EIA-485 Shield Termination
Shield in Full Conduit
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Document 51338 Rev. B 08/24/05 P/N 51338:B
5.2
Shield in Full Conduit
The EIA-485 line allows the FACP to communicate with the LCD-80F
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 con-
nected, 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.
Caution! Do not allow the floating shield end (no connection) to contact
the conduit. The floating end should be insulated from earth ground.
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 communica-
tions 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
EIA-485 Loop
in Conduit
Shield
Earth Ground
Earth Ground
Figure 5-2:
EIA-485 In Conduit
LCD-80F Box
LCD-80F
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
LCD
80F
no
s.
cdr
annunciator
annunciator
annunciator
FACP
