Danfoss VLT Series Programming Manual page 185

Parameter Description
25-54 Alternation Predefined Time
Range:
Size
related 0 ]
*
3 3
25-55 Alternate if Load < 50%
Option:
[0] Disabled The lead pump alternation will take place at any
[1] Enabled The lead pump function will be alternated only if
*
NOTE
Only valid if 25-50 Lead Pump Alternation is different from
Off [0].
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.
The below figure is an example of the Slow transfer
staging. The variable speed pump (top graph) and one
fixed speed pump (bottom graph) are running before the
staging command. When the Slow [0] transfer command is
184
Function:
[ 0 - If optionPredefined Time [3] in
25-51 Alternation Event, is selected, 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).
Function:
If Alternation If Capacity <50% is enabled, the
pump alternation can only occurs 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 interlocked).
N RUNNING
Capacity =
× 100 %
N TOTAL
For the Basic Cascade Controller all pumps are
equal size.
pump capacity.
the numbers of pumps running are providing less
than 50% of total pump capacity.
MG.11.CC.02 - VLT
®
VLT HVAC Drive Programming Guide
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.
Motor speed
high limit
Destaging
speed
Motor speed
low limit
Staging
command
Motor speed
high limit
Staging
speed
Motor speed
low limit
Motor speed
high limit
Destaging
speed
Motor speed
low limit
25-58 Run Next Pump Delay
Range:
0.1 s
*
5.0 s]
25-59 Run on Mains Delay
Range:
0.5 s
*
25-58 - 5.0
s]
®
is a registered Danfoss trademark
Variable speed
pump
Delay
before starting
next pump
Function:
[0.1 - This parameter is only active if the option
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.
Function:
[ par. This parameter is only active if the option
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 Illustration 3.9 for description
of staging and alternation.
Fixed speed
pump
Seconds
Delay before
running
on mains
Variable speed
pump
Seconds
Fixed speed
pump
Seconds