Intelligent Detection Devices - center
Data Sheet
Intelligent Detection Devices
Multi-Criteria Fire Detector
Model OH921
• Multi-criteria addressable fire detector that incorporates photoelectric and thermal sensors
• Compatible with device programmer / loop tester, Model DPU
• Responds to both flaming and smoldering-fire signatures
• Polarity insensitive utilizing SureWireTM technology
• Tri-color detector status LED with 360° viewing
• Remote sensitivity-measurement capability
• Field-selectable application profiles
• Each detector is self-testing:
 complete diagnostics performed every 10 seconds
 self monitored for sensitivity within UL Listed limits
• Superior EM I immunity
• Compatible with DB-11 series mounting bases
• Compatible with FireFinder® XLS (with
Siemens Model ‘H’-series devices on same loop)
• Listed and approved as heat detector
 Rate-of-Rise Detection: 15°F / min. (8.3°C / min),
and fixed 135°F (57°C)
• RoHS compliant
• Automatic environment compensation
• UL Listed and ULC Listed;
FM (#3230, 3210), CSFM (#7272-0067:0258) Approved
Product Overview
The Model OH921 photoelectric detector
incorporates both optical and thermal sensors, and
uses signals in a neural network to create an
intelligent multi-criteria detector. The
encompassing result is a detector that provides
enhanced detection to a wide range of products of
Model OH921 utilizes advanced multi-criteria
detection technology. The multi-criteria detector
also has state-of-the-art microprocessor circuitry
(with error check), as well as detector selfdiagnostics and supervision programs that is used
on Cerberus PRO 50-point (Model FC901), 252point (Model FC922 / FV922) and 504-point (Model
FC924 / FV924) addressable fire alarm control
panels (FACPs).
Cerberus® PRO
Fire Safety Products
Answers for infrastructure
Additionally, Model OH921 is a plug-in, addressable,
two-wire and multi-criteria detector (with both
photoelectric and thermal inputs) that is compatible
with FireFinder® XLS systems.
Model OH921 is compatible with the Siemens ─ Fire
Safety field-device programmer / test unit. Model
DPU is a compact, portable, menu-driven accessory
for electronically programming and testing detectors,
easily and reliably.
Model DPU eliminates the need for cumbersome,
unreliable mechanical programming methods, such
as dials or switches, and reduces installation and
service costs by electronically programming and
testing the detector prior to installation.
Multi-Criteria Fire Detector
Product Overview ─ (continued)
Profile Overview
Each detector consists of a dust-resistant photoelectric
chamber; a solid state, non-mechanical thermal sensor, and
microprocessor-based electronics with a low-profile plastic
housing. Every Model OH921 fire detector is shipped with a
protective dust cover:
Model OH921 provides two (2) different alarm sources that
can be selected individually (ON or OFF) by the control panel.
Alarm Source 1 (Neural Network) – Combines smoke – heat
with the following selectable profiles:
• Sensitive
• Robust
• Standard
Sensitive: This parameter set is practically suitable for areas
where few misleading sources of false alarm are present, and
is appropriate where priority is given to detecting open fires
as soon as possible (e.g. – typically a clean application
with controlled environmental conditions.)
Model OH921 utilizes an infrared light emitting diode (IRLED),
and infrared light-sensing photodiode. Under normal
conditions, light transmitted by the LED is directed away from
the photodiode and scattered through the smoke chamber in a
controlled pattern.
The smoke chamber is designed to manage light dissipation
and extraneous reflections from dust particles or other nonsmoke, airborne contaminants in such a way as to maintain
stable, consistent detector operation. When smoke enters the
detector chamber, light emitted from the IRLED is scattered by
the smoke particles, and is received by the photodiode.
Model OH921 also utilizes a modern, accurate and shockresistant thermistor to sense temperature changes.
The signal processing with detection algorithms allows the
detector to first gather smoke and thermal data, and then
analyze this information in the detector’s ‘neural network.’ By
comparing data received with the common characteristics of
fires or fire signatures, Model OH921 can compare these
signals to those of deceptive phenomena that cause other
detectors to false alarm.
Robust: This parameter set offers improved resistance to
false alarms in areas where misleading sources, such as
cigarette smoke or exhaust fumes, may cause a nuisance
Standard: This parameter set is practically apt for normal
office, hotel lobby type applications and is the default setting.
Alarm Source 2 (Thermistor) – Heat only, provides the
• Static / fixed at 135°F (57°C), default setting
• Rate-of-Rise Detection: 15°F / min. (8.3°C / min)
If the detector is not programmed, Model OH921 will default
to a ‘standard’ profile setting, which allows operation for a
normal office-type environment.
Model OH921 contains a tri-color LED indicator, capable of
flashing any one (1) of three (3) distinct colors: GREEN ,
Y ELLOW, or RED. During each flash interval, the
microprocessor-based detector monitors the following:
• Smoke in its sensing chamber
• Smoke sensitivity is within the range indicated
on the nameplate label
• Internal sensors and electronics
Based on the results of the monitoring, the LED indicator
flashes the following:
Each Model OH921 detector provides three (3) preprogrammed parameter sets that can be selected by the FACP.
No Flash:
(in seconds)
Normal supervisory
operation. Smoke sensitivity
is within rated limits.
Detector is in trouble and
needs replacement.
Alarm condition.
Detector is not powered.
LED can be turned OFF.
Please follow the corresponding description of the panel used.
s Industry, Inc.
Building Technologies Division
Cerberus® PRO
All Model OH921 detectors use a surface-mounting base,
Model DB-11 or Model DB-11E, which mounts on a 4inch octagonal, square or single-gang electrical box.
The base utilizes screw-clamp contacts for electrical
connections and self-wiping contacts for increased
The Model DB-11 base can be used with the optional
Model LK-11 detector locking kit, which contains 50
detector locks and an installation tool to prevent
unauthorized removal of the detector head. Model DB11 has decorative plugs to cover the outer mounting
screw holes.
Model OH921 may be installed on the same initiating
circuit with the Siemens Model ‘H’-series detectors
(Models HFP-11 and HFPT-11); Model ‘HMS’-series
manual stations; Model ‘HTRI’-series interfaces; Model
HCP output-control devices, or Model ‘HZM’-series of
addressable, conventional zone modules for
FireFinder XLS control panels.
All Model OH921 detectors are approved for operation
within the UL-specified temperature range of 32 to
100°F (0 to 38°C).
Model OH921 fire detectors can be applied within the
maximum 30-feet center spacing (900 sq. ft. areas,)
as referenced in NFPA 72. This application guideline is
based on ideal conditions, specifically, smooth ceiling
surfaces, minimal air movement, and no physical
obstructions between potential fire sources and the
actual detector. Do not mount detectors in close
proximity to ventilation or heating and air
conditioning outlets. Exposed joints or beamed
ceilings may also affect safe spacing limitations for
Should questions arise regarding detector placement,
observe NFPA 72 guidelines. Good fire-protection
system engineering and common sense dictate how
and when fire detectors are installed and used. Contact
your local Siemens Industry ─ Fire Safety distributor or
sales office whenever you need assistance applying
Model OH921 in unusual applications. Be sure to
follow NFPA guidelines and UL Listed / ULC Listed
installation instructions ─ included with every Siemens
− Fire Safety detector ─ and local codes as for all fire
protection equipment.
Model DPU
Technical Data
The Device Program / Test Unit accessory is used to
program and verify the address of the detector. The
technician selects the accessory’s program mode, and
enters the desired address. Model DPU automatically
sets and verifies the address and tests the detector.
+32°F (0°C) to 100°F (38°C)
Relative Humidity:
0 - 95%; non-condensing
Air Velocity:
0 − 4,000 ft. / min (0-20m / sec)
Model DPU operates on AC power or rechargeable
batteries, providing flexibility and convenience in
programming and testing equipment from practically
any location.
When in the test mode, Model DPU will perform a
series of diagnostic tests without altering the address
or other stored data, allowing technicians to
determine if the detector is operating properly.
Air Pressure:
No effect
30-foot centers (900 sq. ft.),
per NFPA 72 and ULC-S524 Listed
Input Voltage Range:
Alarm Current:
16VDC − 30VDC
280µA, max.
Application Data
Standby Current:
Installation of the Model OH921 series of fire detectors
requires a two-wire circuit. In many retrofit cases, existing
wiring may be used. ’T-tapping’ is permitted only for ‘Style
4’ (Class B) wiring. Model OH921 is polarity insensitive,
which can greatly reduce installation and debugging time.
Thermal Rating:
 Fixed-temperature set point: 135°F (57°C)
 Rate-of-Rise Detection: 15°F / min. (8.3°C / min)
280µA, max.
Detector Weight:
0.317 lbs. (0.144 kg.)
Mechanical Protection Guard:
UL Listed / ULC Listed
with ST I Guard Model ST I-9604
s Industry, Inc.
Building Technologies Division
Cerberus® PRO
Mounting Diagram
Details for Ordering
OH921 S54320-F6-A2 Addressable Multi-Criteria Fire Detector
500-094151 Detector Mounting Base for Series 11
DB-11E 500-094151E Detector Base {small}
STI -9604
FireFinder XLS
50-point FACP
252-point addressable FACP
252-point intelligent voice
communication panel
504-point addressable FACP
504-point intelligent voice
communication panel
s Cerberus® PRO
Siemens Industry, Inc. ─ Building Technologies Div.
8 Fernwood Road • Florham Park, NJ 07932
Tel: (973) 593-2600 • Fax: (908) 547-6877
Remote Alarm Indicator:
4” octagon-box mount, red
Remote Alarm Indicator:
single-gang box mount, red
500-695350 Base Locking Kit for Series 11 Detectors
STI Mechanical Protection Guard
See: www.ST for further details on ordering
Model ST I-9604.
Building Technologies Division
SII ─ Fire Saf et y
[Printed in U.S.A ]
Compatible FACPs
In Canada, order:
Detector Mounting Base
for Series 11 Detectors ( ULC Listed)
NOTICE ─ The information contained in this data-sheet document is intended only as a summary,
and is subject to change without notice. The devices described here have specific instruction sheets
that cover various technical, limitation and liability information.
Copies of these instruction sheets and the General Product Warning and Limitations document,
which also contains important information, are provided w ith the product and, are available
from the Manuf acturer.
Informat ion cont ained in t hese document s should be consult ed before specifying or using the
product. For further information or assistance concerning particular problems contact the Manufacturer.
March 2015 ─ Supersedes sheet dated 10/2014
(Rev. 7)
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