E17 error; controller indicates buffer tank sensor fault (for systems with buffer/accumulator tank)

Safety: Allow tank fittings to cool before touching sensors.

• Locate the buffer tank sensor in the tank immersion pocket or strapped to the tank surface.
• Check that it is fully inserted and secured.
• Inspect the cable route for mechanical damage or loose junctions.
• Confirm that the sensor type matches the Defro controller requirements (NTC value).

Replace the sensor if resistance readings are out of range or intermittent.