Kromschroder Air pressure switch DL 3AG-9K2 84444452

The Kromschroder DL 3AG-9K2 (SKU 84444452) is an air pressure switch designed for monitoring positive, negative, and differential pressure of air, flue gases, and other non-aggressive gases. It operates within an adjustable set point range of approximately 0.2 to 3 mbar, making it suitable for low differential pressure applications. The switch features a microswitch with high contact reliability and is available with visual indication (LED) in the K2 version. It is commonly used in ventilation, air conditioning, smoke extraction, and burner systems to confirm adequate airflow during pre-purge and running phases.

When selecting a replacement air pressure switch of this type, verify that the switching range, differential, and connection type (hose spigot or threaded port) match the application requirements. The switch must be compatible with the burner control's contact rating and approval class. Installation typically involves mounting the switch in the fan housing or air duct and connecting an impulse tube to the sensing point. Always consult the manufacturer's data sheet for the exact model to ensure proper fit and function.

Common failure modes for air pressure switches include a torn diaphragm, a blocked impulse tube (often due to dirt or condensation), or a drifted setpoint from mechanical wear. These faults typically cause repeated burner lockouts that may mimic ignition problems. Checking the switch function and impulse line is a standard troubleshooting step before replacing the burner control or ignition components.