Section 6: Eia-485 Shield Termination; Shield Not In Conduit - Honeywell Notifier FDU-80 Instruction Manual

The EIA-485 circuit must be wired using a twisted, shielded pair cable with a characteristic impedance of 120 ohms (+/- 20%). Do not
run cable adjacent to or in the same conduit as 120 VAC service, noisy electrical circuits that are powering mechanical bells or horns,
audio circuits above 25 V
NOTE: To ensure static (ESD - electrostatic discharge) protection, all enclosures, including the FDU-80 electrical box, must be connected
to earth ground! Never use the EIA-485 shield for this purpose. The EIA-485 shield is for radiated noise emission protection (RFI, EMI).
Refer to the following figures for details on EIA-485 shield termination.

6.1 Shield Not in 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 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 left floating. The shield entering the second annun-
ciator must be connected to the three-gang box or Earth Ground terminal (P2-7) on the second annunciator. If additional annunciators are
connected, the shield leaving each enclosure must be left floating and the shield entering each must be connected to the three-gang box
or the Earth Ground terminal (P2-7) on the annunciator.
FDU-80 Instruction Manual — P/N 51264:C2 4/24/2019

Section 6: EIA-485 Shield Termination

, motor control circuits or SCR power circuits.
RMS
Connect the drain wire to the outside of the
FACP cabinet via a BX-type connector.
Shield Drain Wire
FACP
Figure 6.1 EIA-485 Without Conduit
FACP Backbox
shield
annunciator
annunciator
EIA-485 Loop
not in conduit
(+) EIA-485
(-) EIA-485
FACP
annunciator
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