Innotech Genesis V4 System - Manual (Page 97)

Installation Instructions for Innotech Genesis Systems
Edition 011100
A-16
WARNING
PARAGRAPHS A-4.2.9.1 AND A-4.2.9.2, BELOW, AND THEIR
REFERENCED FIGURES DESCRIBE IMPROPER EARTH-
CONNECTION CONDITIONS THAT COULD LEAD TO SEVERE
ELECTRICAL SHOCK OR DAMAGE TO EQUIPMENT. READ
AND UNDERSTAND THESE PARAGRAPHS THOROUGHLY
BEFORE MAKING ANY COMMS CONNECTIONS.
A-4.2.9.1. Hazardous Earth-Connections. When the Digital Controllers are
supplied and earthed from two different switchboards, a hazardous situation can be
created. One earth connection is at the local switchboard and the second earth
connection is by way of the screen of the Comms cable (Figure A-15). In the event of a
fault, there could be full supply voltage difference between the two earth connections.
This can destroy the RS485 ICs and anyone touching the screen can receive a severe
electric shock. The RS485 ICs in the three Digital Controllers in Control Panel No.2
will be damaged if the voltage difference exceeds the ratings of the ICs. Because of this
hazard, this arrangement of connection should not be used.
Figure A-15. Hazardous Connection Example, Circuit 1.
Switchboard or
Control Panel No. 2
Screen 1 2
Connect Screen
Screen 1 2
Connect Screen
Switchboard or
Control Panel No. 1
Screen 1 2
Connect Screen
Only four outer
links fitted.
Screen is not
earthed.
Only four outer
links fitted.
Screen is not
earthed.
Only four outer
links fitted.
Screen is not
earthed.
Screen 1 2
Connect Screen
Six outer links
fitted. Screen is
earthed via
Terminal 2.