Siemens Pressure switch QPL15.150B

This pressure switch sensor monitors overpressure, vacuum, and differential pressure. It is compatible with air, flue and non-aggressive gases, and has a body made of industrial heat-resistant plastic. The unit is suited for ventilation, boilers, burners, and HVAC systems, and can be wall-mounted or built-in. It operates on the principle of differential or overpressure monitoring and is intended for use with Siemens automation systems. The device is by Siemens, a brand originating from Germany.

Select a replacement pressure switch of this kind by checking the medium (air or gas), the adjustable switching range, the differential between switch-on and switch-off points, and the connection type (thread or hose spigot). Before ordering, measure the original switch's range, differential, connection size, and electrical contact rating. Confirm the mounting style—wall-mounted or built-in—and verify the new part is compatible with the system's medium and pressure requirements.

When pressure switches of this type fail, the equipment may lock out or refuse to start the ignition sequence. Common causes include a torn diaphragm, a blocked impulse tube, or a drifted setpoint. Check the impulse line for blockage, inspect the diaphragm, and compare the actual switching point with a calibrated pressure gauge.