Pump Spin For Unused Pumps; Total Lifetime Hours; Alternation Of The Lead Pump; Staging / Destaging In Mixed Pump Configurations - Danfoss VLT Series Operating Instructions Manual

1 Extended and Advanced Cascade Controller
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VLT Operating Instructions Option

1.7.4 Pump Spin for unused pumps

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For some installations not all of the pumps are needed or used on a regularly 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.
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. 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 over pressuring the output.

1.7.5 Total lifetime hours

For maintenance purposes the Extended Cascade Controller is designed to help you keep track of the total lifetime hours for each pump it controls.
The Pump Total Lifetime Hours parameter 27-04 displays a running total of the operating hours for each pump. This parameter is updated whenever a
pump is running and is saved to non-volatile memory once every hour.
This parameter can also be set to an initial value to reflect the hours of operation for a pump before it was added to the system.
Lifetime hours will only be accumulated by the Cascade Controller if it is enabled and controlling the pump.

1.7.6 Alternation of the Lead Pump

In a configuration with multiple Drives, the Lead Pump is defined as the last variable speed pump running.
In a configuration with only a single Drive, the Lead Pump is defined as the pump connected to the Drive. More than one pump can be connected to the
Drive through contactors controlled by the Master Drive's relays.
Through normal staging and destaging the cascade controller will alternate the Lead Pump to balancing running hours. It will also alternate the Lead
Pump when starting the system or when exiting sleep mode.
However if the system demand stays below the maximum capacity of the Lead Pump for a long period of time without entering sleep mode then it will
not alternate the pump. If this is likely the Lead Pump can be forced to alternate through a Time Interval parameter 27-52 or through a Time of Day
parameter 27-54.

1.7.7 Staging / Destaging in Mixed Pump Configurations

Two methods are used to decide when pumps should be staged or destaged. The first is the speed of the Drives. The second is the feedback pressure
going outside of the Normal Operating Range. In a Mixed Pump configuration with more than one Drive both methods are used.
In the following example, feedback is referred to as pressure.
Staging:
When the Master Drive receives a start command a variable speed pump is selected, and started using one of the available Drives.
If the system pressure drops, the speed of the Drive increases to meet the demand for more flow. While maintaining the pressure, if the Drive exceeds
the Stage on Speed (27-31), and remains above that speed for the Staging Delay (27-23) time, the next variable speed pump is staged on. This repeats
for all of the variable speed pumps.
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MI.38.C3.02 - VLT is a registered Danfoss trademark