2. DELCOS 3100 Base-Load Sequencing
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2
DELCOS 3100 Base-Lo ad Seq uen cin g
2.1
Overview
Base-load sequencing (BLS) is set in the [BASE LOAD
SELECT.] menu option which is only displayed if the
"base-load sequencing" option is installed (version FS
and SR). BLS is a separate and independent part of the
master's normal compressor control system. It only
requires the following information from the master:
•
Current network pressure
•
Timer setting
The status in which the master machine is operating,
therefore, is immaterial. In other words, the master can
be shut down or even malfunctioning. These are the
only events that result in BLS failure:
•
Master without power supply
•
Fault: network pressure centre
•
[WARNING MS-BUS:A06] (failed relay module for
activating slaves)
The following terms are used below:
BLS:
Base-load sequencing
BLS array::
Array of compressors in relation to the
given network pressure switching points.
Master:
Compressor K1. This is the compressor
to which the slave compressors are
connected via the relay module.
Slave:
Compressors K2 to K5 that are switched
on-load via the relay module.
Relay module A06:
Printed circuit board in the control
cabinet of the master machine that is
provided with floating contacts for
activating slaves and to which (optional)
the fault messages from slaves can be
connected.
CHANGEOVER TIME: Period for which the current
base-load machine is to be retained
before changing over in the BLS array.
Compressors K2 to K5 receive the on-
load/off-load commands from the master
control system. A relay module is
installed in the master control system for
this purpose (see electrical circuit
diagram). The relay contacts must be
integrated in the control system of the
slave in such a way that when a relay
responds (contact closed) the
compressor connected is switched to on-
load operation. To prevent the machine's
normal on-load/off-load controller from
influencing BLS operation, the switching-
point setting must be changed
accordingly on each slave.
Time remaining: Indication of when next changeover will
be selected in the sequence.
For version SR only:
CUT-OUT POINT:
BLS setting that defines the
upper limit of the pressure band.
TARGET PRESSURE: BLS setting to which the speed-
controlled system (master) tries
to adjust.
CUT-IN POINT:
This value results from the setting
for CUT-OUT POINT and
TARGET PRESSURE (see 2.6.5)
2.2
Functional description / attributes
The [CUT-OUT POINT] setting and [TARGET
PRESSURE] (or [CUT-IN POINT] in version FS) setting
in the [BASE LOAD SELECT.] menu defines the network
pressure range that is to be maintained by base-load
sequencing. The control system switches compressors
on and off in relation to network pressure leaving this
range or in relation to wide fluctuations in the demand for
compressed. As the speed is also determined at which
to leave the setpoint range, cut-in and cut-out takes
places either quickly or slowly. The remaining functions
are covered in the descriptions of the various setting
capabilities.
Attributes of BLS:
•
Independent operation, no station failure in
response to a fault or temporary master shutdown.
•
If one compressor fails, the following compressors
move up, the malfunctioning compressor is re-
incorporated after the fault has been eliminated
(requires connection of slave fault messages to the
master machine).
•
Status display of remaining switchover time, on-
load/off-load operation and malfunctioning of
compressors; status display can also be selected in
normal operation without entering the BLS menu.
•
Capability of setting switchover time, remaining
time and current base-load array in operation.
•
Test routine (300s) and blockable switchover time
(fixed BLS sequence)
•
Switchover time runs while base-load system is in
on-load operating mode
•
Using the "LOAD NET IN xx min" parameter, it is
possible to achieve a situation whereby only a
limited number of compressors is switched on for
the classic "Monday morning start".
•
It is possible to define spare compressors that do
not take part in BLS and are thus permanently
allocated as (spare) peak-load compressors.
•
Pressure changeover possible via timer and/or
external contact.
•
Version RS and SR only: the BLS disconnects
slave compressors if their volumetric flow reserve is
sufficient to provide the delivery rate. The status
display shows the delivery rate of an individual
machine and/or of the entire station.
