Kromschroder Gas pressure switch DG400U-3 84447595

The Kromschroder DG400U-3 is a mechanical diaphragm pressure switch designed to monitor pressure changes in gases or air, responding to deviations from a setpoint. It features an adjustable actuation point from 50 to 400 mbar, set via a handwheel. The switch uses a microswitch with a switching contact and is suitable for natural gas, town gas, LPG (gaseous), flue gas, biogas (max. 0.1% by vol. H2S), and air. It has a glass fibre reinforced PBT plastic housing with an AlSi 12 lower section, an NBR diaphragm, and is silicone-free with low gas release. The device is IP54 rated, has screw terminals and an M16 x 1.5 cable gland, and operates within a temperature range of -20 to +80°C for medium and ambient conditions.

When selecting a pressure switch of this type, ensure the pressure range, connection thread, and electrical ratings match the application. The switch must be installed with the diaphragm oriented correctly for the media and pressure type (positive, negative, or differential). Verify the line diameter and cable gland size for proper sealing, and ensure the ambient temperature does not exceed the specified limits to avoid premature aging of elastomer components.

Common failures include diaphragm rupture or leakage, leading to loss of pressure sensing or false triggering. Microswitch contacts may wear or stick, causing the burner to fail to start or shut down unexpectedly. Check for signs of corrosion or contamination on the diaphragm and verify the setpoint accuracy with a manometer. If the switch fails to actuate at the set pressure, inspect the diaphragm for damage and the microswitch for continuity.