Danfoss VLT Programming Manual page 176

Parameter Description
25-56 Staging Mode at Alternation
Option: Function:
This parameter is only active if the option selected in
25-50 Lead Pump Alternation is different from Off [0].
Two 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 just cut
out (coasted).
[0] Slow At alternation, the variable speed pump is ramped up
*
to maximum speed and then ramped down to a stand
still.
[1] Quick At alternation, the variable speed pump is ramped up
to maximum speed and then coasted to stand still.
Illustration 3.7 Slow Transfer Staging
25-58 Run Next Pump Delay
Range: Function:
0.1 s [0.1 - 5.0 This parameter is only active if the option
*
s] selected in 25-50 Lead Pump Alternation, is
different from Off [0].
This parameter sets the time between stopping
the old variable speed pump and starting
another pump as a new variable speed pump.
Refer to 25-56 Staging Mode at Alternation, the
illustration for description of staging and
alternation.
®
VLT HVAC Drive Programming Guide
Motor speed
Variable speed
high limit
pump
Destaging
speed
Motor speed
low limit
Staging Delay
before starting
command
next pump
Motor speed
high limit
Staging
speed
Motor speed
low limit
Motor speed
high limit
Destaging
speed
Motor speed
low limit
®
MG.11.CB.02 - VLT is a registered Danfoss trademark
The variable speed pump (top graph) and one fixed speed
pump (bottom graph) are running before the staging
command, see Illustration 3.7. When the Slow [0] transfer
command is activated, an alternation is carried out by
ramping the variable speed pump to 4-13 Motor Speed High
Limit [RPM] or 4-14 Motor Speed High Limit [Hz], and then
decelerated to zero speed. After a "Delay Before Starting
Next Pump" (25-58 Run Next Pump Delay) the next lead pump
(middle graph) is accelerated and another original lead
pump (top graph) is added after the "Delay Before Running
On Mains" (25-59 Run on Mains Delay) as a fixed speed pump.
The next lead pump (middle graph) is decelerated to Motor
Speed Low Limit and then allowed to vary speed to maintain
system pressure.
Fixed speed
pump
Seconds
Delay before
running
on mains
Variable speed
pump
Seconds
Fixed speed
pump
Seconds
25-59 Run on Mains Delay
Range: Function:
0.5 s [par. 25-58 This parameter is only active if the option
*
- 5.0 s] selected in 25-50 Lead Pump Alternation, is
different from Off [0].
This parameter sets the time between
stopping the old variable speed pump and
starting this pump as a new fixed speed pump.
Refer to 25-56 Staging Mode at Alternation, the
illustration for description of staging and
alternation.
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