Xylem IM255 AQUAVAR Intelligent Pump Controller - Manual (Page 86)

Under pressure function
The Under Pressure Function protects the pump and system by preventing the pump
from running below a specified low pressure for a specified amount of time. This function
can protect the pump from damage caused by running at runout flow and/or can protect
the system from unexpected leakage such as from an open valve or ruptured pipe. Set the
function to Alarm to trip the drive and issue an alarm message on the LCP during an
Under Pressure condition. Set the function to Warning to issue a warning message on the
LCP during an Under Pressure condition. Set the function to Off to disable the function.
NOTE: The Under Pressure Alarm will reset according to Reset Mode [14-20] and
Automatic Restart Time [14-21].
To configure this function the Under Pressure Delay Time [22-51] and Under Pressure
Difference [22-52] must be set. The Under Pressure Delay Time [22-51] is the amount of
time that the system pressure must be below the Under Pressure Difference [22-52] before
issuing the Under Pressure alarm or warning.
NOTE: Setting the Under Pressure Delay Time [22-51] less than the No Water/Loss of
Prime Protection Delay [22-27] will cause the Under Pressure Alarm to trip before the No
Water/Loss of Prime Alarm in cases where the pressure drop in the system is due to the
pump running dry or losing prime. To avoid this set the Under Pressure Delay Time
[22-51] longer than the No Water/Loss of Prime Protection Delay [22-27].
The Under Pressure Difference [22-52] is the difference between the setpoint pressure the
actual pressure that will trigger the Under Pressure function. This pressure is set as a
percent of the [20-14] Maximum Reference/Feedback. For example, the Under Pressure
Delay Time [22-51] is set to 10 seconds, the Under Pressure Difference [22-52] is set to
10%, the pressure setpoint is set to 50 psi and the [20-14] Maximum Reference/Feedback
is set to 300 psi. If the system pressure falls below 20 psi (50 psi – (10% * 300 psi)) for
more than 10 seconds, the controller will issue an Under Pressure Alarm or Warning.
Pump protect function
The Pump Protect Function provides a way to stop the pump based on the state of an
external protection device. The external device must be wired to DI 19 (parameter 5-11)
or DI 27 (parameter 5-12), refer to the Common Terminal Wiring section in this manual for
details. One side of the external device must be wired to 24V (terminals 12 or 13) and the
other is wired to the digital input (terminal 19 for digital input 19 or terminal 27 for digital
input 27). Refer to the Common terminal wiring configurations section in this manual for
details on control terminal wiring.
Operation
84 Aquavar ® Intelligent Pump Controller INSTRUCTION MANUAL