After a time delay, the relay for the fixed-speed pump cuts
in (staged) and this pump becomes the new lead pump.
The new lead pump ramps up to maximum speed and
then down to minimum speed when ramping down and
reaching the staging frequency, the old lead pump is now
cut in (staged) on line power as the new fixed-speed
pump.
If the lead pump has been running at minimum frequency
(fmin) for a programmed amount of time, with a fixed-
speed pump running, the lead pump contributes little to
the system. When the programmed value of the timer
expires, the lead pump is removed, avoiding a heat water-
circulation problem.
6.1.10 System Status and Operation
If the lead pump goes into sleep mode, the function is
displayed on the LCP. It is possible to alternate the lead
pump on a sleep mode condition.
When the Cascade Controller is enabled, the operation
status for each pump and the Cascade Controller is
displayed on the LCP. Information displayed includes:
•
Pumps Status, is a readout of the status for the
relays assigned to each pump. The display shows
pumps that are disabled, off, running on the
Adjustable frequency drive or running on line
power/ the motor starter.
•
Cascade Status, is a readout of the status for the
Cascade Controller. The display shows the
Cascade Controller is disabled, all pumps are off,
and emergency has stopped all pumps, all pumps
are running, fixed-speed pumps are being
staged/de-staged and lead pump alternation is
occurring.
•
De-stage at No-Flow ensures that all fixed-speed
pumps are stopped individually until the no-flow
status disappears.
6.1.11 Fixed Variable Speed Pump Wiring
Diagram
Figure 6.9
6.1.12 Lead Pump Alternation Wiring
Diagram
130BA377.13
L1/L2/L3
FC
L1/L2/L3
L1/L2/L3
k3
k2
k3
k1
K2
K1
K1
K1
K4
K3
K4
K3
R1
R2
Figure 6.10
Every pump must be connected to two contactors (K1/K2
and K3/K4) with a mechanical interlock. Thermal relays or
other motor protection devices must be applied according
to local regulation and/or individual demands.
Application Examples
VLT
®
HVAC Drive Design Guide
6-6
MG11BB22 - VLT
®
is a registered Danfoss trademark
6
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