Danfoss VLT FC 102 Programming Manual page 240

Parameter Descriptions
25-21 Override Bandwidth
Range:
3 3
25-22 Fixed Speed Bandwidth
Range:
Size
related par. 25-21 %]
*
25-23 SBW Staging Delay
Range:
15 s
*
238
Function:
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 completed, set the
OBW to the required value. Initial
value of 10% is suggested.
Function:
[ par. 25-20 - When the cascade control system
runs normally and the frequency
converter issues a trip alarm, it is
important to maintain the system
head. The cascade controller does
this by continuing to stage/destage
the fixed-speed pump on and off.
As keeping the head at the setpoint
would require frequent staging and
destaging when only a fixed-speed
pump is running, a wider fixed
speed bandwidth (FSBW) is used
instead of SBW. In alarm situations,
or if the start signal on the digital
input goes low, it is possible to
stop the fixed speed pumps by
pressing [Off] or [Hand On].
If the issued alarm is a trip lock
alarm, the cascade controller stops
the system immediately by cutting
out all the fixed-speed pumps. This
is basically the same as emergency
stop (coast/coast inverse command)
for the cascade controller.
Function:
[0 - 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 within the SBW before the
timer has elapsed, the timer is
reset.
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®
VLT HVAC Drive FC 102
25-23 SBW Staging Delay
Range:
25-24 SBW Destaging Delay
Range:
15 s
*
Function:
Illustration 3.78 SBW Staging
Delay
Function:
[0 - 3000 s] Immediate destaging of a fixed-
speed pump is not recommended
when a momentary pressure
increases in the system that
exceeds the staging bandwidth
(SBW). Destaging is delayed by the
length of time programmed. If the
pressure decreases within the SBW
before the timer has elapsed, the
timer is reset.
(27-24) SBW destage delay
Illustration 3.79 SBW Destaging
Delay
SBW
(27-20)
Setpoint
SBW
(27-20)
M0010001