What do boiler error codes mean?
The common code categories, the two things you can safely check, and when repeated resetting becomes dangerous.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 2 min
- Safety
- warning
Short answer
Look the code up in the manual or on the manufacturer's site — they are specific to the model. You can safely check pressure and the condensate pipe; everything else needs an engineer, and repeatedly resetting a locked-out boiler is not safe.
Error codes are model-specific, so a code that means one thing on one boiler means something else on another. But the categories are consistent, and two of the common causes are things you can safely check yourself.
Safety
Step by step
- Write down the exact code.Including letters. Photograph the display. It is the first thing an engineer will ask and it shortens the visit considerably.
- Look it up for your specific model.The manual, or the manufacturer's website. Codes are not standardised between manufacturers and a general list will mislead you.
- Check the pressure first.Low pressure is one of the commonest causes of a lockout and it is a user-fixable one. 1-1.5 bar cold. Top up via the filling loop if it is low.
- Check the condensate pipe in cold weather.The other common user-fixable cause. A frozen condensate pipe locks out the boiler and it is very common in a cold snap. Thaw it gently with warm cloths or a hot water bottle — never boiling water or a flame.
- Check the gas supply is on.Other gas appliances working, the meter not on emergency credit, and the gas valve open. Obvious, and it is sometimes the answer.
- Reset once, not repeatedly.A single reset after fixing an obvious cause is reasonable. Repeatedly resetting a boiler that keeps locking out overrides a safety mechanism doing its job.
- Know the categories.Broadly: ignition and flame failure, pressure faults, overheating, fan or flue faults, and sensor faults. Ignition, flue and overheating codes need an engineer promptly.
- Call an engineer for anything else.Give them the code, the model, and what you have already checked. Check their Gas Safe number on the official register.
Tips
- Photograph the boiler's data plate — model and serial number — and keep it on your phone. Every engineer and parts supplier asks for it.
- A frozen condensate pipe is the classic cold-snap lockout and it is entirely user-fixable. Lagging the external section prevents it.
- Keep the manual, or download a PDF. The code list is in it and it saves a call-out surprisingly often.
Questions people ask
Can I reset my boiler when it shows an error?
Once, after checking the obvious causes like pressure and a frozen condensate pipe. Repeatedly resetting a boiler that keeps locking out overrides a safety mechanism and is not safe.
Why does my boiler lock out in cold weather?
Most often a frozen condensate pipe. Thaw it gently with warm cloths or a hot water bottle — never boiling water — and lag the external section to prevent it.