3.23.2 25-2* Bandwidth Settings
Parameters for setting the bandwidth within which the
pressure will be allowed to operate before staging/destaging
fixed speed pumps. Also includes various timers to stabilize
the control.
25-20 Staging Bandwidth
Range:
Function:
10
%
*
[1 -
par.
25-21
%]
Set the staging bandwidth (SBW) percentage to
accommodate normal system pressure fluctuation. 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/Feedb.
and
. For example, if the set-point 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.
SBW
SBW
175ZA670.10
Setpoint
25-21 Override Bandwidth
Range:
Function:
100
%
*
[par.
25-20
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 (
and
) for
immediate response.
The OBW must always be programmed to a higher
value than the value set in
Staging Bandwidth
(SBW),
. The OBW is a percentage of
and
.
25-21 Override Bandwidth
Range:
Function:
- 100
%]
SBW
SBW
Setpoint
Override Bandwidth
175ZA673.10
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
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.
25-22 Fixed Speed Bandwidth
Range:
Function:
Size related
*
[par. 25-20 - par. 25-21 %]
25-23 SBW Staging Delay
Range:
Function:
15
s
*
[1 -
3000 s]
Immediate staging of a fixed speed pump 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.
SBW
SBW
Setpoint
SBW staging delay
175ZA672.11
Parameter Description
VLT
®
HVAC Drive Programming Guide
170
MG.11.CB.02 - VLT
®
is a registered Danfoss trademark
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