Boiler shows code 5, burner off, pump may run, boiler appears to be in anti-cycling delay

Information: Code 5 often indicates an anti-cycling period where the boiler intentionally delays re-firing to prevent short cycling. This is usually normal.

• Wait a few minutes: The boiler should automatically restart once the anti-cycling time has elapsed.
• Check room temperature: If the room is already at or near setpoint, the boiler may legitimately be off.
• System design: If the boiler frequently cycles between firing and code 5, your system may have low water volume or oversized output. Ask an engineer about adding a buffer vessel or adjusting boiler modulation settings.
• Control optimisation: Ensure thermostatic radiator valves (TRVs) are not all closed, which can cause rapid temperature rise and cycling. Keep at least one radiator fully open.
• Engineer check: A heating engineer can adjust anti-cycling parameters in the installer menu and verify correct modulation.