Danfoss VLT AQUA Drive FC 202 Programming Manual page 217

Parameter Description
25-53 Alternation Timer Value
Range: Function:
0 [0 - 7 ] Readout parameter for the alternation time interval
*
value set in parameter 25-52 Alternation Time
Interval.
25-54 Alternation Predefined Time
Range: Function:
Size [ 0 - If selecting [3] Predefined Time in
related 0 ] parameter 25-51 Alternation Event, the variable
*
speed pump alternation is carried out every
day at the specified time set in alternation
predefined time. Default time is midnight
(00:00 or 12:00AM depending on the time
format).
25-55 Alternate if Load < 50%
Option: Function:
NOTICE
Only valid if parameter 25-50 Lead Pump
Alternation is different from [0] Off.
If selecting [1] Enabled, the pump alternation can
only occur if the capacity is equal to or below
50%. The capacity calculation is the ratio of
running pumps (including the variable speed
pump) to the total number of available pumps
(including variable speed pump, but not those
that are interlocked).
N
RUNNING
Capacity =
N
TOTAL
For the basic cascade controller, all pumps are of
equal size.
[0] Disabled The lead pump alternation takes place at any
pump capacity.
[1] Enabled The lead pump function is alternated only if the
*
number of pumps running are providing less
than 50% of total pump capacity.
25-56 Staging Mode at Alternation
Option: Function:
[0] Slow This parameter is only active if the option selected
*
in parameter 25-50 Lead Pump Alternation is different
from [0] Off.
2 types of staging and destaging of pumps are
possible. Slow transfer makes staging and destaging
smooth. Quick transfer makes staging and destaging
as fast as possible; the variable speed pump is cut
out (coasted).
At alternation, the variable speed pump is ramped
up to maximum speed and then ramped down to a
standstill.
MG20OB02
Programming Guide
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25-56 Staging Mode at Alternation
Option: Function:
[1] Quick At alternation, the variable speed pump is ramped
up to maximum speed and then coasted to a
standstill.
Illustration 3.93 and Illustration 3.94 show alternation
in both quick and slow configurations.
Alternation command/PID stops
f
MAX
Destaging freq.
f
MIN.
f
MAX
Staging freq.
Mains operation
Illustration 3.93 Slow Configuration
Coast
200ms-2s (default 500ns)5 s
100ms
Illustration 3.94 Quick Configuration
25-58 Run Next Pump Delay
Range: Function:
0.1 s [0.1 - This parameter is only active if the option
*
5 s] selected in parameter 25-50 Lead Pump
Alternation is different from [0] Off.
This parameter sets the time between stopping
the old variable speed pump and starting
another pump as a new variable speed pump.
Refer to parameter 25-56 Staging Mode at
Alternation for description of staging and
alternation.
25-59 Run on Mains Delay
Range: Function:
0.5 s [ par. This parameter is only active if the option
*
25-58 - 5 selected in parameter 25-50 Lead Pump
s] Alternation is different from [0] Off.
This parameter sets the time between
stopping the old variable speed pump and
starting this pump as a new fixed speed
pump. Refer to Illustration 3.93 for description
of staging and alternation.
Mains operation
Time
PID contr.
starts
5 s Time
Mains operation
Time
Time
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