Unit shuts down with E4 on the display; water may be excessively hot just before shutdown.

Safety: Turn OFF power at the breaker and allow the unit to cool for at least 30 minutes. Do not work on a hot heater.

• Check for restricted flow: Ensure all inlet shutoff valves are fully open. Clean the inlet filter screen. Verify that hot water fixtures are not fitted with extremely low-flow aerators that starve the heater.
• Reset high-limit (if equipped): Remove the front cover and locate the manual reset high-limit thermostat on the heat exchanger or heating module. Press the red reset button firmly until it clicks.
• Inspect for scale: Look for signs of heavy limescale on the heating chambers and internal piping. If your water is hard and the unit has not been descaled, plan a descaling procedure using a pump, hoses, and a descaling solution per EcoSmart instructions.
• Check sensors and wiring: Inspect the high-limit sensor wiring and connector to the control board for damage or looseness.
• Test operation: Restore power and run hot water at a moderate flow. If E4 recurs quickly, discontinue use.
• Call a technician if: The unit overheats even with good flow and a reset high-limit. A stuck heating element relay/triac or faulty control board can cause dangerous overheating and should be serviced by a professional.