2.4.1.1 Selecting Mains Input Voltage
1. Ensure AC mains supply is disconnected from the MCU Control Unit.
2. Rotate the screw located centrally on the yellow cover anti-clockwise until the cover is
released. It is not necessary to completely remove the screw from the cover assembly.
3. Slide the voltage selector switch into the appropriate position dependent upon the AC Mains
Voltage to be used.
Note that the 115V setting is used for 110-120V supplies and the 230V setting is used for
220-240V supplies.
4. Refit yellow cover before connecting AC mains supply.
Note
FS1 (located to the right of the mains input connector) is a T1.0A fuse.
2.4.2 24V DC Connection
The MCU system can be powered from an external power supply. The external PSU must
provide a fused 24V (2A min) supply. The fuse should be F2A rated.
2.5 Cable Routing
Due to the low signal levels generated by gas detectors it is recommended that all wiring to the
sensors by segregated away from AC mains or other high voltage/power lines to avoid
interference.
2.6 Cable Screening
The use of a screened cable is recommended for the installation of all detector heads. The
screening is used to minimise the effects of electrical interference generated by external
equipment e.g. motors, switchgear etc. The correct strategy for connecting the screens depends
upon the area in which the detector head is to be used (i.e. hazardous/ non-hazardous). In all
cases the screen should not be connected at the detector head.
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