Boiler shows E07 and will not fire, often after power interruption or wiring work

Safety: Ensure the system is cool before topping up pressure. Do not exceed the maximum pressure indicated on the gauge (usually 2.5–3 bar).

• Check pressure gauge: Look at the Main boiler’s pressure gauge. If below 0.8–1.0 bar, the boiler may lock out with E07.
• Top up via filling loop:
  • Locate the filling loop (usually a braided hose with two valves under the boiler).
  • Open both valves slowly until the gauge reaches about 1.2–1.5 bar.
  • Close both valves fully and remove the loop if detachable.
• Bleed radiators: If air is present, bleed radiators and re-pressurise as needed.
• Check for leaks: Inspect visible pipework, radiator valves, and the boiler underside for signs of water leakage.
• Engineer checks:
  • Test the water pressure sensor or switch on the Main boiler for correct operation.
  • Check the expansion vessel pre-charge and recharge or replace if the vessel is waterlogged.
  • Inspect the pressure gauge and connecting capillary for blockage.