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Staging and destaging of fixed speed pumps
The parameters 708-709 are only to be set,
when mode 1-8 is selected.
Quick menu 25 Par. 708 Staging frequency
Par. 708 Staging frequency
(STAGING FREQ)
Value:
0 - 100% of F
max
Function:
The adjustable speed pump typically runs at maximum
speed when staging on an additional fixed speed
pump to match the system demand. The instant
effect of the fixed speed pump (Pump X in the figure)
creates a momentary over-pressurization until the
lead pump (Pump 1 in the figure) decelerates. This
is undesirable in most situations. To avoid this, the
drive can be programmed to decelerate to a Staging
frequency before starting the fixed speed pump. The
Cut-in point shows the start of the destaging process,
which is determined by the Staging bandwidth and
Override bandwidth, par. 702-707.
NB!:
Ensure that the staging frequency is set within
the Minimum and Maximum frequency set
in parameters 201 and 202.
Description of choice:
Adjust the Staging frequency to the best compromise
to prevent momentary pressure overshoot and a
pressure drop during transition. A very low value
for the Staging frequency might cause the check
valve at the discharge of the lead pump to close
during the transition, which could add pressure in the
system. Ensure that the Staging frequency setting
allows the check valve to remain open.
102
VLT® 7000 Booster
90%
Quick menu 26 Par. 709 Destaging frequency
Par. 709 Destaging frequency
(DESTAGING FREQ)
Value:
0 - 100% of F
Function:
The opposite process occurs during destaging.
The lead pump (pump 1 in the figure) typically
runs at minimum speed when destaging occurs.
Turning off a fixed speed pump (pump X in the
figure) creates a momentary pressure drop until the
lead pump decelerates. To avoid this, the drive
will accelerate to a Destaging frequency before
turning off the fixed speed pump.
Description of choice:
Adjust the Destaging frequency to the best
compromise to prevent momentary pressure drop
and over-pressurization during transition. A very low
value for the destaging frequency might cause the
check valve at the discharge of the lead pump to
close during the transition, which could add pressure
in the system. Ensure that the Destaging frequency
setting allows the check valve to remain open.
MG.70.A1.02 - VLT is a registered Danfoss trademark
max
50%
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