De Dietrich 100010845 setting thermostat CTI-S-03 (AD239)

De Dietrich 100010845 setting thermostat CTI-S-03 (AD239), catalogue article 336.805.016, is a temperature-sensing component used in boiler and burner control circuits. Parts of this type—mechanical setting thermostats—operate directly by opening or closing a switch at a set temperature point. They serve as limit switches or to signal heat demand, working alongside NTC sensors that report flow, return, cylinder or outdoor temperature to the control board. In a typical system, such a thermostat is placed in the temperature feedback loop, often at the flow or return line, and may be used for boiler regulation or safety cut-out. Selection for a replacement thermostat of this class depends on the switching temperature range, the reset type (manual or automatic), and the probe form—either immersion, clamp-on, or sleeve. The cable length and connector type must also match the existing wiring. Unlike NTC sensors, where the resistance characteristic at 25 °C (e.g., 10 kΩ or 12 kΩ) is critical, a setting thermostat is chosen by its switching point and differential. Common failure modes include a drifted switching point due to mechanical wear, which causes incorrect system modulation or failure to cut off, as well as broken cables or poor thermal contact between a clamp-on probe and the pipe surface. When replacing a part of this type, verify the physical mounting dimensions and the electrical ratings—typically a dry contact rated for the control voltage. The original part number (100010845) and catalogue reference (336.805.016) should be cross-checked against the system documentation to confirm the intended function and temperature setting. No other specifications are revealed by the product data.