Manual Pump Control; Runtime Balancing - Danfoss VLT Series Operating Instructions Manual

1 Extended and Advanced Cascade Controller
Option

1.7.2 Manual Pump Control

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The Extended Cascade Controller allows for complete control of each pump in the system. Through parameter 27-02 pumps can be individually controlled
through their selected relays. A pump can be turned on or off outside of the control of the Extended Cascade Controller or can be forced to alternate the
lead.
This parameter is different than other value related parameters in that selecting one of these options will cause the action to occur and then the parameter
will revert back to its default state.
The choices are as follows:
• No Operation - Default.
• Online - Makes the pump available to the Extended Cascade Controller.
• Alternate On - Forces the selected pump to be the lead pump.
• Offline-Off - Turns the pump off and makes it unavailable for cascading.
• Offline-On - Turns the pump on and makes it unavailable for cascading.
• Offline-Spin - Initiates a pump spin.
If any of the "Offline" selections are chosen the pump will no longer be available to the cascade controller until "Online" is selected.
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.

1.7.3 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
• Spare Pump
The cascade controller selects a pump to be staged or destaged 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 pumps with "Spare Pump" selected.
During destaging the reverse occurs. Spare Pumps are destaged first, followed by Priority 2 pumps, followed by Priority 1 pumps. At each priority level
the pump with the largest Current Runtime Hours will be destaged 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.
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VLT Operating Instructions