Fault Guide
Oil Boiler Lockout: Causes and What to Do
When an oil boiler locks out, a red light comes on and the boiler stops until it’s reset. It’s a safety feature: the boiler has tried to light and couldn’t, or has spotted something wrong. Here’s what causes it, what you can check yourself, and when to leave it to an engineer.
Check these first
- Is there oil in the tank? Tank gauges can stick, so check with a dipstick if you can.
- Is the valve at the tank open?
- Is the boiler getting power, and are the programmer and thermostat calling for heat?
- Has the fire valve on the fuel line tripped? It shuts off the oil if it senses a fire, and it can also trip on its own.
How to reset an oil boiler, and how many times
Press the lockout reset button once and wait a couple of minutes. If the boiler locks out again, you can try once more. OFTEC advises never trying more than twice.
After that, leave it alone. Each failed attempt leaves unburnt oil in the combustion chamber, and pressing reset over and over can flood the burner and make the repair bigger.
What usually causes a lockout
- Running out of oil, or air in the fuel line afterwards. Once the oil is delivered, the line often needs bleeding by an engineer.
- A blocked fuel filter
- A worn or dirty nozzle
- A dirty or failed photocell, which is how the boiler sees the flame
- Faulty ignition electrodes or a failed control box
- A tripped fire valve
- The overheat thermostat tripping
When to call an engineer
Call an OFTEC registered engineer if the boiler locks out again after two resets, if it keeps locking out every few days, or if you smell oil or see smoke. Anything behind the casing, including bleeding the fuel line, is a job for an engineer. The filter, nozzle and photocell faults above are all dealt with on an annual service, which is the best way to stop lockouts happening in the first place.
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