Pool heat pump does not start; display shows E01 shortly after power-up.

Safety first: Turn off the pool heater at the main disconnect and lock out the breaker before opening any panels. High-pressure refrigerant and live electrical circuits can be dangerous.

• Check water circulation: Ensure the pool circulation pump is running and that all valves to and from the Hewalex heat pump are fully open. Clean the pool filter and backwash if pressure is high.
• Inspect water flow to heater: Confirm that the bypass valve (if installed) is correctly set so that sufficient water flows through the heat pump heat exchanger. A partially closed bypass can trigger high pressure.
• Clean the air coil: Remove leaves, dust, and debris from the outdoor evaporator coil using a soft brush and low-pressure water from the inside out. Maintain at least 50 cm of free space around the unit for airflow.
• Reset and test: After restoring water flow and cleaning the coil, restore power and clear the error (follow Hewalex control panel instructions, usually power cycle or reset button). Observe operation; if E01 returns quickly, the high-pressure switch or refrigerant charge may be faulty.
• When to call a technician: If water flow and airflow are normal but E01 persists, a certified refrigeration technician should test the high-pressure switch, measure operating pressures, and check for overcharge or blockage in the refrigerant circuit.