Danfoss VLT CDS302 Operating Instructions Manual page 111

Parameter Descriptions
25-23 SBW Staging Delay
Range: Function:
60 [0-3000 Immediate staging of a fixed speed
sec. sec.] compressor is not desirable when a
*
momentary pressure drop in the system
exceeds the Staging Bandwidth (SBW).
Staging is delayed by the length of time
programmed. If the pressure increases to
within the SBW before the timer has
elapsed, the timer is reset.
Illustration 6.29
25-24 SBW Destaging Delay
Range: Function:
60 [0-3000 Immediate destaging of a fixed speed
sec. sec.] compressor is not desirable when a
*
momentary pressure increase in the system
that exceeds the Staging Bandwidth (SBW).
Destaging is delayed by the length of time
programmed. If the pressure decreases to
within the SBW before the timer has
elapsed, the timer is reset.
Illustration 6.30
MG34M302 - VLT
Operating Instructions VLT
SB W destage dela y
SB W
S etpoin t
SB W
®
is a registered Danfoss trademark/Commercial Compressor
®
CDS302 and CDS303
25-25 OBW Time
Range: Function:
60 [0 – Staging a fixed speed compressor creates a
sec. 300 momentary pressure peak in the system, which
*
sec. ] might exceed the Override Bandwidth (OBW). It
is not desirable to destage a compressor in
response to a staging pressure peak. The OBW
Time can be programmed to prevent staging
until the system pressure has stabilized and
normal control established. Set the timer to a
value that allows the system to stabilize after
staging. The 10 second factory setting is
appropriate in most applications. In highly
dynamic systems, a shorter time may be
desirable.
OBW timer
Illustration 6.31
25-27 Stage Function
Option: Function:
[0] Disabled
*
[1] Enabled If the Stage Function is set to [0] Disabled,
25-28 Stage Function Time will not be activated.
25-28 Stage Function Time
Range: Function:
10 [0 – The Stage Function Time is programmed to
sec. 300 avoid frequent staging of the fixed speed
*
sec.] compressors. The Stage Function Time starts if it
is [1] Enabled by 25-27 Stage Function and when
the variable speed compressor is running at
4-13 Motor Speed High Limit [RPM] or 4-14 Motor
Speed High Limit [Hz] (or at 4-11 Motor Speed
Low Limit [RPM] or 4-12 Motor Speed Low Limit
[Hz] if 7-30 Process PID Normal/ Inverse Control is
programmed to Inverse), with at least one fixed
speed compressor in the stop position. When
the programmed value of the timer expires, a
fixed speed compressor is staged.
25-29 Destage Function
Option: Function:
[0] Disabled
*
[1] Enabled The Destage Function ensures that the lowest
numbers of compressors are running to save
energy. If the Destage Function is set to [0]
6
OBW
SBW
Actual head
Setpoint
SBW
OBW
111
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