BWT pool heater stops heating and displays E02 after running for a short time

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

• Check water flow: Ensure the circulation pump is running and that all valves to and from the heater are fully open. Clean the pool filter if pressure is high.
• Bleed air from system: If your BWT heater has a manual air bleed on the heat exchanger, open it slightly with the pump running until a steady stream of water (no air) flows, then close it.
• Inspect heat exchanger for scaling: Look for reduced flow or temperature spikes at the outlet. If scaling is suspected, follow BWT’s procedure for chemical descaling of the titanium heat exchanger or contact a professional.
• Check high-limit sensor connections: Locate the high-limit temperature sensor on the outlet side of the heat exchanger. Inspect wiring and connectors for corrosion or loose contacts. Reseat connectors firmly.
• Reset and test: After the unit has cooled and any air has been purged, restore power and restart the heater. Monitor inlet and outlet temperatures to ensure they rise gradually.

If E02 reappears quickly, the high-limit sensor or control board may be faulty and should be tested and replaced by a qualified technician.