Danfoss VLT Series Design Manual page 117

®
VLT HVAC Drive Design Guide
6.1.9. Pump Staging with Lead Pump Alternation
With lead pump alternation enabled, a maxi-
mum of two pumps are controlled. At an al-
ternation command, the lead pump will ramp
to minimum frequency (fmin) and after a de-
lay will ramp to maximum frequency (fmax).
When the speed of the lead pump reaches the
destaging frequency, the fixed speed pump
will be cut out (destaged). The lead pump
6.1.10. System Status and Operation
If the lead pump goes into Sleep Mode, the function is displayed on the Local Control Panel. 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 Local Control Panel. Information displayed includes:
•
•
•
Pumps Status, is a read out of the status for the relays assigned to each pump. The
display shows pumps that are disabled, off, running on the frequency converter or run-
ning on the mains/motor starter.
Cascade Status, is a read out 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/destaged and lead
pump alternation is occurring.
Destage at No-Flow ensures that all fixed speed pumps are stopped individually until the
no-flow status disappears.
®
MG.11.B2.02 - VLT is a registered Danfoss trademark
6. Application Examples
continues to ramp up and then ramps down to
a stop and the two relays are cut out.
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 the mains
as the new fixed speed pump.
If the lead pump has been running at mini-
mum frequency (fmin) for a programmed
amount of time, with a fixed speed pump run-
ning, the lead pump contributes little to the
system. When the programmed value of the
timer expires, the lead pump is removed,
avoiding a deal heat water circulation prob-
lem.
6
117