Xylem IM255 AQUAVAR Intelligent Pump Controller - Manual (Page 72)

to Pump Exercise for details on how Duty Standby, Pump Exercise and Start Delay impact
when pumps are expected to run.
Lag pump start frequency and lag pump stop frequency
The Lag Pump Start Frequency and Lag Pump Stop Frequency can be configured to
control the frequency/speed that the lag pump is staged and destaged. This feature is
enabled only when Duty Standby is Disabled. The Lag Pump Start Frequency (staging
frequency) should be set to a frequency close to the maximum speed of the motor/pump.
The default is set to 59Hz with a maximum speed of 60Hz. This will ensure best utilization
of each pump. The Lag Pump Stop Frequency (destaging frequency) should be set to a
frequency above the [4-12] Sleep Frequency/Low Limit [Hz] of the lead pump. For
example, when the [4-12] Sleep Frequency/Low Limit [Hz] is set to 30Hz, the Lag Pump
Stop Frequency should be set to 35Hz. The actual value used depends on system
requirements.
Alternation and alternation time
Enabling Alternation allows the lag pump to become the lead after the Alternation Time
expires. Enabling Alternation allows equalization of loading between the 2 pumps and
controllers. The Alternation Time is based on elapsed time, not pump run time. Because of
this it is recommended to set Alternation Time to a time that is greater than or equal to 24
hours. For example, in a system that has high demand in the morning, setting the
Alternation Time to 24 hours ensures each pump will be the lead pump every other
morning which will equalize the loading between the two pumps.
Note: The lead pump can be manually alternated by pressing the [OK] and right arrow
keys on the lead drive.
Pump exercise
The Pump Exercise Function forces the lead pump to run for a specified time during
lead/lag pump alternation. This function is designed to help prevent the effects that can
occur on a pump as a result of remaining idle for long periods of time. Set the Pump
Exercise Time to the amount of time the new lead pump will run during alternation. For
example, if the Pump Exercise Time is set to 10 seconds, the new lead pump will run for
10 seconds when the lead and lag pumps alternate. Set Pump Exercise Time to 0s to
disable the function.
Operation
70 Aquavar ® Intelligent Pump Controller INSTRUCTION MANUAL