STATUS SCIENTIFIC CONTROLS
MCU System Installation and Hardware Configuration Manual
1.6 Battery Backup
The MCU control units are supplied with a pair of 12V 1.2Ahr maintenance free backup batteries
mounted beneath the main chassis (MCU4 contains 2 pairs of batteries). The batteries are
connected in series enabling them to provide the 24V required by the system in the event of an
external power failure. The power supply for the system provides the charging current required
maintaining the batteries in a fully charged state.
Should the main source of power fail, the system will indicate to the users that it is operating from
its batteries by flashing the green power LED, whilst lighting the yellow fault LED. The fault relay
(RL4) located within the ‘Common Relay Module’ will also operate and therefore trigger any
warning devices added to the system by the user. No audible alarm will be generated.
The backup time provided can not be stated without first considering the configuration of the
system. The backup time is dependent upon:
1. Quantity and type of detector heads used.
2. Time since last power fail and duration of power fail.
3. Alarm status.
4. Relay configuration (whether normally energised or de-energised).
5. External loads placed on the system.
The table below lists the various modules that can be connected to the MCU system and the load
that they place on the system.
Quiescent current of Microcontroller Module + Display
Quiescent current of Input Module
Input Module c/w Toxic Head (Zero Gas)
Input Module c/w Toxic Head (Full Scale)
Input Module c/w Oxygen Head (20.9%)
Input Module c/w Flammable Head (Zero Gas)
Input Module c/w Flammable Head (Full Scale)
Common Relay Module with relays energised.
Input Module Relays with relays energised.
Input Module Analogue Output (Zero Gas)
Input Module Analogue Output (Full Scale)
The time for which the battery will supply power can now be calculated by taking into account the
modules fitted to the system and the configuration of alarm relays (i.e. whether normally
energised or normally de-energised)
To calculate an approximate time for battery backup we need to make several assumptions: -
1. No alarm conditions are encountered during the battery-backed time.
2. Display backlight is off.
3. The batteries are fully charged.
For instances where a longer back up time is required, Status can supply an external battery unit.
This will connect into the system at the Distribution Board and consists of its own internal charger.
Contact Status for more information.
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