•
If
[3] Offline-Off
is selected for a pump that is
running, another pump will be staged on to
compensate for the loss of output.
•
If
[4] Offline-On
is selected for a pump that is off,
another pump will be staged off to compensate
for the excess output.
4.2.3 Runtime Balancing
The Extended Cascade Controller is designed to balance
the running hours of the available pumps.
27-16 Runtime
Balancing
provides a balancing priority for each pump in
the system.
Three levels of priority are available:
•
[0] Balanced Priority 1
•
[1] Balanced Priority 2
•
[2] Spare Pump
The Cascade Controller selects a pump to be staged or de-
staged based on the pump’s maximum capacity
(
27-14 Pump Capacity
),
27-03 Current Runtime Hours
and
27-16 Runtime Balancing
.
During staging the Cascade Controller balances the current
running hours for all pumps set to
[0] Balanced Priority 1
in
27-16 Runtime Balancing
.
If all priority 1 pumps are running, the Cascade Controller
balances the pumps set to
[1] Balanced Priority 2
selected.
If all priority 1 and 2 pumps are running, pumps set to
[2]
Spare Pump
are selected.
During de-staging the reverse occurs. Spare pumps are de-
staged first, followed by Priority 2 pumps, followed by
Priority 1 pumps. At each priority level the pump with the
highest current runtime hours will be de-staged first.
NOTICE
In mixed pump configurations with more than one
frequency converter all variable speed pumps are staged
or de-staged before fixed speed pumps.
Choose
27-19 Reset Current Runtime Hours
to reset the
current runtime hours and restart the balancing process.
This parameter does not affect the Total Lifetime Hours
(
27-04 Pump Total Lifetime Hours
) for each pump. Total
Lifetime Hours is not used for runtime balancing.
4.2.4 Pump Spin for Unused Pumps
If a pump is only needed occasionally, the Cascade
Controller balances the running hours of the pumps
through alternation. If a pump is not used in 72 hours, a
pump spin is triggered.
The spin time can be set with
27-18 Spin Time for Unused
Pumps
. The Spin Time should be long enough to ensure
that the pump stays in good working condition but short
enough not to over pressure the system. Set
27-18 Spin
Time for Unused Pumps
to zero to disable the function.
NOTICE
The Extended Cascade Controller does not compensate
for the extra pressure generated during a pump spin.
Keep the spin time as short as possible to prevent
damage caused by over pressuring the output.
4.2.5 Total Lifetime Hours
The Extended Cascade Controller and the Advanced
Cascade Controller keep track of the total lifetime hours
for each controlled pump.
27-04 Pump Total Lifetime Hours
displays a running total of
the operating hours for each pump. The total lifetime
hours are saved in the non-volatile memory once every
hour.
This parameter can also be set to an initial value that
reflects the hours of operation for a pump before it was
added to the system.
NOTICE
Lifetime hours will only be recorded if the Cascade
Controller is enabled and controlling the pump.
4.2.6 Alternation of the Lead Pump
In a configuration with multiple frequency converters, the
lead pump is defined as the last variable speed pump
running.
In a configuration with only a single frequency converter,
the lead pump is defined as the pump connected to the
frequency converter.
During start-up and normal staging/de-staging the Cascade
Controller balances running hours by alternating the lead
pump.
Alternation of lead pumps can also be forced manually e.g.
through
27-54 Alternation At Time of Day
or through a
digital input. Use alternation time parameters if the system
Configuring the System
VLT
®
AQUA Drive MCO 101/MCO 102
MI38C402 - VLT
®
is a registered Danfoss trademark
19
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