LFS1.21A2 Siemens Flame Detector Relay

Overview

The Siemens LFS1.21A2 is a digital flame safeguard designed for the supervision of oil and gas flames in industrial and commercial burner applications. It is engineered to operate in conjunction with fail-safe programmable logic controllers (PLCs), control units like the LEC1, or burner controls with a flame safeguard input such as the LMV52. The device provides a critical safety interface by communicating the presence or absence of a flame through potential-free contact closures, allowing the central controller to handle sequencing, valve power, and purging functions.

Features

• Designed for continuous operation when used with ionization probes
• Supports intermittent operation when paired with UV flame detectors such as the QRA2, QRA4, or QRA10 series
• Potential-free signal contacts with double insulation for enhanced safety
• Integrated 0 to 10 V DC analog output for flame signal strength monitoring
• BCI communication interface allows for parameterization and diagnostics via the AZL2 display unit
• Multicolor LED signal lamp provides immediate visual status of the flame signal
• Robust and compact design to conserve panel space
• Built-in undervoltage detection for reliable operation during power fluctuations

Specifications

• Model: LFS1.21A2
• Mains Voltage: AC 230 V (-15% to +10%)
• Mains Frequency: 50/60 Hz (+/- 6%)
• Safety Integrity Level: SIL3 (with ionization probe), SIL2 (with UV detector)
• Power Consumption: Approximately 3.5 VA
• Degree of Protection: IP40 (ensure by installation)
• Operating Temperature: -20 C to +60 C
• Weight: Approximately 0.20 kg
• Dimensions: 91 mm x 62.5 mm x 63 mm

Applications

• Supervision of gas and oil burners in industrial heating plants
• Dual supervision systems for main and ignition flames
• Multiflame supervision plants where multiple burners are monitored individually but controlled centrally
• Suitable for use in ship burners and marine environments
• Replacement for legacy LFE10 flame relays (when used with the KF8896 adapter)
• Integration with PLC-based combustion safety systems meeting NFPA 86 criteria