Honeywell Pressure switch 45900438-301B

The Honeywell pressure switch 45900438-301B is a device used to control excess pressure in a working medium containing combustible gases. Its operating range is from 8 to 100 mbar, with a factory setting of 8 mbar. The maximum working pressure is 100 mbar. It has a dust and moisture protection class of IP 00 and connects via a DIN plug. The operating ambient temperature range is from -10 to +75 °C. This switch is a component in burner and boiler control systems, verifying that pressure or airflow remains within the permitted operating band.

Parts of this type are selected according to the medium (air or gas), the required switching range and differential, the type of connection (thread or hose spigot), electrical contact rating, and the applicable approval class for the burner or boiler. When replacing, ensure the switch's setpoint and differential match the original's functional parameters, and that the connection type and thread or hose spigot fit the existing installation.

Typical failure modes include a torn diaphragm, a blocked or leaking impulse tube, or a drifted setpoint. Any of these faults will cause the burner to lock out in a way that can appear similar to an ignition problem. Check the diaphragm, impulse tube, and setpoint calibration when such symptoms occur.