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NO FAILURES -A failure takes a compressor off-line and makes it unavailable for sequenced
operation.
When a compressor determines that it can no longer make capacity adjustments to reduce the system
control parameter it informs the sequencer that it is fully loaded. Compressors are fully loaded when all of
their stages are in use.
Enabling and Disabling the Sequencer
Each sequencer can be enabled or disabled from the sequencer control screen. When a sequencer is enabled or
disabled, all available compressors in the lead list will be sent a sequence stop command. If it is desired that the
compressors continue running, it is suggested that their mode be changed to AUTO before the sequencer is
disabled.
Sequencer Control Groups
A sequencer allows the operator to define up to four different control groups for the system control parameter.
Each control group consists of a control setpoint, a low alarm setpoint and a low failure setpoint. All four control
groups can be modified using the control group select screen.
Sequencer Setpoint Scheduling
Sequencer setpoint scheduling is the automatic switching of control groups based on time of day and day of the
week. Control setpoint groups and the selected lead list can be changed using scheduling. The operator can
define up to seven (7) different daily time schedules and one weekly schedule. Sequencer scheduling can be
enabled or disabled by the operator. All schedule changes are relayed to the compressors and take effect auto-
matically.
Daily Schedules
Each daily time schedule consists of up to eight (8) different time of day slots. For each time of day slot the
operator can define the time, desired setpoint group number, and the desired lead list. Unused time slots are
ignored and the schedule may be entered in any order. When the schedule is saved it is reordered
chronologically. Each daily schedule is identified by a schedule name (SCH1 - SCH7)
Weekly Schedule
The weekly schedule allows the operator to assign different daily schedules to each day of the week. A new
day begins and schedules change at midnight. The sequencer weekly schedule is found on the schedule
setup screen.
Enabling / Disabling Scheduling
The operator may enable or disable setpoint scheduling from the schedule setup screen. When scheduling
is enabled the setpoints are changed to match those defined by the schedule. When scheduling is disabled
the setpoints must be changed manually.
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