SD 500 ARM Addressable Module: Integration with SD505 and SD365-IV Detectors Explained

In commercial fire alarm system design, the ability to monitor duct smoke detectors and other specialized sensors through an addressable loop is a critical capability for modern life-safety installations. The SD 500 ARM addressable remote module is specifically engineered to provide this interface, connecting conventional duct and area smoke detectors to a Notifier or Fire-Lite addressable signaling line circuit. In this comprehensive guide, we explain how the SD 500 ARM works, how it integrates with the SD505 duct smoke detector and the SD365-IV smoke detector, and what fire alarm contractors need to know about system design, wiring, and testing to achieve a compliant, high-performing installation.

What Is the SD 500 ARM?

The SD 500 ARM (Addressable Remote Module) is a product from System Sensor designed to bring addressable intelligence to conventional smoke detectors that are not inherently addressable - most commonly duct smoke detectors and area smoke detectors mounted in commercial HVAC systems. The module connects to a compatible addressable fire alarm control panel via a two-wire SLC (Signaling Line Circuit) loop and provides the interface between the panel and the connected detector's conventional output.

Functionally, the SD 500 ARM monitors the alarm and trouble outputs of a connected conventional detector and reports those states back to the fire alarm panel as addressable events. This gives the panel the ability to identify not just that a duct zone has alarmed, but which specific detector - identified by its unique SLC address - has activated. This device-level reporting is increasingly required by NFPA 72 and by Authorities Having Jurisdiction (AHJs) for duct smoke detector applications in commercial HVAC systems.

Key Technical Specifications of the SD 500 ARM

• Compatible panels: Notifier NFS series, Fire-Lite MS series, and other CLIP/Apollo protocol panels

• SLC current: 0.5 mA standby, 0.5 mA alarm (drawn from SLC loop)

• Auxiliary power output: 24VDC @ 50 mA to power connected detector

• Input monitoring: alarm and trouble circuits from conventional detector

• Remote test input: supports remote test station wiring for NFPA 72 compliance

• Dimensions: compact form factor designed for mounting inside duct detector housing or adjacent junction box

• Operating temperature: 32°F to 120°F (0°C to 49°C)

• UL Listed for use with compatible duct and area smoke detectors

The SD505 Duct Smoke Detector: Overview and Role

The SD505 duct smoke detector is a System Sensor product designed specifically for in-duct fire detection applications in commercial HVAC systems. It is mounted directly to ductwork and uses sampling tubes - an air inlet tube and an exhaust tube - to draw air from the duct through its sensing chamber. When the sampled air contains smoke particles above the detector's calibrated threshold, the SD505 duct smoke detector activates its alarm output.

Duct smoke detectors like the SD505 serve a critical but often misunderstood role in fire protection. Their primary function is not to detect fires in the early stages of ignition - that is the role of area smoke detectors - but rather to prevent a fire that has already started elsewhere in the building from spreading smoke through the HVAC distribution system to other floors or areas. When the SD505 duct smoke detector activates, it signals the fire alarm panel to shut down the air handling unit (AHU), preventing the mechanical system from acting as a smoke distribution network.

Key Specifications of the SD505 Duct Smoke Detector

• Sensing method: photoelectric

• Duct velocity range: 100–4,000 feet per minute

• Operating temperature: 32°F to 158°F (0°C to 70°C)

• Humidity range: 10–93% RH, non-condensing

• Alarm contact: SPDT relay, 2A @ 30VDC or 0.5A @ 120VAC

• Compatible with SD 500 ARM for SLC loop addressability

• Remote test capability via optional remote test station accessory

• UL Listed, meets NFPA 72 and 90A requirements for duct detection

The SD365-IV Smoke Detector: Overview and Role

The SD365-IV smoke detector is a Fire-Lite addressable photoelectric smoke detector finished in ivory, making it suitable for light-colored ceiling environments where white or grey detector bodies would create a visual mismatch. The SD365-IV is a direct successor to the SD355 model and is designed for ceiling-mount area detection in corridors, offices, hotel rooms, and similar commercial and light institutional spaces.

Unlike the SD505 duct smoke detector, which requires duct mounting and HVAC airflow to operate correctly, the SD365-IV smoke detector is designed for ambient air detection in occupied spaces. It connects directly to a Fire-Lite addressable SLC loop as an inherently addressable device - no interface module is needed. Each SD365-IV smoke detector has its own unique SLC address, allowing the panel to identify the exact room or corridor where smoke has been detected.

Key Specifications of the SD365-IV

• Sensing method: photoelectric

• Addressable protocol: Fire-Lite/System Sensor CLIP or SIGA compatible

• Operating voltage: 15–32 VDC (from SLC loop)

• Standby current: 375 µA typical

• Alarm current: 5 mA typical (from SLC)

• Color: ivory (IV designation)

• Compatible base: B710LP or B501 series

• Operating temperature: 32°F to 100°F (0°C to 38°C)

• UL Listed, meets NFPA 72 smoke detector installation requirements

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How the SD 500 ARM Integrates with the SD505 Duct Smoke Detector

Wiring the SD 500 ARM to the SD505

The integration of the SD 500 ARM with the SD505 duct smoke detector is the most common application for this module. The SD 500 ARM is typically mounted inside the SD505's own housing using the available mounting provisions, or in a separate enclosure immediately adjacent to the duct detector if space inside the housing is insufficient.

The SD500 ARM connects to the SD505 via four wires: two for the SLC loop (in and out), and two for the auxiliary 24VDC power output that the ARM provides to power the SD505 detector head. The ARM's alarm monitoring input connects to the SD505's alarm relay output, and the trouble monitoring input connects to the SD505's trouble relay output. This four-wire connection (plus SLC) gives the fire alarm panel complete visibility into the duct detector's status.

Remote Test Station Integration

NFPA 72 requires that duct smoke detectors be testable from an accessible location, which is frequently a requirement because the duct detector itself may be mounted above a suspended ceiling or inside mechanical areas that are not easily accessible during routine inspections. The SD 500 ARM includes a remote test input that connects to an optional remote test station - typically a key switch mounted at a convenient location in the mechanical room or corridor.

When the remote test station is activated, the SD 500 ARM simulates an alarm condition and verifies that the panel responds correctly, the HVAC shuts down, and all alarm signals activate as designed. This test can be performed without requiring the technician to access the duct or remove the detector head, significantly reducing the time and safety risk associated with annual testing.

How the SD 500 ARM Integrates with the SD365-IV Smoke Detector

While the SD365-IV smoke detector is inherently addressable and does not require the SD 500 ARM for standard area detection applications, there are specific scenarios where the SD 500 ARM is used alongside area detectors like the SD365-IV:

1. Legacy panel retrofits: when an older panel without a compatible SLC protocol needs to connect to SD365-IV detectors, the SD 500 ARM can serve as a protocol bridge in some configurations

2. Supervised input monitoring: when the fire alarm system design requires monitoring of a conventional contact output from an SD365-IV (for example, its alarm relay used to trigger a suppression system), the SD 500 ARM can provide supervised monitoring of that contact

3. Mixed-system designs: in buildings with multiple fire alarm systems from different manufacturers, the SD 500 ARM can provide a standardized addressable interface point

System Design Considerations

SLC Loop Capacity Planning

Each SD 500 ARM module occupies one address point on the SLC loop. When integrating multiple SD505 duct smoke detectors - typical in large commercial HVAC systems with multiple air handling units - careful SLC loop capacity planning is essential. A 99-point SLC loop, for example, can accommodate up to 99 modules and detectors combined, so large facilities with both area detectors and multiple duct detector ARM interfaces need to calculate total device counts before finalizing the panel selection.

Power Supply Considerations

The SD 500 ARM provides 24VDC @ 50 mA to power the connected duct detector. This current is sourced from the panel's auxiliary power supply, not the SLC loop itself. In systems with many SD505 duct smoke detector installations, the cumulative auxiliary power draw must be accounted for in the panel's power budget, particularly if the panel is also powering other auxiliary devices such as door holders or relay modules.

Testing and Commissioning Requirements

All SD 500 ARM installations must be tested per NFPA 72 Chapter 14 acceptance testing requirements before the system is placed in service. For duct detector applications, this includes verifying airflow sensitivity using canned smoke or an aerosol smoke detector tester introduced into the duct sampling tube, confirming HVAC shutdown on alarm, and verifying remote test station function if installed.

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Conclusion

The SD 500 ARM addressable remote module is an essential component for any fire alarm system that needs to bring duct smoke detectors or conventional area detectors onto an addressable SLC loop. By integrating seamlessly with the SD505 duct smoke detector for HVAC fire protection and providing compatibility pathways for area detectors like the SD365-IV, the SD 500 ARM gives fire alarm designers the flexibility to build smart, compliant, and serviceable systems across a wide range of commercial applications.

Understanding the wiring requirements, SLC capacity implications, power supply planning, and testing protocols for SD 500 ARM installations allows contractors to deliver systems that perform reliably from day one and remain maintainable over the system's full service life. Whether you are installing a single SD505 duct smoke detector in a small commercial building or designing a multi-AHU HVAC protection system in a large campus facility, the SD 500 ARM is the right tool for addressable duct detector integration.

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Frequently Asked Questions (FAQs)

1. What is the SD 500 ARM used for?

The SD 500 ARM is an addressable remote module that connects conventional smoke detectors - most commonly duct smoke detectors like the SD505 - to an addressable fire alarm panel SLC loop. It enables the panel to monitor alarm and trouble states from conventional detectors with device-level addressable identification.

2. Does the SD 500 ARM work with all fire alarm panels?

The SD 500 ARM is compatible with panels that support the CLIP addressable protocol, including Notifier NFS series and Fire-Lite MS series panels. Compatibility must be verified against the specific panel model and firmware version before installation, as not all addressable protocols are interchangeable.

3. Is the SD505 duct smoke detector required by code in commercial HVAC systems?

NFPA 72 and NFPA 90A require duct smoke detectors in commercial HVAC systems above certain airflow capacities - generally air handling units moving more than 2,000 CFM. The specific requirements depend on the AHJ and local code adoptions, so always confirm with the local Authority Having Jurisdiction before finalizing the design.

4. Can the SD 500 ARM be used with the SD365-IV directly?

The SD365-IV smoke detector is inherently addressable and typically connects directly to a compatible SLC loop without requiring the SD 500 ARM. The ARM is used in scenarios where the SD365-IV's conventional relay output needs to be supervised or where protocol bridging is required between incompatible systems.

5. How is the SD 500 ARM addressed on the SLC loop?

The SD 500 ARM is addressed using a built-in rotary or DIP switch address selector, depending on the module version. Each module must receive a unique address before it is connected to the SLC loop. Duplicate addresses cause communication conflicts that can prevent proper panel operation and alarm reporting.

6. What maintenance does the SD505 duct smoke detector require?

The SD505 duct smoke detector requires annual functional testing per NFPA 72, which includes sensitivity verification and confirming that the HVAC shutdown relay operates correctly on alarm. The sampling tubes should also be inspected for blockage caused by dust accumulation in the ductwork, which can reduce airflow through the sensing chamber.

7. Where can I buy the SD 500 ARM, SD505, and SD365-IV?

QuickShipFire stocks genuine SD 500 ARM modules, SD505 duct smoke detectors, and SD365-IV smoke detectors - all brand new in original manufacturer packaging. Visit quickshipfire.com or call (833) 747-7845 for current availability, pricing, and fast U.S. shipping on all orders.