Display shows E5 and unit shuts down during operation, often with very hot outlet water

Safety first: Turn off power and allow the water to cool. Open a hot water tap to relieve pressure and temperature before working on the outlet side.

Steps to check:

• Inspect the thermostatic mixing valve (if equipped on your CTC model) at the outlet. Ensure it is not fully closed or jammed. Exercise the valve by turning it through its full range.
• Check for restricted flow at aerators and showerheads that can cause superheating. Clean or replace clogged fixtures.
• Descale the heat exchanger (tankless models) or flush the tank (storage models) if there is evidence of heavy mineral buildup.
• Test the outlet temperature limiter or thermal fuse for continuity. Replace if open.
• If the outlet thermistor is reading incorrectly (verified with a thermometer at the tap), replace the outlet thermistor.

Note: Over-temperature faults can be dangerous. If you are unsure of the cause, contact a professional.