Danfoss VLT Programming Manual page 172

Parameter Description
25-24 SBW Destaging Delay
Range: Function:
15 [0 - Immediate destaging of a fixed speed pump is not
s 3000 s] 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.
25-25 OBW Time
Range: Function:
10 [0 - Staging a fixed speed pump creates a momentary
s 300 s] pressure peak in the system, which might exceed
*
the Override Bandwidth (OBW). It is not desirable to
destage a pump 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
®
VLT HVAC Drive Programming Guide
SB W destage dela y
SB W
S etpoin t
SB W
OBW
SBW
Actual head
Setpoint
SBW
OBW
®
MG.11.CB.02 - VLT is a registered Danfoss trademark
25-26 Destage At No-Flow
Option: Function:
The Destage at No-Flow parameter ensures that
when a no-flow situation occurs, the fixed speed
pumps will be destaged one-by-one until the no-
flow signal disappears. This requires that No Flow
Detection is active. See parameter group 22-2*.
If Destage at No-Flow is disabled the Cascade
Controller does not change the normal behavior of
the system.
[0] Disabled
*
[1] Enabled
25-27 Stage Function
Option: Function:
If the Stage Function is set to Disabled [0],
25-28 Stage Function Time will not be activated.
[0] Disabled
[1] Enabled
25-28 Stage Function Time
Range: Function:
15 s [0 - The Stage Function Time is programmed to avoid
*
300 s] frequent staging of the fixed speed pumps. The
Stage Function Time starts if it is Enabled [1] by
25-27 Stage Function, and when the variable speed
pump is running at Motor Speed High Limit,
4-13 Motor Speed High Limit [RPM] or 4-14 Motor
Speed High Limit [Hz], with at least one fixed speed
pump in the stop position. When the programmed
value of the timer expires, a fixed speed pump is
staged.
25-29 Destage Function
Option: Function:
The Destage Function ensures that the lowest
numbers of pumps are running to save energy and
to avoid dead head water circulation in the variable
speed pump. If the Destage Function is set to
Disabled [0], the 25-30 Destage Function Time will not
be activated.
[0] Disabled
[1] Enabled
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