Secutron MRI-5251B Intelligent Heat Detector

The Secutron MRI-5251B Intelligent Heat Detector is a low-profile addressable thermal detector designed for compatible Secutron fire alarm control panels. It uses an electronic thermistor sensing circuit to provide 135°F fixed-temperature heat detection.

The MRI-5251B incorporates intelligent communication, rotary address switches, dual status LEDs, and a plug-in detector design. It is intended for applications where reliable fixed-temperature heat detection is required without a rate-of-rise function.

Product Functions

• Provides intelligent addressable heat detection
• 135°F fixed-temperature operation
• Uses electronic thermistor sensing
• Low-profile detector design
• Provides individual Point ID identification
• Uses rotary address switches
• Provides dual status LEDs
• Supports magnetic functional testing
• Low standby current
• Provides integral addressable communications
• Uses interchangeable detector bases
• Designed for compatible Secutron addressable systems

135°F Fixed-Temperature Detection

The MRI-5251B provides:

Fixed Temperature: 135°F / 57°C

When the detector senses its specified temperature threshold, it reports an alarm condition to the compatible Secutron fire alarm control panel.

Unlike the MRI-5251RB, the MRI-5251B does not provide rate-of-rise thermal detection.

Thermistor Sensing

The MRI-5251B uses an electronic thermistor sensing circuit to monitor ambient temperature.

This provides intelligent electronic thermal detection in a compact, low-profile package and allows the detector to communicate directly with the compatible addressable fire alarm system.

Addressable Operation

The MRI-5251B operates as an individually identifiable device on the compatible Secutron signaling line circuit.

Point ID capability allows the fire alarm control panel to identify the exact detector reporting an alarm rather than identifying only a conventional detection zone.

Rotary Addressing

The detector uses rotary address switches for straightforward field addressing.

This allows technicians to assign the detector’s address directly at the device during commissioning or replacement.

LED Status Indication

The MRI-5251B incorporates dual LEDs for broad visual indication.

During normal communication, the LEDs indicate polling activity. When the detector enters alarm, the LEDs illuminate steadily to provide local visual confirmation.

Compatible Detector Bases

Secutron documentation identifies compatible bases including:

MRI-B210LP — Flanged low-profile mounting base

Other compatible intelligent bases can provide relay, isolator, or sounder functions depending on the system configuration.

Electrical & Detection Information

Model: MRI-5251B

Device Type: Intelligent Heat Detector

Detection: Fixed-Temperature Thermal

Temperature Rating: 135°F / 57°C

Operating Voltage: 15–32 VDC

Typical Current Draw: 300 µA

Addressing: Rotary Switches

Status Indicators: Dual LEDs

Operating Temperature: -4°F to 100°F / -20°C to 38°C

Humidity: 10–93% RH, non-condensing

Rate-of-Rise: No.

MRI-5251B Datasheet