The shorter these time settings, the sooner (and more frequently) the motor stops.
VARIO
The VARIO mode is based on the DUAL control mode. The difference from DUAL being that, under
VARIO, the idling to stop time is automatically varied in order to keep the number of motor starts per
hour (starting frequency) within the prescribed limits.
MODULATING control mode
The MODULATING control mode is an extension of DUAL control. The difference being that, in
DUAL, the delivery of the compressor is steplessly varied within the control range of the machine.
This control mode is not available on frequency-controlled variable speed compressors (SFC).
Compressed air demand Operating states
rises PARTIAL LOAD
LOAD
falls PARTIAL LOAD
IDLE
STOPPED
Tab. 32 Operating states under MODULATING control
4.7 Refrigeration Dryer Control Modes
The controller can operate in the following modes:
■ CONTINUOUS
■ TIMER
CONTINUOUS
In this mode the refrigeration dryer runs continuously, even if the compressor is shut down.
This mode of control is set up at the factory.
TIMER
The refrigeration dryer is time-controlled and is switched on and off when the compressor is stopped.
In this mode, the operating temperature is held within tight limits.
This control mode saves energy.
Which control mode is the most practical, and when?
Control mode Advantage Disadvantage
CONTINUOUS Constant dew point. Higher power consumption when the compres‐
sor is shut down
TIMER Lower power consumption when
the compressor is shut down
Brief increase in dew point when the compres‐
sor re-starts
Tab. 33 Refrigeration dryer control modes
4 Design and Function
4.7 Refrigeration Dryer Control Modes
9_5721 06 USE
Service Manual Screw Compressor
ASD T Tri-Voltage
29
Option C1
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