De Dietrich 97955047 Thermal relay

Pressure switches in a boiler or burner system confirm that pressure or airflow stays within the permitted operating band, giving the burner control permission to continue the start or run sequence. An air pressure switch verifies that the fan is moving air; a gas pressure switch guards minimum and maximum gas pressure. When a pressure switch fails, typical symptoms include a torn diaphragm, a blocked impulse tube, or a drifted setpoint – all of which cause lockouts that look like ignition problems rather than switch faults. Selection for a replacement depends on the medium (air or gas), the switching range and differential, the connection type (thread or hose spigot), the contact rating, and the applicable approval class. This article is listed under the pressure switch category as a De Dietrich thermal relay with manufacturer codes 97955047 and 336.679.001. As with any pressure switch, when sourcing a replacement ensure the switching range and connection match the original component; inspect the impulse tube and mounting position to avoid condensation or blockage issues that would produce false readings.