Digital Heatrae Sadia electric water heater will not heat; display shows E01 and water remains cold.

Safety first: Isolate the heater from the mains supply at the consumer unit and close the cold water isolation valve before removing any covers. Confirm power is off with a suitable tester.

Steps to check and address E01:

• 1. Check water supply and filters: Open the cold isolation valve fully. Remove and clean any inlet filter or strainer on the cold inlet to the heater. Rinse out debris and refit.
• 2. Inspect the flow sensor / flow switch: Remove the front cover following the manufacturer’s instructions. Locate the flow sensor or paddle-type flow switch on the cold inlet manifold. Check for visible limescale or debris; carefully clean the sensor body and paddle using descaler suitable for potable systems.
• 3. Electrical checks: With power still isolated, inspect the wiring harness to the flow sensor for loose connectors, damaged insulation, or corrosion. Reseat any push-fit connectors firmly.
• 4. Test operation: Restore water supply, then restore power. Open a hot tap fully. If the code clears and heating resumes, monitor for recurrence. If E01 persists, the flow sensor is likely defective and should be replaced.
• 5. When to call a professional: If you are not competent to perform electrical continuity tests or the sensor is integrated into a sealed hydraulic block, contact a qualified engineer familiar with Heatrae Sadia units.