Description
The FDX‑551R is a plug-in, intelligent analog rate-of-rise temperature sensor in Notifier’s legacy product line, designed to detect rapid temperature increases indicative of fire.
Technical Specifications
| Condition |
New/Never Used Surplus |
| Brand |
Notifier |
| Category |
Fire Safety |
| Part Number |
FDX-551R |
| Subcategory |
Fire Alarm Systems |
| Device Type |
Fire Detector – Heat Sensor |
| Detection Method |
Rate-of-Rise (≥ 15°F/min) |
| Sensing Components |
Dual Thermistors |
| Detection Modes |
Rate-of-Rise, Fixed Temperature, Fixed High Temperature |
| Communication Type |
Analog Addressable |
| Address Configuration |
Rotary DECADE switches (01–99) |
| Operating Voltage |
15–28 VDC |
| Mounting Base |
Uses common sensor base |
| Remote LED Output |
Standard |
| Visual Indicators |
Dual 360° visible LEDs (blink on poll, steady on alarm) |
| Test Feature |
Built-in magnetic test switch |
| Optional Base Features |
Supports Relay, Isolator, and Sounder bases |
| Tamper-Resistance |
Yes |
| Noise Immunity |
Stable communication with high noise immunity |
| Weight |
0.25 kgs |
Information About FDX-551R
The FDX‑551R is part of Notifier’s legacy line of intelligent rate-of-rise heat detectors, engineered for responsive detection of rapid temperature increases in fire alarm systems. Designed to detect a temperature rise exceeding 15°F per minute, it also features a fixed-temperature threshold for reliable activation under fast-developing fire conditions. Compatible with Notifier’s addressable analog control panels, the FDX‑551R communicates real-time data and status updates while maintaining low standby current and high noise immunity. Its plug-in design, 360° visible LED indicators, and tamper-resistant features make it an ideal solution for commercial and industrial environments requiring thermal detection without the sensitivity of smoke-based sensing.
Key Features:
- Rate-of-Rise Detection: Activates when ambient temperature increases more than 15°F per minute, providing early warning of fast-growing fires.
- Fixed Temperature Backup: Includes a static alarm threshold (typically 135°F) for reliable activation in heat-intensive conditions.
- Analog Addressable Operation: Communicates real-time thermal data to Notifier panels for detailed event tracking and system diagnostics.
- Dual Thermistor Technology: Provides accurate, stable temperature sensing with minimal false alarms.
- 360° LED Visibility: Twin LEDs offer alarm indication from any viewing angle; configurable blink for polling.
- Plug-In Base Compatibility: Easily mounts onto standard Notifier bases (e.g., B501 or BX-501), supporting rapid installation and servicing.
- Magnetic Test Capability: Built-in switch supports activation using an external magnet for simplified functional testing.
- Tamper-Resistant Design: Prevents unauthorized removal or manipulation without tools.
- Optional Base Features: Supports relay, isolator, or sounder bases for enhanced system integration.
- Environmental Ratings: Operates from 32°F to 100°F (0°C to 38°C) with up to 93% non-condensing humidity.
The Notifier FDX‑551R provided fast and intelligent thermal detection in addressable systems where smoke detection may not be suitable. Though discontinued, it remains a reliable legacy solution in many installations and is functionally replaced in modern systems by devices like the FST-951R or NFX-TDIFF-IV.
