Reliance tankless or hybrid water heater displays E5 and shuts down shortly after starting

Safety first: Turn OFF power and gas. Allow the heater to cool completely. Do not reset or bypass safety devices without correcting the cause.

Steps to check:

• 1. Confirm tank is full: Open a hot water faucet and verify a strong, steady flow with no air spurting. If air is present, refill and purge the system before energizing.
• 2. Inspect high-limit (ECO): Remove the access cover and locate the ECO/high-limit thermostat (often a red reset button on electric models). If tripped, press to reset. If it trips repeatedly, there is an underlying overheating issue.
• 3. Check thermostat settings: Ensure the set temperature is within Reliance’s recommended range (typically 120°F). Extremely high settings can contribute to overheating.
• 4. Descale heating surfaces: For tankless/hybrid units, perform a descaling procedure. For standard electric tanks, inspect elements for heavy scale and replace if necessary.
• 5. Verify circulation (hybrid): On heat pump/hybrid models, ensure the internal circulation pump is operating. Listen for pump operation and feel for flow in the piping. Replace the pump if seized or not running.

Warning: Repeated high-limit trips without repair can damage the tank or heat exchanger and create scalding risk.