95
in the Lead Lag group are evaluated individually and outputs are added as needed based on the current process
value. Setpoint based activation mode also incorporates time based activation and can also be configured to trigger
an additional pump (if available) after a specified delay time. This menu selection is available only when the Lead
output is using On/Off or Dual Setpoint control modes.
Example 1: The Lead output (R1) is set for On/Off control of pH with a setpoint of 8.50, a deadband of 0.20 and
a “force lower” control direction. The first Lag output (R2) has a setpoint of 9.00 and a deadband of 0.20. The
second Lag output (R3) has a setpoint of 9.50 and a deadband of 0.20. The delay time is disabled (set for 0:00 min
-
utes). Wear leveling is disabled. When the pH goes above 8.50, R1 energizes. If the pH proceeds to exceed 9.00, R2
energizes. And if the pH rises above 9.50, R3 energizes. When the pH decreases to below 9.30, R3 goes off. When
the pH falls to below 8.80, R2 goes off. And finally, when the pH decreases to below 8.30, R1 is turned off.
Example 2: The same three-pump configuration (R1←R2←R3) as in Example 1 except the delay time is set for 30
minutes. When the pH goes above 8.50, R1 energizes. If 30 minutes passes before the pH exceeds 9.00 or drops
below 8.30, R1 remains on and R2 is energized. If the pH then rises above 9.00, the next output in the group, R3, is
energized. If the pH continues to rise and exceeds 9.50, no additional action is possible. When the pH decreases to
below 8.80, R3 goes off. When the pH falls to below 8.30, both R1 and R2 are turned off.
This control is very similar to the operation if three (3) separate On/Off control outputs are configured all with the
pH as Input and using the setpoints listed above. However, the Lead Lag option improves on this control by incor-
porating backup pump controls and optional time based activation. If the pH rises above 8.50 when pump R1 has
an active Flow Verify alarm or is in HOA Off mode, pump R2 immediately energizes. R3 energizes when the pH
goes above 9.00. Although no third pump is available to activate if the pH continues to rise above 9.50, this control
system is more fault tolerant than the currently available options.
Switch Based
When using switch based activation mode, each Lag output has an Activate With Channels setting that is used
to specify one or more digital input or relay output channels that activates an additional output. Switch based
activation mode incorporates time based activation and can also be configured to trigger an additional output (if
available) after a specified delay time. This menu selection is available only when the Lead output is using Manual
control mode.
Example 1: A lift station includes a tank with a high level switch (D1) and a high-high level switch (D2). Three
pumps are configured as a Lead Lag group (R1←R2←R3). The Lead output (R1) is set for Manual control mode
with an Activate With Channels selection of D1 (high level switch), R1 will be energized if D1 closes. The first Lag
output (R2) has an Activate With Channels selection of D2 (high-high level switch). The last Lag output (R3) has
no Activate With Channels selected. All pumps are in HOA Auto mode. The delay time is disabled (set for 0:00
minutes). Wear leveling is disabled. When the high level switch closes, the R1 pump is activated. If the high-high
level switch closes, the R2 pump is also activated. When D2 opens, R2 is turned off. When D1 opens, R1 is turned
off. In this configuration, the R3 pump serves only as a backup in case one of the pumps is down for maintenance
(in HOA Off mode).
Example 2: The same lift station, two-level switches, three-pump configuration (R1←R2←R3) as in Example 1
except the delay time is set for 1 hour. When the high level switch closes, the R1 pump is activated. If the high-high
level switch closes, the R2 pump is also activated. If the tank level remains above the high-high level switch for
another 1 hour, the R3 pump is activated. When D2 opens, R3 is turned off. When D1 opens, both R2 and R1 are
turned off. In this configuration, the R3 pump serves not only as a backup in case one of the pumps is down for
maintenance, but also provides additional capacity should it be needed.
Advanced Functionality
The examples listed above detail the control behavior if wear leveling or output activation modes are enabled. The
features are implemented independently. Wear Leveling modes are used to determine which output(s) are activated.
Output Activation modes determine how many output(s) are activated at one time. More advanced output control
strategies can be implemented when these features are used in combination.
Example: In a two-pump scenario, the Lead output (R1) is set for On/Off control of pH with a setpoint of 8.50,
deadband of 0.20 and a “force lower” control direction. The Lag output (R2) has a setpoint of 9.00 and a dead
-