Walchem W600 Series Instruction Manual page 74

goes above 8.50, the on-times for each pump are evaluated. If R1 has been on less than 80% of the total time for
the two pumps, it is energized. Otherwise, R2 has been on for less than 20% of the total time, so it is energized. If
the pH remains above the deadband and does not exceed the second setpoint (8.30 < pH < 9.00), the pump selec-
tion is re-evaluated every 15 minutes and, if warranted, the pump in operation is switched. If the pH proceeds to
exceed 9.00, both pumps are energized and wear leveling is no longer a consideration. When the pH fails to below
8.80, the pump on-times are again evaluated and the appropriate pump is turned off.
Note that while this control is quite powerful, it might cause confusion with users because the setpoints entered
for a specific pump within the Lead Lag group may not coincide with the setpoints used to activate that particular
pump during operation. The information shown on the Details pages for each pump should be sufficient to mini-
mize this ambiguity.
Control Mode Conflicts
Some control modes are incompatible with Lag output functionality because of an interactive relationship between
the output and one or more linked inputs:
• Intermittent Sampling – This control mode places a linked sensor into a Hold state during most of its operational
cycle
• Probe Wash – This control mode places one or two linked sensors into a Hold state when a wash cycle is in
progress and for a specified Hold period afterward
The link between the output and the sensor input(s) cannot be easily transferred to other outputs, so these types of
control modes cannot be designated as Lead output for a Lead Lag group. Outputs configured with these types of
control modes are not included on the selection list presented for Lead output. Also, the control mode of an output
that is the Lead output for a Lead Lag group cannot be changed to one of these types. If selected, the controller will
be unable to save the change and an error message will be added to system log.
Output Details
The details for this type of output include the relay on/off state, relay status (HOA mode, Interlock from sensor cal-
ibration, probe wash, or other condition), the current cycle and the total on-times, alarms related to this output, the
output defined as the Lead of the group, the output that is the Last Lag output of the group, the number of outputs
currently energized within the group, the elapsed time since the last change in the number of outputs energized, the
elapsed time since the last wear leveling evaluation, the type of output, and the current control mode setting.
Settings
Touch the Settings icon to view or change the settings related to the relay.
The Lag control mode output defined as the Last Lag within the Lead Lag group offers settings to define the pa-
rameters controlling operation of the entire group.
All Lag mode outputs that are not the Last Lag output in the Lead Lag group (those that are selected as a Lead
output from another Lag mode output) offer a more limited list of settings.
Lag Settings (Menus with * are shown only in the Last Lag output settings)
HOA Setting
Lead
Wear Leveling*
Wear Cycle Time*
Activation Mode*
Select Hand, Off or Auto mode by touching the desired mode
Select the output that will be the lead output for this relay
Select the wear leveling scheme to use. Refer to the detailed description above.
This setting only appears if Time Balanced or Time Unbalanced Wear Leveling has
been selected above. Enter the amount of elapsed time before time on totals for each
output are reevaluated for wear leveling.
This entry is only appears if the control mode of the Lead output is On/Off, Dual
Setpoint, Spike or Manual. Select one of the options that will determine if and when an
additional output will be activated if the primary output is unable to reach the setpoint.
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