Staging Mode At Alternation - Danfoss VLT Programming Manual

3 Parameter Description
25-55 Alternate if Load < 50%
Option:
3
[0] Disabled
[1] * Enabled
NB!
Only valid if par. 25-50

25-56 Staging Mode at Alternation

Option:
[0] * Slow
[1] Quick
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
Motor Speed High Limit [RPM]
par. 4-13
Run Next Pump Delay
Next Pump" (par. 25-58
after the "Delay Before Running On Mains" (par. 25-59
to Motor Speed Low Limit and then allowed to vary speed to maintain system pressure.
250
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
=
N TOTAL
For the Basic Cascade Controller all pumps are equal size.
The lead pump alternation will take place at any pump capacity.
The lead pump function will be alternated only if the numbers of pumps running are providing less
than 50% of total pump capacity.
Lead Pump Alternation
is different from
Function:
This parameter is only active if the option selected in par. 25-50
from Off [0].
Two types of staging and destaging of pumps are possible. Slow transfer makes staging and de-
staging smooth. Quick Transfer makes staging and destaging as fast as possible; the variable speed
pump is just cut out (coasted).
At alternation, the variable speed pump is ramped up to maximum speed and then ramped down
to a stand still.
At alternation, the variable speed pump is ramped up to maximum speed and then coasted to stand
still.
Slow
[0] transfer command is activated, an alternation is carried out by ramping the variable speed pump to
Motor Speed High Limit [Hz]
or par. 4-14
) the next lead pump (middle graph) is accelerated and another original lead pump (top graph) is added
Run on Mains Delay
) as a fixed speed pump. The next lead pump (middle graph) is decelerated
MG.11.C9.02 - VLT
®
VLT HVAC Drive Programming Guide
× 100 %
Off
[0].
, and then decelerated to zero speed. After a "Delay Before Starting
® is a registered Danfoss trademark
Lead Pump Alternation
is different