
OFF
OFF
Operating
ON
ON
OFF
Stop
ON
ON
OFF
<Precautions for control unit clock>
The control unit has a built-in clock.
The clock accuracy is five minute per month difference. Check the clock time regularly, and if there is a difference,
adjust the time. For details on how to check the present time, refer to
<Precautions for pressure measurement>
As a measurement value, a scaling value of pressure measured by the analog input unit (Model: EMU4-AX4) is used.
To set the scaling value, the optional small type display unit (Model: EMU4-D65) is required.
For details on the scaling value, refer to
Energy Measuring Unit Extensio
n Model for Analog Input User’s Manual
(Details).
For details on how to set the scaling value, refer to
Small Type Display Unit for Energy Measuring Unit User’s
Manual (Details).
<Flow of compressor control>
(1) Check the valid and invalid time periods of compressor control set in advance as of the present date.
(2) During the invalid time period of compressor control, all the compressors stop (the contacts of all the control units are
switched to OFF).
(3) When the valid time of compressor control comes, all the compressors start (the contacts of all the control units are
switched to ON).
(4) The compressor control is executed by the upper/lower limit monitoring of measurement values.
(5) When the invalid time of compressor control comes that is set with the calendar setting, all the compressors stop (the
contacts of all the control units are switched to OFF).
➝
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March 9, 2020: Valid/invalid time period of compressor control
Valid
(Control by the upper/lower
limit monitoring)
Invalid
(2)
(5
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Calendar setting
Invalid
