Quick answer: A boiler error code tells you why your boiler has stopped. Most codes fall into four groups: low water pressure, ignition or flame failure, overheating, and circulation or sensor faults. Low pressure is often something you can fix at home. Almost everything else needs a Gas Safe engineer.
A code flashing on the boiler display is rarely good news, but it’s more useful than it looks. It narrows down the problem, tells you whether a quick top-up might sort it, and gives an engineer a head start. This page brings together every boiler error code guide on our site, grouped by brand.
The Edinburgh Boiler Company repairs, services and installs boilers across every Edinburgh postcode from EH1 to EH55, and further afield across central Scotland and the Borders. If your boiler is over 8 years old, out of warranty and throwing up codes more often, a boiler replacement from Edinburgh engineers is often the more reliable long-term fix.
How do boiler error codes work?
When your boiler detects a problem, it stops and shows a code that points to the cause. Some codes are temporary and clear on their own once the problem goes away. Others are lockouts, which keep the boiler off until someone presses reset.
A few ground rules apply whatever boiler you have:
- Reset once. If the code comes straight back, repeated resets won’t fix it.
- Never remove the boiler casing. Anything inside is Gas Safe work.
- If you smell gas, turn the boiler off, open windows and call the National Gas Emergency number on 0800 111 999.
Which boiler brand do you have?
Find your brand below for the full list of its codes. The brand name is usually printed on the front of the boiler or on a data badge underneath.
| Brand | Common codes | Full guide |
|---|---|---|
| Vaillant | F22, F28, F29, F75, F83 | Vaillant boiler error codes |
| Worcester Bosch | EA 227, EA 229, E9 224, C6, A21 | Worcester Bosch boiler error codes |
| Ideal | F1, F2, L2, FD, FL | Ideal boiler fault codes |
| Baxi | E133, E119, E125, E110, H0207 | Baxi boiler error codes |
| Glow-worm | F22, F28, F75 | Glow-worm boiler error codes |
| Viessmann | F4, F2, F5, 0b | Viessmann boiler fault codes |
| Potterton | E119, E133, E110, E125, E168 | Potterton boiler fault codes |
| Alpha | E28, E10, E9, E37 | Alpha boiler fault codes |
Potterton and Main boilers belong to the same group as Baxi and use many of the same codes, so the Baxi guides apply to most of them.
What do the same faults look like on different boilers?
The same fault shows as a different code on each brand. This table lines them up so you can find the right guide quickly.
| Fault | Vaillant | Worcester Bosch | Ideal | Baxi | Glow-worm |
|---|---|---|---|---|---|
| Low water pressure | F22 | See brand guide | F1 | E119 / H0207 | F22 |
| Ignition failure | F28 | EA 227 | L2 | E133 | F28 |
| Flame lost while running | F29 | EA 229 | F2 | See brand guide | See brand guide |
| Overheating | F20 | E9 224 | See brand guide | E110 | See brand guide |
| Circulation or pump | F75 / F83 | See brand guide | See brand guide | E125 | F75 |
What can you safely check yourself?
You can check pressure, radiators, your gas supply and the condensate pipe. That covers a surprising number of lockouts.
| Check | What to look for | Codes it can clear |
|---|---|---|
| Pressure gauge | Around 1 to 1.5 bar when cold. Top up via the filling loop if lower | Low pressure codes, some circulation codes |
| Radiators | Cold at the top means trapped air. Bleed them, then recheck pressure | Circulation and overheat codes |
| Gas supply | Does the hob work? Is there credit on a prepay meter? | Ignition and gas supply codes |
| Condensate pipe | Frozen or blocked plastic pipe outside, common in winter | Ignition codes on many brands |
| Reset button | Press once, as your boiler manual describes | Any one-off lockout |
If the pipe outside has frozen, our guide to thawing a frozen condensate pipe walks you through it.
Which boiler error codes need a Gas Safe engineer?
Any code that returns after one reset needs an engineer. So does anything involving the gas valve, flame sensing, fan, pump or circuit board. By law, only a Gas Safe registered engineer should open a gas boiler or work on its gas parts. You can book a boiler repair with our team online.
Why do boiler error codes spike in Scottish winters?
Cold weather puts boilers under the most strain just when you need them most. Three things drive most winter call-outs in Scotland:
- Frozen condensate pipes. External plastic pipes freeze in a hard frost and force an ignition lockout.
- Pressure drops after summer. Pressure drifts down while the heating is off, then the first cold snap exposes it.
- Long heating cycles. Worn pumps, sensors and fans often fail once the boiler starts running for hours at a time.
A quick look at your pressure gauge and condensate pipe in autumn prevents a lot of these.
Should you repair or replace a boiler that keeps showing error codes?
Repair a boiler that’s under 8 years old or still under warranty. Once it’s older, out of warranty and needing regular repairs, replacement usually works out better.
| Your boiler | Our usual advice |
|---|---|
| Under 8 years, in warranty | Repair. Check whether the warranty covers the part |
| Under 8 years, out of warranty, one-off fault | Repair |
| Over 8 years, out of warranty, first fault in years | Repair, but start budgeting for a replacement |
| Over 8 years, out of warranty, repeat faults | Get a replacement quote before paying for major parts |
| Over 15 years | Replace. Parts get harder to find and efficiency will have dropped |
A new A-rated condensing boiler comes with a fresh manufacturer warranty, often 7 to 10 years when fitted by an approved installer. It’s also more efficient than an older boiler that’s been wearing down for a decade. You can get a free new boiler quote online in a few minutes.
Does a boiler service stop error codes?
A yearly service stops many of them. Engineers clean and check the parts behind most common codes, including electrodes, sensors, the condensate trap, the pump and the expansion vessel. Most manufacturers also need a yearly service to keep your warranty valid. Book a boiler service before winter.
Where do we fix, service and install boilers?
We cover Edinburgh and a wide area around it, with local pages for many towns.
| Area | Boiler repairs | New boiler installation |
|---|---|---|
| West Lothian | Livingston, Bathgate, Broxburn | Livingston, Bathgate |
| East and Midlothian | Musselburgh, Dalkeith, Mayfield | Dunbar, Penicuik |
| Edinburgh edges | Balerno, South Queensferry | Balerno, South Queensferry |
| Fife, Stirling and Perth | – | Dunfermline, Stirling, Perth |
| West of Scotland | – | East Kilbride, Paisley |
| Scottish Borders | – | Peebles, Galashiels, Kelso, Hawick |
Frequently Asked Questions About Boiler Error Codes
Are boiler error codes the same across brands?
No. Each manufacturer uses its own codes, so F22 on a Vaillant means something different from F2 on an Ideal. Use the table above to match your code to the right guide.
How many times should I reset my boiler?
Once. If the code comes back straight away, the fault hasn’t gone, and repeated resets can make some problems worse.
Can I clear a boiler error code without an engineer?
Sometimes. Low pressure, trapped air, a frozen condensate pipe or a gas meter out of credit are all things you can sort yourself. Anything inside the boiler needs a Gas Safe engineer.
Why is my boiler not working but showing no error code?
Check the thermostat, the timer and the power supply first. The boiler may simply not be getting a signal to fire. If those are fine, an engineer can run a diagnosis.
Is it worth fixing a boiler that’s over 8 years old?
For a small, one-off repair, usually yes. If it’s out of warranty and needs a major part like a heat exchanger, gas valve or circuit board, a new boiler is often the better investment for reliability and efficiency.
