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parameter 702. 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 706, Override Bandwidth Timer.
Commissioning the Cascade Controller:
To avoid unintended staging during the commissioning
phase and fine tuning of the controller, initially leave the
OBW at the factory setting of 100%. When the fine
tuning is completed, the OBW should be set to the
desired value. A good initial value may be 10%.
Quick menu 23 Par. 706 Override Bandwidth timer
Par. 706 Override Bandwidth timer
(OVERRIDE TIMER)
Value:
0 - 300 sec.
Function:
Staging a fixed speed pump creates a momentary
pressure peak in the system, which might exceed
the Override bandwidth (OBW). It is not desirable to
destage a pump in response to a staging pressure peak.
The Override bandwidth timer can be programmed to
prevent staging or destaging until the system pressure
has stabilized and normal control established.
Description of choice:
Set the timer to a value that allows the system to
stabilize after staging. The 10 second factory setting
is appropriate in most applications. In highly dynamic
systems, a shorter time might be desirable.
MG.70.A1.02 - VLT is a registered Danfoss trademark
VLT® 7000 Booster
Quick menu 24 Par. 707 Destage by timer
Par. 707 Destage by timer
(DESTAGE BY TIMER)
Value:
0 - 300 sec. (301 = Off)
Function:
The timer starts when the adjustable speed pump is
running at minimum speed with one or more constant
speed pumps in operation and system requirements
satisfied. In this situation, the lead pump contributes
little to the system. When the programmed value of
the timer expires, a fixed speed pump is destaged
and the lead pump accelerated to maintain system
requirement. This saves energy and avoids dead
head water circulation within the lead pump.
10%
Description of choice:
Set the destage timer interval. When sleep mode is
activated, ensure the interval is set lower or equal to
the value of the sleep mode timer (parameter 711).
NB!:
Sleep mode activates when the adjustable
speed pump is the only pump running. To
turn off the destage timer, turn off sleep mode
first. Set parameter 711, Sleep Mode to OFF, then
parameter 707, Destage by Timer to OFF
OFF
101
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