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Section 5
SEQUENCING TIMERS
5.1 RECOVERY TIME AND DELAYED START TIMER
The Recovery Timer is used to keep machines from starting, loading or unloading all at the
same time. The Delayed Start timer is used to keep machines from starting unnecessarily
due to temporary load changes. These timers and the Lowest Pressure Parameter are used
to tune a system so that it is energy efficient but still responds to system demand changes.
Delaying loading and starting of machines will make the system more efficient, but must be
balanced against system demands. For example delaying the start of a machine will be
more energy efficient but could cause system pressure to drop below desired levels.
The Recovery Timer is used in conjunction with the load and unload parameters. There are
also two calculated parameters derived from the load and unload settings. These are the
Sequencing Unload and Sequencing Load pressures. The Sequencing Unload pressure is
2 psi below the unload setting. The Sequencing Load pressure is 2 psi above the load set-
ting. For example, if the Unload Parameter is set to 110 and the Load Delta parameter is
set to 10 then:
110
Unload pressure, all machines unload above this pressure
108
Sequencing unload pressure, trim machine unloads above this pressure
102
Sequencing load pressure, next machine in sequence loads below this pressure
100
Load pressure, all machines load below this pressure
If the system pressure goes above 110 (eg. 111) for any reason, all machines will unload
immediately (regardless of recovery timer). If the system pressure goes below 100 (eg. 99)
all running machines will load (regardless of recovery timer). The recovery timer only comes
into play if the pressure is between 108-110 (for unloading), or 100-102 (for loading). The
following examples will describe operation.
Note: The recovery timer is an accurate timer. However because of system delays caused
by variables like filtering and communications, this may vary from 0 to 5 seconds. So for
example if the recovery timer is set to 10 seconds, the actual delay may be from 10 to 15
seconds.
The Delayed Start Timer and the Lowest Pressure parameter are used to keep machines
from starting unnecessarily due to temporary load changes. If system pressure drops below
the Load Pressure setting, but is above the Lowest Pressure setting, then the Delayed Start
Timer is used to time the start of the next machine in sequence. This timer starts at 120 sec-
onds but will time out sooner if the pressure drops. The length of time is prorated over the
difference between the Load Pressure setting and the Lowest Pressure setting. For exam-
ple if the Load pressure is 100 and the Lowest Pressure is 70 then.
If System Pressure is above 100 and drops to (and stays at) :
99, machine will start in about 2 minutes.
85, machine will start in about 1 minute.
70, machine will start in about 30 seconds.
Because of varying pressures and other delays these times are approximate. The following
examples show how the Recovery and Delayed Start timers work.
Summary of Contents for Supervisor 2 Deluxe
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