Error E28

Safety precautions:

1. If you smell gas, leave the property immediately and call the gas emergency number. Do not attempt any work on the boiler.

2. Turn the boiler off at its control panel. If you will be working near the appliance, switch off the electricity at the consumer unit (fuse box) as well.

3. Never use open flames to thaw pipes. Don’t open or dismantle the boiler casing unless you are Gas Safe registered.

Initial checks a homeowner can do (safe, external checks):

1. Check the condensate pipe route outside: find the small plastic pipe that runs from the boiler to outside. Look for frost, visible ice or a solid blockage at the outlet.

2. Inspect the flue terminal (the white pipe/vent on an external wall): look for birds’ nests, leaves, snow or debris blocking the outlet.

3. If external, check the condensate outlet and nearby drains for blockage or slow drainage (sometimes household drain issues cause condensate back-up).

4. Note any other house drainage problems (e.g. sink slow to drain) — this can point to a shared blockage.

Safe DIY fixes you can try:

1. Thaw a frozen condensate pipe: turn off the boiler and electricity first. Apply gentle heat with warm (not boiling) water poured slowly over the frozen section, use a warm towel, or a hairdryer on low held a short distance away. Work slowly and avoid overheating plastic. Once thawed, insulate the external run or fit a condensate trace heater/lagging to prevent recurrence. Do not use a naked flame.

2. Clear obvious flue terminal obstructions: only remove light debris visible at the outside end. Do not insert tools deep into the flue. If the terminal is blocked inside or you are unsure, stop and call an engineer.

3. Reset the boiler: after you have cleared a thawed condensate or obvious external blockage, restore power/gas and reset the boiler per the manufacturer's instructions or use the reset button. If it runs normally the problem is likely resolved.

What to avoid as a homeowner:

1. Do not open the boiler or touch gas valves, internal wiring, sensors, the thermistor, the PCB or the air pressure switch. These tasks require a Gas Safe registered engineer.

2. Do not use boiling water on plastic condensate pipework; do not force tools into the flue terminal; do not bridge safety switches.

When to call a professional and what they will check:

1. Call a Gas Safe registered engineer if thawing or clearing the outside terminal does not clear the fault, if the fault returns repeatedly, or if you are uncomfortable performing the external checks.

2. A qualified engineer will safely isolate the appliance, remove covers, check electrical continuity on the thermistor/flue circuit and the air pressure switch, inspect and clean the condensate trap and drain, check the flue internals, and replace faulty components (thermistor, pressure switch or PCB) if needed. They will also carry out post-repair safety checks and 26.9-type combustion/installation checks where required.

Additional notes:

- Repeated E28 faults in cold weather commonly indicate condensate freezing or a blocked condensate/drain connection. Insulating the condensate pipe or installing a trace heater/longer fall to the drain can prevent recurrence.

- If an engineer finds damaged wiring, a faulty air pressure switch, failed thermistor or PCB fault, these must be repaired or replaced by a Gas Safe engineer for safety and compliance.

Summary: perform only the safe external checks and thawing methods described above. If the code remains after those checks or if you are unsure at any stage, contact a qualified Gas Safe engineer to diagnose and repair the fault.