Design Considerations
20 PN 15842:K 7/23/2002
Section 3 Design Considerations
3.1 Limits
The standard Notifier EIA-485 circuit can drive up to 32 annunciators with
expanders. One system can mix ACM-24AT, ACM-48A, ACM-16AT, ACM-
32A, and their expanders with other ACS devices such as LDM, TM-4, etc. An
end-of-line resistor must be installed or enabled on the last ACS device on the
circuit. The number of annunciators that can engage in two-way communication
depends on the number of addresses available with a given fire alarm control
panel. The actual number of ACS devices that can be powered in a particular
system depends on the current available from the control panel’s power supply.
Refer to the installation manual for the particular control panel for more details.
For information on boosting the EIA-485 circuit signal or adding additional
devices (not addresses), see the RPT-485W/RPT-485WF Installation Manual.
3.2 Wire Runs
Communication between the control panel and ACS annunciators occurs over a
power-limited 2-wire EIA-485 serial interface. This communication is
supervised by the fire alarm control panel. Each annunciator/expander module
also requires a power-limited 24 VDC power connection. This power circuit is
inherently supervised; loss of power registers as a communication failure at the
control panel. The ACS can also be powered from a power-limited and
regulated remote power supply listed for fire-protective signalling use
Note: (AM2020/AFP1010 installations only) SIB-2048A/SIB-NET can support
two EIA-485 circuits, each capable of spanning 6,000 feet at 16 AWG. For more
details, refer to Appendix P.
3.3 EIA-485 Wiring Specifications
Wire the EIA-485 circuit as shown in Section 4.5 “EIA-485 Circuit
Connections”. These requirements must be followed:
• The EIA-485 circuit cannot be T-Tapped; it must be wired in a
continuous fashion to function properly.
• There is a maximum of 6,000 feet at 16 AWG between the panel and the
last annunciator on the EIA-485 circuit (subject to your system’s power
restrictions).
Annunciator
Fire Alarm
Control Panel
ACS Power
(12 to 18 AWG)
filtered & power-limited
Two-wire EIA-485 Circuit
(Maximum of 6,000 feet)
power-limited & supervised
caba3.wmf,
ACM-24ATface.cdr
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