Honeywell NOTIFIER SCS Series Operation And Installation Manual page 51

SCS-8L⁄SCE-8L Installation
LDM-R32
EIA-485
Communication between the FACP and the SCS-8L is accomplished over a two-wire EIA-485 serial interface. Up to 32 EIA-485 devices
may be installed on an EIA-485 circuit. The data communication and wiring are supervised by the fire alarm control panel. All SCS-8L
Smoke Control Stations must be in the same room as the FACP/Network Annunciator when in FSCS mode.

Wiring Specifications
The EIA-485 circuit cannot be T-Tapped; it must be wired in a continuous fashion from the control panel to the SCS-8L. The maximum wir-
ing distance between the panel and the last SCS-8L or annunciator is 6000 feet @ 16 AWG. However, all SCS-8L⁄SCE-8L modules must be
contained in the same room with the FACP/Network Annunciator when in FSCS mode. The wiring size must be a 12 to 18 AWG twisted pair
cable having Characteristic Impedance of 120 ohms, +/-20% (Shielded cable is recommended). Limit the total wire resistance to 100 ohms
on the EIA-485 circuit, and 10 ohms on the SCS-8L power circuit. Do not run cable adjacent to, or in the same conduit as, 120 volts AC ser-
vice, noisy electrical circuits that are powering mechanical bells or horns, audio circuits above 25 volts (RMS), motor control circuits, or
SCR power circuits.

Terminal Wiring
The following should be considered when connecting terminal wiring:
• Do not "T-Tap" the EIA-485 circuit; it will not function properly. Wire it as shown in Figure 3.27.
• Install the built-in 120 ohm resistor on the SCS-8L module if it is located at the physical end of the EIA-485 Loop, by turning ON
dipswitch 8 on the SCS-8L. Turn OFF dipswitch 8 on all other SCS-8L modules. If an EIA-485 device other than an SCS-8L⁄SCE-8L is
at the physical end of the EIA-485 loop, install a R-120 resistor across the EIA-485 out terminals of the device and ensure that
dipswitch 8 is turned OFF on all SCS-8L modules.
• Connect Earth Ground to a mounting screw on the backbox or cabinet.
• Connect 24 VDC Power to the SCS-8L. This power need not be supervised by a power supervision relay since it is inherently
supervised by the control panel (loss of communications is registered during loss of power to the SCS-8L).
When the EIA-485 shield is in conduit: Connect it to the system reference (system common). The shield can enter the cabinet, but must be
insulated from the cabinet (no electrical contact). Between Smoke Control Stations, wire-nut multiple shields together and insulate. Treat the
shield like a system wire making certain it does not come in contact with other wires or earth ground.
SCS Series Manual — P/N 15712:L 7/18/16
SCS-8L
Figure 3.24 LDM Ribbon Cable Connection
The SCS⁄SCE
SCS-8L LDM-R32
51