Potterton Sensor Tube/Pocket 521343

The sensor tube/pocket, part number 521343, is a Potterton Commercial component used on Potterton Commercial Sirius 2 FS Cascade boiler installations. The pocket holds the temperature sensor in position against the appliance's water or flow path so that the sensor can read system temperature accurately. It is supplied as a service part for the Sirius 2 FS Cascade KIT range.

• Temperature readings from the appliance are erratic or inconsistent with the actual system condition.
• The boiler locks out or cycles unexpectedly despite the sensor itself testing correctly.
• The pocket is corroded, scaled or visibly damaged where it contacts the sensor or the waterway.
• The sensor no longer seats correctly in the pocket, giving a loose or poor contact.
• Moisture or seepage is present around the pocket joint.

• Confirm the appliance model and output match one of the Sirius 2 FS Cascade KIT variants listed above.
• Check that the existing sensor tube/pocket carries the same part number, 521343.
• Inspect the sensor and its wiring before ordering, as a faulty sensor can produce symptoms similar to a faulty pocket.
• Verify the sensor body diameter and thread of the existing pocket against the part being removed.