LFS1.21A1 Siemens Flame Detector Relay

Overview

The Siemens LFS1.21A1 is a compact flame detector relay designed for the supervision of oil and gas flames in industrial and commercial burner systems. Functioning as a flame safeguard or switch, it provides reliable flame presence signaling to programmable logic controllers (PLCs) or other burner control units. It serves as a modern replacement for the obsolete LFE10-110V series, offering a space-saving design and advanced diagnostic capabilities for high-demand burner environments.

Features

• Compact footprint designed to save premium panel space in multi-burner applications
• Integrated multicolor LED signal lamp for immediate visual status and flame signaling
• Analog 0-10V DC output to report flame signal strength to external monitoring systems
• Potential-free signal contacts with double insulation for increased safety and reliability
• Safety integrity level up to SIL3 for continuous operation with ionization probes
• Integrated BCI communication interface for parameterization and system diagnostics
• Built-in detection for undervoltage and overvoltage to ensure stable operation

Specifications

• Operating Voltage: AC 120 V (50/60 Hz)
• Compatible Detectors: Ionization probes, QRA series UV detectors, and RAR9 photocells
• Operating Mode: Continuous operation for ionization and intermittent for UV detectors
• Protection Rating: IP40
• Temperature Range: -20 C to +60 C
• Output Signal: 0-10 VDC flame strength signal (1 mA maximum)
• Contact Rating: 1 A maximum for relay output contacts
• Design Life: 250,000 burner startup cycles under normal operating conditions

Applications

• Supervision of oil or gas flames in industrial and commercial burner systems
• Integration with PLC-based combustion safeguards for sequence and safety control
• High-security applications requiring SIL2 or SIL3 safety ratings
• Multi-flame supervision in plants where several burners are monitored centrally
• Retrofitting existing burner installations as a replacement for LFE10-110V units