Danfoss VLT AQUA Drive FC 202 Programming Manual page 211

Parameter Description
3.22.2 25-2* Bandwidth Settings
Parameters for setting the bandwidth within which the
pressure is allowed to operate before staging/destaging
fixed speed pumps. Also includes various timers to stabilize
the control.
25-20 Staging Bandwidth
Range: Function:
Size [ 1 - Set the staging bandwidth (SBW) percentage
related par. to accommodate normal system pressure
*
25-21 fluctuation. In cascade control systems, to
%] avoid frequent switching of fixed speed
pumps, the system pressure is typically kept
within a bandwidth rather than at a constant
level.
The SBW is programmed as a percentage of
parameter 3-03 Maximum Reference. For
example, if the maximum reference is 6 bar,
the setpoint is 5 bar and the SBW is set to
10%, a system pressure between 4.5 bar and
5.5 bar is tolerated. No staging or destaging
occurs within this bandwidth.
Illustration 3.80 Staging Bandwidth
Size [ 1 - Set the staging bandwidth (SBW) percentage
related par. to accommodate normal system pressure
*
25-21 fluctuation. In cascade control systems, to
%] avoid frequent switching of fixed speed
pumps, the system pressure is typically kept
within a bandwidth rather than at a constant
level.
The SBW is programmed as a percentage of
parameter 3-03 Maximum Reference and
parameter 3-04 Reference Function. For example,
if the setpoint is 5 bar and the SBW is set to
10%, a system pressure of 4.5–5.5 bar is
tolerated. No staging or destaging occurs
within this bandwidth.
MG20OB02
Programming Guide
25-20 Staging Bandwidth
Range:
25-21 Override Bandwidth
Range:
100
% 25-20 -
*
100 %]
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Function:
Illustration 3.81 Staging Bandwidth
Function:
[ par. When a large and quick change in the system
demand occurs (such as a sudden water
demand), the system pressure rapidly changes
and an immediate staging or destaging of a
fixed speed pump becomes necessary to match
the requirement. The override bandwidth (OBW)
is programmed to override the staging/
destaging timer (parameter 25-23 SBW Staging
Delay and parameter 25-24 SBW Destaging Delay)
for immediate response.
Always program the OBW to a higher value than
the value set in parameter 25-20 Staging
Bandwidth. The OBW is a percentage of
parameter 3-02 Minimum Reference and
parameter 3-03 Maximum Reference.
Illustration 3.83
Setting the OBW too close to the SBW could
defeat the purpose with frequent staging at
momentary pressure changes. Setting the OBW
too high might lead to unacceptably high or
low pressure in the system while the SBW
timers are running. The value can be optimized
with increased familiarity with the system. See
parameter 25-25 OBW Time.
To avoid unintended staging during the
commissioning phase and fine-tuning of the
controller, initially leave the OBW at the factory
setting of 100% (Off). When the fine-tuning is
3
Override Bandwidth
SBW
Setpoint
SBW
209
3