EIA-485 Shield Termination
Shield in Full Conduit
26
Document 53244 Rev. A 03/14/08 P/N 53244:A
5.2
Shield in Full Conduit
The EIA-485 line allows the FACP to communicate with the LCD-80FC
Indicator. 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 indicator if it is the first or only
device on the EIA-485 line. If a second indicator is connected, the shield
leaving the first indicator must be floating. The shield entering the sec-
ond indicator must be connected to the Earth Ground terminal (P2-7) on
the second indicator. If additional indicators are connected, the shield
leaving each indicator must be left floating and the shield entering the
following unit must be connected to the Earth Ground terminal (P2-7)
on the indicator.
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-80FC Box
LCD-80FC
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 Indicator
Shield Drain Wire
L
CD80F
nos
.c
dr
Indicator
Indicator
Indicator
FACP
