
25-25 OBW Time
Range:
Function:
10 sec.
*
[0 – 300 sec. ]
Staging a fixed speed pump creates a momentary 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 ap-
propriate in most applications. In highly dynamic systems, a shorter time may be desirable.
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
par. 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],
par. 25-28, Stage Timer
, will not be activated.
[0]
Disabled
[1]
*
Enabled
25-28 Stage Function Time
Range:
Function:
15 sec.
*
[0 – 300 sec.]
The Stage Function Time is programmed to avoid frequent staging of the fixed speed pumps. The Stage Function
Time starts if it is
Enabled
[1] by
Stage Feature
, par. 25-27, and when the variable speed pump is running at
Motor Speed High Limit
, par. 4-13 or 4-14, 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
Destage
Timer
, par. 25-30, will not be activated.
VLT
®
HVAC Drive Programming Guide
3. Parameter Description
MG.11.C5.02 - VLT
®
is a registered Danfoss trademark
213
3