Kromschroder Air pressure switch DL 4,5K-3 84444730

The Kromschroder DL 4,5K-3 (SKU 84444730) is an air pressure switch made in Germany. It monitors positive, negative, or differential air and flue gas pressure in burner and boiler systems. The switching point is adjustable from 0.3 to 5 mbar via a manual wheel. It features screw terminals for electrical connection and is used to confirm adequate airflow during pre-purge before ignition.

When selecting a replacement pressure switch of this type, verify the switching range and differential (difference between setpoint and reset point) match the original. Check the connection type (thread or hose spigot) and the contact rating. Ensure the switch is approved for air service, not gas. Before installation, inspect the impulse line for blockages or debris.

Common failure modes include a torn diaphragm, blocked impulse tube, or drifted setpoint. These can cause nuisance lockouts or repeated ignition failures. The burner may fail to start or shut down unexpectedly. Check the impulse line for soot or debris and verify the switch operation with a manometer.