Siemens LFL1 Series Industrial Burner Controllers
Product Description
Siemens Burner Controllers LFL Series
Siemens Burner Controllers LFL Series (LFL1) are automatic burner control units engineered for medium- to high-capacity industrial gas, oil and dual-fuel combustion systems.
The controllers manage the startup sequence of multistage and modulating burners, including prepurge, ignition, fuel valve operation, checked air damper control and flame supervision.
LFL1 is intended for intermittent operation and requires at least one controlled shutdown every 24 hours. The series is principally used with forced-draft burners, while the LFL1.638 variant also supports specified large atmospheric burner applications.
Key Features
- Applicable to compatible gas, oil and dual-fuel burner systems
- Designed for medium- and high-capacity combustion equipment
- Supports multistage and modulating burner operation
- Automatic startup, prepurge and ignition sequencing
- Flame supervision with QRA2, QRA4 or QRA10 UV detectors or an ionization probe
- Checked air damper positioning at OPEN, CLOSE and MIN
- Air pressure switch monitoring and flame failure supervision
- Safety lockout in specified fault conditions
- Remote lockout indication and reset provisions
- Type-tested and approved according to DIN EN 298
Operating Sequence and Safety
During startup, LFL1 checks the relevant safety conditions and controls the air damper and burner fan for prepurging. After the required conditions are satisfied, ignition and fuel valve outputs are enabled according to the model-specific program.
The unit continuously monitors the flame while the burner operates. An unsafe flame signal, failure to establish flame within the ignition safety time (TSA), or specified air pressure faults causes safety lockout.
For oil or dual-fuel applications, Siemens specifies two oil shutoff valves connected in series. The air damper actuator and flame detector must be selected according to the burner manufacturer's wiring diagram.
Industrial Applications
- Industrial steam and hot water boilers
- Forced-draft gas and oil burner systems
- Dual-fuel burner installations
- Stationary industrial air heaters
- Industrial process heating equipment
- Multistage and modulating combustion systems
Available LFL1 Models
The Siemens range includes LFL1.122, LFL1.133, LFL1.322, LFL1.333, LFL1.335, LFL1.622, LFL1.635 and LFL1.638. Models differ in prepurge duration, ignition safety time and operating sequence. LFL1.638 is intended for compatible large atmospheric burner applications.
Product Selection Guidelines
Confirm the complete model code, fuel type, burner control arrangement, supply voltage, QRA or ionization detector compatibility, air damper actuator, prepurge time, safety time and plug-in base before selecting or replacing an LFL1 controller.
Safety Note: Installation, replacement and commissioning must be performed by qualified personnel following Siemens CC1N7451en and applicable safety regulations.
Specifications
Siemens LFL Series Technical Specifications
| Brand | Siemens |
|---|---|
| Series | LFL1 Series |
| Product Type | Burner Control Unit |
| Fuel Type | Gas / Oil / Dual-Fuel |
| Burner Type | Forced-Draft Burner, Multistage / Modulating; selected large atmospheric burner applications |
| Operating Mode | Intermittent Operation (at least one controlled shutdown every 24 hours) |
| Supply Voltage | AC 230 V (-15% / +10%); AC 100–110 V, model-dependent |
| Supply Frequency | 50–60 Hz ±6% |
| Power Consumption | Approx. 3.5 VA |
| Built-in Fuse | T6.3H250V |
| External Primary Fuse | Max. 10 A (Slow-Blow) |
| Degree of Protection | IP40 when correctly installed, excluding terminal base |
| Safety Class | Class II |
| Weight | Approx. 1,000 g |
| Operating Temperature | -20 to +60 °C |
| Relative Humidity | Below 95% RH, non-condensing |
| Installation Altitude | Max. 2,000 m above sea level |
| Flame Detection | QRA2 / QRA4 / QRA10 UV Flame Detectors or Ionization Probe |
| Minimum Ionization Current | 6 µA |
| Minimum UV Detector Current | 70 µA |
| Ionization Detector Cable | Standard: Max. 80 m Shielded: Max. 140 m |
| UV Detector Cable | Standard: Max. 100 m Shielded: Max. 200 m |
| Air Damper Control | Checked OPEN / CLOSE / MIN positions |
| Compatible Plug-in Bases | AGM410490550 / AGM14.1 (ordered separately) |
| Applicable Standards | DIN EN 298 / DIN EN 13611 / DIN EN 60730-2-5 |
| Designed Lifetime | 250,000 burner startup cycles or approximately 10 years under specified conditions |
| Technical Reference | Siemens CC1N7451en (22.08.2025) |
Model Comparison
| Model | Series | Prepurge (t1) | Safety Time (TSA) |
|---|---|---|---|
| LFL1.122 | 02 | 10 s | 2 s |
| LFL1.133 | 02 | 9 s | 3 s |
| LFL1.322 | 02 | 36 s | 2 s |
| LFL1.333 | 02 | 31 s | 3 s |
| LFL1.335 | 01 | 37 s | 2.5 s |
| LFL1.622 | 02 | 65 s | 2 s |
| LFL1.635 | 01 | 66 s | 2.5 s |
| LFL1.638 | 01 | 66 s | 2.5 s |
Technical Note: t1 is the prepurge time with the air damper open, excluding actuator travel time. TSA is the ignition safety time. The specified switching times apply at 50 Hz; at 60 Hz, they are approximately 17% shorter. Some applications with pilot burners also require consideration of TSA' and second safety time t9.
The external primary fuse must not exceed 10 A (slow-blow). If it blows due to an overload or a short circuit at the controller terminals, Siemens requires replacement of the LFL1 unit. Verify the complete product reference and accessories against CC1N7451en before installation.
Product Specifications
Siemens LFL Series Technical Specifications
| Brand | Siemens |
|---|---|
| Series | LFL1 Series |
| Product Type | Burner Control Unit |
| Fuel Type | Gas / Oil / Dual-Fuel |
| Burner Type | Forced-Draft Burner, Multistage / Modulating; selected large atmospheric burner applications |
| Operating Mode | Intermittent Operation (at least one controlled shutdown every 24 hours) |
| Supply Voltage | AC 230 V (-15% / +10%); AC 100–110 V, model-dependent |
| Supply Frequency | 50–60 Hz ±6% |
| Power Consumption | Approx. 3.5 VA |
| Built-in Fuse | T6.3H250V |
| External Primary Fuse | Max. 10 A (Slow-Blow) |
| Degree of Protection | IP40 when correctly installed, excluding terminal base |
| Safety Class | Class II |
| Weight | Approx. 1,000 g |
| Operating Temperature | -20 to +60 °C |
| Relative Humidity | Below 95% RH, non-condensing |
| Installation Altitude | Max. 2,000 m above sea level |
| Flame Detection | QRA2 / QRA4 / QRA10 UV Flame Detectors or Ionization Probe |
| Minimum Ionization Current | 6 µA |
| Minimum UV Detector Current | 70 µA |
| Ionization Detector Cable | Standard: Max. 80 m Shielded: Max. 140 m |
| UV Detector Cable | Standard: Max. 100 m Shielded: Max. 200 m |
| Air Damper Control | Checked OPEN / CLOSE / MIN positions |
| Compatible Plug-in Bases | AGM410490550 / AGM14.1 (ordered separately) |
| Applicable Standards | DIN EN 298 / DIN EN 13611 / DIN EN 60730-2-5 |
| Designed Lifetime | 250,000 burner startup cycles or approximately 10 years under specified conditions |
| Technical Reference | Siemens CC1N7451en (22.08.2025) |
Model Comparison
| Model | Series | Prepurge (t1) | Safety Time (TSA) |
|---|---|---|---|
| LFL1.122 | 02 | 10 s | 2 s |
| LFL1.133 | 02 | 9 s | 3 s |
| LFL1.322 | 02 | 36 s | 2 s |
| LFL1.333 | 02 | 31 s | 3 s |
| LFL1.335 | 01 | 37 s | 2.5 s |
| LFL1.622 | 02 | 65 s | 2 s |
| LFL1.635 | 01 | 66 s | 2.5 s |
| LFL1.638 | 01 | 66 s | 2.5 s |
Technical Note: t1 is the prepurge time with the air damper open, excluding actuator travel time. TSA is the ignition safety time. The specified switching times apply at 50 Hz; at 60 Hz, they are approximately 17% shorter. Some applications with pilot burners also require consideration of TSA' and second safety time t9.
The external primary fuse must not exceed 10 A (slow-blow). If it blows due to an overload or a short circuit at the controller terminals, Siemens requires replacement of the LFL1 unit. Verify the complete product reference and accessories against CC1N7451en before installation.
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