Siemens QPL Series
Air Pressure Switches for Industrial Burner Safety Systems. Essential safety monitoring for reliable combustion control.
Series Overview
The Siemens QPL Series consists of differential air pressure switches designed for combustion air monitoring in industrial and commercial burner systems. These pressure switches are safety-relevant components used to verify sufficient airflow before and during burner operation. By continuously monitoring air pressure conditions, QPL units ensure that combustion can only occur under safe airflow conditions.
Within a burner management system, the QPL Series functions as a protective interlock device that prevents fuel release if proper combustion air pressure is not established.
Functional Role in Burner Systems
In a typical industrial gas burner control architecture, the QPL air pressure switch works alongside:
- Burner control units (e.g., LME / LDU / LMV systems)
- Combustion air fans
- Gas valve assemblies
- Flame supervision systems
Before ignition, the burner controller verifies that the QPL pressure switch confirms adequate airflow. If airflow drops below the defined threshold during operation, the QPL switch interrupts the safety circuit, triggering shutdown. This makes the QPL Series a critical safety component rather than a performance accessory.
Typical Applications
QPL Series pressure switches are widely used in:
- Industrial gas burners
- Commercial boilers
- Forced-draft combustion systems
- Process heating equipment
- Furnace and oven burner systems
They are particularly suited for systems requiring reliable airflow supervision prior to fuel admission.
Safety Interlock
Prevents fuel release if proper combustion air pressure is not established, ensuring safe operation.
Industrial Design
Robust housing and mechanical switching mechanism designed for long-term stability in harsh environments.
Core Technical Characteristics
Although model variants differ in switching ranges, the QPL Series generally features:
- Differential pressure monitoring
- Adjustable switching thresholds
- Robust industrial housing
- Mechanical switching mechanism
- Compatibility with standard burner control circuits
- Designed for combustion air applications
These switches are engineered for long-term operational stability in combustion environments.
Model Differentiation Logic
Different QPL models are defined primarily by:
- Pressure adjustment range
- Switching sensitivity
- Electrical contact configuration
- Mechanical mounting style
The selection of a specific model depends on:
- Required air pressure setpoint
- Fan system characteristics
- Burner size and airflow requirements
- System wiring configuration
Unlike generic pressure switches, QPL models are specifically calibrated for combustion air monitoring applications.
QPL Series Variants
| Model | Pressure Range Type | Typical Application |
|---|---|---|
| QPL15 Series | Low pressure range | Small industrial burners |
| QPL25 Series | Medium pressure range | Commercial boiler systems |
| QPL Series (Extended Range Versions) | Higher differential settings | Larger forced-draft burners |
Note: Exact switching ranges and electrical specifications vary by model.
System Integration & Safety Positioning
Within the overall burner safety chain, the QPL Series operates as:
Airflow Verification → Safety Interlock → Fuel Release Permission
This means:
- Combustion fan starts.
- QPL confirms sufficient airflow.
- Burner control unit allows ignition sequence.
- If airflow fails, system locks out.
Because of this positioning, the QPL Series is classified as a safety-relevant monitoring device within combustion control systems.
QPL Series in the Siemens Combustion Portfolio
Within Siemens burner system architecture, the QPL Series is positioned as:
- A combustion air supervision component
- A safety chain input device
- A mandatory interlock element in forced-draft burners
It complements burner control units such as LME, LDU, and LMV systems by ensuring safe preconditions for ignition and operation.
Selection Guide
Select low-range QPL models (QPL15 Series) for systems with limited airflow pressure.
Use medium-range variants (QPL25 Series) for standard commercial gas boiler systems.
Choose higher-range versions for forced-draft combustion systems requiring stronger airflow monitoring.
Need Technical Support?
Our engineering team can help you select the correct QPL pressure switch for your burner system application.
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