System Sensor DNR Intelligent Duct Smoke Detector

The System Sensor DNR Intelligent Duct Smoke Detector is an addressable non-relay duct smoke detector housing designed to detect smoke traveling through HVAC ductwork. It uses compatible intelligent detector heads to sample air moving through the duct and communicate alarm or trouble conditions to a compatible fire alarm control panel.

The DNR is part of the InnovairFlex family and incorporates low-flow detection technology that supports air velocities from 100 to 4,000 feet per minute. Its pivoting housing can be configured with either a rectangular or square footprint, allowing installation on round or rectangular ductwork.

Product Functions

• Provides intelligent smoke detection for HVAC duct systems
• Uses smoke detection technology with a compatible sensor head
• Operates in air velocities from 100 to 4,000 FPM
• Supports duct widths from 6 inches to 12 feet
• Communicates directly with a compatible addressable fire alarm control panel
• Requires communication-line power only
• Uses a compatible intelligent detector head sold separately
• Provides remote test capability
• Includes a front-accessible test/reset button
• Supports remote annunciator and test accessories
• Features a pivoting housing for square or rectangular installation
• Mounts to round or rectangular ductwork
• Uses tool-free sampling tube installation
• Allows sampling tube installation from either side of the housing
• Provides a cover tamper trouble signal
• Includes increased internal wiring space
• Provides a 3/4-inch conduit knockout
• Can accommodate an optional addressable relay module where Form C relay operation is required
• UL, FM, and CSFM listed or approved as documented by Honeywell/System Sensor

Duct Smoke Detection

The DNR uses detection technology to monitor air passing through an HVAC duct.

Air from the duct is directed through the detector housing by an inlet sampling tube. The detector analyzes the sampled air for smoke particles and, when sufficient smoke is detected, the compatible intelligent sensor communicates an alarm condition to the fire alarm control panel.

The fire alarm system can then initiate programmed responses such as shutting down fans or blowers, controlling air-handling equipment, or activating other life-safety functions intended to reduce the distribution of smoke and fire gases through the HVAC system.

Airflow Range

The System Sensor DNR is designed to operate over a broad range of HVAC airflow conditions.

Air Velocity Range: 100–4,000 ft/min
Metric Range: 0.5–20.3 m/s

Duct Size Compatibility

The DNR can accommodate duct widths ranging from approximately:

Minimum Duct Width: 6 inches
Maximum Duct Width: 12 feet

Sampling Tube Installation

The DNR uses a patented sampling tube system designed to simplify installation and service.

The sampling tube:

• Installs without tools
• Can be inserted from the front or rear side of the housing
• Is available in multiple lengths for different duct widths
• Directs moving duct air through the detector chamber
• Uses a separate exhaust tube to return sampled air to the duct

The appropriate DST-series sampling tube must be selected based on the width of the HVAC duct.

Proper sampling tube orientation and sizing are essential for reliable duct smoke detection.

Flexible Housing Configuration

One of the main design features of the InnovairFlex DNR is its pivoting detector housing.

The housing can be configured in either a rectangular or square footprint, providing greater flexibility when mounting the detector to different HVAC duct arrangements.

Supported mounting arrangements include:

• Rectangular ductwork
• Round ductwork
• Horizontal duct installations
• Vertical duct installations where permitted
• Tight mechanical spaces where enclosure orientation is important

This configuration allows the wiring compartment and sensor section to be positioned for easier installation and servicing.

Addressable Operation

The DNR is designed for intelligent addressable fire alarm systems.

The compatible detector head contains the address-setting code wheels and communicates with the fire alarm control panel through the system communication line. Honeywell notes that the detector requires communication-line power only, eliminating the need for a separate detector operating power circuit in standard configurations.

The exact detector head and communication protocol depend on the fire alarm control panel being used. Compatibility should therefore be confirmed using the current System Sensor/Honeywell detector-base cross-reference or control panel documentation.

Remote Testing

The DNR supports remote testing and annunciation accessories.

Common compatible accessory families include:

• RTS151 Remote Test Station
• RTS151KEY Key-Operated Remote Test Station
• RA100Z Remote Annunciator

Accessory compatibility should be confirmed for the specific installed detector head and system configuration.

Optional Relay Module

The standard DNR is a non-relay duct detector.

This allows system designers to add relay control capability without requiring a separate remote enclosure in many applications.

Physical Dimensions

The DNR can be configured in two different housing footprints.

Rectangular Configuration

Length: 14.38 in / approximately 37 cm
Width: 5.0 in / 12.7 cm
Depth: 2.5 in / 6.36 cm

Square Configuration

Length: 7.75 in / 19.7 cm
Width: 9.0 in / 22.9 cm
Depth: 2.5 in / 6.35 cm

Weight: Approximately 1.6 lb / 0.73 kg

The pivoting design allows the same detector housing to be adapted to different duct and installation space requirements.

Environmental Specifications

The DNR is designed for use in HVAC environments within the manufacturer’s specified temperature and humidity limits.

Operating Temperature: −4°F to 158°F / −20°C to 70°C
Operating Temperature with Module Installed: 32°F to 120°F / 0°C to 49°C
Storage Temperature: −22°F to 158°F / −30°C to 70°C
Relative Humidity: 0% to 93%, non-condensing
Air Velocity: 100–4,000 ft/min / 0.5–20.3 m/s

Installation Information

Installation of the DNR typically includes:

• Selecting a proper mounting location on the HVAC duct
• Confirming airflow direction
• Measuring duct airflow velocity
• Selecting the correct sampling tube
• Drilling the required mounting and sampling tube openings
• Mounting the detector housing securely to the duct
• Installing the inlet sampling tube
• Installing the exhaust tube
• Connecting SLC communication wiring
• Installing the compatible intelligent sensor head
• Setting the sensor address
• Installing an optional relay module where specified
• Verifying proper cover installation
• Testing detector operation after installation

System Sensor specifies that the DNR must be installed within the stated airflow and environmental limits for reliable operation.

Testing & Maintenance

Testing should confirm:

• Proper communication with the fire alarm control panel
• Correct detector address
• Proper detector head installation
• Proper sampling tube installation
• Correct airflow through the detector
• Proper fire alarm control panel indication
• Correct remote test station operation where installed
• Proper remote annunciator indication
• Correct cover tamper trouble operation
• Proper optional relay operation where installed
• Secure field wiring and terminal connections
• Proper system restoration after testing

The front-cover test/reset feature helps simplify routine testing and servicing.

Product Identification

Manufacturer: System Sensor / Honeywell
Model: DNR
Series: InnovairFlex
Product Type: Intelligent Duct Smoke Detector Housing
Primary Function: HVAC Duct Smoke Detection
System Type: Intelligent Addressable Fire Alarm System
Relay: Non-Relay Standard Configuration
Optional Relay Capability: Addressable Form C Relay Module
Operating Air Velocity: 100–4,000 FPM
Duct Width Range: 6 in to 12 ft
Housing Configuration: Pivoting Square / Rectangular
Rectangular Dimensions: 14.38 × 5 × 2.5 in
Square Dimensions: 7.75 × 9 × 2.5 in
Weight: Approximately 1.6 lb / 0.73 kg
Operating Temperature: −4°F to 158°F / −20°C to 70°C
Humidity: 0%–93%, non-condensing
Sampling Tube: DST Series, sold separately
Remote Testing: Supported
Cover Tamper Supervision: Yes
Conduit Knockout: 3/4 in
Listings / Approvals: UL, FM, CSFM

Protection & Applications

Suitable applications include:

• Commercial Fire Alarm Systems
• Intelligent Addressable Fire Alarm Systems
• HVAC Duct Smoke Detection
• Air Handling Units
• Supply Air Ducts
• Return Air Ducts
• Mechanical Rooms
• Air Conditioning Systems
• Ventilation Systems
• Smoke Control Systems
• Fan Shutdown Applications
• Office Buildings
• Hospitals and Healthcare Facilities
• Schools and Universities
• Hotels
• Government Buildings
• High-Rise Buildings
• Data Centers
• Industrial Facilities
• Warehouses
• Manufacturing Facilities
• Institutional Buildings
• Commercial Life Safety Systems