Heatrae Sadia instantaneous electric water heater trips to E02 and stops heating during use.

Safety first: Switch off the heater at the isolator and consumer unit. Allow the unit to cool fully before working on it.

Steps to address E02:

• 1. Check flow rate: Ensure all isolation valves are fully open and that hot taps provide a strong flow. Low flow can cause overheating. Clean inlet strainers and any external filters.
• 2. Reset the thermal cut-out: Remove the front cover. Locate the manual reset overheat thermostat (usually a small device with a red or black reset button mounted on the heat exchanger). Press the reset button firmly until it clicks. Do not repeatedly reset without finding the cause.
• 3. Inspect for limescale: In hard water areas, limescale can insulate the element and cause local overheating. Check the heat exchanger body for signs of scale and overheating. If heavily scaled, the heat exchanger or element assembly may need descaling or replacement.
• 4. Check wiring and sensors: Inspect the wiring to the overheat thermostat and temperature sensors for damage or loose connections. Reseat connectors on the control PCB.
• 5. Test: Refit the cover, restore power and water, and run a hot tap. If E02 reappears quickly, the thermostat or heat exchanger assembly is likely faulty and should be replaced by a qualified technician.