Boiler does not start; display shows E01 and heating/hot water demand is not met.

Safety first: Switch off the boiler at the isolation switch and turn off the circuit breaker. Allow the unit to cool before opening any covers. Only a competent person should remove the front panel.

Steps:

• Check system pressure and airlocks: Verify that the heating system is correctly filled and bled. On Elnur electric boilers, ensure all radiators are bled and that the circulation pump is running freely.
• Inspect the flow switch/sensor: Locate the flow switch or flow sensor assembly on the primary flow pipe inside the boiler. Check for loose connectors or damaged wiring to the main PCB. Reseat the plug firmly.
• Clean strainers/filters: If fitted, isolate the boiler, close the flow and return valves, and remove any inline filter or strainer on the boiler flow. Clean out sludge or debris and refit, ensuring seals are intact.
• Check pump operation: With power restored, call for heat and listen/feel for the circulation pump running. If the pump is seized or noisy, it may not generate enough flow to activate the flow switch.
• Reset and test: Restore power, reset the boiler according to the user manual, and check if E01 clears. If the error persists after confirming flow and wiring, the flow switch/sensor is likely defective and should be replaced.

Warning: Do not bypass the flow switch for testing; this is a critical safety device.