Siemens Pressure switch QPL25.010

This pressure switch from Siemens, SKU QPL25.010, monitors differential or overpressure in air, flue gas, and non-aggressive gases. It is built with industrial heat-resistant plastic and is intended for ventilation systems, boilers, burners, and HVAC installations. The switch can be wall-mounted or built into equipment and is compatible with Siemens automation systems. Its brand country is Germany.

Pressure switches of this type are selected by comparing the switching medium (air or gas), the required switching range and differential, and the connection thread or hose spigot size with the existing installation. The contact rating and applicable approval class must also match. The switch can be wall-mounted or built-in, so check the available fixing positions on the equipment before ordering. After fitting, verify that the impulse line is clean and correctly routed, and check the setpoint with a manometer.

If the diaphragm tears, the impulse tube blocks, or the setpoint drifts, the pressure switch will not open or close at the correct pressure. The burner control then prevents ignition or goes into lockout, which may look like an ignition fault. Check the impulse line for blockages, inspect the diaphragm for damage, and verify the setpoint with a manometer.