Danfoss VLT FC 100 Series Programming Manual page 193

Parameter Description
25-30 Destage Function Time
Range:
15 [0 -
3 3
s 300 s]
*
Figure 3.75
3.23.3 25-4* Staging Settings
Parameters determining conditions for staging/de-staging
the pumps.
25-40 Ramp-down Delay
Range:
10.0 s [0.0 -
*
120.0 s]
3-166
Function:
The Destage Function Timer is programmable to
avoid frequent staging/destaging of the fixed-
speed pumps. The Destage Function Time starts
when the adjustable speed pump is running at
4-11 Motor Speed Low Limit [RPM] or 4-12 Motor
Speed Low Limit [Hz], with one or more fixed-
speed pumps in operation and system
requirements satisfied. In this situation, the
adjustable speed pump contributes a little to the
system. When the programmed value of the timer
expires, a stage is removed, avoiding dead head
water circulation in the adjustable speed pump.
Function:
When adding a fixed-speed pump controlled
by a soft starter, it is possible to delay the
ramp-down of the lead pump until a preset
time after the start of the fixed-speed pump
to eliminate pressure surges or water
hammer in the system.
Only to be used if Soft Starter [1] is selected
in 25-02 Motor Start.
MG11CD22 - VLT
®
VLT HVAC Drive Programming Guide
25-41 Ramp-up Delay
Range:
2.0 s
*
12.0 s]
Figure 3.76
25-42 Staging Threshold
Range:
Size
related
*
® is a registered Danfoss trademark
Function:
[0.0 - When removing a fixed-speed pump controlled
by a soft starter, it is possible to delay the
ramp-up of the lead pump until a preset time
after the stopping of the fixed-speed pump to
eliminate pressure surges or water hammer in
the system.
Only to be used if Soft Starter [1] is selected in
25-02 Motor Start.
Function:
[ 0 When adding a fixed-speed pump, in order to
- 100 prevent an overshoot of pressure, the variable-
%] speed pump ramps down to a lower speed.
When the variable-speed pump reaches the
"Staging Speed", the fixed-speed pump is
staged on. The Staging Threshold is used to
calculate the speed of the variable-speed pump
when the "cut-in point" of the fixed-speed
pump occurs. The calculation of the staging
threshold is the ratio of 4-11 Motor Speed Low
Limit [RPM] or 4-12 Motor Speed Low Limit [Hz],
to the 4-13 Motor Speed High Limit [RPM] or
4-14 Motor Speed High Limit [Hz], expressed in
percent.
Staging Threshold must range from
LOW
= × 100 %
HIGH
STAGE %
to 100%, where n is Motor Speed Low Limit
LOW
and n is Motor Speed High Limit.
HIGH