To reset a boiler, find the reset button on the control panel, usually marked with a circular arrow or the word reset, press it once for a second or two and wait for the boiler to run through its start-up. If it fires and stays running, the lockout was a one-off. If it locks out again, or shows the same fault code, do not keep pressing. A lockout is the boiler detecting a fault and refusing to run until it is cleared, and repeated resets can turn a small problem into a bigger one, particularly on an oil boiler where each attempt puts fuel into the chamber.
This guide explains what a reset does, how to do it on gas and oil boilers, why a boiler sometimes will not work after a reset or a power cut, and the codes and symptoms that mean it is time to call an engineer.
What a reset actually does
Modern boilers monitor themselves constantly: flame, pressure, temperature, fan speed, flue gases and more. When a reading falls outside the safe range the boiler shuts down, displays a fault code and waits. The reset clears the fault memory and lets the boiler try again. It does not fix anything. If the cause was momentary, such as a gust down the flue or a brief pressure dip, the boiler runs. If the cause is still there, it locks out again.
How to reset a gas boiler
- Read the fault code on the display and look it up in the manual before resetting. It tells you what the boiler saw.
- Check the obvious: pressure above 1 bar, gas supply on, no smell of gas.
- Press the reset button once, for a second or so. Some boilers use a dial turned to a reset position, others a button behind a flap.
- Wait. The fan runs, the ignition clicks and the boiler should fire within a minute.
- If it runs, note the code and the date. If it locks out again, stop and call an engineer.
How to reset an oil boiler
The reset is on the burner control box, usually a red or orange lockout light with a button. Press it once and wait. The fan runs, there is a pause and the burner lights with a soft whoosh. If it locks out again, do not reset a second time; each failed attempt sprays oil into the chamber. Our guide to resetting an oil boiler lockout covers the causes.
Why a boiler will not work after a reset
- The fault is still there. Low pressure, a blocked condensate pipe, an ignition fault or a failed component. The boiler will keep locking out until it is fixed.
- Too many resets. Some boilers limit resets and need a period with the power off before they will accept another.
- Frozen condensate pipe. In winter, the commonest cause of a boiler that resets and locks out again immediately. Thaw the pipe and reset once. Our guide to a frozen condensate pipe explains how.
- Low pressure. Some boilers show a pressure code, others just refuse to fire. Check the gauge.
- Gas or oil supply. A closed valve, an empty oil tank or a gas supply interruption.
Why a boiler will not work after a power cut
A power cut can leave a boiler in a locked-out state, reset its clock and programmer, or trip the fused spur. Check the spur and the fuse, reset the boiler once, and then check the programmer’s time and schedule, which may have reverted to defaults. Wireless thermostats sometimes need re-pairing after a long outage. If the boiler still does nothing, a surge may have damaged the board, which is an engineer’s job.
When not to reset
- if you can smell gas or oil
- if there is water leaking from the boiler
- if the boiler has already locked out twice in a row
- if the fault code indicates a flue, combustion or overheat problem
- if the reset button itself does nothing, which points to a board or power fault
Persistent resetting on a boiler with a flue or combustion fault risks carbon monoxide. Make sure your alarm works and call a registered engineer.
Common fault codes and what they usually mean
Codes vary by manufacturer, but the themes are consistent: ignition or flame loss, low pressure, overheat, fan or flue faults and sensor errors. Our guides to Vaillant fault codes, Worcester Bosch boiler problems and Ideal boiler problems cover the codes on three of the most common brands.
How DCI Boilers can help
DCI Boilers diagnoses and fixes lockouts and fault codes on gas and oil boilers across Cornwall and Devon, with Gas Safe and OFTEC registered engineers and fixed prices agreed before work starts. Book boiler repairs, or if you have no heat, our emergency boiler call-out runs around the clock. A boiler that locks out regularly is also a boiler that is overdue a boiler servicing visit.
Need help now? Call DCI Boilers on 07888 862 603 or get a free quote.
Frequently asked questions
Where is the reset button on a boiler?
On the front control panel, often marked with a circular arrow, sometimes behind a flap. Oil boilers have it on the burner control box.
How many times can I reset my boiler?
Once. If it locks out again, the fault needs finding rather than clearing.
Does resetting a boiler damage it?
A single reset does not. Repeated resets on a boiler with an ignition, combustion or oil supply fault can.
Why does my boiler need resetting every day?
Something is marginal: pressure, a partly blocked condensate pipe, a weak ignition or a failing sensor. An engineer can find it in one visit.