Error F.28

Safety first

1) If you smell gas or suspect a gas leak: get everyone out of the building, do not use electrical switches or phones indoors, do not light matches, and call the national gas emergency number immediately. Do not try to fix a gas leak yourself.

2) Turn the boiler off and isolate electrical power before touching or inspecting the boiler casing. If you are not confident, stop and call a professional.

3) Do not open or attempt to repair gas components, ignition electrodes, the gas valve or PCB yourself — these must be handled by a Gas Safe registered engineer.

Initial homeowner checks (safe, simple steps)

1) Record the fault: note the exact code (F.28), any lights, noises (clicking from ignition), and when it appeared. This helps the engineer.

2) Try a single reset: follow your boiler manual (typically press and hold the reset button for 3–5 seconds). Wait to see if the boiler fires. Do not repeatedly reset the boiler more than once or twice — persistent lockouts should be investigated, not repeatedly overridden.

3) Check other gas appliances: light the hob or gas fire to confirm your home has a gas supply. If none of your gas appliances work, the problem is likely with the gas supply or meter — contact your gas supplier.

4) Check the gas isolation valve at the boiler: make sure the small shut-off under the boiler is in the open (inline) position. Do not loosen or remove fittings.

5) Check boiler water pressure: look at the pressure gauge. Correct working pressure is normally about 1.0–1.5 bar. If pressure is below about 0.8 bar the boiler may refuse to ignite. If low, repressurise carefully using the filling loop per your manual (open valves slowly, watch the gauge to reach about 1.0–1.5 bar, then close valves). After repressurising, switch the boiler on and try again.

6) Inspect the condensate pipe (external): in cold weather the external condensate pipe can freeze. If visible and suspected frozen, thaw with warm (not boiling) water or a hot water bottle and try reset. Do not pour boiling water.

7) Check the flue and air intake: look at the outside flue terminal for blockages (nesting material, debris, a bucket, etc.). Ensure nothing blocks the intake or exhaust. Remove obvious external obstructions if safe to do so. Replace any housing panels on the boiler before testing.

What to watch for during checks

1) When attempting to ignite, you may hear a few clicks (ignition sparks). If you hear clicking but no flame, this suggests ignition is attempting but failing (could be electrode, ignition lead, or gas supply issue).

2) If nothing happens at all when the boiler tries to fire (no click, no gas sound), this points more to gas supply/isolation or an electrical/PCB fault.

When to stop and call a professional

1) If the F.28 returns after simple checks (reset once, pressure correct, condensate thawed, flue clear, gas supply confirmed), stop troubleshooting and call a Gas Safe registered engineer.

2) Call a Gas Safe engineer immediately if you suspect internal faults: stuck or faulty gas valve, faulty ignition electrodes or ignition transformer, faulty flame sensor, PCB/wiring faults, or if you are asked to remove internal components.

3) If you see signs of a gas leak, carbon monoxide symptoms (sooting, pilot lights going out, headaches, dizziness), or any unsafe condition, isolate the property and call emergency services/gas emergency.

What the engineer will check and do (so you know what to expect)

A Gas Safe engineer will check gas supply pressure at the boiler, confirm the isolation valve, test the gas valve operation, inspect and test ignition electrodes and ignition leads, check the flame detection circuit, examine the condensate trap/pipe and flue for blockages, check system pressure and filling loop, inspect PCB and wiring, and run controlled ignition tests. They may clean or replace electrodes, replace leads, repair or replace a sticking gas valve, rectify wiring or PCB faults, or clear condensate/flue blockages. Request that the engineer shows you what caused the lockout and provides a clear safety check before they leave.

Additional notes and safe practice

1) Keep the boiler manual and service history handy for the engineer. Note the exact model and firmware/display messages.

2) Avoid repeatedly resetting the boiler to chase intermittent faults — repeated lockouts can mask underlying failures and increase wear.

3) Regular servicing (annual) by a Gas Safe engineer reduces the chance of these faults and maintains warranty and safety.

4) Only a Gas Safe registered engineer should carry out internal repairs, gas appliance replacements or any work on gas pipes and valves.