Siemens OH921 Addressable Optical and Thermal Smoke Detector P/N: S54320-F6-A2

The Siemens OH921 Addressable Optical and Thermal Smoke Detector P/N: S54320-F6-A2 is an intelligent multi-criteria detector designed for compatible Siemens fire alarm systems, including Cerberus PRO and FireFinder XLS. It combines photoelectric smoke sensing with electronic thermal detection to analyze both combustion particles and temperature conditions.

The OH921 uses intelligent signal processing to provide enhanced fire detection while helping reject nuisance sources such as dust, steam, and aerosols. Siemens identifies OH921 / S54320-F6-A2 as an active optical and thermal smoke detector.

Product Functions

• Provides intelligent addressable smoke detection
• Combines optical and thermal sensing
• Uses multi-criteria fire detection
• Provides 135°F fixed-temperature heat detection
• Provides rate-of-rise thermal detection
• Supports electronic addressing
• Supports addresses 001–252
• Provides individual point identification
• Provides continuous self-diagnostics
• Monitors detector sensitivity
• Supports built-in dual isolation on applicable versions
• Supports polarity-insensitive operation
• Supports open-area applications
• Supports direct-in-duct applications

Optical Smoke Detection

The OH921 uses photoelectric optical sensing technology to detect smoke particles and other products of combustion.

The detector evaluates information from its optical sensing chamber together with temperature information from its thermal sensor. This multi-criteria approach provides enhanced detection across a broad range of fire conditions.

Thermal Detection

The OH921 incorporates electronic heat detection in addition to its optical smoke sensor.

Fixed Temperature: 135°F / 57°C

Rate-of-Rise: 15°F/min / 8.3°C/min

The thermal element allows the detector to respond to temperature changes as well as smoke conditions.

Multi-Criteria Processing

The OH921 intelligently analyzes information from both its optical and thermal sensing elements.

This processing provides enhanced detection while helping reject nuisance-alarm sources such as:

• Dust
• Steam
• Aerosols
• Other deceptive airborne phenomena

Electronic Addressing

The OH921 uses electronic addressing instead of conventional mechanical address switches.

Supported address range:

001–252

Address programming is performed using compatible Siemens programming equipment, providing individual detector identification on the signaling line circuit.

Built-In Isolation

Applicable OH921 versions incorporate dual built-in isolators.

When configured in isolator mode, the detector can isolate a signaling-line short occurring before or after the device, helping unaffected sections of the circuit continue operating. Siemens specifies isolator mode for product version 17 and later with compatible control equipment.

Self-Diagnostics

The OH921 continuously monitors its sensing chamber, sensitivity, internal sensors, and electronics.

These diagnostic functions help the compatible fire alarm system identify abnormal detector conditions and maintenance requirements.

Open-Area & Duct Detection

The OH921 supports both open-area and direct-in-duct applications.

Open-Area Air Velocity: 0–300 ft/min

Direct-in-Duct Air Velocity: 0–4,000 ft/min

Operating Temperature: 32°F to 100°F / 0°C to 38°C

Maximum Humidity: 95% RH, non-condensing.

Electrical & Detection Information

Model: OH921

Part Number: S54320-F6-A2

Device Type: Addressable Optical and Thermal Smoke Detector

Smoke Sensing: Photoelectric / Optical

Heat Sensing: Electronic Thermal

Fixed Temperature: 135°F / 57°C

Rate-of-Rise: 15°F/min / 8.3°C/min

Address Range: 001–252

Built-In Isolation: Supported on applicable versions

Compatible Bases: DB-11 / DB-11E

Compatible Systems: Cerberus PRO / FireFinder XLS

Product Status: Active.

OH921 Datasheet