Lockout vs fault: what a reset actually does
When a boiler detects a problem, it responds in one of two ways.
- A blocking fault stops the boiler while the problem exists, then clears on its own once it goes away. Some low pressure and overheat codes behave like this on certain models.
- A lockout stops the boiler and keeps it stopped until someone presses reset, even if the cause has gone. Ignition and flame failure codes are usually lockouts, because the boiler wants a person to check before it tries to light gas again.
A reset does not repair anything. It tells the boiler to clear the lockout and try again. If the cause is still there, the boiler will lock out again, which is why repeated resetting does not help and can hide a real fault.
Where the reset is on common boilers
Controls vary between models and change over the years, so treat the table below as a general guide and always check the user manual for your model. The make and model are usually printed on the front panel or on the data badge.
| Brand | Where you usually find the reset | How it usually works |
|---|---|---|
| Worcester Bosch | A reset button, often marked with a reset or flame symbol, on the control panel | Press, or press and hold for a few seconds on some Greenstar models |
| Vaillant | A reset button on the ecoTEC control panel | Press once and wait for the boiler to restart |
| Ideal | The mode knob on many Logic and Vogue models has a reset position | Turn to reset, hold a few seconds, then turn back |
| Baxi and Potterton | A reset button, often marked R or with a reset symbol | Press, or hold for a few seconds depending on model |
| Glow-worm | A reset button on the control panel | Press once and wait |
| Viessmann | A reset button or reset option in the display menu | Follow the prompt on the screen |
Older boilers with a pilot light work differently and may need relighting rather than resetting. Follow the manual exactly, and if you are unsure, call an engineer.
How to reset a boiler safely, step by step
- Write down the fault code or the pattern of lights before you do anything. You will need it if you call an engineer.
- Look up the code. It often tells you the cause. For example, Ideal L2, Vaillant F28, Worcester Bosch EA 227 and Baxi E133 all relate to ignition or flame problems.
- Fix the likely cause first. Check other gas appliances work and that you have credit on a prepayment meter. Check the gas isolation valve under the boiler is open (handle in line with the pipe). If the pressure is under 1 bar with the system cold, top it up to 1 to 1.5 bar. In freezing weather, thaw the condensate pipe with warm water.
- Press or hold the reset as your manual describes.
- Wait. Many boilers take a minute or two to go through their start-up checks. Do not press reset again while it is trying to light.
- Check it runs. Turn on a hot tap or turn up the thermostat to make it fire and watch for the code returning.
The 2 or 3 attempt limit
If the boiler locks out again after 2 or 3 resets, stop. Repeated lockouts mean the cause is still there, and it is almost always one an engineer needs to deal with, such as a worn ignition electrode, a faulty gas valve, a fan problem or a flue issue. Some boilers also limit the number of resets allowed in a set period and will then refuse to restart until the power is cycled or an engineer attends.
Switching the power off and on at the fused spur is not a substitute for finding the fault. It counts as another reset.
If the display is blank
A boiler with no lights at all is not locked out, it has no power. Check the fused spur switch next to the boiler is on, check the plug if it has one, and look at your consumer unit for a tripped switch. If the power is on and the display is still blank, the fuse in the spur or a part inside the boiler may have failed, which is a job for an engineer.
After a power cut
Most boilers restart on their own once the power returns. Some go into lockout if the cut happened while they were firing, and one reset usually brings them back. Check the timer or programmer too, because many lose their clock settings, which can make it look as though the boiler is not working when it is simply outside its on period.
When not to reset your boiler
Do not reset, and get help, if you notice any of the following:
- a smell of gas anywhere in the home
- water dripping from the boiler casing, not just the pipes underneath
- scorch marks, soot or discolouration on or around the boiler
- a burning or electrical smell
- loud banging, or the boiler has made a bang before stopping
- a carbon monoxide alarm has sounded
- you have already reset it 2 or 3 times
If you smell gas or your CO alarm sounds, do not reset the boiler or operate electrical switches. Open doors and windows, turn off the gas at the meter if you can, leave the property and call the National Gas Emergency Service on 0800 111 999.
These signs point to a problem that a reset could make worse, such as a gas leak, a flue fault or water getting onto electrical parts. Switch the boiler off at the controls and leave it off until a Gas Safe registered engineer has checked it.
If the code is a low pressure code, reset only after you have topped up. Our guide to repressurising a boiler shows how. If the code relates to the condensate, thaw the pipe first using our frozen condensate pipe guide.
What an engineer will do
A Gas Safe registered engineer will read the fault history, test the gas supply and pressure at the boiler, check the ignition and flame sensing parts and look at the flue and fan. Typical UK costs are below and vary with the brand, part and your area.
| Job | Typical UK cost |
|---|---|
| Diagnostic call-out | Typically £60 to £120 |
| Ignition or flame sensing electrode | Typically £100 to £200 |
| Fan replacement | Typically £200 to £400 |
| Gas valve replacement | Typically £250 to £450 |