De Dietrich 100010844 room sensor AD238

This De Dietrich room sensor AD238 is an NTC temperature sensor intended for indoor temperature measurement. Parts of this type close the heating control loop by reporting the ambient temperature to the boiler’s control board, which then modulates the burner output to maintain the setpoint. NTC sensors change resistance with temperature; the resistance characteristic (such as 10 kΩ or 12 kΩ at 25 °C) must match the control board that reads it. Other selection parameters for such sensors include the probe form—for room sensors this is typically a small plastic housing with ventilation openings—the cable length and connector type, and whether the sensor is wired or wireless (this article is a wired room sensor based on the codes). When replacing a room NTC sensor, confirm that the resistance curve matches the original specification; a mismatched sensor will cause the boiler to over- or underheat. Common failure modes include drifting resistance values (which makes the boiler modulate incorrectly), a broken cable, or poor contact at the connector. Ensure the sensor is installed in a representative location away from drafts, direct sunlight, or heat sources to avoid false readings.