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FDU-80 Instruction Manual —
P/N 51264:C2 4/24/2019
EIA-485 Shield Termination
Shield in Full Conduit
6.2 Shield in Full Conduit
The EIA-485 line allows the FACP to communicate with the FDU-80 Annunciator. The shield for the EIA-485 line must be connected to
earth ground at the FACP (both exiting and entering the FACP) but must be left floating (no connection) at the annunciator if it is the first
or only device on the EIA-485 line. If a second annunciator is connected, the shield leaving the first annunciator must be floating. The
shield entering the second annunciator must be connected to the Earth Ground terminal (P2-7) on the second annunciator. If additional
annunciators are connected, the shield leaving each annunciator must be left floating and the shield entering the following unit must be
connected to the Earth Ground terminal (P2-7) on the annunciator.
Notes:
1.
Power-limited 24 VDC power may be run in the same conduit as the EIA-485 wiring
2.
Twisted, shielded wire is recommended for the EIA-485 communications loop
3.
Each electrical backbox is connected to earth ground via the conduit
4.
Shield is connected to the FACP cabinet (earth ground) leaving and entering the FACP
!
CAUTION: INSULATE SHIELD
DO NOT ALLOW THE FLOATING SHIELD END (NO CONNECTION) TO CONTACT THE CONDUIT. THE FLOATING
END SHOULD BE INSULATED FROM EARTH GROUND.
FDU-80 Box
FDU-80
P1-2 (+)
EIA-485 (IN)
P1-4 (-)
EIA-485 (IN)
P2-7 Earth
Ground (IN)
Connect the shield drain wire to the Earth
Ground Terminal on the Annunciator
Shield Drain Wire
annunciator
annunciator
annunciator
FACP
Earth Ground
Earth Ground
EIA-485 Loop
not in conduit
shield
Figure 6.2 EIA-485 in Conduit
