Innotech Genesis V4 System - Manual (Page 105)

Installation Instructions for Innotech Genesis Systems
Edition 011100
A-24
A-4.2.12. GENII MPI with Non-Isolated Comms. When using a GENII MPI
Modem and Printer Interface which has standard RS485 ICs, the RS485 connection is not
isolated. Connecting a printer or a PC to the MPI will earth it. To prevent earth loops all
other devices on that section of Comms cable must isolate the screen from the electrical
earth.
Figure A-23 shows one local and three remote Genesis II non-isolated Digital Controllers,
all of which have only the four outer links fitted. In this situation it is better to fit GENII
485I Isolated RS485 Comms cards to the three remote Digital Controllers.
Figure A-23. Use of GENII MPI, 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.
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.
Printer
Modem
MPI
Printer
PC M
C