Boiler in standby, no central heating or hot water demand active, display shows code 0

Safety first: This condition is usually normal and not a fault. If you need heat or hot water and the boiler stays on code 0, follow these steps. Do not open the boiler casing; internal work must be done by a Gas Safe registered engineer.

• Check controls: Ensure the room thermostat is turned up above room temperature and set to 'heat' mode. Verify the programmer/time clock is set to 'ON' or 'AUTO' and not to 'OFF' or 'HOLIDAY'.
• Check hot water demand: Open a hot water tap fully. On Intergas combi models, the boiler should leave standby and show a different code (e.g. 1 or 2). If it remains at 0, there may be an issue with the flow sensor or controls.
• Check system pressure: Look at the pressure gauge on the boiler or system. It should typically be around 1.0–1.5 bar when cold. If it is below 0.8 bar, the boiler may not respond to demand. Top up via the filling loop according to the user manual, then reset the boiler if needed.
• Check external wiring: If you have access to the wiring centre (without removing the boiler case), visually inspect for loose thermostat or programmer connections. Do not touch live terminals; isolate power first.
• If still no response: If the boiler remains on 0 despite confirmed demand and correct pressure, contact a qualified engineer to test the low-voltage control circuits, PCB inputs, and flow sensor.