Unit shows E11 and stops; may be accompanied by very high water temperature reading.

Safety first: Turn off power and allow the unit to cool before touching any internal components or plumbing.

• Check setpoint: Verify that the desired pool temperature on the SPRSUN controller is reasonable (e.g., 26–30°C / 79–86°F). Reduce if set excessively high.
• Verify circulation: Ensure the pool pump is running whenever the heater is enabled. Check for closed valves or clogged filter that could reduce flow.
• Inspect heat exchanger: If your pool has hard water, scale can build up inside the titanium heat exchanger, restricting flow. Have a technician inspect and chemically clean if necessary.
• Reset and test: After restoring proper flow, reset the error and monitor operation. If E11 recurs quickly, the overheat sensor or control board may be faulty.
• Replace sensor/limit: A technician can test and replace the high-limit thermostat or water temperature sensor as needed.