LDM Series Instruction Manual —
P/N 15885:H3 8/12/2019
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EIA-485 Shield in Conduit
Wiring Considerations
4.4 EIA-485 Shield in Conduit
When the EIA-485 wiring is in conduit, connect the shield to system common. The shield can enter the cabinet, but must be insulated
from the cabinet (no electrical contact). Between LDMs, wire-nut multiple shields together (which can be inside of the respective LDM
enclosure but ensure that the shield does not contact earth ground).
4.5 EIA-485 Shield Not in Conduit
When the EIA-485 wiring is not in conduit, terminate the shield at the outside of the FACP cabinet. Do not allow the shield to enter or
even touch the cabinet housing the LDMs. Between LDMs, wire-nut multiple shields together
outside of
the respective enclosures.
Ensure that the shield does not touch earth ground at any junction points.
4.6 EIA-485, Power and Relay Wiring
EIA-485 - TB2, Terminals 1 to 4
•
Do not T-tap the EIA-485 circuit. It will not function properly. Wire as shown below. Must be power-limited. See Section 4.3 “EIA-
485 Wiring Specifications” for full details.
•
Leave a 120 ohm resistor installed across the EIA-485 Out terminals at the last LDM on the circuit (see below). All other LDMs
should not have a resistor installed.
Power, Earth Grnd and Relay - TB1, Terminals 1 to 7
•
Connect Earth Ground (TB1-1) to a mounting screw on the backbox or cabinet.
•
Power must be turned off when connecting the 24 VDC Power to the annunciator. Power must be filtered and power-limited. A
power supervision relay is not needed since the annunciator is inherently supervised by the control panel (loss of communication is
registered during loss of power to the annunciator).
Enclosure
Annunciator
Figure 4.3 Terminating the Shield - Conduit
Enclosure
Annunciator
Figure 4.4 Terminating the Shield - No Conduit