Siemens LFL1.635 Gas, Oil and Dual-Fuel Burner Sequence Controller
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Product Information
The Siemens LFL1.635 is a burner sequence controller for medium- to high-capacity gas, oil and dual-fuel burners. It manages the fixed electromechanical sequence for air damper operation, pre-purge, ignition and continued burner operation in multistage or modulating systems. The controller operates from a 230 V AC supply at 50-60 Hz and is designed for intermittent burner operation.
A replacement LFL1.635 uses a fixed, pre-programmed sequence and does not require software configuration or parameter storage. Before commissioning, confirm the 230 V AC supply, the installed burner wiring, the actuator and flame detector arrangement, and the connection base. The LFL1 family supports Siemens SQN70, SQN71, SQN72, SQN74, SQN75 and SQN9 actuator series and Siemens QRA series UV flame detectors. AGM14.1 and AGM410490550 are suitable plug-in connection bases; the controller is supplied without a plug-in base, so an existing base must be suitable or a separate base must be provided.
For troubleshooting, follow the sequence indicator and check the air damper position during the burner operating sequence. The 66-second pre-purge, 2.5-second ignition safety time and 5-second secondary safety time provide practical timing points when checking a replacement. Confirm that the burner system performs a controlled shutdown at least once every 24 hours for safety self-testing. A correct replacement check should include supply voltage, actuator compatibility, QRA flame supervision and terminal configuration before the unit is returned to service.
Technical Specifications
| Manufacturer | Siemens |
| Part number | LFL1.635 |
| Model/type | Gas, Oil and Dual-Fuel Burner Sequence Controller |
| Component type | Burner sequence controller |
| Product family | LFL1 |
| Supply voltage | 230 V AC |
| Supply frequency | 50-60 Hz |
| Power consumption | 3.5 VA |
| Rated continuous input current | 5 A |
| Pre-purge time | 66 s |
| Ignition safety time | 2.5 s |
| Secondary safety time | 5 s |
| Burner application | Medium- to high-capacity gas, oil and dual-fuel burners with multistage or modulating control |
| Sequence control | Fixed electromechanical, pre-programmed sequence control |
| Operating mode | Intermittent operation with controlled shutdown at least once every 24 hours |
| Protection rating | IP40, excluding connection area |
| Actuator compatibility | Siemens SQN70, SQN71, SQN72, SQN74, SQN75 and SQN9 actuator series |
| Flame detector compatibility | Siemens QRA series UV flame detectors |
| Plug-in connection bases | Siemens AGM14.1 and AGM410490550 |
| Connection base | Supplied without a plug-in base |
Diagnostics and Status Indication
The LFL1.635 supports visual sequence tracking through its sequence indicator and damper control supervision. During commissioning or troubleshooting, observe the burner sequence and verify that the air damper reaches the required position during operation.
Use the defined timing points to assess sequence progress: 66 s pre-purge with the damper open, 2.5 s ignition safety time and 5 s secondary safety time. Also confirm the supply, actuator arrangement, flame detector arrangement and burner wiring when a replacement does not complete the expected sequence.
Replacement and Spare Part Considerations
For an LFL1.635 replacement, match the Siemens part number, 230 V AC supply, burner sequence requirements and installed actuator and flame detector arrangement. The LFL1 family supports SQN70, SQN71, SQN72, SQN74, SQN75 and SQN9 actuator series together with QRA series UV flame detectors.
The controller is supplied without a plug-in connection base. Check whether the existing base is suitable, or provide a Siemens AGM14.1 or AGM410490550 base separately. Confirm the terminal configuration and burner wiring before energizing the replacement.
The fixed electromechanical sequence requires no software configuration or parameter transfer. After installation, verify the pre-purge and ignition timing, air damper position, flame supervision arrangement and the required controlled shutdown at least once every 24 hours.
Frequently Asked Questions
What is the Siemens LFL1.635 used for?
The Siemens LFL1.635 controls ignition, pre-purge and burner operating sequences for medium- to high-capacity gas, oil and dual-fuel burners with multistage or modulating control.
What supply does the LFL1.635 require?
The controller requires a 230 V AC supply at 50-60 Hz. Its power consumption is 3.5 VA and its rated continuous input current is 5 A.
Which actuators and flame detectors are compatible with the LFL1.635?
The LFL1 family supports Siemens SQN70, SQN71, SQN72, SQN74, SQN75 and SQN9 actuator series. Flame supervision can use Siemens QRA series UV flame detectors.
Does the Siemens LFL1.635 require software configuration?
No. The LFL1.635 uses a fixed, pre-programmed electromechanical sequence and does not require software configuration or parameter storage.
Is a plug-in connection base included with the LFL1.635?
No. The controller is supplied without a plug-in base. Suitable bases include Siemens AGM14.1 and AGM410490550, subject to the installed burner connection arrangement.
What timing should be checked during commissioning?
Check the 66-second pre-purge, 2.5-second ignition safety time and 5-second secondary safety time. Also verify the air damper position and confirm a controlled shutdown at least once every 24 hours.
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