Boiler shows E05; heating elements do not energise even though there is demand.

Safety first: Isolate the boiler at the main switch and lock out the breaker if possible. Heating elements operate at mains voltage and can be lethal.

• Visual inspection: Remove the front cover and inspect the heating element bank. Look for burnt connectors, discoloured insulation, or signs of overheating.
• Check wiring tightness: With power off, tighten all screw terminals on the element connections and associated contactors/relays.
• Test elements (qualified persons only): Using a multimeter set to resistance, measure each element between its terminals. An open circuit (infinite resistance) indicates a failed element. Also check for earth leakage by measuring between each terminal and earth.
• Check PCB relays/contactors: If elements test OK, listen for the click of relays/contactors when there is a call for heat. No click may indicate a control board or relay fault.
• Replace faulty element: If an element is open or leaking to earth, replace it with the correct Elnur element assembly. Ensure all seals and gaskets are correctly fitted to prevent leaks.

Warning: Element replacement involves exposure to live parts and sometimes draining the boiler. This should be done by a qualified technician.