Xylem IM255 AQUAVAR Intelligent Pump Controller - Manual (Page 73)

NOTE: If Pump Exercise is enabled, the pump will run after alternation of the lead pump
even if there is no demand in the system.
NOTE: If Duty Standby is enabled, Pump Exercise cannot be disabled. Refer to the table
below for details.
The settings for Duty Standby, Pump Exercise and Start Delay can impact when a pump is
expected to start. The table below shows how these settings impact when a pump will
start.
Duty Standby Pump Exercise Explanation
Disabled Disabled If both controls are given a start command at the same
time or both controls are reset from a fault at the same
time, both pumps will run until the lead pump and lag
pump roles are established. With both functions
disabled, the duplex system will operate as a lead/lag
system. On Alternation, the new lead pump will not run
unless there is demand in the system.
Disabled Enabled The lag pump will start when the lead pump wakes up
from sleep or if the lead pump is stopped and is then
given a start command. For these conditions the lag
pump will run for the time specified in Pump Exercise
Time [22-40]. The lag will continue to run if the speed
command from the lead pump is greater than the Lag
Pump Stop Frequency [4-12].
On Alternation, the new lead pump will run for the time
specified in Pump Exercise Time. After the Pump Exercise
Time, the pump will continue to run if demand is present
or will go to sleep if there is no demand.
Enabled Enabled On Alternation and no demand, the new lead pump will
start and run for the time specified by Pump Exercise
Time [22-40] or Sleep Delay [22-24], whichever is longer.
The pump will then go to sleep, if enabled.
On Alternation with demand, the new lead pump will
ramp up while the previous lead pump is ramping down.
In order to ensure both pumps do not run at the same
time in this condition, set the Start Delay [1-71] time
longer than the Ramp Down Time [3-42].
Start delay
The Start Delay Function delays the lead pump from starting for the time specified. This
function can be used to prevent rapid cycling of the system or to prevent the new lead
pump from starting up while the lag pump is ramping down during alternation. For
example, if the Start Delay Time is set to 10 seconds and the pump is given a start
command, the pump will start 10 seconds after the command to start is received by the
controller. In a Duplex System with the Start Delay set to 10 seconds, if Alternation is
enabled and the Alternation Time expires the new lead pump will start after a 10 second
delay. If Duty Standby is enabled, set the Start Delay longer than the Ramp Down Time
[3-42] of the other pump to ensure both pumps do not run at the same time.
Operation
Aquavar ® Intelligent Pump Controller INSTRUCTION MANUAL 71