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Lead/Lag Set-up
System Configuration must be set to one of the constant pressure modes when using lead/lag control. See
Section 5.5, System Configuration for details. Lead/lag control is enabled when the number of lag pumps is
set to a value greater than zero in the parameter 1.5.1 NUMBER LAG PUMPS.
Programming Steps:
1. Use the keypad to navigate to 1.5.1 NUMBER LAG PUMPS and use the arrow keys to set the
number of auxiliary pumps in the system.
2. If necessary, adjust the remaining Lead/Lag parameters after reading the following description of
their functions, or after operating conditions dictate.
Lag pumps are turned on and off, or “staged” and “destaged” by programmable relays accessed through the
Control Terminals. The drive calls for lag pumps in ascending order, beginning with Relay 1. Figure 22,
provides a wiring diagram.
Lead Lag Parameters (Table 21) are used to smoothly stage the pumps in and out, mitigating pressure
oscillation, short cycling, and water hammer. When the master pump cannot maintain pressure, the drive will
stage in an auxiliary pump. The drive will destage the pump when flow increases pressure beyond the control
point.
Two conditions must be met to stage a pump:
1. The system measured value (PSI, GPM, FT) has decreased to a value equal to 1.4.1 ANALOG
SETPOINT 1 minus 1.5.15 STAGE ANALOG LAG. For example, if the 1.4.1 ANALOG SETPOINT
1 is 50 psi and you want to stage a pump in at 45 psi, 1.5.15 STAGE ANALOG LAG should be set
to a 5.
2. The time set by 1.5.2 STAGE PUMP DELAY has expired. This delay allows momentary drop in
system measured value without calling for a pump to stage in.
Pumps are staged in the following sequence:
1. The relay will open to destage the pump.
2. The speed of the master pump will increase to a value equal to 1.1.1 MIN FREQUENCY plus
1.5.11 DESTAGE FREQUENCY BOOST 1. For example, if 1.1.1 MIN FREQUENCY is 30 Hz and
DESTAGE FREQUENCY BOOST 1 is 5 Hz, the pump speed will be reduced to 35 Hz.
3. The master pump will operate at increased speed for a period set by 1.5.5 DESTAGE TIME.
4. When DESTAGE TIME has expired the system will resume normal constant pressure control.
Pumps are destaged when the drive has slowed the master pump to maintain control pressure/flow/tank level
and the auxiliary pump(s) causes a rise in pressure/flow/tank level.
Three conditions must be met to destage a pump:
1. The system measured value (PSI, GPM, FT) has increased to the value set by 1.5.16 DESTAGE
ANLOG LAG above 1.4.1 ANALOG SETPOINT 1. For example, if 1.4.1 ANALOG SETPOINT 1 is
500 GPM and 1.5.16 DESTAGE ANALOG LAG is 50 the pump will destage at 550 GPM.
2. The time set by 1.5.3 DESTAGE PUMP DELAY has expired. This delay prevents destaging the
auxiliary pump due to momentary overshoot.
3. The drive frequency to the master pump is between 1.1.1 MIN FREQUENCY and the value of 1.5.6
DESTAGE MIN FREQUENCY plus 1.1.1 MIN FREQUENCY. For example, if 1.1.1 MIN
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