Danfoss VLT FC 100 Series Programming Manual page 212

3. Parameter Description
25-22 Fixed Speed Bandwidth [%]
Range:
*
10% [1 - 100%]
3
25-23 SBW Staging Delay
Range:
*
15 sec. [0-3000 sec.]
25-24 SBW Destaging Delay
Range:
*
15 sec. [0-3000 sec.]
212
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, the OBW should be set to the
desired value. An initial value of 10% is suggested.
Function:
When the cascade control system is running 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. Due to the fact that 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. It is possible to stop the fixed speed pumps, in case of an alarm situation, by pressing the LCP OFF or
HAND ON keys or if the signal programmed for Start on digital input goes low.
In case the issued alarm is a trip-lock alarm then the Cascade Controller must stop the system immediately by
cutting out all the fixed speed pumps. This is basically the same as Emergency Stop (Coast/Coast inverse Com-
mand) for the Cascade Controller.
Function:
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.
Function:
Immediate destaging of a fixed speed pump is not desirable when a momentary pressure increase in the system
that exceeds the Staging Bandwidth (SBW). Destaging is delayed by the length of time programmed. If the
pressure decreases to within the SBW before the timer has elapsed, the timer is reset.
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VLT HVAC Drive Programming Guide