BoilerFaultCodesThe 4 most common faults
01
Burner Lock-out High DIY-safe
Your boiler's safety system has detected a problem with the burner and has shut the unit down to prevent damage or unsafe operation.
What to try first
Check that you have enough oil in your storage tank.Ensure the oil supply valve is fully open.Wait one minute, then press the illuminated reset button on the burner cover once only.
02
Safety thermostat High DIY-safe
Your boiler has switched itself off because its internal temperature has become too hot, triggered by a safety sensor to protect the system.
What to try first
Locate the high-limit thermostat reset button, which is usually found behind the front casing or under a small plastic screw cap.Press the button firmly once to reset the safety switch.Check that your radiator valves are open and that the system pressure is between 1.0 and 1.5 bar.
03
lock-out High DIY-safe
Your boiler is starting up briefly but then shutting itself down because it cannot maintain a stable flame.
What to try first
Check that you have sufficient heating oil in your storage tankEnsure the oil supply valves are fully openPress the illuminated reset button on the burner once only
04
10 Emergency Engineer
Your boiler system is leaking fuel or fumes, which is causing a noticeable smell of heating oil around the unit.
Full guide for 10on the Grant Vortex Blue / Vortex Outdoor
Oil nozzlePhotocellOil pumpFuel filterSafety Limit ThermostatCirculation Pump
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Grant shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue