Siemens LFS1.21A2 Flame Detector Safeguard Controller

The Siemens LFS1.21A2 is a flame safeguard (flame relay) that is based on a microprocessor. It is designed for OEM usage and is a straight replacement for the earlier LFE10 when used with adapter KF8896. It is used to continuously monitor oil and gas burners. It works with ionization probes, photocell RAR9, and UV flame detectors QRA2/QRA4/QRA10 for industrial and maritime burners that need to be very safe. ​

Siemens LFS1.21A2 Product Description

LFS1.21A2 is a plug-in flame safety module that includes a power supply, a device to boost the flame signal, and relay contacts that send a flame or no-flame alert to burner controllers or It has a multicolor LED that shows the flame and an analog 0…10 V DC output that is proportionate to the brightness of the flame signal. This makes it easy to set up and keep an eye on.

The device can run continuously with oil and gas flames and ionization or photocell detection, or it can run intermittently with UV detectors (QRA2/QRA4/QRA10 families). In industrial, process, and ship burner systems, it is typically used with the LEC1 control unit, LME39…RP burner control, or programmable PLCs. ​

Key features

• Key features include the surveillance of one or more gas or oil burners, which enables monitoring of the main flame and ignition, as well as main flame surveillance with one or two safety features. ​
• The ionization probes, photocell RAR9, and UV detectors are all types of flame detectors that are compatible with this system. QRA2, QRA2M, QRA4, QRA4M, QRA10, and QRA10M. ​
• The system incorporates automatic fail-safe behavior and undervoltage monitoring to provide continuous flame monitoring, as well as changeover contacts that are free of voltage and feature double insulation between terminal groups. ​
• 0 to 10 V DC flame intensity output at terminal 7 for measuring or showing the flame level, plus a BCI communication interface for adjusting settings and performing diagnostics (like with the AZL2 display unit).

Technical details:

-> Function: This device checks for the presence of a flame and acts as a flame safeguard or flame relay for burners. However, it cannot be used as a sequence controller on its own. ​

-> The supply voltage (LFS1.21A2) is 230 V AC (usually 220 to 240 V, 50/60 Hz). ​

-> There are different sorts of detectors, such as ionization, photocell RAR9, and UV QRA2/QRA4/QRA10 series, depending on the type of burner and how it works. ​

-> Output contacts: flame signal relay contacts that are free of potential; made to connect to a burner control or PLC; double insulation between terminals 1…7 and 9…12. ​

-> Signal indication: an analog output of 0 to 10 V DC and a multicolor LED that shows the status, flame strength, and faults. ​

-> Interface: BCI communication interface on the bottom for setting parameters and showing the numerical flame value (for example, using AZL2). ​

Approvals for operating mode:

• Continuous operation for oil and gas with an ionization probe or RAR9. ​
• UV detectors QRA2/QRA4/QRA10 work only sometimes. ​

Ratings and information on the environment

• Power supply type: LFS1.21A2 = AC 230 V; (sister type LFS1.21A1 = AC 120 V, not your model but often stated together). ​
• IP40 (device housing) is the level of protection. ​
• The temperature range for operation is −20 to +60 °C. ​
• Installation: Connect the plug-in design to the terminal base (AGK11.7) and use the optional adapter KF8896 for replacing the LFE10. Follow the Siemens specifications for the longest and shortest lengths of the detector cables and their required separations. ​