System Sensor 2412AT, 2424AT, 2424AIT User Manual

INSTALLATION AND MAINTENANCE INSTRUCTIONS

2412AT, 2424AT, and 2424AIT
Direct Wire Photoelectronic with

3825 Ohio Avenue, St. Charles, Illinois 60174

Fixed Heat Smoke Detectors

Specifications

Diameter: 5.5 inches (14 cm)
Height, with Thermal: 3.19 inches (8.1 cm)
Weight: 0.7 lb. (310 g)
Operating Temperature: 0° to 38°C (32° to 100°F)
Operating Humidity: 10% to 95% Relative Humidity Non-condensing
Visual Indicator: Solid State LED
Locking Alarm: Reset by momentary power interruption
Audible Signal: 85dBA minimum interrupted tone when individual unit is in alarm or when the

supply voltage is reversed.

Electrical Ratings: 2412AT 2424AT or 2424AIT

Operating Voltage: 12VDC 24VDC

Full-wave, Unfiltered Full-wave, Unfiltered

Current

Standby: 120 µA Max. 120 µA Max.
Alarm: 51mA 43mA

(Add 7mA Maximum with RA400Z Remote Annunciator LED)
Reversed Supply: 8mA 15mA
Start-up Time: 36 seconds maximum
Relay Characteristics: One Form A (SPST-NO) for alarm initiation 1.25A at 30 VAC/DC

1-800-SENSOR2, FAX: [phone]

A Division of Pittway

Before Installing

Please thoroughly read the System Sensor manual I56-407­XX, Guide for Proper Use of System Smoke Detectors, which
provides detailed information on detector spacing,
placement, zoning, wiring, and special applications. Copies
of this manual are available at no charge from System
Sensor. (For installations in Canada refer to CAN\ULC­S524, Standard for the Installation of Fire Alarm Systems
and CEC Part 1, Sec. 32.)

General Description

System Sensor 2412AT, 2424AT and 2424AIT
photoelectronic smoke detectors are designed to provide
open area protection and to be used with UL-listed 4-wire
control panels. The 2412AT operates at 12 VDC and the
2424AT and 2424AIT operate at 24 VDC. The sensor in this
detector operates on the light scattering principle and
features a unique photo-optic sensing chamber that
provides good smoke entry while minimizing the effects of
ambient light. These detectors also provide restorable
135°F fixed-temperature heat detection. The 2412AT and
2424AT heat detection unit is integrated with the
photoelectronic sensor while the 2424AIT’s heat detection
unit is isolated from the photoelectronic smoke sensor and
can be monitored separately. In addition, a piezoelectric
horn in each detector produces an interrupted, 85 dBA

minimum tone when the individual detector alarms or
when the supply voltage polarity is reversed.

An LED on each detector lights to provide a local alarm
indication and will remain on when the supply polarity is
reversed. A screw terminal is provided for a remote LED
annunciator optional accessory (RA400Z). These detectors
are listed to UL268 and are latching type system detectors.
The alarm can be reset only by momentary power
interruption. For testing, these detectors have a test switch
or may be tested by inserting a calibrated test card in a test
slot after removing the detector’s cover.

Each detector contains one Form A (SPST-NO) contact for
connection to an alarm-initiating circuit. Supervision of the
detector power is accomplished by installing a Power
Supervisory End-of-Line Relay Module (A77-716) at the end
of the detector power loop. When power is applied to and
through the detectors, the EOL Power Supervisory Module
is energized. Its relay contacts close and provide a closed
series circuit in the control panel’s alarm-initiating loop. A
power failure or break in the detector power loop de­energizes the EOL Module. The relay contacts open and
trigger a trouble signal at the control panel.

D400-04-00 1 I56-288-05

Figure 1. Flush mounting of detector on 4-inch
octagon box:

Figure 2. Detector mounting bracket:

TAMPER

RESISTANT

TAB

A78-1411-00

Mounting Instructions

Each 2400 Series detector unit is supplied with a mounting
bracket kit that permits several mounting techniques:

1. Units may be mounted directly to a 3-inch or 4-inch octagonal,
11/2 inch deep electrical box. (See Figures 1 and 2.)

2. Units may be mounted to a 4-inch square electrical box by
using plaster ring with the supplied mounting bracket kit.

Tamper-proof Feature

This detector includes a tamper-proof feature that, when
activated, prevents removal of the detector without the use
of a tool. To activate this feature, cut off smaller tab at the
scribe line on tamper-proof tab located on the detector
mounting bracket (see Figure 2). Install the detector. To
remove the detector from the bracket once the tamper­proof feature has been activated, depress the tamper-proof
tab located in the slot on the mounting bracket and turn the
detector counterclockwise for removal.

Installation In Australia Only

The installation temperature range for Australia is 5° to
45°C and has been tested per the Australian Standard.
Ignore installation temperatures specified for all other
applications when installing detectors in Australia.
Detectors should be installed by qualified technicians.
Installation of a mains connected power supply unit must
be performed by qualified electricians only. The primary
power will be provided by a panel type system. A recharge­able battery is required as a backup to the external power
supply in case of a mains failure. In standby operation, the
backup battery (fully charged) must be capable of
providing uninterrupted power for at least 7 days to the

TO MAKE DETECTOR TAMPER RESISTANT,

BREAK OFF TAB EXTENSION

AT SCRIBED LINE

A78-534-00

system and all smoke alarms before the panel gives the
required battery-low signal. When the battery-low signal is
given, the battery should be capable of providing power for
another 7 days, after which the backup battery should have
enough energy left to allow a 4-minute alarm signal to be
given by all connected smoke alarms.

Wiring Installation Guidelines

All wiring must be in compliance with the National
Electrical Code and the applicable local codes, and any
special requirements of the local authority having
jurisdiction. Proper wire gauges should be used. The
conductors used to connect smoke detectors to control
panels and accessory devices should be color-coded to
prevent wiring mistakes. Improper connections can prevent
a system from responding properly in the event of a fire.
For signal wiring (the wiring between interconnected
detectors), wire no smaller than 18 AWG is recommended.
Wire sizes up to 12 AWG may be used. For best system
performance, the power (+and –) loop wires should be
twisted pair and installed in separate grounded conduit or
shielded cable to protect the loop from extraneous electrical
interference. If a cable shield is provided, the shield con­nection to and from the detector must be continuous by
using wire nuts, crimping, or soldering as appropriate for a
reliable connection.
Wire connections are made by stripping about 3/8" of
insulation from the end of the wire (use strip gauge molded
in base), sliding the bare end of the wire under the
clamping plate, and tightening the clamping plate screw.
Do not loop the wire under the clamping plate.

Figure 3. Class A or Class B wiring diagram for model 2412AT and 2424AT detectors used with four-wire
control panels:

D400-04-00 2 I56-288-05