Brahma Immersion temperature sensor ST09 M/1 18200452

This immersion temperature sensor, model ST09 M/1 (SKU 18200452), is a Brahma NTC107 type sensor with a G1/8 connection and a modular green connector. It uses an NTC element with a resistance characteristic of 10 kΩ or 12 kΩ at 25 °C. The sensor measures the temperature of the heat transfer fluid and sends a continuous resistance signal to the control board. It is intended for use in Brahma floor-standing boilers, wall-mounted boilers with a hot water tank, storage water heaters, instantaneous water heaters, and storage/instantaneous water heater combinations. The sensor provides overheating protection and has dimensions of 40 x 20 x 15 mm, with a net weight of 0.015 kg and gross weight of 0.020 kg.

When replacing a sensor of this type, verify the resistance characteristic (10 kΩ or 12 kΩ at 25 °C), probe form (immersion, clamp-on, or sleeve), cable length, and connector type against the control board and the physical mounting. The resistance curve must match the board. Ensure the immersion probe fits the existing thermowell or tapping. Install the sensor so that it makes good thermal contact with the fluid or pipe.

Failures of this sensor type include drifting resistance, broken cables, or poor thermal contact. A drifting resistance causes incorrect temperature readings and unstable burner modulation. Broken cables can lead to an open circuit, often triggering an error code. Poor thermal contact between the probe and the pipe results in inaccurate measurements and inefficient operation.