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P O W E R I N G T E C H N O L O G Y
Document Number: MS0031-MAN rev. 7
guardian_access_ms31-man-rev7-0521.indd
2.4 System Components
With the exception of the rectifier modules the Guardian Access system is delivered with
all components mounted according to the ordered configuration. The main components are
described below and in later chapters of this manual.
2.4.1 System Controller
The Guardian power system can be controlled by the ACX Advanced controller. The
description and operation of these controllers is covered in separate manuals which are
available at:
ACX Advanced:
https://www.unipowerco.com/pdf/acx-man.pdf
2.4.2 DC Distribution Unit
The distribution unit includes configurable load breakers, battery breakers, a shunt for
battery current measurement and fuse alarms for load and battery breakers.
The distribution unit has no special operation other than switching the load and battery
breakers on and off. All trip states of breakers are supervised by measuring the voltage
drop across each breaker.
Breakers that are not connected to any load will not cause a breaker alarm even if they
are left open.
A battery fuse alarm may not be triggered instantly when a battery breaker is off. The
alarm is triggered only when the voltage drop between the system voltage and the battery
voltage is more than 1.5V. The interval that the voltage drop increases to 1.5V depends
on the battery status.
Due to a small leakage current (2.5-3mA) through the alarm circuit, the voltage measured
with a Digital Volt Meter (DVM) on an open breaker output will be nearly equal to the
rectifier output voltage.
The distribution module has common “+Ve” with load breakers in “-Ve” leg. For more
information see schematic drawing in Appendix A - Drawings.
2.4.2.1 Low Voltage Disconnect (LVD)
Generally, the system is equipped with low voltage battery disconnection, which
prevents the batteries from deep discharging, thus prolonging the battery life. A
disconnection requires a detected mains failure at the supervision unit.
If disconnection occurs, the batteries will not supply power to the load until they have
been recharged to set voltage level, which can be adjusted by the user.
