Innotech Genesis II Digital Controller (v5) - Manual (Page 117)

Page 117
Genesis II Installation Instructions
© Mass Electronics Pty Ltd 2010 Chapter 5 – Network Installation
5-3.5.6 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 5-15, below). 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.
Switchboard or
Control Panel No. 2
Screen 1 2
Connect Screen
89 90 91 92 93
Screen 1 2
Connect Screen
89 90 91 92 93
Switchboard or
Control Panel No. 1
Screen 1 2
Connect Screen
89 90 91 92 93
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.
89 90 91 92 93
Screen 1 2
Connect Screen
Six outer links
fitted. Screen is
earthed via
Terminal 2.
D
ANGER
OUS EAR
TH C
ONNEC
TION!
NO
T
TO BE USED!
Section 5-3.5.6 below, and their referenced figures, describe improper earth connection condition that could lead to
severe electrical shock damage to equipment. Read and understand these paragraphs thoroughly before making
any comms connections.
CAUTION
Figure 5-15: Hazardous Connection Example, Circuit 1