Danfoss VLT AQUA Drive FC 200 Programming Manual page 175

Parameter Description
3.22.2 25-2* Bandwidth Settings
Parameters for setting the bandwidth within which the
pressure will be allowed to operate before staging/de-
staging fixed-speed pumps. Also includes various timers to
stabilize the control.
25-20 Staging Bandwidth
Range: Function:
10 [ 1 - Set the staging bandwidth (SBW) percentage to
% par. accommodate normal system pressure fluctuation.
*
25-21 In cascade control systems, to avoid frequent
%] switching of fixed-speed pumps, the desired system
pressure is typically kept within a bandwidth rather
than at a constant level.
The SBW is programmed as a percentage of 20-13
Minimum Reference and 20-14 Maximum Reference.
For example, if the setpoint is 5 bar and the SBW is
set to 10%, a system pressure between 4.5 and 5.5
bar is tolerated. No staging or de-staging will occur
within this bandwidth.
Figure 3.67
25-21 Override Bandwidth
Range: Function:
100 [ par. When a large and quick change in the system
% 25-20 demand occurs (such as a sudden water demand),
*
- 100 the system pressure rapidly changes and an
%] immediate staging or de-staging of a fixed-speed
pump becomes necessary to match the
requirement. The override bandwidth (OBW) is
programmed to override the staging/de-staging
timer (25-23 SBW Staging Delay and 25-24 SBW De-
staging Delay) for immediate response.
The OBW must always be programmed to a higher
value than the value set in Staging Bandwidth
(SBW), 25-20 Staging Bandwidth. The OBW is a
percentage of and .
®
VLT AQUA Drive Programming Guide
®
MG20O622 - VLT is a registered Danfoss trademark
25-21 Override Bandwidth
Range: Function:
Figure 3.69
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 25-25 OBW Time.
To avoid unintended staging during the commis-
sioning phase and fine tuning of the controller,
initially leave the OBW at the factory setting of
100% (Off). When the fine tuning is completed, the
OBW should be set to the desired value. An initial
value of 10% is suggested.
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