Andrews E29 Fault Code: Causes, Fixes & Repair Costs
What does the Andrews E29 fault code mean?
The E29 code on an Andrews boiler indicates a flame-loss lockout. Unlike a fault where the boiler fails to ignite in the first place, E29 means the boiler successfully established a flame but then lost it during operation — and has shut itself down as a safety measure. The control system detected that a safe, stable flame could not be maintained, so it locked out rather than continuing to attempt ignition. This is normal protective behaviour; the boiler is doing exactly what it should. The fault needs to be investigated and resolved before the boiler will fire again. Note that the precise trigger can vary between Andrews models (including commercial water heater ranges), so always cross-reference with your specific model's service manual or contact Andrews directly if you are unsure.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Interrupted or insufficient gas supply Common
If the gas supply to the boiler is too low in pressure or is intermittently cut off, the flame will collapse mid-operation and trigger a lockout. This can be caused by a meter issue, a closed isolation valve, an empty pre-payment meter, or a wider network interruption affecting the street supply.
- Faulty or sticking gas valve Common
The gas valve controls fuel delivery to the burner. If it sticks, fails to open fully, or closes unexpectedly during firing, the flame will be starved and lost. This is one of the most frequently diagnosed mechanical causes of flame-loss lockouts on Andrews appliances.
- Dirty or damaged flame sensor (ionisation electrode) Common
The flame sensor detects whether a burner flame is present by measuring a small electrical current through the flame. Carbon deposits or physical damage can prevent it from reading the flame correctly, causing the boiler to believe the flame has gone out even when it has not.
- Frozen or blocked condensate pipe Common
In cold weather, the plastic condensate drain pipe that runs outside the property can freeze solid. The resulting blockage prevents condensate from draining, which can cause the boiler to shut down and lock out. This is especially common during prolonged freezing spells and is one of the few causes a homeowner can resolve themselves.
- Flue blockage or flue gas recirculation Sometimes
If the flue outlet is partially obstructed — by bird nests, debris, or a poorly positioned terminal — exhaust gases can be drawn back into the combustion air intake. This disrupts combustion and starves the flame. The boiler will lock out to prevent the release of harmful gases including carbon monoxide into the building.
- Poor electrical earthing Sometimes
Inadequate earthing of the boiler or its components can interfere with the small electrical signal the flame sensor uses to confirm flame presence. The PCB may register a flame loss even when the burner is alight, resulting in a spurious lockout.
- Ignition electrode misalignment or contact with burner Sometimes
If the control or ignition electrode has shifted position and is making contact with the burner body, the flame signal can be disrupted or earthed out. Physical wear, vibration over time, or an incorrect previous repair can cause this.
- Faulty PCB (printed circuit board) Rare
If the PCB is failing, it may not correctly process the flame signal even when the sensor and flame are functioning properly. A telltale sign is a boiler that works for a period after reset but repeatedly returns to the same lockout code. PCB faults are relatively rare and are usually diagnosed after other components have been ruled out.
How to fix it
- Check that your gas supply is active DIY safe
Check whether other gas appliances in your home — such as a gas hob or gas fire — are working normally. If nothing gas-powered is working, the issue may be with your meter, a closed isolation valve, or a wider supply interruption. Contact your gas supplier if you suspect a network issue. If gas supply is confirmed as normal, move on to the next step.
- Inspect the condensate pipe for freezing (cold weather only) DIY safe
Locate the white plastic pipe that exits your boiler and runs outside, usually discharging near a drain. If the weather is at or below freezing and the pipe feels solid, it is likely frozen. Gently pour warm — not boiling — water along the frozen section until it clears. Dry the pipe, then attempt a reset. Consider lagging the pipe with foam insulation to prevent a recurrence.
- Reset the boiler once DIY safe
Press and hold the reset button on your Andrews boiler as described in your user guide. Allow the boiler a full ignition attempt — this typically takes 30–60 seconds. If it fires up and runs normally, monitor it over the next few hours. Do not reset more than two or three times in quick succession; repeated resets without resolving the underlying cause can cause further damage and mask the real fault.
- Check system pressure if applicable to your model DIY safe
Some Andrews boilers operate with a sealed system that has a pressure gauge. If the gauge reads below 1 bar, the system may need topping up via the filling loop. Consult your user manual for the correct procedure. Note that not all Andrews appliances use a pressurised system — check whether this applies to your model before proceeding.
- Do not attempt to open the boiler casing or inspect internal components Gas Safe engineer
Internal inspection of the gas valve, burner, ignition electrodes, flame sensor, flue, or PCB must only be carried out by a Gas Safe registered engineer. Removing the casing and working on gas components without the correct qualifications is illegal under UK gas safety regulations and will invalidate your warranty.
- Contact a Gas Safe registered engineer to diagnose and repair the fault Gas Safe engineer
If the boiler has not recovered after the steps above, a qualified engineer needs to attend. They will carry out systematic checks including gas inlet pressure, valve operation, electrode condition and alignment, flame sensor signal, flue integrity, and PCB function. You can verify any engineer's Gas Safe registration at gassaferegister.co.uk before they begin work.
Parts you may need
- Flame sensor / ionisation electrode · from £25
- Ignition electrode and lead assembly · from £45
- Gas valve (Andrews-compatible replacement) · from £120
- PCB (printed circuit board) · from £180
- Condensate pipe insulation lagging · from £8
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £80–£350, depending on the underlying cause.
Frequently asked questions
Can I reset my Andrews boiler myself when E29 appears?
Yes — a single reset attempt is safe and sensible. Press the reset button and allow the boiler a full ignition cycle. If it lights and runs normally, keep an eye on it over the next day or two. However, if E29 returns after one or two resets, repeated resetting is not advisable. The boiler is locking out for a reason, and masking the fault by continually resetting can cause further component wear. At that point, call a Gas Safe registered engineer.
Is E29 dangerous — do I need to evacuate my home?
The E29 lockout itself means the boiler has already shut down safely, so there is no ongoing combustion risk from the appliance. However, if you smell gas at any point, do not reset the boiler — leave the property immediately, avoid using any switches or flames, and call the National Gas Emergency Service on 0800 111 999. If you have any suspicion of a carbon monoxide leak (symptoms include headaches, dizziness, or nausea), evacuate and call 999.
My Andrews boiler keeps coming back to E29 after being reset — what does that mean?
A recurring E29 lockout almost always points to a component fault rather than a one-off event. The most common culprits are a gas valve that is sticking or failing, a flame sensor that is coated in deposits and needs cleaning or replacing, or — less commonly — a PCB that is not processing the flame signal correctly. A Gas Safe engineer can measure the flame ionisation signal with test equipment to pinpoint which component is at fault. If your boiler is over 12–15 years old and has already had several repairs, it may be worth discussing replacement with your engineer rather than investing further in an ageing appliance.
How much does it typically cost to fix an Andrews E29 fault?
For the most common repairs — cleaning or replacing the flame sensor and electrode — most homeowners pay in the region of £80–£200 including labour. Replacing a gas valve typically adds up to around £250–£350 all-in. These figures cover the majority of E29 faults. In rarer cases where the PCB needs replacing, costs can rise to £400–£600 depending on the model and part availability; if that applies to your situation your engineer will advise you before proceeding.