Error E28

Safety precautions:

- If you smell gas, evacuate the property immediately and call the emergency gas number—do not stay to investigate.

- Turn the boiler off at the control panel and isolate the electrical supply at the fused spur or consumer unit before doing any close inspection. Do not attempt internal repairs, wiring or component replacement unless you are Gas Safe registered.

- Do not use naked flames to thaw pipes. Do not pour boiling water on plastic pipes; use warm water only. Wear gloves and eye protection if working outside in cold conditions.

Initial visual checks homeowners can do:

1. Look at the condensate pipe (usually a small plastic pipe running from the boiler to outside and discharging near the drain). If there is frost, ice, or visible blockage, that is a likely cause.

2. Inspect the flue terminal (the white/metal pipe outlet on the outside wall). Check for snow, leaves, bird nests or debris. Do not push objects into the flue; you can gently remove visible debris by hand.

3. Check the boiler pressure gauge; if the system pressure is very low (below about 1.0 bar) note it, but low pressure is not the usual direct cause of E28.

Specific diagnostic and fix steps:

1. Turn the boiler off at the control and isolate power before touching the condensate pipe or flue area. Leave the gas alone.

2. If you suspect the condensate pipe is frozen: apply warm (not boiling) water to the frozen section, or wrap the pipe with a warm towel, or use a hairdryer on a low/medium setting to gently warm it until the ice clears. Start thawing from the outdoor end toward the boiler so water can run away. Avoid overheating the pipe or using open flame.

3. Once thawed, allow any standing water to drain, switch the boiler power back on and follow the manufacturer reset procedure (hold the reset button for the time stated in the manual or turn the boiler off and on). Watch for the fault to clear and for the boiler to run normally.

4. If the flue terminal had visible blockages that you can remove safely by hand, clear them and then reset the boiler. Do not insert tools deep into the flue or dismantle the terminal.

5. If the E28 returns after thawing and clearing external blockages, do not keep resetting. Intermittent faults or repeated lockouts point to a faulty flue thermistor, damaged wiring or a control board issue.

When to call a professional:

- Call a Gas Safe registered engineer if the fault persists after thawing and simple external checks, if you find damaged wiring, if the flue appears damaged or heavily obstructed, or if you are uncomfortable performing the safe checks above. The thermistor and internal diagnostics/repairs must be carried out by a qualified engineer.

- Keep a record of when the error occurs (times, weather conditions, any noises) to help the engineer diagnose intermittent problems.

Final note: E28 is a safety lockout. Simple outside fixes (thawing condensate, clearing flue) commonly restore operation, but recurring or internal faults require a Gas Safe engineer. Do not attempt internal repairs or component replacement yourself.