How to Reset a Worcester Boiler, and When Resetting Is the Wrong Move

To reset a Worcester Bosch boiler, press and hold the reset button on the front control panel for a few seconds, then wait while the boiler runs through its start-up. On most Greenstar models the button is marked with a flame symbol or the word reset, and a few models use a combination of buttons, so check your user manual if you cannot see one. Before you press it, check the gas supply, the pressure gauge and, in cold weather, the condensate pipe. One reset is fine. If the blue light starts flashing again with the same code, the fault has not gone away and needs a Gas Safe registered engineer.

Where Is the Reset Button on a Worcester Boiler?

On most Worcester Bosch Greenstar boilers the reset button sits on the front control panel, usually beside the display, and is marked with a flame symbol or the word reset. You never need to remove the casing or open a flap held on with screws to reach it.

Layouts differ between older Greenstar i and Si models, the Greenstar 4000 and 8000 ranges and the Bosch-branded boilers, and some reset through a menu or a pair of buttons pressed together. If you are not sure, the model name is printed on the front of the boiler, and the user manual for that model shows the reset in its controls diagram. The steady or flashing blue light next to the display is also worth a look: a flashing blue light with a code usually means the boiler has locked out, which is exactly the situation the reset is for. Our article on the Worcester flashing blue light explains the light patterns.

Four Checks Before You Press Reset

A reset clears the lockout, but it does not remove the cause. If one of these simple causes is behind it, the boiler will lock out again within seconds, so check them first.

• Gas supply: does the hob light, and does a prepayment meter have credit? Is the gas valve under the boiler open, with its lever in line with the pipe?
• Pressure: the gauge should read roughly 1 to 1.5 bar with the system cold. A CE1 code means low pressure, and the fix is topping up through the filling loop, not a reset.
• Condensate pipe: in freezing weather, the plastic pipe running outside can freeze and trigger a lockout, shown on some models as D5.
• Power: after a power cut or a tripped fused spur, the boiler may need a reset to start again. Check the switch next to the boiler is on.

If you smell gas, do not reset the boiler or operate any switches. Open the windows, leave the property and call the National Gas Emergency Service on 0800 111 999.

How to Reset It, Step by Step

Press and hold the reset button for a few seconds, release it and give the boiler a minute or two to restart. Then create a demand for heat to check it fires.

1. Write down the code on the display exactly as shown, including any number that appears with it, such as EA and 227.
2. Press and hold the reset button for a few seconds, then release.
3. Wait while the boiler runs its start-up sequence. The fan usually runs first, then it tries to light. Do not keep pressing the button while this happens.
4. Run a hot tap or turn the heating up. The blue light should go steady and the display should return to normal.

If the code comes straight back, or the boiler lights and then locks out again a few minutes later, stop there. The step-by-step is the same for a second attempt, but the answer will not be.

Which Codes a Reset Is Meant For

A reset is meant for lockouts, where the boiler has shut down for safety and is waiting for someone to restart it. It does nothing for faults that are still present, such as low pressure, and some lockouts should not be reset more than once.

• EA and 227, failed ignition: the boiler tried to light and did not detect a flame. After checking the gas supply, one reset is reasonable. If fault 227 on a Worcester boiler returns, the ignition electrode, flame sensing or gas valve needs checking by an engineer.
• E9, overheat: the safety limiter on the heating flow has tripped. You can reset it once, but an E9 overheat lockout that comes back usually means poor circulation, from a pump fault, a blockage or low pressure, and repeated resets on an overheating boiler are a bad idea.
• CE1, low pressure: top up the pressure first. A reset on its own will not clear it.
• D5, condensate: thaw or clear the condensate pipe first, then reset.

Reset Worked, Then It Locked Out Again

A boiler that resets and runs, then locks out again hours or days later, has a fault that comes and goes. That pattern is useful to an engineer, so record it rather than resetting your way through it.

Note the code each time, the time of day and what the boiler was doing. An EA that only appears on the first firing of a cold morning points one way, and an E9 that appears only when the heating runs hard points another. Repeated resets can wear ignition parts and hide a fault that is getting worse, which is why the manual itself limits how often you should try. If your Worcester is shutting down without a clear code at all, our article on why a Worcester Bosch boiler keeps turning off covers the other causes.

When to Stop and Call an Engineer

Stop after one unsuccessful reset, after any overheat code that returns, and straight away if you see water leaking, hear loud banging or smell gas. Beyond the gas supply, the pressure, the condensate pipe and a single reset, the work involves opening the boiler, which by law is for a Gas Safe registered engineer.

When you book, give the model name, the code and how often it has appeared. With that, an engineer can usually narrow the fault to the ignition, circulation or control side before the casing comes off, which makes it more likely the right part is on the van for the first visit.