Runtime Balancing; Pump Spin For Unused Pumps - Danfoss MCO 101 Manual

5 Cascade Controller Features
If a pump is taken offline through parameter 27-02, the cascade controller will attempt to compensate for the unavailable pump.
• If "Offline-Off" is selected for a pump that is running, a different pump will be staged on to compensate for the loss of output.
• If "Offline-On" is selected for a pump that is currently off, a different pump will be staged off to compensate for the excess output.

5.2.3 Runtime Balancing

The extended cascade controller is designed to balance the running hours between the available pumps. Parameter 27-16 provides a balancing priority
for each pump in the system.
Three levels of priority are available:
• Balanced Priority 1
• Balanced Priority 2
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• Spare Pump
The cascade controller selects a pump to be staged or de-staged based on the pump's maximum capacity (27-14), the Current Runtime Hours (27-03)
and the Runtime Balancing (27-16) parameter.
In selecting the pump to be turned on during staging, the cascade controller will first attempt to evenly balance the current running hours for all of the
pumps with a "Balanced Priority 1" in parameter 27-16.
If all of the Priority 1 pumps are running, it will then try to evenly balance the pumps with "Balanced Priority 2" selected.
If all of the Priority 1 and 2 pumps are running, it will then select a pump with "Spare Pump" selected.
During de-staging, this process takes place in reverse. Spare pumps are de-staged first, followed by Priority 2 pumps, followed by Priority 1 pumps. At
each priority level, the pump with the greatest number of current runtime hours will be de-staged first.
An exception to this occurs in Mixed Pump configurations with more than one drive. All variable speed pumps are staged on before fixed speed pumps.
Variable speed pumps are also staged off before fixed speed pumps. Parameter 27-19 is used to reset the current runtime hours for all of the pumps and
restart the balancing process. This parameter will not affect the Total Lifetime Hours (27-04) for each pump. Total Lifetime Hours is not used for runtime
balancing.

5.2.4 Pump Spin for unused pumps

For some installations, not all of the pumps are needed or used on a regular basis. When this occurs, the extended cascade controller will first try to
balance the running hours between pumps by alternating when possible. If, however, it is unable to use a pump for 72 hours, it will initiate a pump spin
for that pump.
This feature is intended to make sure that no pump is allowed to sit idle for an extended period of time. The Spin Time can be set with parameter 27-18.
Spin time should be long enough to ensure that the pump stays in good working condition, but short enough to not create excess pressure within the
system. Setting 27-18 to zero disables the function.
The extended cascade controller will not compensate for the extra pressure generated during a pump spin. It is advisable to keep the spin time as short
as possible to prevent damage caused by creating excess pressure in the output.
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MI.38.C2.22 - VLT is a registered Danfoss trademark
Extended and Advanced Cascade Controller
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