Boiler Sensors: Types and Key Functions for Your Comfort

The general purpose of the sensor is to communicate to the board the current temperature status inside your boiler. Through this detection, the boiler prepares to divert heat through the three-way valve or for flame modulation.

Sensors differ by type of housing and ohmic value, we find then:

Immersion Sensors

They have a fine thread pitch, with a dedicated housing where the probe is screwed in. Some have a sealing O-ring, others require thread sealing.

These sensors are normally used to sense the supply and return temperature of the boiler.

Sometimes they are also found on the sanitary side in storage boilers, only in boilers that are equipped with a sensor pocket.

Probe Sensors

These sensors are typically employed in the boiler’s storage, in a dedicated pocket. Their long connection allows them to reach a mid-position inside the boiler. Indeed, if placed too low, they are influenced by the cold water from the aqueduct. Conversely, placed too high in the storage, they sense temperatures that are too high.

Contact Sensors

Contact sensors have evolved, in very old boilers they required a housing where the sensor was placed and tightened with a strap. In modern boilers, they have a clip that attaches the sensor to the pipes.

Sensor Lifespan

The most commonly replaced sensors are the supply sensors and immersion sensors. This is due to the fact that in storage boilers, the supply temperature is usually very high during the heating of the boiler’s tank. Limescale significantly contributes to this issue, with the increase of limescale deposits, the boiler tends to heat the supply water between 65 and 75 degrees, which is detrimental for the immersion sensor and for the gas valve which is forced to open and close frequently.